1 00:00:09,999 --> 00:00:10,669 OK. 2 00:00:10,669 --> 00:00:13,379 Good morning everyone. 3 00:00:13,379 --> 00:00:21,439 As I mentioned at the last lecture, we're now moving into the nitty-gritty of the subsystems. 4 00:00:21,439 --> 00:00:28,660 And we have quite an extraordinary list of speakers who actually worked on the original 5 00:00:28,660 --> 00:00:30,140 design of these systems. 6 00:00:30,140 --> 00:00:34,430 And, as Professor Cohen mentioned, not only did they design these systems for the shuttle 7 00:00:34,430 --> 00:00:41,440 but, in most cases, they came from having designed essentially the same systems on the 8 00:00:41,440 --> 00:00:42,380 Apollo program. 9 00:00:42,380 --> 00:00:46,460 So, in the question and answer period, if there are some things that you'd like to know 10 00:00:46,460 --> 00:00:51,570 about the comparison of Apollo and Shuttle, and also any questions about the future since 11 00:00:51,570 --> 00:00:57,910 some of you will be writing up possibilities for future development of some of these systems, 12 00:00:57,910 --> 00:00:59,079 please ask the questions. 13 00:00:59,079 --> 00:01:08,390 And I spoke with Tom Moser, and he's fully prepared to handle questions during the talk. 14 00:01:08,390 --> 00:01:13,460 Because there will be a lot of fairly detailed technical stuff, so if there's something that 15 00:01:13,460 --> 00:01:18,560 you're not familiar with, you don't understand or just have questions about, please ask while 16 00:01:18,560 --> 00:01:19,700 the lecture is going on. 17 00:01:19,700 --> 00:01:27,990 I want to remind you, we have fairly extensive bios for all the speakers. 18 00:01:27,990 --> 00:01:32,158 Rather than take the time in class to read through this, I've posted them all on the 19 00:01:32,158 --> 00:01:33,770 class website. 20 00:01:33,770 --> 00:01:43,840 So my suggestion is go to the class website before each class and just see the background 21 00:01:43,840 --> 00:01:47,500 of the lecture. 22 00:01:47,500 --> 00:01:53,189 Professor Cohen is going to make some personal remarks about, well, whatever it is that you 23 00:01:53,189 --> 00:01:55,210 want to say about our speaker. 24 00:01:55,210 --> 00:01:57,799 Before we go into that, two things. 25 00:01:57,799 --> 00:02:04,380 Tom Moser asked me if we had this book. 26 00:02:04,380 --> 00:02:06,570 This actually is my personal copy. 27 00:02:06,570 --> 00:02:08,399 I'm going to put it on reserve. 28 00:02:08,399 --> 00:02:10,478 We may actually have it in the library as well. 29 00:02:10,478 --> 00:02:15,810 I'll check, and I'll make sure that this gets on reserve. 30 00:02:15,810 --> 00:02:19,099 This really is a rather complete book. 31 00:02:19,099 --> 00:02:24,900 A lot the material that you've seen, the early design of the shuttle is in here, discussions 32 00:02:24,900 --> 00:02:32,040 of subsystems, and then detailed discussions of the individual flights all the way up through 33 00:02:32,040 --> 00:02:34,370 the first hundred shuttle flights. 34 00:02:34,370 --> 00:02:39,739 It's a very nice resource, and we'll have it on reserve in the library. 35 00:02:39,739 --> 00:02:42,480 The next thing. 36 00:02:42,480 --> 00:02:52,690 I believe I have now indications from everybody about what you want to do your paper on. 37 00:02:52,690 --> 00:02:56,829 We have two groups doing GN&C. 38 00:02:56,829 --> 00:03:01,310 One group doing displays and controls. 39 00:03:01,310 --> 00:03:05,519 We had two small groups interested in the propulsion system. 40 00:03:05,519 --> 00:03:12,129 And I've asked Brian and other people, you've gotten together? 41 00:03:12,129 --> 00:03:15,170 OK. 42 00:03:15,170 --> 00:03:20,190 Only one person, Dan, I think, indicated an interest in the thermal protection system. 43 00:03:20,190 --> 00:03:24,579 I know we've got a lot people on GN&C. 44 00:03:24,579 --> 00:03:29,030 One of you, I think, had actually indicated an interest in thermal protection. 45 00:03:29,030 --> 00:03:31,959 I will leave that up to you. 46 00:03:31,959 --> 00:03:39,780 If somebody would like to work on thermal protection with Dan, he's back there and is 47 00:03:39,780 --> 00:03:41,500 available, I guess. 48 00:03:41,500 --> 00:03:48,540 We have one group which is going to do a little bit of a different sort of project on modularity 49 00:03:48,540 --> 00:03:54,519 and some of the design methods that went into the shuttle compared to modern techniques 50 00:03:54,519 --> 00:03:59,090 that are available now, so we'll be interested in seeing what you'll come up with. 51 00:03:59,090 --> 00:04:04,510 And then we had a group that wants to look at the propulsion system, but from the point 52 00:04:04,510 --> 00:04:10,489 of view of fuel storage and what the system would have looked like if we had possibly 53 00:04:10,489 --> 00:04:11,750 used alternate fuels. 54 00:04:11,750 --> 00:04:17,079 We've got a nice spectrum of things that people will look at. 55 00:04:17,079 --> 00:04:23,599 Any time you'd like to come and talk with me, with Professor Cohen or take advantage 56 00:04:23,599 --> 00:04:28,240 of one of the speakers who happens to be talking about the area that you're interested in, 57 00:04:28,240 --> 00:04:30,780 please do that. 58 00:04:30,780 --> 00:04:35,909 We do have time usually after class, if you're free. 59 00:04:35,909 --> 00:04:40,490 The speakers will generally be available so take advantage of it. 60 00:04:40,490 --> 00:04:40,710 OK. 61 00:04:40,710 --> 00:04:43,790 That's enough talking from me. 62 00:04:43,790 --> 00:04:57,940 Aaron, I'll give this to you.. 63 00:04:57,940 --> 00:05:02,040 I just have a few personal comments about Mr. Moser. 64 00:05:02,040 --> 00:05:08,440 He is going to talk to you today, lecture you today about the structures on the space 65 00:05:08,440 --> 00:05:09,500 shuttle. 66 00:05:09,500 --> 00:05:15,190 But Tom, as Jeff mentioned, did the same work on the Apollo program. 67 00:05:15,190 --> 00:05:20,419 I was the manager of the Command and Service Module on Apollo and on the Space Shuttle 68 00:05:20,419 --> 00:05:23,430 Orbiter, so Tom and I have been working tighter for many years. 69 00:05:23,430 --> 00:05:26,560 And I relied very, very heavily on Tom throughout the years. 70 00:05:26,560 --> 00:05:32,180 I told a little anecdote the other day, and just let me say it again because the person 71 00:05:32,180 --> 00:05:34,860 that helped me with it is Tom Moser. 72 00:05:34,860 --> 00:05:39,229 During one of the shuttle missions, we were getting ready to come back, about 11:00 at 73 00:05:39,229 --> 00:05:43,650 night, I was getting ready to leave my house to go to the Control Center, which I live 74 00:05:43,650 --> 00:05:49,289 about ten minutes away, and we were getting ready to make the de-orbit burn, I got a call 75 00:05:49,289 --> 00:05:55,800 from Rockwell International, their head of the program there. 76 00:05:55,800 --> 00:05:58,409 And he said, Aaron, we just did this test. 77 00:05:58,409 --> 00:06:05,210 We took the panel of tiles and dumped it into a bucket of waterproofing agent and all the 78 00:06:05,210 --> 00:06:05,960 tiles came off. 79 00:06:05,960 --> 00:06:10,350 I said what do you want me to do with that information? 80 00:06:10,350 --> 00:06:14,639 I said they're getting ready to come back and there's not much I can do about that. 81 00:06:14,639 --> 00:06:16,850 You're telling me all the tiles are going to come off? 82 00:06:16,850 --> 00:06:19,669 He said no, they're not because that's not really what we did on the shuttle. 83 00:06:19,669 --> 00:06:20,819 I said well, why did you do that test? 84 00:06:20,819 --> 00:06:21,830 That's sort of a dumb test. 85 00:06:21,830 --> 00:06:27,759 I had a decision to make, whether I'd call the people in the Control Center like Chris 86 00:06:27,759 --> 00:06:33,560 Kraft and tell him we did this test and all the tiles are going to come off. 87 00:06:33,560 --> 00:06:33,819 But we've got to come back. 88 00:06:33,819 --> 00:06:38,360 I decided what I would do is call my good colleague Tom Moser. 89 00:06:38,360 --> 00:06:39,940 I said Tom, what should we do? 90 00:06:39,940 --> 00:06:43,810 We talked for a while and talked for a while, and we decided to keep this information to 91 00:06:43,810 --> 00:06:46,130 ourselves until after the landing. 92 00:06:46,130 --> 00:06:48,120 It turns out it all worked out fine. 93 00:06:48,120 --> 00:06:50,659 There were no problems. 94 00:06:50,659 --> 00:06:53,610 But my point to you is that how much I relied on Tom. 95 00:06:53,610 --> 00:06:58,319 The other point is you may find yourself in that type of situation some day on a project 96 00:06:58,319 --> 00:07:00,020 maybe not associated with that. 97 00:07:00,020 --> 00:07:09,060 Tom turned out to be afterward my Deputy Manager in the Orbiter Project Office. 98 00:07:09,060 --> 00:07:13,539 Then he went on to become Head of Engineering at the Johnson Space Center and then went 99 00:07:13,539 --> 00:07:20,380 on to be Director of the Space Station in Washington, DC and now is a consultant. 100 00:07:20,380 --> 00:07:26,660 So, with no further ado, let me turn it over to Tom. 101 00:07:26,660 --> 00:07:30,840 One thing I learned to do is have my own mic because Aaron will keep it. 102 00:07:30,840 --> 00:07:36,770 One of the advantages to having a gray beard, besides some of the folks in the back, is 103 00:07:36,770 --> 00:07:41,909 I'm not going to refer to him as Professor Cohen or as Professor Hoffman. 104 00:07:41,909 --> 00:07:44,159 It's Jeff and Aaron. 105 00:07:44,159 --> 00:07:45,699 It's not out of disrespect. 106 00:07:45,699 --> 00:07:53,409 It's just the way I grew up so that's OK to do. 107 00:07:53,409 --> 00:07:58,860 When Aaron asked me to do this, and Jeff, I thought that's easy, I'll just pull out 108 00:07:58,860 --> 00:08:02,270 some of my old notes and stuff like that and I will be up the next day. 109 00:08:02,270 --> 00:08:09,789 Until Jeff sent me the syllabus and what it was to do, it made me start thinking about 110 00:08:09,789 --> 00:08:11,919 what I'd spent a good part of my life doing. 111 00:08:11,919 --> 00:08:15,690 And that was designing and development of the shuttle with Aaron and some of the others, 112 00:08:15,690 --> 00:08:20,080 but from a systems engineering perspective which you guys are doing. 113 00:08:20,080 --> 00:08:24,220 So, what I did is I went back and looked at everything from a systems engineering point 114 00:08:24,220 --> 00:08:28,879 of view from 1968 all the way until '81 when the shuttle flew. 115 00:08:28,879 --> 00:08:32,068 But I looked at it through the knothole of a structure and thermal person. 116 00:08:32,068 --> 00:08:34,568 So, that's what I'm going to present to you today. 117 00:08:34,568 --> 00:08:38,690 And, as you go through each phase of the program it changes. 118 00:08:38,690 --> 00:08:44,800 And sometimes it's down to the minute detail and other times it is the macro. 119 00:08:44,800 --> 00:08:46,740 That's my objective, and I hope we accomplish that. 120 00:08:46,740 --> 00:08:53,600 Ask me any questions any time that you want to. 121 00:08:53,600 --> 00:08:58,760 Just a little bit of credit and recognition of some of the people that made this thing 122 00:08:58,760 --> 00:08:59,040 happen. 123 00:08:59,040 --> 00:09:01,760 You're going to hear from a lot of these people. 124 00:09:01,760 --> 00:09:09,019 You won't hear from John Yardley or Max Faget because they are deceased now, but these people 125 00:09:09,019 --> 00:09:11,360 up here made this program go. 126 00:09:11,360 --> 00:09:16,740 And then you will have also some references that give you a lot more detail than I'm going 127 00:09:16,740 --> 00:09:20,170 to give you today, even though I'm going to cover a lot of it. 128 00:09:20,170 --> 00:09:26,450 There is one unique thing about a program like this that is complex. 129 00:09:26,450 --> 00:09:31,760 And that is the technical team and the management team have to work together and get together. 130 00:09:31,760 --> 00:09:43,700 Everybody that is listed up there stayed on this program from day one, and that is key. 131 00:09:43,700 --> 00:09:47,760 I don't think there has been a program since then that that has happened. 132 00:09:47,760 --> 00:09:53,060 And I think that if people judge the Shuttle Program as being successful, I think that 133 00:09:53,060 --> 00:10:02,370 that's a major contribution to that success. 134 00:10:02,370 --> 00:10:08,820 Beginning in '68 when the concept studies began, all the way down to operations from 135 00:10:08,820 --> 00:10:14,200 a structural perspective, what is important at each one of those phases in its weight 136 00:10:14,200 --> 00:10:16,769 and cost and produceability from day one. 137 00:10:16,769 --> 00:10:22,399 But then it gets into the certification phase, the last part of the program, how are you 138 00:10:22,399 --> 00:10:23,519 going to certify this thing? 139 00:10:23,519 --> 00:10:25,860 How are you going to prove that it's good for flight? 140 00:10:25,860 --> 00:10:27,860 How are you going to prove that the crew is safe? 141 00:10:27,860 --> 00:10:29,839 And you have to do it on the ground. 142 00:10:29,839 --> 00:10:34,040 So, it's a completely different knothole you're looking through and a completely different 143 00:10:34,040 --> 00:10:37,339 set of parameters. 144 00:10:37,339 --> 00:10:41,010 I didn't start on Apollo at the beginning like Aaron did. 145 00:10:41,010 --> 00:10:43,850 I came out a little bit later. 146 00:10:43,850 --> 00:10:51,060 But, in this program, I had the good fortune of working on it from sketchpad to launch 147 00:10:51,060 --> 00:10:52,240 pad. 148 00:10:52,240 --> 00:10:53,910 And that's the way I characterized it. 149 00:10:53,910 --> 00:10:57,839 And Aaron didn't know this, but at the end I would have worked for free to complete the 150 00:10:57,839 --> 00:11:01,180 program because I was going to see something from beginning to end. 151 00:11:01,180 --> 00:11:06,620 And so if you ever had that opportunity to get on the program at the very beginning, 152 00:11:06,620 --> 00:11:12,140 I don't care what knothole you're looking at it through, stay on that program if you 153 00:11:12,140 --> 00:11:18,700 can because it's a completely different life at every step along the way. 154 00:11:18,700 --> 00:11:21,940 So, from the knothole of Orbiter structure, I'm going to break this thing into two pieces, 155 00:11:21,940 --> 00:11:36,589 Orbiter structure and the thermal protection system.. 156 00:11:36,589 --> 00:11:41,600 On the concept studies that began in '68, what was the objective of those concept studies? 157 00:11:41,600 --> 00:11:47,560 Conceiving, characterizing and characterizing by qualitative and quantitative concepts that 158 00:11:47,560 --> 00:11:48,779 would appear to work. 159 00:11:48,779 --> 00:11:56,950 So, it was determining really the feasibility of the concepts. 160 00:11:56,950 --> 00:12:04,510 When that began, the only requirement in the Shuttle Program was to have a reusable space 161 00:12:04,510 --> 00:12:05,910 transportation system. 162 00:12:05,910 --> 00:12:12,370 Get something that goes from earth to low earth orbit and back reliably and reusable. 163 00:12:12,370 --> 00:12:17,079 There wasn't a requirement on payload size, there wasn't a requirement on number of missions, 164 00:12:17,079 --> 00:12:20,209 there wasn't a requirement on any of those things. 165 00:12:20,209 --> 00:12:21,510 That's what it was. 166 00:12:21,510 --> 00:12:27,990 The variables that we all looked at, though, were budgets, yearly budgets, developments 167 00:12:27,990 --> 00:12:28,990 costs, operations cost. 168 00:12:28,990 --> 00:12:34,170 And you'll see, as you go through some of this stuff, and probably some of the stuff 169 00:12:34,170 --> 00:12:39,350 that Dale Myers showed you, is development cost, you can spend a lot of money on development 170 00:12:39,350 --> 00:12:42,910 and reduce the operations cost or you can spend a little bit of money on development 171 00:12:42,910 --> 00:12:45,089 and have very high operational cost. 172 00:12:45,089 --> 00:12:45,970 So, there's a trade there. 173 00:12:45,970 --> 00:12:50,480 And when you're dealing with budgets that you really don't understand exactly what they 174 00:12:50,480 --> 00:12:53,700 are, that's a very important variable. 175 00:12:53,700 --> 00:12:58,470 Payload mass and size is important from a structural and thermal standpoint because 176 00:12:58,470 --> 00:13:04,459 it has to do with mass and it has to do with energy that has to be dissipated during reentry. 177 00:13:04,459 --> 00:13:06,519 The operational orbit is important. 178 00:13:06,519 --> 00:13:12,300 Fully reusable flight systems or partially reusable, and that's a trade on cost and weight. 179 00:13:12,300 --> 00:13:14,660 Turnaround time and cross-range. 180 00:13:14,660 --> 00:13:20,800 Cross-range was critical to us at this point because NASA didn't have a requirement for 181 00:13:20,800 --> 00:13:21,529 cross-range. 182 00:13:21,529 --> 00:13:25,519 And that's cross-range after you come back into the atmosphere to be able to deviate 183 00:13:25,519 --> 00:13:29,540 your normal ballistic trajectory coming back in. 184 00:13:29,540 --> 00:13:35,920 But the Air Force thought that they had a requirement so we had to include that. 185 00:13:35,920 --> 00:13:46,589 And then, as we got into the next phase of it, looking at what was important from a structural 186 00:13:46,589 --> 00:13:53,510 standpoint is the efficiency of the load path, the weight, the payload size, the aerodynamic 187 00:13:53,510 --> 00:13:57,370 surface loading, now we're beginning to get in and look at what are the wing loads, et 188 00:13:57,370 --> 00:14:10,040 cetera, and how does that manifest itself in weight and produceability? 189 00:14:10,040 --> 00:14:18,829 We did that under two years of contracted effort. 190 00:14:18,829 --> 00:14:24,339 Then within JSC, the Johnson Space Center, which was formally the Manned Space Craft 191 00:14:24,339 --> 00:14:29,300 Center, we conceptionally looked at designs in-house. 192 00:14:29,300 --> 00:14:31,459 And we looked at 53 different designs. 193 00:14:31,459 --> 00:14:36,959 You talk about a systems engineering thing, what we did was got a group of people about 194 00:14:36,959 --> 00:14:41,040 the size of this room and went away and locked ourselves up. 195 00:14:41,040 --> 00:14:47,660 But we had expertise in every area, propulsion, guidance and control, aerodynamics, aero heating, 196 00:14:47,660 --> 00:14:48,209 that kind of stuff. 197 00:14:48,209 --> 00:14:51,660 And we were almost doing a configuration a week when we did that. 198 00:14:51,660 --> 00:14:59,910 So, when you look at 53 different configurations over basically a two-year period, we were 199 00:14:59,910 --> 00:15:08,019 not only just looking at it but we were quantifying then, what it meant in terms of all the parameters 200 00:15:08,019 --> 00:15:09,959 that I showed you a while ago. 201 00:15:09,959 --> 00:15:10,970 How much did it cost? 202 00:15:10,970 --> 00:15:12,269 What was the development cost? 203 00:15:12,269 --> 00:15:13,699 What was the operations cost? 204 00:15:13,699 --> 00:15:14,740 What was the weight? 205 00:15:14,740 --> 00:15:17,649 What was the maximum temperature as we saw on the vehicle? 206 00:15:17,649 --> 00:15:23,959 Was there a thermal protection system that could accommodate those types of temperatures? 207 00:15:23,959 --> 00:15:29,709 That was the characterization in the systems engineering parameters that we used. 208 00:15:29,709 --> 00:15:32,120 Tom, where these designs kind of refined? 209 00:15:32,120 --> 00:15:37,730 Were you refining with each iteration or was it like we'll try this for a couple iterations 210 00:15:37,730 --> 00:15:39,910 and then maybe try something completely different? 211 00:15:39,910 --> 00:15:42,009 Were you working towards a final [OVERLAPPING VOICES]? 212 00:15:42,009 --> 00:15:44,889 Well, what we were doing was looking at the variables. 213 00:15:44,889 --> 00:15:50,990 In other words, like here, when we looked at 53 different things, we looked at payloads 214 00:15:50,990 --> 00:15:53,420 ranging anywhere from 15,000 to 40,000 pounds. 215 00:15:53,420 --> 00:15:57,149 We didn't know what the answer was going to be. 216 00:15:57,149 --> 00:16:01,779 The driving thing there was reusability and cost profile. 217 00:16:01,779 --> 00:16:04,759 We thought we knew what we could afford to do. 218 00:16:04,759 --> 00:16:09,720 We looked at payloads from 8 feet in diameter to 15 feet in diameter, 30 feet long to 75 219 00:16:09,720 --> 00:16:10,350 feet long. 220 00:16:10,350 --> 00:16:13,570 We were looking at all of those things. 221 00:16:13,570 --> 00:16:17,690 And, as we did that, we changed configuration from a straight wing, which is not good for 222 00:16:17,690 --> 00:16:23,730 cross-range, to a delta wing which is better for a cross-range, to a double delta wing 223 00:16:23,730 --> 00:16:27,540 which is even more structurally efficient. 224 00:16:27,540 --> 00:16:29,579 Landing weights then was important. 225 00:16:29,579 --> 00:16:32,990 Just like everybody saw the plane landing last night, it had to get that landing weight 226 00:16:32,990 --> 00:16:35,230 down to where it could control it. 227 00:16:35,230 --> 00:16:36,949 Well, that was the same thing we were doing. 228 00:16:36,949 --> 00:16:43,050 We were looking at landing weights, not only from a controllability but also from a produceability. 229 00:16:43,050 --> 00:16:49,910 We looked at weights from 70,000 to 215,000 pounds, boosters from fully reusable to partially 230 00:16:49,910 --> 00:16:53,540 reusable, propulsion systems and various types of things. 231 00:16:53,540 --> 00:16:57,839 We even looked at air breathers so that they didn't have to come back a dead stick like 232 00:16:57,839 --> 00:17:00,839 they do now when Jeff was in the vehicle. 233 00:17:00,839 --> 00:17:04,539 And pressure fed and pump fed systems. 234 00:17:04,539 --> 00:17:07,819 There was simplicity and complications in all of them. 235 00:17:07,819 --> 00:17:10,049 Tankage, internal or external to the Orbiter. 236 00:17:10,049 --> 00:17:18,000 Could you maybe say, for people's benefit here who have grown up in the computer age, 237 00:17:18,000 --> 00:17:20,510 something about the tools that you had? 238 00:17:20,510 --> 00:17:22,299 I am going to do that in a minute. 239 00:17:22,299 --> 00:17:23,349 You are, OK. 240 00:17:23,349 --> 00:17:26,939 I'm going to give you a challenge, too. 241 00:17:26,939 --> 00:17:28,039 So, we looked at all of those. 242 00:17:28,039 --> 00:17:32,450 And, we not only looked at it, we quantified it to the extent that we could get the first 243 00:17:32,450 --> 00:17:36,510 order estimates on what the cost in all those things where. 244 00:17:36,510 --> 00:17:39,960 Now then, I chose a couple of them here. 245 00:17:39,960 --> 00:17:44,809 This was one of the early designs of the Orbiter. 246 00:17:44,809 --> 00:17:47,169 Look where the locks and hydrogen are. 247 00:17:47,169 --> 00:17:48,160 It's inside the Orbiter. 248 00:17:48,160 --> 00:17:56,280 It has a straight wing so it was fairly lightweight, except for having to carry all that tankage. 249 00:17:56,280 --> 00:18:01,270 The engines were on the Orbiter itself, but the payload was really small. 250 00:18:01,270 --> 00:18:03,020 Very low cross-range, very low payload. 251 00:18:03,020 --> 00:18:07,730 So that was probably the 8 foot diameter 40,000 pound payload. 252 00:18:07,730 --> 00:18:15,330 We evolved that over a series of studies until we finally got down to about February of '72 253 00:18:15,330 --> 00:18:19,360 where we said we're going to have to have a larger payload than this. 254 00:18:19,360 --> 00:18:20,710 And the cost profile didn't fit. 255 00:18:20,710 --> 00:18:25,880 What we did is we came up with a configuration that's almost like the shuttle that you see 256 00:18:25,880 --> 00:18:26,660 today. 257 00:18:26,660 --> 00:18:31,919 Large payload, all the propulsion systems, the main propulsion systems are outside the 258 00:18:31,919 --> 00:18:32,020 Orbiter. 259 00:18:32,020 --> 00:18:34,690 And it's a fly back, and part of it was throwaway. 260 00:18:34,690 --> 00:18:40,179 In this case, we had a booster in line with the external tank rather than in parallel 261 00:18:40,179 --> 00:18:42,929 with it like the SRBs are today. 262 00:18:42,929 --> 00:18:47,830 Basically that's what we started the detailed design and development with, but not exactly. 263 00:18:47,830 --> 00:18:48,380 And I'll show you that. 264 00:18:48,380 --> 00:18:57,860 Now then, some of us who like to worry about load pass and simplicity and low weight of 265 00:18:57,860 --> 00:19:00,610 the structure, we said ah-ha. 266 00:19:00,610 --> 00:19:08,289 What we will do is put the engines on the external tank. 267 00:19:08,289 --> 00:19:10,070 All the mass is down here. 268 00:19:10,070 --> 00:19:14,970 Very little mass up here. 269 00:19:14,970 --> 00:19:20,990 And for boost reduce the weight of the Orbiter, which is going to reduce development and operations 270 00:19:20,990 --> 00:19:25,950 costs a whole bunch and thermal protection system, but we have to swing these engines 271 00:19:25,950 --> 00:19:31,780 for reusability from the external tank back up the Orbiter and stow them for entry. 272 00:19:31,780 --> 00:19:36,740 Well, our brother in mechanical engineers, they beat us pretty hard. 273 00:19:36,740 --> 00:19:38,760 They beat us black and blue. 274 00:19:38,760 --> 00:19:43,140 Anyway, that was a concept that we looked at very late in the program. 275 00:19:43,140 --> 00:19:47,559 And that didn't go anywhere, even though Max Faget and I wanted to do it pretty badly. 276 00:19:47,559 --> 00:19:51,559 As we continue now. 277 00:19:51,559 --> 00:19:56,120 Now we're four years into the thing, we've done all these systems engineering analysis, 278 00:19:56,120 --> 00:19:58,100 so we end up with a final concept. 279 00:19:58,100 --> 00:19:59,250 Here's what we want. 280 00:19:59,250 --> 00:20:06,480 We want a 2.5 stage launch vehicle because it costs too much basically to fly back the 281 00:20:06,480 --> 00:20:07,900 booster. 282 00:20:07,900 --> 00:20:13,130 We just didn't have the money so we said we want to have the most important part be fully 283 00:20:13,130 --> 00:20:14,409 reusable, so that was the Orbiter. 284 00:20:14,409 --> 00:20:15,780 It was going to be a delta wing. 285 00:20:15,780 --> 00:20:24,140 We figured that the mission life, we had a mission model of 500 total missions, 100 missions 286 00:20:24,140 --> 00:20:28,460 per vehicle, and there were five vehicles. 287 00:20:28,460 --> 00:20:30,960 We had an ascent acceleration of 3 g's. 288 00:20:30,960 --> 00:20:33,419 Why was that? 289 00:20:33,419 --> 00:20:37,940 Really, the requirement was to keep down the inertia loads, but it was also to let people 290 00:20:37,940 --> 00:20:39,390 off the street flying the thing. 291 00:20:39,390 --> 00:20:39,659 Go ahead. 292 00:20:39,659 --> 00:20:42,169 What constitutes half a stage? 293 00:20:42,169 --> 00:20:49,260 Half a stage means that the external tank is like a half a stage. 294 00:20:49,260 --> 00:20:54,770 The SRB is a stage, the engine, the Orbiter is a stage, but the tank is a half a stage. 295 00:20:54,770 --> 00:21:07,850 We kept the max dynamic pressure down because that was a major driver for control systems 296 00:21:07,850 --> 00:21:09,250 and for aerodynamic services. 297 00:21:09,250 --> 00:21:12,980 You would love not to have the wings on the Orbiter going uphill. 298 00:21:12,980 --> 00:21:15,070 That's a penalty that you pay. 299 00:21:15,070 --> 00:21:19,919 So, one of the things to help reduce that is to keep that aerodynamic load down on the 300 00:21:19,919 --> 00:21:21,309 wings. 301 00:21:21,309 --> 00:21:24,370 Then for atmospheric flights, and I'm going to talk a little bit more about that, we said 302 00:21:24,370 --> 00:21:26,260 this thing is going to come back like an airplane. 303 00:21:26,260 --> 00:21:27,059 Let's fly it. 304 00:21:27,059 --> 00:21:32,200 Let's design it like an airplane 2.5 g normal maneuver load factor and a negative 1 g. 305 00:21:32,200 --> 00:21:35,059 A crew of four for one week. 306 00:21:35,059 --> 00:21:39,830 That becomes kind of important because that sized the crew module, that sized a lot of 307 00:21:39,830 --> 00:21:45,159 the environmental control systems you'll hear about later and other things in the life support 308 00:21:45,159 --> 00:21:46,870 systems. 309 00:21:46,870 --> 00:21:52,669 So, without a lot of changes, to show you what the flexibility and capability of this 310 00:21:52,669 --> 00:21:58,840 vehicle is, the Orbiter is now flying seven people for two weeks. 311 00:21:58,840 --> 00:22:06,429 So, it went from 28 man days to 63 man days basically. 312 00:22:06,429 --> 00:22:10,539 And I don't think a lot of people understand what that has done. 313 00:22:10,539 --> 00:22:16,370 And there is a lot more robustness in the Orbiter, in the shuttle system that was not 314 00:22:16,370 --> 00:22:19,110 designed into it but had some inherent capability. 315 00:22:19,110 --> 00:22:22,870 And also some of it was a little bit of forethought in the thing. 316 00:22:22,870 --> 00:22:24,270 Here comes the Air Force stuff. 317 00:22:24,270 --> 00:22:26,020 65,000 pounds up. 318 00:22:26,020 --> 00:22:30,659 40,000 pounds return. 319 00:22:30,659 --> 00:22:32,120 That was the requirements. 320 00:22:32,120 --> 00:22:33,789 15 x 60. 321 00:22:33,789 --> 00:22:38,370 Another important thing is we didn't know what they'd be but maybe up to five payloads 322 00:22:38,370 --> 00:22:39,030 at a time. 323 00:22:39,030 --> 00:22:43,110 And that's going to become a problem, I'll show you about in a minute, as we start peeling 324 00:22:43,110 --> 00:22:49,830 this systems engineering onion of getting down into the details. 325 00:22:49,830 --> 00:22:52,020 And deployable payloads. 326 00:22:52,020 --> 00:22:52,020 Cross-range. A little less than 1300 nautical miles cross-range. 327 00:22:55,549 --> 00:22:56,960 TPS material. 328 00:22:56,960 --> 00:23:02,100 We didn't know what the hell it was going to be, but that's what we started with. 329 00:23:02,100 --> 00:23:09,929 So, we began the contract for design, development, test and evaluation. 330 00:23:09,929 --> 00:23:12,929 NASA does pretty good stuff in-house. 331 00:23:12,929 --> 00:23:14,970 And I think with Dr. 332 00:23:14,970 --> 00:23:19,820 Mike Griffin at the helm now you're going to see a lot more of that coming into NASA 333 00:23:19,820 --> 00:23:21,190 where they're doing a lot of stuff in-house. 334 00:23:21,190 --> 00:23:28,049 But when it gets down to doing the detail, design and manufacturing and cost-control, 335 00:23:28,049 --> 00:23:32,850 down to the detailed parts and manifesting everything around, that's where the contract 336 00:23:32,850 --> 00:23:32,940 is. 337 00:23:32,940 --> 00:23:35,460 NASA doesn't have that capability in a large program. 338 00:23:35,460 --> 00:23:39,000 So, this is where we gave a contract to Rockwell International. 339 00:23:39,000 --> 00:23:43,220 They had the integration contract. 340 00:23:43,220 --> 00:23:46,090 And another company, Martin, had the external tank. 341 00:23:46,090 --> 00:23:48,610 [Backhaul?] had the SRBs. 342 00:23:48,610 --> 00:23:49,980 And who else am I missing? 343 00:23:49,980 --> 00:23:53,860 And Rockwell had the integration and Orbiter contract, both. 344 00:23:53,860 --> 00:23:55,570 This is what they started with. 345 00:23:55,570 --> 00:24:02,580 That was their authority to proceed configuration, even though this is shown as in 1972. 346 00:24:02,580 --> 00:24:08,850 But you see there is very little difference in the configuration then and what the configuration 347 00:24:08,850 --> 00:24:11,740 is today. 348 00:24:11,740 --> 00:24:16,390 There was some minor mods which are not worthy of even talking about right now. 349 00:24:16,390 --> 00:24:25,740 But let me give Aaron a lot of credit. 350 00:24:25,740 --> 00:24:29,419 His favorite word, the whole time he was the project manager, was no. 351 00:24:29,419 --> 00:24:37,580 And he had above his blackboard better is the enemy of good. 352 00:24:37,580 --> 00:24:38,409 We've got something. 353 00:24:38,409 --> 00:24:39,460 We know it will work. 354 00:24:39,460 --> 00:24:42,570 We knew that damn configuration would work. 355 00:24:42,570 --> 00:24:47,250 And Aaron got inundated with people coming back after we started the program. 356 00:24:47,250 --> 00:24:55,590 Aaron, if you put reaction control jets out on the wing tips and here and up on the vertical 357 00:24:55,590 --> 00:24:57,720 stabilizer you get a lot more control authority. 358 00:24:57,720 --> 00:25:02,279 And when you guys start looking at this guidance and control stuff in propulsion you're going 359 00:25:02,279 --> 00:25:03,549 to come up with that. 360 00:25:03,549 --> 00:25:07,900 But it complicated the entry in the thermal protection system. 361 00:25:07,900 --> 00:25:12,900 It complicated getting the fuel to those things, so Aaron said no, no, no. 362 00:25:12,900 --> 00:25:14,870 And the astronauts would come in. 363 00:25:14,870 --> 00:25:19,029 They'll always meet with Aaron at 7:00 in the morning because that's when they would 364 00:25:19,029 --> 00:25:20,350 get their word in. 365 00:25:20,350 --> 00:25:24,159 And so they would have to go do flight training or something like that. 366 00:25:24,159 --> 00:25:26,110 And, as they walked out the door, Aaron would say no. 367 00:25:26,110 --> 00:25:29,220 They didn't hear him, but it was always no. 368 00:25:29,220 --> 00:25:32,000 And that was critical in this thing. 369 00:25:32,000 --> 00:25:35,760 And so the program came in at $5.1 billion. 370 00:25:35,760 --> 00:25:37,510 It started $5.1 billion. 371 00:25:37,510 --> 00:25:40,210 It came in at $5.1 billion. 372 00:25:40,210 --> 00:25:43,039 It was only because of being able to say no. 373 00:25:43,039 --> 00:25:48,020 But to say no you better do a good systems engineering job at the beginning. 374 00:25:48,020 --> 00:25:49,799 And were there some faults and errors? 375 00:25:49,799 --> 00:25:50,010 Yeah. 376 00:25:50,010 --> 00:25:57,179 I'll confess and open my kimono here on the few of the things, but all in all it wasn't 377 00:25:57,179 --> 00:25:58,730 too bad. 378 00:25:58,730 --> 00:26:05,549 And I will say one other thing about systems engineering. 379 00:26:05,549 --> 00:26:12,460 It was interesting to watch four or five different large companies look at the various concepts. 380 00:26:12,460 --> 00:26:18,600 I can say this now because none of these companies even exist in the form that they were then. 381 00:26:18,600 --> 00:26:24,020 Grumman had a very large systems engineering organization. 382 00:26:24,020 --> 00:26:29,929 Rockwell had a very small systems engineering organization, almost down to one or two people, 383 00:26:29,929 --> 00:26:32,330 but they were extremely good. 384 00:26:32,330 --> 00:26:34,870 They were extremely good systems engineers. 385 00:26:34,870 --> 00:26:45,520 NASA went with Rockwell for a number of reasons, but one of the things that probably benefited 386 00:26:45,520 --> 00:26:52,350 the program was having a very concentrated set of engineering requirements coming out 387 00:26:52,350 --> 00:26:57,130 of a systems engineer which almost turned out to be one guy, Ed Smith. 388 00:26:57,130 --> 00:27:00,039 And he was very, very good at that. 389 00:27:00,039 --> 00:27:05,539 The reason I bring that up to you, the thing that's most defficient, from my perspective 390 00:27:05,539 --> 00:27:11,120 now in the United States today, are good systems engineers. 391 00:27:11,120 --> 00:27:14,640 Very good thermal engineers, good structural engineers, good propulsion engineers. 392 00:27:14,640 --> 00:27:19,240 There are very few systems engineers that are good. 393 00:27:19,240 --> 00:27:27,169 If you make a note of that and become one of those, you'd be highly sought after. 394 00:27:27,169 --> 00:27:29,690 So, a little bit of this is a repeat. 395 00:27:29,690 --> 00:27:38,390 As we went into these requirements, and from a government system's perspective, now the 396 00:27:38,390 --> 00:27:44,169 challenge was to give the contractor the requirements that they need but don't over-specify the 397 00:27:44,169 --> 00:27:45,470 requirements. 398 00:27:45,470 --> 00:27:51,500 We were very careful to say here are the top level requirements, don't ask us what the 399 00:27:51,500 --> 00:27:54,270 internal loads on the wing are because we're not going to tell you what that is. 400 00:27:54,270 --> 00:27:56,510 That is for you to decide. 401 00:27:56,510 --> 00:28:00,750 And, if you want to change something within these constraints, you can change it. 402 00:28:00,750 --> 00:28:05,809 But the burden is on you to make everything else right. 403 00:28:05,809 --> 00:28:11,840 That is something that I think the Orbiter did probably better than the external tank. 404 00:28:11,840 --> 00:28:14,779 I'll just say it like it is. 405 00:28:14,779 --> 00:28:15,360 Go ahead. 406 00:28:15,360 --> 00:28:21,059 I'm just wondering, sir, what happened to the canard configuration with the delta wing? 407 00:28:21,059 --> 00:28:22,809 What happened to it? 408 00:28:22,809 --> 00:28:22,970 Yeah. 409 00:28:22,970 --> 00:28:24,059 It was not selected. 410 00:28:24,059 --> 00:28:28,720 And I don't remember why it was not selected. 411 00:28:28,720 --> 00:28:30,880 What was driving it, I don't know. 412 00:28:30,880 --> 00:28:35,990 I don't have those notes anymore. 413 00:28:35,990 --> 00:28:38,419 It could have been cross-range. 414 00:28:38,419 --> 00:28:44,840 I don't remember that particular configuration, if it had the required cross-range for the 415 00:28:44,840 --> 00:28:45,580 payload mass. 416 00:28:45,580 --> 00:28:47,100 I just don't remember. 417 00:28:47,100 --> 00:28:48,590 I don't think it would have been cost. 418 00:28:48,590 --> 00:28:53,710 I think it was a lot of complexity. 419 00:28:53,710 --> 00:28:54,990 Well, it did have complexity so it had to add some cost. 420 00:28:54,990 --> 00:29:02,640 Weight-wise, it probably was not too different just because of the control authority of having 421 00:29:02,640 --> 00:29:03,559 the canards there. 422 00:29:03,559 --> 00:29:04,399 But that's a good question. 423 00:29:04,399 --> 00:29:11,330 Tom, you might mention [UNINTELLIGIBLE PHRASE]. 424 00:29:11,330 --> 00:29:15,159 I'm going to touch on that, again, a little bit in a minute about what we did in surveying 425 00:29:15,159 --> 00:29:16,610 and determining the loads. 426 00:29:16,610 --> 00:29:23,770 And let me hold that if I can. 427 00:29:23,770 --> 00:29:28,210 Now we have begun with the design.. 428 00:29:28,210 --> 00:29:45,909 When you use the term top level requirements, what does the top level refer to as opposed 429 00:29:45,909 --> 00:29:53,679 to just requirements or performance requirements? 430 00:29:53,679 --> 00:29:58,080 Well, the top level requirement changes as the phase changes. 431 00:29:58,080 --> 00:30:03,039 The very beginning, in '68, the top level requirement was a transportation system. 432 00:30:03,039 --> 00:30:07,970 We don't know what it's going to be, reusable, and we don't know how much payload it is going 433 00:30:07,970 --> 00:30:08,970 to have to carry. 434 00:30:08,970 --> 00:30:10,820 So, that was the top level requirement. 435 00:30:10,820 --> 00:30:18,169 Then it was to look at all of the combinations of things that you could create. 436 00:30:18,169 --> 00:30:23,760 The solution was it is feasible and we think that this is about what it's going to cost. 437 00:30:23,760 --> 00:30:28,130 Now, as we get into this point, these are the top level requirements. 438 00:30:28,130 --> 00:30:35,690 So, the granularity of the requirements increases as the program advances. 439 00:30:35,690 --> 00:30:44,270 Good question.. 440 00:30:44,270 --> 00:30:49,279 For the challenges, now I'm going to call it the challenges of beginning this thing, 441 00:30:49,279 --> 00:30:53,539 we know what the configuration is, you know what the design life is, et cetera, all that 442 00:30:53,539 --> 00:30:59,570 kind of stuff, but we still haven't decided on what the material of the airframe is going 443 00:30:59,570 --> 00:31:00,169 to be. 444 00:31:00,169 --> 00:31:04,330 We estimated some stuff because it could be aluminum or it could be titanium and this 445 00:31:04,330 --> 00:31:05,120 is what it would be. 446 00:31:05,120 --> 00:31:11,460 And it all fits within the right cost and performance envelopes, but let's optimize 447 00:31:11,460 --> 00:31:13,950 that from a systems standpoint a little bit and see what that is. 448 00:31:13,950 --> 00:31:18,980 Some of the challenges in structural design, and I'm going to talk about each one of these 449 00:31:18,980 --> 00:31:24,269 things that's listed on here separately, should the cabin be an integral part of the fuselage 450 00:31:24,269 --> 00:31:27,659 or should it be a pressure vessel floating within the fuselage? 451 00:31:27,659 --> 00:31:28,779 Trade to be made. 452 00:31:28,779 --> 00:31:31,070 How are we going to account for thermal stress in this? 453 00:31:31,070 --> 00:31:32,840 Well, what the hell is thermal stress? 454 00:31:32,840 --> 00:31:36,620 Apollo, we didn't care a whole lot about thermal stress. 455 00:31:36,620 --> 00:31:40,899 It really wasn't an issue, not to the extent that a vehicle like this is. 456 00:31:40,899 --> 00:31:43,399 It was very sensitive for thermal stress. 457 00:31:43,399 --> 00:31:44,279 Compartment venting. 458 00:31:44,279 --> 00:31:47,080 We'll talk more about that. 459 00:31:47,080 --> 00:31:49,929 Major structure concept trades to reduce weight basically. 460 00:31:49,929 --> 00:31:56,919 And then how in the hell do we get the design loads on this thing? 461 00:31:56,919 --> 00:32:03,210 From a structural design criteria we said, well, let's start with 1.5. 462 00:32:03,210 --> 00:32:05,970 That's what all airplanes are designed for so we'll do that. 463 00:32:05,970 --> 00:32:09,000 Even though some of the boosters were designed for 1.25. 464 00:32:09,000 --> 00:32:12,580 Does everybody know what an ultimate factor safety is? 465 00:32:12,580 --> 00:32:20,299 That's the allowable of the material that you've decided to use compared to the maximum 466 00:32:20,299 --> 00:32:24,019 expected load that you will ever want to see, three sigma kind of loads. 467 00:32:24,019 --> 00:32:28,970 And then whatever the factor is about that, that's the factor of safety. 468 00:32:28,970 --> 00:32:34,899 So, you simply take the maximum loads you can expect to find, multiply it by 1.4 and 469 00:32:34,899 --> 00:32:36,659 it better meet what the allowable is. 470 00:32:36,659 --> 00:32:40,950 If there's margin in that allowable then that's called a design margin. 471 00:32:40,950 --> 00:32:44,320 Ideally, you would like to have zero margin. 472 00:32:44,320 --> 00:32:47,269 That still gives you a 40% factor of safety. 473 00:32:47,269 --> 00:32:50,600 Everybody with me? 474 00:32:50,600 --> 00:32:55,370 Yield is classically something that you decided on material. 475 00:32:55,370 --> 00:32:57,700 Well, I want to also have a factor safety on yield. 476 00:32:57,700 --> 00:33:01,250 And we sat around and asked ourselves why the hell do we care about that? 477 00:33:01,250 --> 00:33:06,510 The only thing you don't want it to do is you don't want it to deform such that it won't 478 00:33:06,510 --> 00:33:12,010 operate so doors won't open, hinges won't work, et cetera. 479 00:33:12,010 --> 00:33:17,669 We did not impose that on the program of the yield factor safety. 480 00:33:17,669 --> 00:33:19,480 We didn't on the Orbiter. 481 00:33:19,480 --> 00:33:20,880 The external tank did. 482 00:33:20,880 --> 00:33:27,390 And they paid a weight for that because if you put a 1.2 factor safety on yield for some 483 00:33:27,390 --> 00:33:31,590 materials, that gives you a lower allowable than an ultimate factor safety when you're 484 00:33:31,590 --> 00:33:36,710 really only interested in ultimate strength. 485 00:33:36,710 --> 00:33:41,990 And then we had said thermal stress is going to be important, but we don't want to be so 486 00:33:41,990 --> 00:33:48,289 conservative that we let the thermal stress add in such a way that it adds conservatism. 487 00:33:48,289 --> 00:33:53,980 But, at the same time, we don't want it to count on it if it's relieving when we cannot 488 00:33:53,980 --> 00:33:55,090 really rely on it to be there. 489 00:33:55,090 --> 00:34:00,779 So, it is decreasing from the stress point of view. 490 00:34:00,779 --> 00:34:04,909 A scatter factor of four on life for a hundred missions. 491 00:34:04,909 --> 00:34:07,309 What is scatter factor? 492 00:34:07,309 --> 00:34:09,629 Scatter factor just means a factor of four. 493 00:34:09,629 --> 00:34:18,260 If you have 10,000 cycles at 20,000 psi stress then you have to certify it for 40,000 cycles. 494 00:34:18,260 --> 00:34:27,969 Typically, most airplanes you fly around on, they have a design life of about 20,000 flight 495 00:34:27,969 --> 00:34:28,449 hours. 496 00:34:28,449 --> 00:34:29,750 I think that's about right. 497 00:34:29,750 --> 00:34:37,668 They are fatigue tested to 80,000 flight hours to make sure that they have that kind of factor 498 00:34:37,668 --> 00:34:39,300 on life. 499 00:34:39,300 --> 00:34:42,310 And then we said well, this thing is going to be used a lot, we've never looked at that 500 00:34:42,310 --> 00:34:47,859 before so we will arbitrarily say we'll use a 1.2 factor at the end of life or ultimate. 501 00:34:47,859 --> 00:34:54,168 And then these are just classical engineering material allowables that everybody uses today. 502 00:34:54,168 --> 00:35:07,630 A lot of people have mentioned lately, as we were thinking of the end of the life of 503 00:35:07,630 --> 00:35:11,780 the shuttle, that although it was designed for a hundred missions, I guess it was always 504 00:35:11,780 --> 00:35:14,839 assumed that those hundred missions would be flown over the course of just a few years. 505 00:35:14,839 --> 00:35:20,859 And so, I think it's true, you more concerned with the long-term effects of stress than 506 00:35:20,859 --> 00:35:27,089 things like weathering or being exposed to salt, air over 20 years. 507 00:35:27,089 --> 00:35:30,210 Is that correct? 508 00:35:30,210 --> 00:35:32,280 Well, you hit a very key point. 509 00:35:32,280 --> 00:35:33,550 And you're exactly right. 510 00:35:33,550 --> 00:35:38,140 It turns out a hundred missions wasn't really designing anything. 511 00:35:38,140 --> 00:35:39,960 I mean it could have. 512 00:35:39,960 --> 00:35:41,260 Well, as a matter of fact, it didn't. 513 00:35:41,260 --> 00:35:42,490 I don't know of anything. 514 00:35:42,490 --> 00:35:48,710 A hundred missions design is for a cyclic stress, high cycle, low stress fatigue or 515 00:35:48,710 --> 00:35:50,310 low cycle high stress. 516 00:35:50,310 --> 00:35:51,430 It didn't. 517 00:35:51,430 --> 00:35:58,300 But the environment sitting around or the life of the material exposed has. 518 00:35:58,300 --> 00:36:03,650 The leading edge turned out to be there is a degradation in the strength of the leading 519 00:36:03,650 --> 00:36:09,570 edge material, the carbon-carbon material because of being exposed to the conditions. 520 00:36:09,570 --> 00:36:13,420 There was some corrosion found in the wings during an inspection. 521 00:36:13,420 --> 00:36:17,970 Nothing was wrong with the low carrying capability, except it was beginning to corrode. 522 00:36:17,970 --> 00:36:27,810 [UNINTELLIGIBLE PHRASE] You've got me mixed up with somebody else. 523 00:36:27,810 --> 00:36:29,560 I'm not talking about avionics. 524 00:36:29,560 --> 00:36:33,339 [LAUGHTER] No, but it's true. 525 00:36:33,339 --> 00:36:39,270 There, I think, just to bring that up, the idea was they would not be good for that length 526 00:36:39,270 --> 00:36:43,250 of time so change them out, we're going to have to upgrade them anyway. 527 00:36:43,250 --> 00:36:52,160 Aaron, I think, just left being program manager when they decided to change,no you still were 528 00:36:52,160 --> 00:36:57,170 there, they decided to change the general-purpose computers. 529 00:36:57,170 --> 00:37:01,940 It took ten years to change the general-purpose computers because of all the certification. 530 00:37:01,940 --> 00:37:05,920 Did the use and safety factors, like what numbers you were using, how much did the Apollo 531 00:37:05,920 --> 00:37:11,010 program [UNINTELLIGIBLE PHRASE] aircraft safety factors? 532 00:37:11,010 --> 00:37:21,880 The Apollo program was like 1.2 factor of safety, as I recall, because it was a single 533 00:37:21,880 --> 00:37:23,490 use item. 534 00:37:23,490 --> 00:37:30,940 And I'm going to take the opportunity to go back and verify that, but I think that's was 535 00:37:30,940 --> 00:37:32,089 right for some conditions. 536 00:37:32,089 --> 00:37:35,070 And it could have been 1.5 on others. 537 00:37:35,070 --> 00:37:41,680 I know on pressure alone it was 1.5 psi. 538 00:37:41,680 --> 00:37:44,170 You say, well, why was it different for pressure than it was for others? 539 00:37:44,170 --> 00:37:49,839 Because there was some historical data there that NASA had that said that was the right 540 00:37:49,839 --> 00:37:50,920 thing to use. 541 00:37:50,920 --> 00:37:51,790 But that's a good question. 542 00:37:51,790 --> 00:37:53,460 Now you've caught me. 543 00:37:53,460 --> 00:38:01,400 I can remember on the boosters it was 1.25, but on the command module itself, let me retract 544 00:38:01,400 --> 00:38:03,980 that, it was probably 1.5. 545 00:38:03,980 --> 00:38:18,170 It was 1.25 on the boosters and 1.5 on the crude part of the vehicle. 546 00:38:18,170 --> 00:38:23,740 One of the challenges that we had here was to establish a criteria. 547 00:38:23,740 --> 00:38:25,579 These were our objectives. 548 00:38:25,579 --> 00:38:30,770 To assure that there was a realistic stress that we're putting in the vehicle and we weren't 549 00:38:30,770 --> 00:38:32,770 being overly conservative with it. 550 00:38:32,770 --> 00:38:35,630 We were not reducing the stress because of thermal gradients. 551 00:38:35,630 --> 00:38:38,960 And then we were incorporating the classical pressure induced stress. 552 00:38:38,960 --> 00:38:41,060 And now what were the details of that? 553 00:38:41,060 --> 00:38:45,430 Here were the details. 554 00:38:45,430 --> 00:38:53,740 We came up with this algorithm that says we will use a factor of 1.4 on all external loads 555 00:38:53,740 --> 00:38:57,270 because that's aerodynamic loads, inertia loads and so forth. 556 00:38:57,270 --> 00:39:04,119 We will use a factor of 1.4 on the thermally induced loads, if you will. 557 00:39:04,119 --> 00:39:06,010 They are really thermally induced strains and stress. 558 00:39:06,010 --> 00:39:12,329 We'll use a 1.4 factor on that if it's additive to the mechanical, but if it's subtractive 559 00:39:12,329 --> 00:39:16,990 we'll only use one because we probably won't reach the maximum thermal conditions so you 560 00:39:16,990 --> 00:39:17,720 cannot rely on that. 561 00:39:17,720 --> 00:39:21,430 On pressure, we used 1.4. 562 00:39:21,430 --> 00:39:25,270 Unless it was pressure alone, we used 1.5. 563 00:39:25,270 --> 00:39:31,599 But the whole thing is we would never have less than 1.4 of the total combined load. 564 00:39:31,599 --> 00:39:33,450 So, that's what we did. 565 00:39:33,450 --> 00:39:35,520 And so you say why in the hell did you do that? 566 00:39:35,520 --> 00:39:38,500 Why did you have to go to that kind of detail? 567 00:39:38,500 --> 00:39:42,970 The reason being is because you probably had about 30,000 stress engineers working on the 568 00:39:42,970 --> 00:39:46,500 program, and they needed to know how to combine this stuff. 569 00:39:46,500 --> 00:39:50,040 If you didn't, this guy is going to do one thing and this guy is going to do something 570 00:39:50,040 --> 00:39:51,200 different. 571 00:39:51,200 --> 00:39:55,380 We got it down to that level to save weight in the vehicle and save complexity in the 572 00:39:55,380 --> 00:39:58,450 vehicle. 573 00:39:58,450 --> 00:40:03,000 Well, we have our criteria set now. 574 00:40:03,000 --> 00:40:06,940 Let me give one more story on marginal safety. 575 00:40:06,940 --> 00:40:12,050 One of the people that I showed you at the top of the credits list was John Yardley. 576 00:40:12,050 --> 00:40:19,490 And probably Aaron and Larry Young and other people would probably agree with this, John 577 00:40:19,490 --> 00:40:23,349 Yardley is probably the best engineer that I ever knew in my entire life. 578 00:40:23,349 --> 00:40:28,329 He's probably one of the best managers I ever knew. 579 00:40:28,329 --> 00:40:35,210 John Yardley had the job of being the Program Manager on McDonnell Douglas F4 aircraft. 580 00:40:35,210 --> 00:40:38,130 And he was an old stress guy. 581 00:40:38,130 --> 00:40:43,089 He knew that weight was going to be a critical parameter in the success of that program and 582 00:40:43,089 --> 00:40:46,420 he had to keep the weight out. 583 00:40:46,420 --> 00:40:50,670 What he did, on that previous slide where I showed you the stress criteria and make 584 00:40:50,670 --> 00:40:55,150 sure that you have a zero margin of safety with a factor of 1.4, is he told all the stress 585 00:40:55,150 --> 00:40:59,060 engineers, because they all worked for him, design to a negative 10%. 586 00:40:59,060 --> 00:41:03,410 Which means if you really do your job right this thing is not going to be able to reach 587 00:41:03,410 --> 00:41:03,930 ultimate load. 588 00:41:03,930 --> 00:41:05,760 It's going to break. 589 00:41:05,760 --> 00:41:11,140 But he also knew that they were probably conservative because he was one of those guys. 590 00:41:11,140 --> 00:41:16,160 And he also had in his hip pocket, if he's wrong he would find out because he had the 591 00:41:16,160 --> 00:41:20,410 opportunity to do an ultimate load test on the airframe. 592 00:41:20,410 --> 00:41:25,810 It turns out he did the ultimate load test, it passed the ultimate load capability and 593 00:41:25,810 --> 00:41:30,859 he saved a bunch of weight in airplane which made it a very successful airplane. 594 00:41:30,859 --> 00:41:38,119 Sometimes from a systems perspective, it's what you learn in the details or in the trenches 595 00:41:38,119 --> 00:41:43,079 as you're coming up and being able to apply it the same way that Aaron did a lot of stuff 596 00:41:43,079 --> 00:41:46,280 as he was managing the program. 597 00:41:46,280 --> 00:41:53,160 On the airframe we looked at a lot of different structural materials, we looked at a lot of 598 00:41:53,160 --> 00:42:00,640 different TPS materials, and some of the parameters that were coming out in there was not only 599 00:42:00,640 --> 00:42:03,390 strength of the material but how much heat sink there was because you were having to 600 00:42:03,390 --> 00:42:05,460 rely on that to keep the weights down. 601 00:42:05,460 --> 00:42:10,579 And let me go up one slide and show you something here. 602 00:42:10,579 --> 00:42:20,030 I don't know if you can read that, but on the left side what it was is it was all aluminum 603 00:42:20,030 --> 00:42:20,599 airframe. 604 00:42:20,599 --> 00:42:23,700 It had an ablator thermal protection system on it. 605 00:42:23,700 --> 00:42:26,650 And you said, well, I thought you said it was going to be fully reusable. 606 00:42:26,650 --> 00:42:29,160 Well, we also had a cost constraint. 607 00:42:29,160 --> 00:42:31,430 So we put that in there as a reference point. 608 00:42:31,430 --> 00:42:34,800 And that was the lowest cost. 609 00:42:34,800 --> 00:42:36,099 And here's weight up here. 610 00:42:36,099 --> 00:42:43,119 It wasn't quite the lowest weight, it was pretty low, but it still was violating the 611 00:42:43,119 --> 00:42:44,310 objectives and requirements that we had. 612 00:42:44,310 --> 00:42:46,369 And we said that will be our reference point. 613 00:42:46,369 --> 00:42:48,589 Then we looked at different types of aluminum. 614 00:42:48,589 --> 00:42:49,790 We looked a beryllium. 615 00:42:49,790 --> 00:42:50,960 We looked at titanium. 616 00:42:50,960 --> 00:42:56,410 We looked at the thermal protection system on a beryllium substrate. 617 00:42:56,410 --> 00:42:58,480 Every kind of combination you could think of. 618 00:42:58,480 --> 00:43:01,640 The interesting thing was, look where the whites were staying. 619 00:43:01,640 --> 00:43:09,819 They were all staying within the 60,000 to 80,000 pound total weight envelope. 620 00:43:09,819 --> 00:43:15,420 What was happening is we were decreasing the thermal protection system thickness. 621 00:43:15,420 --> 00:43:20,339 If we were using titanium, which we could operate to 600 degrees, the TPS weight was 622 00:43:20,339 --> 00:43:20,839 going down. 623 00:43:20,839 --> 00:43:30,140 Titanium was not as good a heat sink as aluminum, even though we're working it to a higher temperature. 624 00:43:30,140 --> 00:43:38,670 And it turned out that the combination of TPS plus structure was pretty much a constant. 625 00:43:38,670 --> 00:43:40,869 I'm oversimplifying it, but that's basically what it was. 626 00:43:40,869 --> 00:43:44,579 And you can see where the cost was. 627 00:43:44,579 --> 00:43:49,000 This is beryllium titanium. 628 00:43:49,000 --> 00:43:54,369 The cost was way out of whack compared to everything else, so we said we're not going 629 00:43:54,369 --> 00:43:55,890 to do that. 630 00:43:55,890 --> 00:43:59,300 And there were some other exotic materials over here for hot structures. 631 00:43:59,300 --> 00:44:03,359 We said let's now decide what this airframe material is going to be. 632 00:44:03,359 --> 00:44:06,920 It's going to either be aluminum or titanium. 633 00:44:06,920 --> 00:44:14,290 And total weight, total cost doesn't make any difference, they're about the same. 634 00:44:14,290 --> 00:44:18,390 We weren't' smart enough to decide so we went out to the skunk works. 635 00:44:18,390 --> 00:44:22,319 Kelly Johnson skunk works, I don't know if you know what that means. 636 00:44:22,319 --> 00:44:29,030 Kelly Johnson designed and built more airplanes in a short period of time. 637 00:44:29,030 --> 00:44:37,710 And they were the ones, Larry, was it in the `50s, the SR-71 was designed, the Black Bird? 638 00:44:37,710 --> 00:44:48,210 I think it was in the 1950s. 639 00:44:48,210 --> 00:44:49,170 It was somewhere in there. 640 00:44:49,170 --> 00:44:53,010 They had to develop titanium for that airplane. 641 00:44:53,010 --> 00:44:55,470 It was a hot structure design. 642 00:44:55,470 --> 00:44:57,740 We went out and spent some time with Kelly Johnson. 643 00:44:57,740 --> 00:44:59,760 We went through all this stuff with him. 644 00:44:59,760 --> 00:45:00,710 All right, Mr. 645 00:45:00,710 --> 00:45:04,260 Johnson, at the end of the day it's a mix for us. 646 00:45:04,260 --> 00:45:07,170 Would you build it out of aluminum or titanium? 647 00:45:07,170 --> 00:45:09,210 He said aluminum. 648 00:45:09,210 --> 00:45:15,790 And the reason being is because titanium was so difficult to work to produce. 649 00:45:15,790 --> 00:45:17,490 The manufacturing was difficult. 650 00:45:17,490 --> 00:45:21,180 Today it's a lot less difficult than it was then. 651 00:45:21,180 --> 00:45:25,990 We made the decision and went with aluminum, so we had to protect that structure to 350 652 00:45:25,990 --> 00:45:28,150 degrees. 653 00:45:28,150 --> 00:45:33,720 That was a lot of work and a lot of analysis to make that decision. 654 00:45:33,720 --> 00:45:39,520 And we talked to Aaron and said that's what we want to do, and he said go for it. 655 00:45:39,520 --> 00:45:46,319 The next thing we looked at, we got the airframe design, now we're starting to put together 656 00:45:46,319 --> 00:45:48,180 the fuselage. 657 00:45:48,180 --> 00:45:54,280 We said we can put this crew cabin as part of an integral part of the fuselage or we 658 00:45:54,280 --> 00:45:57,490 can make it a separate pressure vessel inside. 659 00:45:57,490 --> 00:45:59,260 Went through the trades on this. 660 00:45:59,260 --> 00:46:04,880 And we came up with some of the discrete advantages. 661 00:46:04,880 --> 00:46:09,560 It's a purely simple pressure vessel when you don't have any inertia loads, except the 662 00:46:09,560 --> 00:46:13,700 mass that is inside the crew module itself. 663 00:46:13,700 --> 00:46:18,650 There is a discrete attachment between the crew module and the forward fuselage which 664 00:46:18,650 --> 00:46:24,180 means you could start the design and construction of these two things in parallel. 665 00:46:24,180 --> 00:46:26,540 And simple interfaces are important. 666 00:46:26,540 --> 00:46:30,970 Somebody mentioned modularity, and it's probably modularity in some analytical tools. 667 00:46:30,970 --> 00:46:39,380 But simple interfaces where you're putting things together are extremely important. 668 00:46:39,380 --> 00:46:42,790 So, this created a very simple interface for us. 669 00:46:42,790 --> 00:46:45,109 Also, we didn't have a lot of heat transfer to the crew module. 670 00:46:45,109 --> 00:46:49,099 It was easy to control the environment within the crew module. 671 00:46:49,099 --> 00:46:56,380 And we designed it out of a material, a 2219 aluminum, which had an inherent advantage 672 00:46:56,380 --> 00:47:03,020 of if it gets a crack, the crack doesn't grow catastrophically under the operating stress 673 00:47:03,020 --> 00:47:04,750 before it starts leaking a lot. 674 00:47:04,750 --> 00:47:11,450 Well, that's good because, from a crew safety standpoint, you know that if the seals are 675 00:47:11,450 --> 00:47:15,720 working and it's still leaking you've got a crack in that pressure vessel but it's not 676 00:47:15,720 --> 00:47:23,560 going to be a crack that is going to propagate to be a catastrophic failure. 677 00:47:23,560 --> 00:47:25,970 We chose the floating design. 678 00:47:25,970 --> 00:47:33,400 When I talked a while ago about the crew of seven in two weeks now compared to four for 679 00:47:33,400 --> 00:47:41,020 seven days, back in '72 we said we don't know what the requirements are going to be, but 680 00:47:41,020 --> 00:47:47,069 let's make this thing as robust as we can without penalizing ourselves weight-wise. 681 00:47:47,069 --> 00:47:52,849 So, we went back to Apollo and said what were all the densities in the Command Module for 682 00:47:52,849 --> 00:47:53,460 the Crew Module? 683 00:47:53,460 --> 00:47:55,430 We figured out a density and a volume. 684 00:47:55,430 --> 00:47:58,190 We said that will be our baseline. 685 00:47:58,190 --> 00:47:59,930 That's what we came up with. 686 00:47:59,930 --> 00:48:07,200 Well, for another 50 pounds of weight, we could increase the carrying capability of 687 00:48:07,200 --> 00:48:10,190 the crew module by about 500 pounds. 688 00:48:10,190 --> 00:48:13,380 That was a good trade at that time so we did it. 689 00:48:13,380 --> 00:48:15,069 We just said we're going to design this thing. 690 00:48:15,069 --> 00:48:22,540 Instead of for 25,000 pounds we'll design it for 30,000 pounds of payload carrying capability 691 00:48:22,540 --> 00:48:23,619 within the crew module. 692 00:48:23,619 --> 00:48:26,020 It turned out to be a good decision. 693 00:48:26,020 --> 00:48:31,760 We weren't smart enough to know operationally we'll need larger crews for a longer period 694 00:48:31,760 --> 00:48:36,030 of time, but that helped us out a lot. 695 00:48:36,030 --> 00:48:46,319 You probably also want to mention, when you look at the structure of the crew cabin, in 696 00:48:46,319 --> 00:48:58,180 both of the shuttle disasters, the Challenger and Columbia, we have every indication that 697 00:48:58,180 --> 00:49:00,430 the crew cabin actually survived the breakup of the Orbiter. 698 00:49:00,430 --> 00:49:01,069 So, it really was an excellent structure. 699 00:49:01,069 --> 00:49:01,069 I'm glad you brought that up. As a matter of fact, I have a note here to bring it up myself. 700 00:49:02,829 --> 00:49:11,550 Jeff is exactly right that that's what it did, but it was never designed to be a crew 701 00:49:11,550 --> 00:49:13,900 escape module. 702 00:49:13,900 --> 00:49:20,760 It had some inherent capabilities, probably could survive some things that it couldn't 703 00:49:20,760 --> 00:49:26,099 had it been part of the fuselage, different flight regime, so it had that inherent capability. 704 00:49:26,099 --> 00:49:36,190 But it was never designed -- And I know there was a lot of talk after Challenger that it 705 00:49:36,190 --> 00:49:41,050 looked like it would have survived all the way, but it would have never made it all the 706 00:49:41,050 --> 00:49:41,050 way. But it would have under a lot of conditions. 707 00:49:47,940 --> 00:49:53,630 We said Apollo didn't have a lot of thermal stress issues, but we know this vehicle now 708 00:49:53,630 --> 00:50:02,280 we've skinnied down weight-wise as much as we can to the extent that the thermal gradients 709 00:50:02,280 --> 00:50:07,520 between any two different pieces of structure, where they were different materials or different 710 00:50:07,520 --> 00:50:10,359 masses is going to cause a thermal gradient. 711 00:50:10,359 --> 00:50:13,329 And thermal gradient cause thermal stresses. 712 00:50:13,329 --> 00:50:16,740 And you will see in a minute that was not only important to stress but is important 713 00:50:16,740 --> 00:50:19,640 to all these tiles we were sticking on the outside of this thing. 714 00:50:19,640 --> 00:50:25,200 So we said we have to look at every one of these thermal gradients and we have to understand 715 00:50:25,200 --> 00:50:29,220 what that induced stress is because we had an indication it was going to probably contribute 716 00:50:29,220 --> 00:50:31,390 about 30% of the total stress in the vehicle. 717 00:50:31,390 --> 00:50:34,410 It was going to be from thermal stressors at different flight regimes. 718 00:50:34,410 --> 00:50:42,000 Kelly Johnson helped us out pretty well deciding on aluminum and titanium. 719 00:50:42,000 --> 00:50:44,420 We said why don't we just fix this thing? 720 00:50:44,420 --> 00:50:46,160 We'll design around all the thermal stress. 721 00:50:46,160 --> 00:50:51,770 We'll put stress relief in it, like expansion joints along the sidewalk. 722 00:50:51,770 --> 00:50:55,780 We'll do all these kinds of cute things and we'll simplify the heck out of this. 723 00:50:55,780 --> 00:51:03,450 As a matter of fact, the SR-71, the Black Bird, it had huge thermal stress problems. 724 00:51:03,450 --> 00:51:09,890 So the wing on an SR-71, normally the skin carries a lot of the wing bending. 725 00:51:09,890 --> 00:51:11,920 Not true on an SR-71. 726 00:51:11,920 --> 00:51:15,490 It's corrugated skin so it can expand and contract. 727 00:51:15,490 --> 00:51:21,490 All the wing bending is carried in the spar caps, the frames that go out the entire wing, 728 00:51:21,490 --> 00:51:23,210 and the caps themselves. 729 00:51:23,210 --> 00:51:26,849 They paid a penalty but avoided the thermal stress issue. 730 00:51:26,849 --> 00:51:28,420 We said we'll be smart with that. 731 00:51:28,420 --> 00:51:30,190 We'll go talk to the SR-71 guys. 732 00:51:30,190 --> 00:51:32,319 And we'll go talk to the Concorde. 733 00:51:32,319 --> 00:51:37,380 The Concorde was an airplane that had high thermal stress, even though it wasn't that 734 00:51:37,380 --> 00:51:38,809 high a temperature. 735 00:51:38,809 --> 00:51:44,800 I think it was reaching 500 or 600 degrees outside, but it was moving fuel around all 736 00:51:44,800 --> 00:51:45,700 over the vehicle. 737 00:51:45,700 --> 00:51:50,569 So when it moved this high mass of fuel from one part of the vehicle to the other, it was 738 00:51:50,569 --> 00:51:51,790 creating big thermal stresses. 739 00:51:51,790 --> 00:51:54,329 They knew what to do. 740 00:51:54,329 --> 00:51:59,660 They designed in stress relief at these high points. 741 00:51:59,660 --> 00:52:00,540 It bit them. 742 00:52:00,540 --> 00:52:03,309 Every time they did it they had fatigue failures. 743 00:52:03,309 --> 00:52:04,250 Every time they did that. 744 00:52:04,250 --> 00:52:07,490 They finally gave up and said just accommodate. 745 00:52:07,490 --> 00:52:09,849 We said we'll do that. 746 00:52:09,849 --> 00:52:13,490 Now then, we decided on that criteria. 747 00:52:13,490 --> 00:52:16,730 We're going to account for thermal stress, but how can we do it? 748 00:52:16,730 --> 00:52:24,730 We don't have a 3D model that we can apply mechanical loads to, I'll call aero loads 749 00:52:24,730 --> 00:52:27,520 mechanical loads, and temperature distribution. 750 00:52:27,520 --> 00:52:29,119 The finite element model didn't exist. 751 00:52:29,119 --> 00:52:34,349 We had a finite element model that had 50,000 degrees of freedom, but we didn't have a computing 752 00:52:34,349 --> 00:52:38,730 capability to combine thermal and mechanical loads on there at the same time to be able 753 00:52:38,730 --> 00:52:40,970 to decide how to size the structure. 754 00:52:40,970 --> 00:52:44,300 We said now we've got a problem. 755 00:52:44,300 --> 00:52:45,450 What the hell are we going to do about that? 756 00:52:45,450 --> 00:52:57,559 What we did is looked at what were the conditions causing the thermal stress? 757 00:52:57,559 --> 00:52:59,440 Going uphill thermal stress is not an issue. 758 00:52:59,440 --> 00:53:03,410 It's all coming back in, in the entry phase. 759 00:53:03,410 --> 00:53:08,089 We knew we had initial conditions that were going to primarily be the cause of it. 760 00:53:08,089 --> 00:53:12,030 Coming back where the vehicle had been sitting in top sun for a long time, bottom sun for 761 00:53:12,030 --> 00:53:17,569 a long time, side sun for a long time, so we looked at those initial conditions as being 762 00:53:17,569 --> 00:53:17,980 the worse. 763 00:53:17,980 --> 00:53:20,670 And we proved to ourselves that it was the worst. 764 00:53:20,670 --> 00:53:27,650 Then what we cleverly did is we went around the vehicle where we had a detailed structural 765 00:53:27,650 --> 00:53:28,890 model of a lot of stuff. 766 00:53:28,890 --> 00:53:35,790 And we created a hundred different thermal models of different types of structure. 767 00:53:35,790 --> 00:53:38,500 This is one that was in the wing truss. 768 00:53:38,500 --> 00:53:42,450 We had a wing skin panel, we had a truss member and a lower wing skin panel. 769 00:53:42,450 --> 00:53:46,630 And we did a detailed thermal analysis of these hundred models. 770 00:53:46,630 --> 00:53:54,589 We then applied that to a structural model simplified, which was giving us the internal 771 00:53:54,589 --> 00:53:59,470 loads and stresses that we needed, and then we hand extrapolated that over the entire 772 00:53:59,470 --> 00:54:01,990 vehicle. 773 00:54:01,990 --> 00:54:03,230 There was no other way to do it. 774 00:54:03,230 --> 00:54:10,069 So, as you look at your analytical capability probably on your damn laptop now, computing 775 00:54:10,069 --> 00:54:15,369 capability, you couldn't really do it on that, but think about that. 776 00:54:15,369 --> 00:54:19,440 And I noticed nobody wants to talk about structures as one of these groups. 777 00:54:19,440 --> 00:54:24,339 If one of you changes then I'm going to feel really good when I go back and fight the hurricane 778 00:54:24,339 --> 00:54:27,119 in Texas. 779 00:54:27,119 --> 00:54:29,780 But that's the way we did that. 780 00:54:29,780 --> 00:54:35,809 It was a necessity that we had, but we didn't have the capability so we invented a way to 781 00:54:35,809 --> 00:54:36,869 do it. 782 00:54:36,869 --> 00:54:41,210 And, I'll show you in a minute, it worked. 783 00:54:41,210 --> 00:54:43,869 Another issue that we had. 784 00:54:43,869 --> 00:54:48,369 Normally you'd like to just vent everything through one area in the vehicle, but we couldn't 785 00:54:48,369 --> 00:54:51,869 do that because the payload bay had to be very clean. 786 00:54:51,869 --> 00:54:53,960 It had to be contamination free. 787 00:54:53,960 --> 00:54:57,140 And there was hydrogen in the backend of the vehicle. 788 00:54:57,140 --> 00:55:01,500 There was a pressure vessel in the front-end and a bulkhead up there. 789 00:55:01,500 --> 00:55:07,299 We said what we've got to do is we have dictated to ourselves that we have to design a venting 790 00:55:07,299 --> 00:55:08,190 system. 791 00:55:08,190 --> 00:55:12,970 This turned out to be a major part of a lot of internal loads in the vehicle because of 792 00:55:12,970 --> 00:55:14,960 venting from one compartment to the other. 793 00:55:14,960 --> 00:55:18,130 And, stop and think about it, we had vents all along the fuselage. 794 00:55:18,130 --> 00:55:23,180 We had a different pressure coefficient at each one of these vents for our various attitudes 795 00:55:23,180 --> 00:55:29,319 during ascent, for our various attitudes during entry, so we now had a whole myriad of complicated 796 00:55:29,319 --> 00:55:31,730 internal pressures that we had to accommodate. 797 00:55:31,730 --> 00:55:33,640 But that was pretty straightforward. 798 00:55:33,640 --> 00:55:39,059 We just complicated our design with the venting system that we had, but we had to do it to 799 00:55:39,059 --> 00:55:39,839 meet the requirement. 800 00:55:39,839 --> 00:55:41,230 I don't know that people are actually aware that there are all these vent doors because 801 00:55:41,230 --> 00:55:48,760 it's not something that you would normally pay attention to in the pictures. 802 00:55:48,760 --> 00:55:49,549 That's right, you don't. 803 00:55:49,549 --> 00:55:56,210 As a matter of fact, in this book that Jeff referenced, it shows where all the vent doors 804 00:55:56,210 --> 00:55:59,770 are. 805 00:55:59,770 --> 00:56:01,280 I didn't show that detail to you today. 806 00:56:01,280 --> 00:56:11,880 And they do open and close at different times during ascent and entry. 807 00:56:11,880 --> 00:56:12,520 Venting just for carbon dioxide gases? 808 00:56:12,520 --> 00:56:12,619 No. 809 00:56:12,619 --> 00:56:13,619 When you start off you're at one atmosphere, right? 810 00:56:13,619 --> 00:56:23,020 As you rapidly go uphill there's a delta p across internal bulkheads and internal compartments, 811 00:56:23,020 --> 00:56:25,760 internal and outside the vehicle. 812 00:56:25,760 --> 00:56:29,710 And, depending on what the flight regime is and where the shockwave is and where the vent 813 00:56:29,710 --> 00:56:33,750 door is, it's changing the whole venting thing. 814 00:56:33,750 --> 00:56:36,329 That's a whole lecture in itself on what we did. 815 00:56:36,329 --> 00:56:44,609 The crew compartment is designed to have a delta pressure of one atmosphere, but inside 816 00:56:44,609 --> 00:56:48,540 the payload bay, that's not designed to be a pressurized environment. 817 00:56:48,540 --> 00:56:56,490 And so you need to be sure that the air can get out of the payload bay fast enough that 818 00:56:56,490 --> 00:57:06,520 you don't over-pressurize, for instance, the payload bay doors or other parts of the structure. 819 00:57:06,520 --> 00:57:09,530 There were some other trades that we had to make. 820 00:57:09,530 --> 00:57:12,210 Let me skip forward so you can better understand this. 821 00:57:12,210 --> 00:57:24,859 For reference purposes, the main engines are here, 1.5 million pounds of thrust coming 822 00:57:24,859 --> 00:57:27,440 into this part of the vehicle. 823 00:57:27,440 --> 00:57:30,290 There is a Longeron that goes all the way along here. 824 00:57:30,290 --> 00:57:32,329 A big mass up here with a crew module. 825 00:57:32,329 --> 00:57:37,210 And the crew module, I showed you, had just discrete attachment points. 826 00:57:37,210 --> 00:57:43,910 All of the ascent inertia loads are reacted right here, so all these loads go along this 827 00:57:43,910 --> 00:57:44,730 Longeron. 828 00:57:44,730 --> 00:57:52,290 Now, all of a sudden we have a very good and efficient load path. 829 00:57:52,290 --> 00:57:56,270 The wing right here, this is a primary load carrying member of the wing. 830 00:57:56,270 --> 00:57:57,660 That's a spar. 831 00:57:57,660 --> 00:58:01,390 And it ties into this big bulkhead which is right here. 832 00:58:01,390 --> 00:58:12,640 When Jeff talks about the pressure differential, don't forget this thing is 15 feet in diameter 833 00:58:12,640 --> 00:58:17,540 here so you can imagine the total loads you have on that with a couple of psi delta p. 834 00:58:17,540 --> 00:58:19,349 It's big. 835 00:58:19,349 --> 00:58:24,329 That was a significant part of the driving stresses in that. 836 00:58:24,329 --> 00:58:30,619 Another point I want to make about this is -- Well, I talked about simple interfaces 837 00:58:30,619 --> 00:58:39,030 between the crew module and the forward fuselage with bolted attachments. 838 00:58:39,030 --> 00:58:43,299 We had a simple interface between the wing and the mid fuselage. 839 00:58:43,299 --> 00:58:47,380 A simple interface between the mid fuselage and the aft fuselage. 840 00:58:47,380 --> 00:58:52,559 The same thing with the vertical stabilizer and aft fuselage and these orbital maneuvering 841 00:58:52,559 --> 00:58:55,260 propulsion system. 842 00:58:55,260 --> 00:59:01,750 That was important, from a structural point of view, to be able to modularize and analyze 843 00:59:01,750 --> 00:59:02,160 these things. 844 00:59:02,160 --> 00:59:08,790 But it was also important because four different contractors built all these parts so they 845 00:59:08,790 --> 00:59:13,180 had to have an interface that they could not only design and analyze to but that they could 846 00:59:13,180 --> 00:59:16,549 physically attach to. 847 00:59:16,549 --> 00:59:21,450 Sometimes, when you have just a sketch on a piece of paper, you don't think about that. 848 00:59:21,450 --> 00:59:30,150 And it does cause a little bit of complexity sometimes in a program. 849 00:59:30,150 --> 00:59:34,530 The main thrust structure is carrying 1.5 million pounds of load from the engines. 850 00:59:34,530 --> 00:59:35,450 How do we design that? 851 00:59:35,450 --> 00:59:39,819 Well, we could have done a space frame or we could have done a truss configuration. 852 00:59:39,819 --> 00:59:45,670 We decided to go with the space frame or the truss rather than a plate girder, the term 853 00:59:45,670 --> 00:59:48,030 I didn't use correctly. 854 00:59:48,030 --> 00:59:51,980 And with that we saved 1700 pounds of weight in the vehicle. 855 00:59:51,980 --> 00:59:53,780 We used titanium. 856 00:59:53,780 --> 00:59:58,240 And this is a compression design. 857 00:59:58,240 --> 01:00:01,099 We thought we needed to get a little bit more weight out of this thing. 858 01:00:01,099 --> 01:00:04,970 What can we do to increase the compression modulus of titanium? 859 01:00:04,970 --> 01:00:14,540 We put boron/epoxy, scabbed it on the axial load members of the thrust structure, and 860 01:00:14,540 --> 01:00:18,030 that's the way we got a lot of that weight out. 861 01:00:18,030 --> 01:00:23,170 That was a manufacturing problem, I won't go into now, of how you build this thrust 862 01:00:23,170 --> 01:00:28,640 structure, but it works fine. 863 01:00:28,640 --> 01:00:31,170 The aft wing carried through -- Excuse me. 864 01:00:31,170 --> 01:00:31,869 Go ahead. 865 01:00:31,869 --> 01:00:32,150 I just had a quick question. 866 01:00:32,150 --> 01:00:32,200 Sure. 867 01:00:32,200 --> 01:00:39,680 We heard earlier that there was a CG problem in that the CG was too far forward in the 868 01:00:39,680 --> 01:00:43,819 aft [but bled in the back?] for a number a number of missions. 869 01:00:43,819 --> 01:00:46,619 I was wondering how that weight that they had to add to the CG compared to the weight 870 01:00:46,619 --> 01:00:48,299 that you guys saved. 871 01:00:48,299 --> 01:00:52,280 The weight of the payloads themselves, you're saying that there was a problem if heavy weights 872 01:00:52,280 --> 01:00:55,130 were too far aft or too far forward? 873 01:00:55,130 --> 01:00:55,640 The Orbiter. 874 01:00:55,640 --> 01:01:01,490 I guess the CG location was too far forward and they had to adjust it on certain missions 875 01:01:01,490 --> 01:01:05,990 by adding weight near the back. 876 01:01:05,990 --> 01:01:10,109 Well, what that is, that is true and that's a problem. 877 01:01:10,109 --> 01:01:11,240 It's not a problem. 878 01:01:11,240 --> 01:01:14,240 It's something that has to be addressed on every mission, depending on what the payload 879 01:01:14,240 --> 01:01:16,089 is that you're carrying. 880 01:01:16,089 --> 01:01:22,240 If you have a real heavy forward payload, yeah, you have to add some ballast to the 881 01:01:22,240 --> 01:01:23,210 aft end of the thing. 882 01:01:23,210 --> 01:01:27,270 Now, normally the way they do it is they'll find some payload that can fit in the aft 883 01:01:27,270 --> 01:01:28,240 end to help ballast that. 884 01:01:28,240 --> 01:01:33,079 But I think, in some of the early flights, we put some ballast in the back for CG control. 885 01:01:33,079 --> 01:01:42,700 We've carried many tons of lead into orbit, so it was ballasting the thing for control 886 01:01:42,700 --> 01:01:43,099 purposes. 887 01:01:43,099 --> 01:01:49,900 The same way yesterday in Jet Blue, a lot of people had to move to the back end of the 888 01:01:49,900 --> 01:01:57,720 airplane because they wanted that CG for a little bit different landing performance. 889 01:01:57,720 --> 01:02:00,750 1307 bulkhead, we saved about 500 pounds there. 890 01:02:00,750 --> 01:02:02,890 Now, see what we're doing? 891 01:02:02,890 --> 01:02:07,440 We started out with the initial trades in the early concept phases. 892 01:02:07,440 --> 01:02:09,329 What's the wing loading? 893 01:02:09,329 --> 01:02:13,799 We didn't care about what the internal structure trades were. 894 01:02:13,799 --> 01:02:20,660 Now we're getting down to trading all the stuff at a semi-macro level. 895 01:02:20,660 --> 01:02:25,280 And I'll show you in a minute a micro-level that we had to get into, which was pretty 896 01:02:25,280 --> 01:02:26,230 interesting. 897 01:02:26,230 --> 01:02:27,680 How are we doing time-wise? 898 01:02:27,680 --> 01:02:28,380 We're OK. 899 01:02:28,380 --> 01:02:30,660 So, we saved some weight there. 900 01:02:30,660 --> 01:02:37,730 An interesting thing about the payload bay doors. 901 01:02:37,730 --> 01:02:49,270 We decided that for this vehicle to be safe and to re-enter those doors had to close. 902 01:02:49,270 --> 01:02:54,640 We had a lot of trouble in Gemini with things on orbit not working. 903 01:02:54,640 --> 01:02:57,839 Mechanical systems quite often are problems. 904 01:02:57,839 --> 01:02:59,859 Docking systems are problems. 905 01:02:59,859 --> 01:03:04,400 There have been a lot of door problems on orbit in spacecraft. 906 01:03:04,400 --> 01:03:07,839 And you design them and you put them in thermal vacuum chambers and they all work, but you 907 01:03:07,839 --> 01:03:09,960 get on orbit and sometimes they don't work. 908 01:03:09,960 --> 01:03:12,220 Maybe it's thermal distortion that we're not accounting for. 909 01:03:12,220 --> 01:03:13,980 So, we said that is critical. 910 01:03:13,980 --> 01:03:16,859 We've got to close these payload bay doors. 911 01:03:16,859 --> 01:03:23,510 What we did was say the way we're going to do that is the payload doors will carry only 912 01:03:23,510 --> 01:03:24,450 two types of load. 913 01:03:24,450 --> 01:03:32,059 They will carry pressure loads, like Jeff talked about, and they'll carry torsion loads. 914 01:03:32,059 --> 01:03:37,799 Because, if they are closed, we know that it is good for torsion in the vehicle, reacting 915 01:03:37,799 --> 01:03:39,359 torsional loads. 916 01:03:39,359 --> 01:03:44,160 But we will not let them carry body bending loads or else we cannot make them flexible 917 01:03:44,160 --> 01:03:44,500 enough. 918 01:03:44,500 --> 01:03:52,940 What we did is all of the body bending in this vehicle is carried along this Longeron 919 01:03:52,940 --> 01:03:56,150 through this section in the lower skin of the vehicle. 920 01:03:56,150 --> 01:04:01,309 This is the modulus of the vehicle, if you will, at a cross-section here between this 921 01:04:01,309 --> 01:04:03,280 Longeron and the lower skin. 922 01:04:03,280 --> 01:04:05,160 Payload bay doors don't come into being. 923 01:04:05,160 --> 01:04:13,410 And the way the doors close on orbit is they start zipping along from here up to the top 924 01:04:13,410 --> 01:04:14,970 because they are flexible. 925 01:04:14,970 --> 01:04:21,240 And the same way back here, they zip closed, zipping just a latch at a time. 926 01:04:21,240 --> 01:04:22,720 They were sort of ratcheting themselves closed. 927 01:04:22,720 --> 01:04:24,700 And then they close along the center line. 928 01:04:24,700 --> 01:04:30,869 There has never been a problem with payload bay door closures on orbit. 929 01:04:30,869 --> 01:04:34,730 It was something we decided to add to the design. 930 01:04:34,730 --> 01:04:40,559 We could have made the vehicle lighter had we not done that, but we would have also complicated 931 01:04:40,559 --> 01:04:46,930 the safety of the vehicle if we had done it. 932 01:04:46,930 --> 01:04:54,859 Sort of in line, but it's not the CG thing, we had a payload attachment issue. 933 01:04:54,859 --> 01:05:03,849 And, when we were laying out all this stuff in the early `70s, we didn't know what the 934 01:05:03,849 --> 01:05:04,349 payloads were. 935 01:05:04,349 --> 01:05:06,910 We knew what the total mass was. 936 01:05:06,910 --> 01:05:09,599 We knew there may be five at a time. 937 01:05:09,599 --> 01:05:11,180 We didn't know what they were. 938 01:05:11,180 --> 01:05:17,609 Now, you can just go in and bolt a payload into the fuselage of the Orbiter. 939 01:05:17,609 --> 01:05:22,849 And if you just do that randomly or without thinking about it, now all of a sudden you 940 01:05:22,849 --> 01:05:27,109 start analyzing the Orbiter and you start twisting it, what happens? 941 01:05:27,109 --> 01:05:29,410 The payload becomes part of the load path. 942 01:05:29,410 --> 01:05:34,349 Now, all of a sudden, you have impacted the design of the payload or maybe you have impacted 943 01:05:34,349 --> 01:05:37,400 the design of the Orbiter depending on what is happening in the payload. 944 01:05:37,400 --> 01:05:41,849 We said ah-ha, what we'll do is make it so it's statically determinant. 945 01:05:41,849 --> 01:05:48,150 If two things are attached statically determinately they cannot interact with one another as far 946 01:05:48,150 --> 01:05:50,910 as their stiffnesses are concerned. 947 01:05:50,910 --> 01:05:52,440 We said that's what we're going to do. 948 01:05:52,440 --> 01:05:58,369 We'll put attachments along the Longerons to carry the axial loads, some along the keel 949 01:05:58,369 --> 01:05:59,920 to carry some of the lateral loads. 950 01:05:59,920 --> 01:06:01,569 Viola, we've got it. 951 01:06:01,569 --> 01:06:05,849 So, the requirement became that we would design it that way. 952 01:06:05,849 --> 01:06:11,788 Our next step was, and you can ask Al Louviere when he comes up about that because Al Louviere 953 01:06:11,788 --> 01:06:17,410 and Max Faget told me they would never fly with those Longerons that way. 954 01:06:17,410 --> 01:06:20,319 We did it anyway. 955 01:06:20,319 --> 01:06:24,029 What we had to do then was say now we understand what the attachment is. 956 01:06:24,029 --> 01:06:30,920 How do we determine within the CG constraints for these different masses -- And we had to 957 01:06:30,920 --> 01:06:34,220 assume what they were not knowing exactly the definition of the payloads. 958 01:06:34,220 --> 01:06:36,809 We did a Monte Carlo analysis. 959 01:06:36,809 --> 01:06:40,730 Ten million cases of combined payloads. 960 01:06:40,730 --> 01:06:44,510 CG locations, numbers of payloads, forward, aft, all that. 961 01:06:44,510 --> 01:06:46,319 And we did that with a Monte Carlo analysis. 962 01:06:46,319 --> 01:06:48,970 We said voila, that's where we're going to design the mid fuselage. 963 01:06:48,970 --> 01:06:55,609 That's the way we did it. 964 01:06:55,609 --> 01:06:58,940 Now getting into the detail design loads. 965 01:06:58,940 --> 01:07:00,680 How do we determine all these things now? 966 01:07:00,680 --> 01:07:04,788 Because now it's coming down to sizing the vehicle. 967 01:07:04,788 --> 01:07:15,950 This part of the flight regime from liftoff through max Q, that's a critical loading condition, 968 01:07:15,950 --> 01:07:18,510 a critical design for the Orbiter. 969 01:07:18,510 --> 01:07:21,809 When it gets into orbit pretty benign. 970 01:07:21,809 --> 01:07:26,799 Nothing is really happening up there except some temperatures which are going to be important 971 01:07:26,799 --> 01:07:32,029 at this point over here, because now all of a sudden you start adding more heat into it. 972 01:07:32,029 --> 01:07:36,950 Now you get into the regime where you're maneuvering in the atmosphere. 973 01:07:36,950 --> 01:07:41,520 Now you're in a different loading regime which becomes critical. 974 01:07:41,520 --> 01:07:48,640 So, critical as far as the airframe is concerned, is here and over here only. 975 01:07:48,640 --> 01:07:52,799 Let me break that down into the constituent portions there. 976 01:07:52,799 --> 01:07:54,440 Liftoff loads. 977 01:07:54,440 --> 01:08:00,500 We had another statistical challenge here because what we had to do was needed to look 978 01:08:00,500 --> 01:08:04,270 at all the variables associated with the rocket engines. 979 01:08:04,270 --> 01:08:05,520 They have start sequences. 980 01:08:05,520 --> 01:08:08,869 We've got three main engines that are not going to start exactly the same time. 981 01:08:08,869 --> 01:08:15,410 They're not going to come up with the same thrust profile as they start up. 982 01:08:15,410 --> 01:08:18,710 The thrust vector misalignment is going to be different. 983 01:08:18,710 --> 01:08:21,279 And we also had to look at ignition over pressure. 984 01:08:21,279 --> 01:08:24,259 And I'll show you that was a surprise to us. 985 01:08:24,259 --> 01:08:30,279 Also part of liftoff we had to look at winds and gusts, vortex shedding, proximity of aerodynamics 986 01:08:30,279 --> 01:08:35,440 to the other structures is on the gantry in the pad. 987 01:08:35,440 --> 01:08:41,818 And then we had to do the pressurization and also look at shrinkage of these vehicles that 988 01:08:41,818 --> 01:08:46,080 components or elements at cryo-temperatures. 989 01:08:46,080 --> 01:08:52,940 Here was a cross-section, in a generic sense, of what's happening during liftoff. 990 01:08:52,940 --> 01:08:57,979 There is some combination of winds that you have to account for. 991 01:08:57,979 --> 01:08:59,559 And I will show you what we did there. 992 01:08:59,559 --> 01:09:02,609 The thrust profile from the SSMEs. 993 01:09:02,609 --> 01:09:09,479 The SRBs come up to thrust after you get confirmation that the engines are operating at full performance. 994 01:09:09,479 --> 01:09:14,399 And there is a lot of vibration acceleration going on. 995 01:09:14,399 --> 01:09:18,979 Here is something that becomes pretty obvious after a while. 996 01:09:18,979 --> 01:09:25,440 When you have a vehicle that is tied down here with a base moment and you put 1.5 million 997 01:09:25,440 --> 01:09:28,729 pounds of thrust on it, this vehicle is going to bend over this way. 998 01:09:28,729 --> 01:09:35,318 There is a lot of strained energy in the solid rocket motors when that happens. 999 01:09:35,318 --> 01:09:43,649 If you were to ignite the SRBs, when that vehicle is over here, the party is over because 1000 01:09:43,649 --> 01:09:47,210 it releases all that strained energy and the SRBs couldn't take it. 1001 01:09:47,210 --> 01:09:54,049 When you see the Orbiter prior to liftoff, the SSMEs will come up, you will see the vehicle 1002 01:09:54,049 --> 01:09:55,190 do like this. 1003 01:09:55,190 --> 01:10:00,170 And then, when it comes back over zero, viola, you kick off the SRBs. 1004 01:10:00,170 --> 01:10:06,059 But you have to wait until it gets back to that neutral point. 1005 01:10:06,059 --> 01:10:08,230 A little detail that is pretty important. 1006 01:10:08,230 --> 01:10:13,340 Ascent. 1007 01:10:13,340 --> 01:10:25,570 A really complicated part of the design of the vehicle, especially with the aerodynamic 1008 01:10:25,570 --> 01:10:25,570 surfaces. As I said before, you would like for these things not to be there during ascent. 1009 01:10:29,520 --> 01:10:31,050 They don't buy you anything. 1010 01:10:31,050 --> 01:10:35,610 You just need them coming back. 1011 01:10:35,610 --> 01:10:45,150 Some other complications here are the acoustic effects will become important, as I'll show 1012 01:10:45,150 --> 01:10:47,050 you, in acoustic fatigue for the vehicle. 1013 01:10:47,050 --> 01:10:48,110 I showed you life. 1014 01:10:48,110 --> 01:10:50,380 Well, that's going to be a critical thing. 1015 01:10:50,380 --> 01:10:56,400 Another thing is the plumes of the vehicle are changing the pressure distribution as 1016 01:10:56,400 --> 01:10:57,630 you're going up. 1017 01:10:57,630 --> 01:11:04,150 The pressure distribution along the Orbiter, especially the wing, is changing the whole 1018 01:11:04,150 --> 01:11:08,989 times you're accelerating, not only through the various mach regimes but also because 1019 01:11:08,989 --> 01:11:13,300 of the blockage from the plume expansion. 1020 01:11:13,300 --> 01:11:15,460 We said how in the world are going to do that? 1021 01:11:15,460 --> 01:11:17,860 We cannot analyze all those things. 1022 01:11:17,860 --> 01:11:24,840 If we do it deterministically, you won't get a capability that you need, we thought, operational. 1023 01:11:24,840 --> 01:11:30,630 We said what we'll do is one piece of data that we had, we had synthetic wind profiles 1024 01:11:30,630 --> 01:11:32,800 for everything that existed at the Cape. 1025 01:11:32,800 --> 01:11:34,030 We said that's a given. 1026 01:11:34,030 --> 01:11:40,280 We'll use these synthetic wind profiles as a guideline to all of our winds aloft. 1027 01:11:40,280 --> 01:11:46,480 What we need to do is decide what the angle of attack and the side slip is going to be 1028 01:11:46,480 --> 01:11:50,860 through this vehicle flying through these winds and a control system that's changing 1029 01:11:50,860 --> 01:11:52,770 the attitude of the vehicle. 1030 01:11:52,770 --> 01:11:57,850 That's a factor that we have to consider and that's going to be important for the design 1031 01:11:57,850 --> 01:12:01,420 of the elevon surfaces and all because they're getting loaded up pretty heavily at that time. 1032 01:12:01,420 --> 01:12:08,600 There are dispersions in the propulsion system that have to be added. 1033 01:12:08,600 --> 01:12:16,380 And then what we decided to do, after we looked at all that, we said what we're going to do 1034 01:12:16,380 --> 01:12:21,559 is we're going to take all these parameters, and you won't find this in any textbook, but 1035 01:12:21,559 --> 01:12:23,300 we created something called a squatcheloid. 1036 01:12:23,300 --> 01:12:26,260 And I forgot to look up what squatcheloid means. 1037 01:12:26,260 --> 01:12:28,610 It must be a Greek term that was really good. 1038 01:12:28,610 --> 01:12:35,150 But what we did was flew the vehicle through different mach numbers. 1039 01:12:35,150 --> 01:12:44,179 And we looked at the various conditions we could get at for combinations of dynamic pressure 1040 01:12:44,179 --> 01:12:50,440 and angle of attack and dynamic pressure and side slip for all the mach numbers, and then 1041 01:12:50,440 --> 01:12:56,969 we said is that realistic to do, not only from a control systems standpoint but from 1042 01:12:56,969 --> 01:12:59,260 a standpoint of the propulsion system capability? 1043 01:12:59,260 --> 01:13:05,780 And we said it is feasible to do so we ought to design within those envelopes. 1044 01:13:05,780 --> 01:13:12,390 What we did was walked our way around all of these external points with pressure and 1045 01:13:12,390 --> 01:13:17,309 inertial loads and everything else and we looked at the structural model that we had 1046 01:13:17,309 --> 01:13:17,750 simplified. 1047 01:13:17,750 --> 01:13:22,000 And we said we found the points that were critical for the vertical stabilizer, for 1048 01:13:22,000 --> 01:13:28,860 the outboard elevon, et cetera, and that's the way we designed the vehicle for ascent 1049 01:13:28,860 --> 01:13:30,130 loads. 1050 01:13:30,130 --> 01:13:38,760 The thing that that enabled us to do, too, is it enabled us to do a rational combination 1051 01:13:38,760 --> 01:13:39,960 that Aaron brought up a while ago. 1052 01:13:39,960 --> 01:13:42,830 What did you do with the SSMEs for engine out and that kind of stuff? 1053 01:13:42,830 --> 01:13:51,650 It let us do a rational combination of engine out and also engine vector control. 1054 01:13:51,650 --> 01:13:57,400 You could design the thrust structure so that the engines went out to the extremes, but 1055 01:13:57,400 --> 01:14:00,150 it didn't make sense as far as the control system was concerned. 1056 01:14:00,150 --> 01:14:05,710 What we did is we saved a lot of weight in the vehicle by using a deterministic or realistic, 1057 01:14:05,710 --> 01:14:16,489 I should say, SSME thrust profile and vector characteristics. 1058 01:14:16,489 --> 01:14:18,790 Well, I just mention that. 1059 01:14:18,790 --> 01:14:21,690 That's what the squatcheloid did for it. 1060 01:14:21,690 --> 01:14:28,130 Also what it did was then gave the guys who were designing ascent trajectories, now they 1061 01:14:28,130 --> 01:14:36,000 had an envelope to design to, which was key for their operations. 1062 01:14:36,000 --> 01:14:36,770 Next problem. 1063 01:14:36,770 --> 01:14:38,400 Now we come back to descent loads. 1064 01:14:38,400 --> 01:14:51,620 When you said that you designed it for realistic cases instead of worst cases, does that mean 1065 01:14:51,620 --> 01:14:53,480 the engines were never able to vector all the way out to maximum? 1066 01:14:53,480 --> 01:14:53,480 Right. It just could not happen? 1067 01:14:56,980 --> 01:14:57,699 It could not happen. 1068 01:14:57,699 --> 01:15:01,370 That was a failure mode that it had enough redundancy and it couldn't happen, and there 1069 01:15:01,370 --> 01:15:04,610 wasn't any need of creating a load condition like that. 1070 01:15:04,610 --> 01:15:05,190 It couldn't happen. 1071 01:15:05,190 --> 01:15:08,650 OK, so you looked for it. 1072 01:15:08,650 --> 01:15:14,440 We looked for the cases where you could be in the worst case winds, the worst case misalignment 1073 01:15:14,440 --> 01:15:18,860 with the SRB, with the different throttling of the engines. 1074 01:15:18,860 --> 01:15:23,659 And we did all that and said to control this vehicle, because if you cannot control the 1075 01:15:23,659 --> 01:15:26,250 vehicle there's no need to look at that load case. 1076 01:15:26,250 --> 01:15:31,840 We said to control it within those environments, what's the extreme of the engines? 1077 01:15:31,840 --> 01:15:37,900 We said that's a design case for the thrust structure. 1078 01:15:37,900 --> 01:15:40,449 Good question. 1079 01:15:40,449 --> 01:15:44,449 Descent loads. 1080 01:15:44,449 --> 01:15:45,489 This was pretty easy. 1081 01:15:45,489 --> 01:15:49,780 The structure guys said this is a piece of cake because this vehicle is coming back in, 1082 01:15:49,780 --> 01:15:53,260 in a ballistic trajectory. 1083 01:15:53,260 --> 01:15:55,710 And, viola, there are not even loads on this vehicle. 1084 01:15:55,710 --> 01:16:00,030 Well, that didn't make a whole lot of sense because we knew that there would have to be 1085 01:16:00,030 --> 01:16:03,840 more maneuvering capability than anybody was fessing up to. 1086 01:16:03,840 --> 01:16:09,460 Not that they weren't trying to hide it, but we weren't smart enough. 1087 01:16:09,460 --> 01:16:14,380 The Aaron Cohen guys weren't smart enough to know all the conditions we would have to 1088 01:16:14,380 --> 01:16:14,860 fly it to. 1089 01:16:14,860 --> 01:16:23,710 What we did was we went through the classical Venn diagram where you're plotting for different 1090 01:16:23,710 --> 01:16:28,100 mach numbers. 1091 01:16:28,100 --> 01:16:34,230 The normal load factor versus the velocity of the vehicle that it can fly in that flight 1092 01:16:34,230 --> 01:16:35,710 regime. 1093 01:16:35,710 --> 01:16:40,760 We said if this thing is going to behave like an airplane and have to perform like an airplane, 1094 01:16:40,760 --> 01:16:42,809 we are going to design it like an airplane. 1095 01:16:42,809 --> 01:16:44,370 We caught a lot of guff. 1096 01:16:44,370 --> 01:16:50,150 When Bass Redd comes in and talks in the future ask him about this because he fought us on 1097 01:16:50,150 --> 01:16:52,340 this hand and foot. 1098 01:16:52,340 --> 01:16:54,690 He said you guys don't have to design it that way. 1099 01:16:54,690 --> 01:17:00,010 We said well, we're going to, but let him have capability in his aerodynamics and talk 1100 01:17:00,010 --> 01:17:02,170 to the control system guys about that, too. 1101 01:17:02,170 --> 01:17:05,760 And I see the Draper guys left on that. 1102 01:17:05,760 --> 01:17:12,210 [LAUGHTER] We said we're going to build in that capability for this thing to maneuver 1103 01:17:12,210 --> 01:17:12,900 like an airplane. 1104 01:17:12,900 --> 01:17:15,610 2.5 g's normal load factor. 1105 01:17:15,610 --> 01:17:21,110 Follow-up classical Venn diagram where we have equivalent airspeed of 375 psf. 1106 01:17:21,110 --> 01:17:27,380 We were determining what the equivalent air speed for those conditions was. 1107 01:17:27,380 --> 01:17:31,909 And then we did it. 1108 01:17:31,909 --> 01:17:38,460 Now we've gotten up to a point I'll call CDR, and a point I should have mentioned a while 1109 01:17:38,460 --> 01:17:39,449 ago. 1110 01:17:39,449 --> 01:17:46,210 When I showed the authority to proceed, there aren't any drawings which exist, except some 1111 01:17:46,210 --> 01:17:46,929 sketches. 1112 01:17:46,929 --> 01:17:50,270 I mean there are mol line drawings and that's about it. 1113 01:17:50,270 --> 01:17:54,429 And the mol line of the vehicle was what came out of all the other studies. 1114 01:17:54,429 --> 01:17:58,610 It said that's it, we've got to put everything within this mol line for this vehicle to perform 1115 01:17:58,610 --> 01:17:59,860 like it is. 1116 01:17:59,860 --> 01:18:01,719 But there are no detailed drawings. 1117 01:18:01,719 --> 01:18:06,850 When you get to a preliminary design review in a classical design and development program, 1118 01:18:06,850 --> 01:18:13,659 typically that's about where you reach 10% of your drawings that are released. 1119 01:18:13,659 --> 01:18:15,440 And what does it mean to release a drawing? 1120 01:18:15,440 --> 01:18:22,620 That means you sign it off, whatever your discipline is, and it say we can make this 1121 01:18:22,620 --> 01:18:28,630 airplane to these drawings and it's given to the people to go make it. 1122 01:18:28,630 --> 01:18:33,179 So, once you release a drawing you don't ever want to bring it back and change it because 1123 01:18:33,179 --> 01:18:34,600 it costs you a lot of money. 1124 01:18:34,600 --> 01:18:44,550 The PDR, which was somewhere like about '73, '74, somewhere like that, that was the state 1125 01:18:44,550 --> 01:18:45,920 which we existed. 1126 01:18:45,920 --> 01:18:50,330 We hadn't defined everything on the structural low pass like I told you about a while ago, 1127 01:18:50,330 --> 01:18:52,260 nor the materials. 1128 01:18:52,260 --> 01:18:53,570 Now we're at the detail design. 1129 01:18:53,570 --> 01:19:00,469 Now we're into CDR, that's the critical design review, and 90% of all your drawings are released. 1130 01:19:00,469 --> 01:19:03,989 And now it gets very expensive to go back and change. 1131 01:19:03,989 --> 01:19:09,059 You can just see how it would ripple through the entire operation if you change a drawing 1132 01:19:09,059 --> 01:19:09,590 at that time. 1133 01:19:09,590 --> 01:19:13,570 You have to, to make it work sometimes, but you like not to change it. 1134 01:19:13,570 --> 01:19:18,020 What we have to do here, our challenge from a structural point of view is to complete 1135 01:19:18,020 --> 01:19:22,659 the design, do some of the details which means get weight out of the vehicle where you can 1136 01:19:22,659 --> 01:19:25,179 scrape it without really changing a lot of stuff. 1137 01:19:25,179 --> 01:19:29,020 And then also decide how you're going to certify the vehicle. 1138 01:19:29,020 --> 01:19:34,900 It means what you're going to do on the ground to say it's really safe for the crew to get 1139 01:19:34,900 --> 01:19:36,340 in. 1140 01:19:36,340 --> 01:19:37,010 That's what that was. 1141 01:19:37,010 --> 01:19:41,730 Weight reduction is a major part of the program. 1142 01:19:41,730 --> 01:19:44,850 Here are some of the things that we took out about this timeframe. 1143 01:19:44,850 --> 01:19:48,340 We took out 900 pounds of weight in the payload bay doors. 1144 01:19:48,340 --> 01:19:54,469 We didn't change the configuration, they were still flexible, but they were aluminum honeycomb. 1145 01:19:54,469 --> 01:19:57,710 We said we can save 900 pounds if we go to graphite/epoxy. 1146 01:19:57,710 --> 01:20:03,530 Graphite/epoxy characterization of the material didn't even exist then. 1147 01:20:03,530 --> 01:20:08,270 Literally Aaron, myself and three or four other guys sat around. 1148 01:20:08,270 --> 01:20:12,659 We said OK, Aaron, this is what we have, this is what we know about it, here are the risks 1149 01:20:12,659 --> 01:20:15,040 associated and here is the weight savings. 1150 01:20:15,040 --> 01:20:16,120 Go for it. 1151 01:20:16,120 --> 01:20:17,929 So, we went for it and it worked. 1152 01:20:17,929 --> 01:20:21,659 That was the largest graphite/epoxy structure ever flown. 1153 01:20:21,659 --> 01:20:26,510 We characterized it, passed that on to the industry and that helped a bunch. 1154 01:20:26,510 --> 01:20:30,809 Another little interesting thing -- I have to watch my time here. 1155 01:20:30,809 --> 01:20:34,350 I mentioned the spending profile. 1156 01:20:34,350 --> 01:20:40,010 Well, we got into the program about the time we were starting to make the payload bay doors, 1157 01:20:40,010 --> 01:20:43,559 which is probably '75, '76. 1158 01:20:43,559 --> 01:20:46,750 And Aaron didn't get all the money that he needed. 1159 01:20:46,750 --> 01:20:54,780 We built the first set of payload bay doors, which is people process dependant. 1160 01:20:54,780 --> 01:20:55,870 It's like laying up fiberglass. 1161 01:20:55,870 --> 01:21:00,239 It was all hand layup with epoxy and bake it and all that kind of stuff. 1162 01:21:00,239 --> 01:21:05,190 We got the first set built and we fired everybody because we didn't have enough money to keep 1163 01:21:05,190 --> 01:21:07,290 them on the payroll for the rest of that year. 1164 01:21:07,290 --> 01:21:13,150 We literally laid everybody off at Rockwell in Tulsa. 1165 01:21:13,150 --> 01:21:17,650 And they came back a year later, not all of them, but we had to start over again. 1166 01:21:17,650 --> 01:21:21,100 So, there is a risk associated with that. 1167 01:21:21,100 --> 01:21:21,690 Thrust structure. 1168 01:21:21,690 --> 01:21:26,670 We saved 1200 pounds by stiffening, like I told you about a while ago. 1169 01:21:26,670 --> 01:21:31,199 And then we used a bunch of other composites. 1170 01:21:31,199 --> 01:21:36,030 A lot of people said, especially after Challenger, let's get rid of this vehicle because it's 1171 01:21:36,030 --> 01:21:37,900 antiquated and was designed too long ago. 1172 01:21:37,900 --> 01:21:46,710 That probably is still one of the most advanced composite structure vehicles flying today. 1173 01:21:46,710 --> 01:21:51,880 Except, where there is a lot of aluminum honeycomb, you probably could go with graphite/epoxy. 1174 01:21:51,880 --> 01:21:55,110 And I will give you a challenge with that later on. 1175 01:21:55,110 --> 01:21:59,670 But there are beryllium aluminum struts in here. 1176 01:21:59,670 --> 01:22:03,260 There are boron/epoxy scab on devices. 1177 01:22:03,260 --> 01:22:05,949 There is graphite/epoxy all over the vehicle. 1178 01:22:05,949 --> 01:22:07,110 Not all over the vehicle. 1179 01:22:07,110 --> 01:22:08,800 In a lot of places in the vehicle. 1180 01:22:08,800 --> 01:22:11,380 The vehicle has got a lot of composites. 1181 01:22:11,380 --> 01:22:17,059 And we stretched to be able to do that. 1182 01:22:17,059 --> 01:22:17,540 Certification. 1183 01:22:17,540 --> 01:22:20,429 Now we've got the thing pretty well designed. 1184 01:22:20,429 --> 01:22:22,870 What are we going to do to certify this thing? 1185 01:22:22,870 --> 01:22:27,590 This is where we deviated from the norm and were pretty innovative. 1186 01:22:27,590 --> 01:22:34,719 Classically, in the way this program started off, there was a dedicated structural test 1187 01:22:34,719 --> 01:22:40,190 article and there was a dedicated fatigue test article. 1188 01:22:40,190 --> 01:22:42,070 There were a couple of problems with that. 1189 01:22:42,070 --> 01:22:46,940 If you don't need it, you might as well not build it, even though that was in the program. 1190 01:22:46,940 --> 01:22:52,699 The situation was, as I showed you a while ago, thermal stress was a major part of that. 1191 01:22:52,699 --> 01:22:59,580 You couldn't apply a mechanical and thermal load to this vehicle and still be practical. 1192 01:22:59,580 --> 01:23:01,590 Concorde did it. 1193 01:23:01,590 --> 01:23:08,100 The way that Concorde was designed and certified, they applied mechanical loads in an environment 1194 01:23:08,100 --> 01:23:13,020 in which they could induce the temperature by convective heating on that vehicle. 1195 01:23:13,020 --> 01:23:16,460 And it took them like three years to test the vehicle. 1196 01:23:16,460 --> 01:23:19,030 And it was extremely expensive. 1197 01:23:19,030 --> 01:23:24,760 It was a big jobs program for Greg Britton and France and some of the others, but we 1198 01:23:24,760 --> 01:23:28,949 decided we couldn't afford to do that so we are going to have to figure out how else to 1199 01:23:28,949 --> 01:23:29,219 do it. 1200 01:23:29,219 --> 01:23:37,010 Besides that, Aaron had $100 million problem that year. 1201 01:23:37,010 --> 01:23:40,530 What can you guy help us do? 1202 01:23:40,530 --> 01:23:51,070 What we'll do, we think we can do this, is take an airframe and we will apply 110% of 1203 01:23:51,070 --> 01:23:54,940 the limit mechanical loads only to it. 1204 01:23:54,940 --> 01:23:56,989 And that doesn't certify anything. 1205 01:23:56,989 --> 01:24:00,170 And then we will put strain gauges all over this vehicle. 1206 01:24:00,170 --> 01:24:07,360 And we will pre-predict what the strain response is going to be for 3,000 points on the vehicle. 1207 01:24:07,360 --> 01:24:13,050 If we can pre-predict what the strain response is for applying a bunch of different loads 1208 01:24:13,050 --> 01:24:17,440 then we know how to analyze the vehicle. 1209 01:24:17,440 --> 01:24:19,800 That proves we know how to analyze it. 1210 01:24:19,800 --> 01:24:29,620 We can extrapolate to 140% to our ultimate load capability from mechanical, and we will 1211 01:24:29,620 --> 01:24:32,739 add the thermal stress to it analytically. 1212 01:24:32,739 --> 01:24:34,889 So, we did that. 1213 01:24:34,889 --> 01:24:39,550 And then we refurbished the vehicle and that became Challenger. 1214 01:24:39,550 --> 01:24:43,080 The test article is going to cost $100 million. 1215 01:24:43,080 --> 01:24:44,429 We said we don't need it. 1216 01:24:44,429 --> 01:24:47,179 We'll use it for a flight airframe. 1217 01:24:47,179 --> 01:24:51,320 And Aaron gave us a little ceramic eagle for doing it. 1218 01:24:51,320 --> 01:24:57,469 Don't anybody expect As out of this deal, if Aaron has anything to do with it. 1219 01:24:57,469 --> 01:24:57,800 There it was. 1220 01:24:57,800 --> 01:25:05,620 We applied the million and a half pounds of load at the backend. 1221 01:25:05,620 --> 01:25:11,690 We concentrated through loading fixtures, loads on the wings of the fuselage, put pressure 1222 01:25:11,690 --> 01:25:18,380 differential at various points on the vehicle, and we did exactly what I said. 1223 01:25:18,380 --> 01:25:20,179 Fatigue life. 1224 01:25:20,179 --> 01:25:21,780 Mechanical fatigue was not a problem. 1225 01:25:21,780 --> 01:25:26,190 Acoustic fatigue was an issue because we had some really lightweight structures and really 1226 01:25:26,190 --> 01:25:27,389 high acoustic levels. 1227 01:25:27,389 --> 01:25:29,820 You cannot see it here. 1228 01:25:29,820 --> 01:25:37,780 It was like 165 DB around the base-end of the thing, lower levels on other portions, 1229 01:25:37,780 --> 01:25:39,130 so we said how are we going to do that? 1230 01:25:39,130 --> 01:25:42,559 We came up with a different way to do it. 1231 01:25:42,559 --> 01:25:49,880 What we will do is we'll go around the vehicle and we will identify a characteristic structure, 1232 01:25:49,880 --> 01:25:58,309 graphite/epoxy, aluminum, 7075-T6 aluminum fuselage up here, wing elevon, aluminum honeycomb, 1233 01:25:58,309 --> 01:25:59,900 et cetera. 1234 01:25:59,900 --> 01:26:03,980 We identified 44 test articles. 1235 01:26:03,980 --> 01:26:05,870 We said that's what we'll do. 1236 01:26:05,870 --> 01:26:11,550 We went to Aaron and said it's going to take us 44 test articles. 1237 01:26:11,550 --> 01:26:18,170 We went through all the rationale with each one of them, and he said you can have 14. 1238 01:26:18,170 --> 01:26:20,199 And so we said but that won't work. 1239 01:26:20,199 --> 01:26:21,710 He said go figure it out. 1240 01:26:21,710 --> 01:26:23,610 We went back and scratched out heads. 1241 01:26:23,610 --> 01:26:26,429 Sure enough, we figured out how to do more extrapolation. 1242 01:26:26,429 --> 01:26:29,280 So, we had 14 test articles that you see. 1243 01:26:29,280 --> 01:26:33,360 And then what we did was say now we've got our test articles. 1244 01:26:33,360 --> 01:26:40,239 Our approach to this thing was we would test them to failure acoustically. 1245 01:26:40,239 --> 01:26:46,170 Now we have an acoustic allowable for that type of structure because it's a function 1246 01:26:46,170 --> 01:26:47,070 of the details. 1247 01:26:47,070 --> 01:26:48,210 I mean it had to be the detail. 1248 01:26:48,210 --> 01:26:54,320 And, in addition to making sure we have a good test, if this was our acoustic fatigue 1249 01:26:54,320 --> 01:26:59,070 test article, only the center third was a viable part of the test because the rest of 1250 01:26:59,070 --> 01:27:02,820 it is boundary conditions that weren't right because they were clamped along the edges 1251 01:27:02,820 --> 01:27:03,550 or whatever. 1252 01:27:03,550 --> 01:27:07,719 We said only the middle third of the test article is viable. 1253 01:27:07,719 --> 01:27:14,090 We tested that, we got a fatigue allowable from acoustics and then we degraded it analytically 1254 01:27:14,090 --> 01:27:17,449 for combined mechanical and combined thermal. 1255 01:27:17,449 --> 01:27:21,090 We did that and said also we know that it's probably not going to fail on the first flight 1256 01:27:21,090 --> 01:27:22,190 so we'll do some inspections. 1257 01:27:22,190 --> 01:27:24,550 Tom, let me just make a comment. 1258 01:27:24,550 --> 01:27:26,600 He made it sound a lot simpler than it was. 1259 01:27:26,600 --> 01:27:31,409 One thing that's important, whenever you do a project or you're in charge of something, 1260 01:27:31,409 --> 01:27:35,389 you don't want to have yes people around you. 1261 01:27:35,389 --> 01:27:38,929 You want to have people that say you're not doing it right. 1262 01:27:38,929 --> 01:27:39,489 And it didn't go down that simple. 1263 01:27:39,489 --> 01:27:41,219 They were not yes people, believe me. 1264 01:27:41,219 --> 01:27:45,190 They were certainly not yes, sir, we're going to go do this. 1265 01:27:45,190 --> 01:27:49,080 That's very important. 1266 01:27:49,080 --> 01:27:52,429 It's a wonder we still speak to one another. 1267 01:27:52,429 --> 01:27:53,309 [LAUGHTER] I'm sorry. 1268 01:27:53,309 --> 01:27:54,940 I don't know what a test article is. 1269 01:27:54,940 --> 01:27:55,770 It's a test specimen. 1270 01:27:55,770 --> 01:28:00,850 If you wanted to put so much mass in here and you weren't sure whether this seam was 1271 01:28:00,850 --> 01:28:01,320 going to work. 1272 01:28:01,320 --> 01:28:03,210 You just put that much mass in here. 1273 01:28:03,210 --> 01:28:05,940 You add a little bit more to it and you see if that seam breaks. 1274 01:28:05,940 --> 01:28:07,780 That's your test article. 1275 01:28:07,780 --> 01:28:10,870 That's what it is, just a test specimen, test article. 1276 01:28:10,870 --> 01:28:19,139 But that's a good point because, don't forget, we start off with two entire $100 million 1277 01:28:19,139 --> 01:28:22,870 test articles for static test and for fatigue test. 1278 01:28:22,870 --> 01:28:24,830 Not counting acoustic fatigue. 1279 01:28:24,830 --> 01:28:26,580 That was just mechanical fatigue. 1280 01:28:26,580 --> 01:28:30,300 As we got into it we said we don't need that. 1281 01:28:30,300 --> 01:28:34,750 Did the Challenger's mission life drop because of the test? 1282 01:28:34,750 --> 01:28:35,880 No. 1283 01:28:35,880 --> 01:28:39,080 As a matter of fact, that's a very good question. 1284 01:28:39,080 --> 01:28:44,580 That was one of the questions that was asked by the investigation is what's different about 1285 01:28:44,580 --> 01:28:45,920 this vehicle than any other vehicles? 1286 01:28:45,920 --> 01:28:47,489 Well, it was a static test article. 1287 01:28:47,489 --> 01:28:55,650 And we showed ad nauseam that had nothing to do with the failure of Challenger. 1288 01:28:55,650 --> 01:29:02,460 The leading edge was not -- Oh, no, excuse me. 1289 01:29:02,460 --> 01:29:03,780 I'm off on Columbia now. 1290 01:29:03,780 --> 01:29:08,420 No, it didn't have anything to do with it. 1291 01:29:08,420 --> 01:29:16,760 As a matter of fact, this is getting into detailed details now, when you apply above 1292 01:29:16,760 --> 01:29:25,320 a limit load on a vehicle like we did on Challenger it puts a lot of the joints in residual compression. 1293 01:29:25,320 --> 01:29:29,370 There is compression at the joint just as you load it and you unload it. 1294 01:29:29,370 --> 01:29:35,320 And residual compression increases the fatigue life of the vehicle. 1295 01:29:35,320 --> 01:29:40,219 And the reason it does is because fatigue is the function of tensile cycles, not compressive 1296 01:29:40,219 --> 01:29:42,630 cycles normally. 1297 01:29:42,630 --> 01:29:49,719 When McDonnell Douglas tested a DC-10 and they proof load a vehicle, it carries a premium 1298 01:29:49,719 --> 01:29:55,610 on the selling price for that because it theoretically has a longer life than one that hasn't been 1299 01:29:55,610 --> 01:29:56,380 loaded. 1300 01:29:56,380 --> 01:29:57,550 Good question. 1301 01:29:57,550 --> 01:30:00,520 Tom, one more question. 1302 01:30:00,520 --> 01:30:01,260 Yeah. 1303 01:30:01,260 --> 01:30:04,469 How much did an increase in computer processing speed and availability allow you to do these 1304 01:30:04,469 --> 01:30:09,889 extrapolations and like do the thermal testing just analytically? 1305 01:30:09,889 --> 01:30:15,130 Was that a key factor? 1306 01:30:15,130 --> 01:30:16,830 You mean how much as it increased? 1307 01:30:16,830 --> 01:30:20,750 Well, how much did it increase between like, say, Apollo and designing the Shuttle. 1308 01:30:20,750 --> 01:30:22,719 Not a whole lot. 1309 01:30:22,719 --> 01:30:29,080 As far as the analytical capabilities of the finite element models and all, you could get 1310 01:30:29,080 --> 01:30:31,710 more detail through simplification. 1311 01:30:31,710 --> 01:30:34,159 There are more elements available, let me put it that way. 1312 01:30:34,159 --> 01:30:39,350 But as far as the crunching capability, it increased somewhat but we were still, you 1313 01:30:39,350 --> 01:30:43,850 know, if you have to go from here to here, we were about here. 1314 01:30:43,850 --> 01:30:46,420 That isn't a quantitative answer for you, but we're still a long way. 1315 01:30:46,420 --> 01:30:48,590 We basically used mainframes, and we did have the NASTRAN model. 1316 01:30:48,590 --> 01:30:51,389 Yeah, we had NASTRAN. 1317 01:30:51,389 --> 01:30:59,889 But NASTRAN didn't have, on a large model like that, the large capability for structural 1318 01:30:59,889 --> 01:31:00,550 loads and thermal loads. 1319 01:31:00,550 --> 01:31:08,350 But you used to put your cards in one day and it would take a couple days before you 1320 01:31:08,350 --> 01:31:09,040 got your answer. 1321 01:31:09,040 --> 01:31:17,150 To do a complete load cycle on this vehicle for internal loads it was something like three 1322 01:31:17,150 --> 01:31:20,120 months it would take us to do that. 1323 01:31:20,120 --> 01:31:27,590 And so it was quite [OVERLAPPING VOICES]. 1324 01:31:27,590 --> 01:31:28,219 That's another story. 1325 01:31:28,219 --> 01:31:30,889 Thermal protection system. 1326 01:31:30,889 --> 01:31:32,030 Change gears now. 1327 01:31:32,030 --> 01:31:36,309 Let's talk about the thing that protects the vehicle. 1328 01:31:36,309 --> 01:31:44,170 Now I'm going to switch back and go back to get ready to proceed toward preliminary design. 1329 01:31:44,170 --> 01:31:46,650 What were the requirements on the thermal protection system? 1330 01:31:46,650 --> 01:31:52,820 It had to protect the vehicle from max temperatures like about 2800 degrees on the surface, reusable 1331 01:31:52,820 --> 01:31:56,300 100 times, it had to be lightweight and had to be cost-effective. 1332 01:31:56,300 --> 01:31:58,489 Pretty simple high-level requirements. 1333 01:31:58,489 --> 01:31:58,600 And Dr. 1334 01:31:58,600 --> 01:32:06,790 Bob Ried will talk to you about the things that they derived as far as the aerothermal 1335 01:32:06,790 --> 01:32:11,260 in this and how it became that, but it was a given to us. 1336 01:32:11,260 --> 01:32:13,050 What did we know about this thing? 1337 01:32:13,050 --> 01:32:17,190 Well, we had some ablative TPS experience from Apollo. 1338 01:32:17,190 --> 01:32:24,000 Gemini had some metallic TPS on it primarily Rene 41 and some other exotic materials. 1339 01:32:24,000 --> 01:32:29,510 Mercury had an ablative TPS, but they weren't reusable. 1340 01:32:29,510 --> 01:32:36,179 They were hot structure designs which existed but that we didn't have materials that could 1341 01:32:36,179 --> 01:32:41,010 carry the load at temperature such that it could be a fully hot structural design, and 1342 01:32:41,010 --> 01:32:43,100 that was extremely complex. 1343 01:32:43,100 --> 01:32:51,309 Metallic TPS, we could get there theoretically with some fairly exotic materials called columbium 1344 01:32:51,309 --> 01:32:59,679 and Rene 41 and some other things, but the devil is in the detail in that. 1345 01:32:59,679 --> 01:33:03,850 Let me tell you a story about that. 1346 01:33:03,850 --> 01:33:07,719 We were looking at some Haynes 188 panels. 1347 01:33:07,719 --> 01:33:13,940 And so we had a test article, a big panel about the size of the desk that you're sitting 1348 01:33:13,940 --> 01:33:19,889 at, any one of you there, and it was corrugated so that it could expand and contract. 1349 01:33:19,889 --> 01:33:26,610 And it was good for 1800 degrees, so we tested it to 1800 degrees in the center of the panel 1350 01:33:26,610 --> 01:33:27,489 multiple times. 1351 01:33:27,489 --> 01:33:34,370 And it had a frame around it where the panel could move around because it needed to, to 1352 01:33:34,370 --> 01:33:36,760 be able to thermally expand. 1353 01:33:36,760 --> 01:33:42,780 And the center of the panel was 1800 degrees, the edge of the panel where the heat sink 1354 01:33:42,780 --> 01:33:47,080 was, was 40 degrees lower temperature than the center. 1355 01:33:47,080 --> 01:33:54,940 And the panel floated within a gap maybe about like that, so it could move around pretty 1356 01:33:54,940 --> 01:33:55,580 good. 1357 01:33:55,580 --> 01:34:00,840 But what it also did, with that temperature differential of 40 degrees, we got something 1358 01:34:00,840 --> 01:34:02,699 called creep buckling. 1359 01:34:02,699 --> 01:34:08,389 The structure expanded and crept and deformed permanently. 1360 01:34:08,389 --> 01:34:12,460 Had we flown that vehicle, had we designed a vehicle like that, what that would have 1361 01:34:12,460 --> 01:34:19,320 done is would have allowed plasma to flow through the shingles, if you will, and into 1362 01:34:19,320 --> 01:34:20,260 the structure. 1363 01:34:20,260 --> 01:34:23,530 And that's exactly what happened in Columbia. 1364 01:34:23,530 --> 01:34:28,880 Letting the hot plasma gas get in the vehicle, you cannot stand it. 1365 01:34:28,880 --> 01:34:31,070 It's the details about that. 1366 01:34:31,070 --> 01:34:33,290 We said we're not going to go with a metallic design. 1367 01:34:33,290 --> 01:34:35,540 Plus, if you scratch it, it oxidizes. 1368 01:34:35,540 --> 01:34:38,870 And, if it oxidizes, then it can fail. 1369 01:34:38,870 --> 01:34:46,969 So we went with something that was just coming online, and that was a fused silica material. 1370 01:34:46,969 --> 01:34:54,260 And fused silica is pure sand, pure silica material. 1371 01:34:54,260 --> 01:34:56,679 That's all in the world it is. 1372 01:34:56,679 --> 01:35:04,670 The process is you make it into a fibrous structure, if you will. 1373 01:35:04,670 --> 01:35:06,550 Fibrous material is a better term. 1374 01:35:06,550 --> 01:35:10,500 A fibrous material that is mostly air. 1375 01:35:10,500 --> 01:35:13,540 It is about the same density as balsa wood. 1376 01:35:13,540 --> 01:35:21,330 It has an ultimate strength of about 12 psi, tensile load is about all that it can take, 1377 01:35:21,330 --> 01:35:24,969 but it has a thermal performance that is fantastic. 1378 01:35:24,969 --> 01:35:36,889 As you will recall this chart here, when you look at LI-1500, is what that was with aluminum, 1379 01:35:36,889 --> 01:35:42,330 and that's what we went with, we used this same characterization to decide what the material 1380 01:35:42,330 --> 01:35:49,909 we were going to use was on the vehicle from a weight standpoint and a cost standpoint. 1381 01:35:49,909 --> 01:36:01,239 The way the tiles work thermally like this is the low strength brittle, almost like glassy 1382 01:36:01,239 --> 01:36:10,080 material, it's a ceramic, is coated with literally a glass coating on the outside about 60-thousandths 1383 01:36:10,080 --> 01:36:12,659 of an inch thick and it's black. 1384 01:36:12,659 --> 01:36:19,650 As the vehicle comes back in and dissipates its energy through drag and heating, 90% of 1385 01:36:19,650 --> 01:36:25,590 the heat is radiated away from the vehicle, 10% of it goes into the vehicle. 1386 01:36:25,590 --> 01:36:32,119 But this is such a good thermal isolator, a poor thermal conductor, by the time the 1387 01:36:32,119 --> 01:36:39,889 heat gets to the vehicle, the vehicle is back into an atmosphere where it's not heating 1388 01:36:39,889 --> 01:36:40,630 anymore. 1389 01:36:40,630 --> 01:36:47,739 That dictated the thickness of these tiles, of this silica material. 1390 01:36:47,739 --> 01:37:00,460 The vehicle has got almost 21,000 tiles on it, and they vary anywhere from a half inch 1391 01:37:00,460 --> 01:37:03,949 thick up to about three inches thick. 1392 01:37:03,949 --> 01:37:08,800 It's sculptured to stay within the mol line because the aerodynamicist told us what it 1393 01:37:08,800 --> 01:37:09,510 has to be. 1394 01:37:09,510 --> 01:37:18,880 And so what we did was sculptured the TPS so that we didn't have any more than we needed. 1395 01:37:18,880 --> 01:37:21,420 Great job by all the thermal analysts. 1396 01:37:21,420 --> 01:37:23,719 I mean they did this fantastic. 1397 01:37:23,719 --> 01:37:27,090 I want to mention, when that says 9 pound or 22 pound tiles, that's not the weight of 1398 01:37:27,090 --> 01:37:29,550 each individual tile, that's the density per cubic foot. 1399 01:37:29,550 --> 01:37:29,699 Per cubic foot, correct. 1400 01:37:29,699 --> 01:37:29,809 Thank you, Jeff. 1401 01:37:29,809 --> 01:37:33,239 What was the footnote about Columbia on that? 1402 01:37:33,239 --> 01:37:38,230 On the last chart, Tom, there is a footnote about the difference in the Columbia. 1403 01:37:38,230 --> 01:37:47,130 Let me come back to that in just one second. 1404 01:37:47,130 --> 01:37:52,250 What I want to talk to you about right now, this is something I had from some old material. 1405 01:37:52,250 --> 01:37:54,050 I was just trying to get a characterization. 1406 01:37:54,050 --> 01:37:58,909 What that said is on Columbia there was an infrared sensor as an experiment. 1407 01:37:58,909 --> 01:38:02,949 So, the number of tiles varied on that vehicle compared to all the other vehicles because 1408 01:38:02,949 --> 01:38:06,570 of this infrared thing at the top of the vertical stabilizer. 1409 01:38:06,570 --> 01:38:10,699 I should have cut that off. 1410 01:38:10,699 --> 01:38:11,650 You're reading too close. 1411 01:38:11,650 --> 01:38:22,880 [LAUGHTER] We thought let's figure out how to take this fragile material and put it on 1412 01:38:22,880 --> 01:38:26,219 this aluminum structure which has a high thermal coefficient of expansion. 1413 01:38:26,219 --> 01:38:30,809 The tiles have almost a zero thermal coefficient expansion. 1414 01:38:30,809 --> 01:38:33,199 We said we've got to isolate that. 1415 01:38:33,199 --> 01:38:39,030 We put a strain isolation pad [UNINTELLIGIBLE PHRASE]. 1416 01:38:39,030 --> 01:38:44,659 Why do they vary in density? 1417 01:38:44,659 --> 01:38:45,600 Yeah. 1418 01:38:45,600 --> 01:38:50,790 Because primarily for strength, for one of the things. 1419 01:38:50,790 --> 01:38:56,199 And the LI-2200 was a little bit higher temperature capability. 1420 01:38:56,199 --> 01:39:00,730 And I don't remember [OVERLAPPING VOICES]. 1421 01:39:00,730 --> 01:39:06,940 But it had a little higher peak temperature capability. 1422 01:39:06,940 --> 01:39:14,630 And that was dictated by what one of the failure modes of a tile was if you exceed the temperature 1423 01:39:14,630 --> 01:39:15,960 too much it starts slumping. 1424 01:39:15,960 --> 01:39:19,619 I don't want to say melting but it begins to distort. 1425 01:39:19,619 --> 01:39:26,580 And a LI-2200 didn't distort to the same extent that a LI-900 tile did. 1426 01:39:26,580 --> 01:39:37,980 We said let's isolate the structure here from this material up here which is required to 1427 01:39:37,980 --> 01:39:42,119 keep from failing all these tiles, so we put something between them. 1428 01:39:42,119 --> 01:39:47,679 It was just a very loosely woven felt material. 1429 01:39:47,679 --> 01:39:53,230 Now we proved that the aluminum can expand all it wants to, or within limits, we looked 1430 01:39:53,230 --> 01:39:59,550 at it realistically, and that the tile was OK, except the tile couldn't be too large 1431 01:39:59,550 --> 01:40:02,320 because of this relative expansion and contraction. 1432 01:40:02,320 --> 01:40:05,719 So, that dictated the size of the tile. 1433 01:40:05,719 --> 01:40:08,570 We literally pre-cracked them, if you will. 1434 01:40:08,570 --> 01:40:12,139 We put expansion joints is another way of looking at it. 1435 01:40:12,139 --> 01:40:17,889 A typical tile is 6 inches by 6 inches when it gets into the highly heated area. 1436 01:40:17,889 --> 01:40:22,489 Now all of a sudden we've got some room for the title to move relative to one another, 1437 01:40:22,489 --> 01:40:26,550 structure to move underneath it because of the strain isolation pad. 1438 01:40:26,550 --> 01:40:29,540 And we said, viola, we've got this problem fixed. 1439 01:40:29,540 --> 01:40:31,630 We're good to go.. 1440 01:40:31,630 --> 01:40:50,960 We said we've got 25,000 of these tiles that we now have to certify that they're good to 1441 01:40:50,960 --> 01:40:51,540 go for the vehicle. 1442 01:40:51,540 --> 01:40:53,920 There were gaps between the tiles? 1443 01:40:53,920 --> 01:40:54,309 Correct. 1444 01:40:54,309 --> 01:40:59,869 But, when you re-enter, do the tiles expand so that there are no gaps? 1445 01:40:59,869 --> 01:41:00,260 No. 1446 01:41:00,260 --> 01:41:06,909 What we do is make sure that the gap can just close but not close such that you're loading 1447 01:41:06,909 --> 01:41:09,340 one tile relative to the other. 1448 01:41:09,340 --> 01:41:10,559 That set the gap. 1449 01:41:10,559 --> 01:41:16,989 And, if during manufacturing which is not that precise, if the gap was too large we 1450 01:41:16,989 --> 01:41:18,679 just stuck a gap filler in. 1451 01:41:18,679 --> 01:41:20,420 Not the one that was on the last vehicle. 1452 01:41:20,420 --> 01:41:21,429 It's a different kind of gap fill. 1453 01:41:21,429 --> 01:41:28,780 Just a piece of Nomex or SIP material strain isolation pad coated with rubber or with RTV, 1454 01:41:28,780 --> 01:41:32,989 and we stuck it in between the tile just to reduce the flow if the gap was too large. 1455 01:41:32,989 --> 01:41:40,480 So there is no chance that you would have hot plasma coming in between them? 1456 01:41:40,480 --> 01:41:42,340 Yes, there is a chance you can have plasma going through there if the gap is too large. 1457 01:41:42,340 --> 01:41:44,750 We had a very specific requirement. 1458 01:41:44,750 --> 01:41:48,530 I think it was like 90-thousandths of an inch between tiles. 1459 01:41:48,530 --> 01:41:54,650 And if it were, say, 130-thousandths of an inch, as installed because of tolerance buildup 1460 01:41:54,650 --> 01:42:00,350 and all that kind of stuff, then what we did was stuck a plasma flow preclude, if you will, 1461 01:42:00,350 --> 01:42:06,440 a gap filler between those to stop the plasma flow from getting between the tiles. 1462 01:42:06,440 --> 01:42:13,420 And we had some experience where we lost some gap fillers, plasma flowed between the tiles, 1463 01:42:13,420 --> 01:42:17,869 caused excessive heating on the tiles and started causing them to slump and melt a little 1464 01:42:17,869 --> 01:42:22,530 bit, did a little bit of structural deformation but nothing significant. 1465 01:42:22,530 --> 01:42:27,929 Losing gap filler was a turnaround issue, not a safety of flight issue. 1466 01:42:27,929 --> 01:42:29,309 We made sure of that. 1467 01:42:29,309 --> 01:42:29,670 Excellent question. 1468 01:42:29,670 --> 01:42:33,170 This is more of a general question, but I'm wondering if since then anybody has done any 1469 01:42:33,170 --> 01:42:37,199 work to find a material that could accomplish both tasks, the structure and the thermal 1470 01:42:37,199 --> 01:42:46,030 protection rather than having to deal with these types of issues. 1471 01:42:46,030 --> 01:42:51,380 That was back to one of my trades were we said let's take that approach and see if we 1472 01:42:51,380 --> 01:42:57,389 cannot design a vehicle that can take the temperature and the loads, too, both. 1473 01:42:57,389 --> 01:42:59,130 There was no material that existed. 1474 01:42:59,130 --> 01:43:04,559 I don't think a material exists today that I know of to be worked to a high enough stress 1475 01:43:04,559 --> 01:43:08,619 that you can keep the weight down to have those kinds of temperatures and to be worked 1476 01:43:08,619 --> 01:43:10,020 at a high temperature. 1477 01:43:10,020 --> 01:43:18,460 I think on the X-33 design they were talking once again of trying to make it out of a metallic 1478 01:43:18,460 --> 01:43:18,710 structure. 1479 01:43:18,710 --> 01:43:21,469 Part of it was structure and part of it was tons. 1480 01:43:21,469 --> 01:43:28,350 But we never got to the point of being able to fly and test it. 1481 01:43:28,350 --> 01:43:35,389 But they also were using a thermal isolation system like tiles over part of the vehicle 1482 01:43:35,389 --> 01:43:36,500 on the X-33. 1483 01:43:36,500 --> 01:43:51,110 The Buran, which was the Soviet copy of the Shuttle, they were very anxious to get away 1484 01:43:51,110 --> 01:43:53,369 from the expense of the tiles. 1485 01:43:53,369 --> 01:43:54,540 And they ended up with a thermal protection system not very different than what you said. 1486 01:43:54,540 --> 01:43:55,350 You mean they had tiles? 1487 01:43:55,350 --> 01:43:55,940 Yeah. 1488 01:43:55,940 --> 01:44:00,510 As a matter of fact, I remember they were more like bigger blankets. 1489 01:44:00,510 --> 01:44:01,409 That's a good point, Larry. 1490 01:44:01,409 --> 01:44:03,480 I was about to skip over it. 1491 01:44:03,480 --> 01:44:08,880 I said they were typically 6 inches where they were really thick, but in other areas 1492 01:44:08,880 --> 01:44:14,690 we made like 12 or 15 inch tiles that were very thin. 1493 01:44:14,690 --> 01:44:22,400 And the reason we could do that is we decided if they crack it doesn't matter because the 1494 01:44:22,400 --> 01:44:26,929 gap wouldn't be large enough for the plasma flow to go through there and it would simply 1495 01:44:26,929 --> 01:44:27,869 be a self-relieving. 1496 01:44:27,869 --> 01:44:33,619 So, we tried to reduce the cost of manufacturing by making some of these tiles larger. 1497 01:44:33,619 --> 01:44:35,670 And I will show you that in just a second. 1498 01:44:35,670 --> 01:44:53,290 I'm going to skip forward here and show you one thing.. 1499 01:44:53,290 --> 01:44:57,960 That's 50-thousandths of an inch. 1500 01:44:57,960 --> 01:45:08,940 The allowable for the tile was 12 psi. 1501 01:45:08,940 --> 01:45:12,230 The ultimate stress was 12 psi. 1502 01:45:12,230 --> 01:45:14,610 The allowable stress was about 8 psi. 1503 01:45:14,610 --> 01:45:19,219 And that's with the total loads combined on the tile. 1504 01:45:19,219 --> 01:45:25,360 What do you have to consider in one of these 25,000 tiles that you have to assure is not 1505 01:45:25,360 --> 01:45:26,230 going to come off the vehicle? 1506 01:45:26,230 --> 01:45:32,570 Remember I said when we looked in the early phase studies of the vehicle we were looking 1507 01:45:32,570 --> 01:45:34,440 at wing loads and stuff like that? 1508 01:45:34,440 --> 01:45:39,139 Then we got into how is the wing going to carry the load into the fuselage to the spar 1509 01:45:39,139 --> 01:45:40,619 and what was our design trade on that? 1510 01:45:40,619 --> 01:45:45,630 Those were sort of macro and semi-macro systems engineering studies. 1511 01:45:45,630 --> 01:45:47,409 Now we're into a micro. 1512 01:45:47,409 --> 01:45:51,869 Now we've got this little critical part, 6 inches by 6 inches. 1513 01:45:51,869 --> 01:45:54,690 Lose any one of about 10,000 and you lose the vehicle. 1514 01:45:54,690 --> 01:45:59,489 It's got an 8 psi allowable strength. 1515 01:45:59,489 --> 01:46:01,480 We said well, that's no big deal. 1516 01:46:01,480 --> 01:46:04,239 What are all the environments on this thing? 1517 01:46:04,239 --> 01:46:09,429 We started looking at pre-liftoff, liftoff, ascent, et cetera. 1518 01:46:09,429 --> 01:46:12,770 There is always something called mismatch. 1519 01:46:12,770 --> 01:46:18,219 When you take something that is not perfectly smooth and you bond something to it and they 1520 01:46:18,219 --> 01:46:25,520 are not to the same flatness, if you will, there is going to be a stress induced into 1521 01:46:25,520 --> 01:46:26,219 both parts of those. 1522 01:46:26,219 --> 01:46:30,510 Well, the structure doesn't care about that stress but this little 8 psi allowable tile 1523 01:46:30,510 --> 01:46:30,790 does. 1524 01:46:30,790 --> 01:46:38,050 It says we cannot exceed about 19-thousandths of an inch under one of these tiles for this 1525 01:46:38,050 --> 01:46:39,869 to happen. 1526 01:46:39,869 --> 01:46:43,010 There is ignition over pressure during ascent. 1527 01:46:43,010 --> 01:46:47,320 There is acoustic and vibration and that kind of stuff that has to be considered. 1528 01:46:47,320 --> 01:46:53,480 On ascent there are gradients because of shock moving across the tile. 1529 01:46:53,480 --> 01:46:54,790 There is internal pressure. 1530 01:46:54,790 --> 01:46:58,429 There is skin friction and drag on the tile, so you've got to consider that. 1531 01:46:58,429 --> 01:47:02,889 You have to consider the dynamics, the inertial loads induced in it. 1532 01:47:02,889 --> 01:47:06,710 And the out of plane deflection is now the vehicle flying. 1533 01:47:06,710 --> 01:47:08,030 The structure is deforming. 1534 01:47:08,030 --> 01:47:10,210 So, you've got to consider that. 1535 01:47:10,210 --> 01:47:15,650 Now you can see you've got 25,000 tiles with all these combinations of load conditions 1536 01:47:15,650 --> 01:47:20,750 so how in the hell do you design that? 1537 01:47:20,750 --> 01:47:22,480 This is the characterization of it. 1538 01:47:22,480 --> 01:47:33,590 This is what happens with a structural deformation of like 10-thousandths of an inch deflection 1539 01:47:33,590 --> 01:47:35,010 underneath a tile. 1540 01:47:35,010 --> 01:47:38,050 With that kind of formation it causes 1 psi. 1541 01:47:38,050 --> 01:47:40,420 And it linear almost. 1542 01:47:40,420 --> 01:47:44,670 So, 20-thousandths of an inch deflection is going to cause 2 psi. 1543 01:47:44,670 --> 01:47:50,260 Well, 2 psi is not a lot but it's a quarter of your allowable. 1544 01:47:50,260 --> 01:47:52,389 We said we've got to consider that. 1545 01:47:52,389 --> 01:47:57,880 We have to understand what is happening to this structure as you fly it, a condition. 1546 01:47:57,880 --> 01:48:03,170 This is a free body, if you will, of the pressure distribution on a tile. 1547 01:48:03,170 --> 01:48:06,190 It has internal pressure within the tile. 1548 01:48:06,190 --> 01:48:10,230 It has a pressure differential on the outside of the tile because of a shockwave moving 1549 01:48:10,230 --> 01:48:14,480 across it because of the pressure as it varies around the vehicle. 1550 01:48:14,480 --> 01:48:18,360 So, you have to consider all of that. 1551 01:48:18,360 --> 01:48:26,130 We did all that and said we've got a problem, because what happened was all of a sudden 1552 01:48:26,130 --> 01:48:31,559 our allowable on our tile was decreased by half. 1553 01:48:31,559 --> 01:48:36,040 And this was not good. 1554 01:48:36,040 --> 01:48:39,949 We screwed up, in the systems engineering point of view, when we did this. 1555 01:48:39,949 --> 01:48:46,830 Remember we put the strain isolation pad underneath the tile and we did all these other loads 1556 01:48:46,830 --> 01:48:47,520 on it? 1557 01:48:47,520 --> 01:48:53,460 What we forgot, or what we didn't realize was this strain isolation pad had little stiff 1558 01:48:53,460 --> 01:49:00,880 spots in it because of the way it was stitched to keep the strain isolation pad together. 1559 01:49:00,880 --> 01:49:05,570 And every stiff spot acted like a hard point. 1560 01:49:05,570 --> 01:49:10,429 Now, when you take a tile and you put external loads on it and there is a stress concentration 1561 01:49:10,429 --> 01:49:14,989 on each one of those things, that stress concentration had an amplification of two. 1562 01:49:14,989 --> 01:49:18,900 All of a sudden our allowable were decreased by a factor of two. 1563 01:49:18,900 --> 01:49:22,170 And we thought we have a major problem. 1564 01:49:22,170 --> 01:49:26,760 This is when Aaron and I got to know one another better than we ever wanted to. 1565 01:49:26,760 --> 01:49:28,929 We met every day on this thing. 1566 01:49:28,929 --> 01:49:31,820 We had tiles bonded all over the vehicle. 1567 01:49:31,820 --> 01:49:33,380 Necessity was the mother of invention. 1568 01:49:33,380 --> 01:49:41,099 What we had to do was dissipate this stress concentration. 1569 01:49:41,099 --> 01:49:45,820 We said we'll put a plate underneath it, a graphite/epoxy plate or something like that. 1570 01:49:45,820 --> 01:49:47,690 That would have added a lot of weight to the vehicle. 1571 01:49:47,690 --> 01:49:55,639 Glen Ecord, a materials guy came up with the idea in the lab one weekend, he took silica 1572 01:49:55,639 --> 01:50:00,840 powder in water and just painted it on the bottom of the tile. 1573 01:50:00,840 --> 01:50:06,369 What it did was fill all the pours in the tile for about three-sixteenths of an inch. 1574 01:50:06,369 --> 01:50:11,690 And just compacted themselves in there. 1575 01:50:11,690 --> 01:50:18,929 And that was an inherent capability of a tile with that powder packed in it, if you will, 1576 01:50:18,929 --> 01:50:20,360 that doubled the strength of the tile. 1577 01:50:20,360 --> 01:50:24,380 What it did is it dissipated the load from being concentrated into the tile. 1578 01:50:24,380 --> 01:50:31,270 So, without any weight, some cost, we had to pull some tiles off the vehicle and densify 1579 01:50:31,270 --> 01:50:31,449 them. 1580 01:50:31,449 --> 01:50:33,710 Now all tiles are densified. 1581 01:50:33,710 --> 01:50:38,780 I meant to bring one to show you today but I didn't. 1582 01:50:38,780 --> 01:50:41,929 Analytically, we went through 25,000 tiles. 1583 01:50:41,929 --> 01:50:46,280 Here was our factor of safety distribution over the entire vehicle. 1584 01:50:46,280 --> 01:50:55,230 We said we're good for that, but the thing we don't know is if the tile is really bonded 1585 01:50:55,230 --> 01:50:57,860 on the vehicle like it should be. 1586 01:50:57,860 --> 01:51:01,409 We said we can fix that problem. 1587 01:51:01,409 --> 01:51:02,250 We will verify it. 1588 01:51:02,250 --> 01:51:09,710 We will pull on every tile and make sure that it has a capability of the maximum expected 1589 01:51:09,710 --> 01:51:12,190 mechanical load that it is going to see. 1590 01:51:12,190 --> 01:51:14,440 And so we pulled on every tile. 1591 01:51:14,440 --> 01:51:20,270 And John Yardley, being an old stress guy, says let me ask you a question. 1592 01:51:20,270 --> 01:51:25,040 When you pull on every tile, how do you know you haven't induced more damage and decreased 1593 01:51:25,040 --> 01:51:29,639 the allowable of the title because of your proof test? 1594 01:51:29,639 --> 01:51:30,119 Good question. 1595 01:51:30,119 --> 01:51:31,690 Easy answer. 1596 01:51:31,690 --> 01:51:37,360 We'll put a microphone on every tile and we will characterize the sound of the tile as 1597 01:51:37,360 --> 01:51:43,440 we pull up on it, and we will get a sound allowable, if you will, for proof-testing 1598 01:51:43,440 --> 01:51:43,989 the tile. 1599 01:51:43,989 --> 01:51:46,739 We did that on every tile that had to be proof-tested. 1600 01:51:46,739 --> 01:51:53,290 We had an acoustic emission device, we had a microphone on there, we characterized all 1601 01:51:53,290 --> 01:51:56,760 these tiles and we did it. 1602 01:51:56,760 --> 01:52:03,280 Another little mother's necessity of invention. 1603 01:52:03,280 --> 01:52:04,380 And I'm not going to go through this. 1604 01:52:04,380 --> 01:52:05,550 You'll get a handout of this. 1605 01:52:05,550 --> 01:52:10,219 What this did is said you cannot proof load every tile, every tile is not densified, some 1606 01:52:10,219 --> 01:52:19,330 tiles are thick, some tiles are thin, but prove under no uncertain conditions that you're 1607 01:52:19,330 --> 01:52:20,699 safe to fly. 1608 01:52:20,699 --> 01:52:24,099 We went through this logic on everything. 1609 01:52:24,099 --> 01:52:27,309 Some of these things had gates that said go directly to fly. 1610 01:52:27,309 --> 01:52:28,780 Others we had to go through. 1611 01:52:28,780 --> 01:52:34,449 Others we had to pull off the vehicle and densify and proof load and do a bunch of other 1612 01:52:34,449 --> 01:52:37,909 things to prove that they were OK. 1613 01:52:37,909 --> 01:52:39,349 We got there. 1614 01:52:39,349 --> 01:52:41,080 Now we're into operations. 1615 01:52:41,080 --> 01:52:42,580 We're just about out of time. 1616 01:52:42,580 --> 01:52:43,080 I know. 1617 01:52:43,080 --> 01:52:44,290 I've got three minutes left. 1618 01:52:44,290 --> 01:52:45,639 Can I have all three? 1619 01:52:45,639 --> 01:52:45,849 OK. 1620 01:52:45,849 --> 01:52:49,889 Here is what we did. 1621 01:52:49,889 --> 01:52:53,800 We did some pretty innovative things on this thing, and I think I've shown you some of 1622 01:52:53,800 --> 01:52:54,260 that stuff. 1623 01:52:54,260 --> 01:52:58,290 But what were the surprises we had on the first flight? 1624 01:52:58,290 --> 01:52:59,409 Not very many. 1625 01:52:59,409 --> 01:53:04,730 As we were going uphill, I told you about the plume effect from the engines blocking 1626 01:53:04,730 --> 01:53:09,650 the flow, that causes the pressure distribution on the wing to be different than we designed 1627 01:53:09,650 --> 01:53:09,830 for. 1628 01:53:09,830 --> 01:53:13,050 The center pressure was further aft and outboard. 1629 01:53:13,050 --> 01:53:14,869 That loaded up the wing more. 1630 01:53:14,869 --> 01:53:19,639 It could not fly to the design conditions that we needed to under worse case. 1631 01:53:19,639 --> 01:53:22,270 And I'll tell you what we did on that. 1632 01:53:22,270 --> 01:53:23,639 Well, let me just tell you right now. 1633 01:53:23,639 --> 01:53:30,699 What we did was almost day-of-launch wind analysis, loads analysis for the wings with 1634 01:53:30,699 --> 01:53:36,199 load indicators in the wing to understand what a specific flight regime was going to 1635 01:53:36,199 --> 01:53:37,309 do for that vehicle. 1636 01:53:37,309 --> 01:53:42,500 And we literally designed the trajectories for the first six or eight or ten shuttle 1637 01:53:42,500 --> 01:53:47,980 flights so it stayed within a reduced capability of the vehicle. 1638 01:53:47,980 --> 01:53:50,699 Because we characterized it so well, we could do that. 1639 01:53:50,699 --> 01:53:59,659 The other thing was the overpressure of the vehicle, when the main engines let off there 1640 01:53:59,659 --> 01:54:02,440 was an accumulation of hydrogen gas underneath the vehicle. 1641 01:54:02,440 --> 01:54:10,349 And as soon as the engines fired it ignited that hydrogen and sent a big shockwave up 1642 01:54:10,349 --> 01:54:10,800 the vehicle. 1643 01:54:10,800 --> 01:54:16,909 It could have been pretty bad but it wasn't, so we fixed that by isolating the isolation 1644 01:54:16,909 --> 01:54:19,610 and also burning it off prior to engine ignition. 1645 01:54:19,610 --> 01:54:25,059 And then we got some tile damage from external tank. 1646 01:54:25,059 --> 01:54:26,750 We fixed that. 1647 01:54:26,750 --> 01:54:31,219 After about the second or third flight on the external tank, we changed the foam process 1648 01:54:31,219 --> 01:54:33,590 and controlled that. 1649 01:54:33,590 --> 01:54:36,590 And so those were our only surprises. 1650 01:54:36,590 --> 01:54:42,900 You remember the chart that I showed you of all the combined environments on a tile? 1651 01:54:42,900 --> 01:54:46,880 This is not politically correct what I'm going to say, but I'm going to say it anyway. 1652 01:54:46,880 --> 01:54:51,639 The shockwaves, the pressure, the out of plane deformation, all that, you didn't see debris 1653 01:54:51,639 --> 01:54:54,679 anyplace on that chart. 1654 01:54:54,679 --> 01:54:58,780 Those tiles are not designed for debris, period. 1655 01:54:58,780 --> 01:54:59,929 You can rationalize it. 1656 01:54:59,929 --> 01:55:00,699 You can arm wave it. 1657 01:55:00,699 --> 01:55:02,570 You can statistically analyze it. 1658 01:55:02,570 --> 01:55:06,090 The vehicle is not designed to fly in debris. 1659 01:55:06,090 --> 01:55:10,599 It can take every other thing it's designed for, but it cannot take what it's not designed 1660 01:55:10,599 --> 01:55:11,260 for. 1661 01:55:11,260 --> 01:55:12,909 The engineers today have two choices. 1662 01:55:12,909 --> 01:55:18,670 They can either eliminate the debris from the external tank or, in my judgment, they 1663 01:55:18,670 --> 01:55:22,619 can go back and recertify the tiles for the expected debris. 1664 01:55:22,619 --> 01:55:27,739 And that's probably not too big a deal, but they cannot say we're ready to fly, going 1665 01:55:27,739 --> 01:55:32,010 through a logic matrix like I did, until they do that. 1666 01:55:32,010 --> 01:55:35,010 OK, guys and gals. 1667 01:55:35,010 --> 01:55:36,929 Here are some challenges for you. 1668 01:55:36,929 --> 01:55:42,290 As you go through from the beginning of a program, I would like you to be looking at 1669 01:55:42,290 --> 01:55:48,260 this crew exploration vehicle, what other parameters would you look at other than what 1670 01:55:48,260 --> 01:55:52,699 I've shown you here and what tools would you use? 1671 01:55:52,699 --> 01:55:56,480 On the combined thermal mechanical, I think a lot can be done on that. 1672 01:55:56,480 --> 01:56:00,480 I don't know what all the computing capability is today, but I think that you could really 1673 01:56:00,480 --> 01:56:09,030 simplify and probably decrease the weight of the vehicle by doing that. 1674 01:56:09,030 --> 01:56:10,520 Could they be made more rugged? 1675 01:56:10,520 --> 01:56:11,580 Yeah, they probably could. 1676 01:56:11,580 --> 01:56:14,050 But be careful. 1677 01:56:14,050 --> 01:56:18,559 This is a big systems engineering issue and it's a political issue. 1678 01:56:18,559 --> 01:56:22,449 And I'm going to get off the stage here in one second. 1679 01:56:22,449 --> 01:56:30,199 Should there be a dedicated crew escape system or should the reliability be built in the 1680 01:56:30,199 --> 01:56:31,110 vehicle? 1681 01:56:31,110 --> 01:56:34,570 And I'll promise you that answer is not known. 1682 01:56:34,570 --> 01:56:39,150 It may be known from a political standpoint that you have to have a crew escape system, 1683 01:56:39,150 --> 01:56:40,790 and that's OK. 1684 01:56:40,790 --> 01:56:45,730 If that's a requirement, that's a requirement, but in a total system crew safety reliability 1685 01:56:45,730 --> 01:56:47,559 that's not obvious. 1686 01:56:47,559 --> 01:56:52,980 It depends on what the design is and what the reliability of the constituent elements 1687 01:56:52,980 --> 01:56:54,780 are. 1688 01:56:54,780 --> 01:56:56,360 How would you fix the ET? 1689 01:56:56,360 --> 01:56:59,050 Put shrink wrap all over it. 1690 01:56:59,050 --> 01:57:05,440 Another thing that's not part of the curriculum here is political systems engineering. 1691 01:57:05,440 --> 01:57:09,869 You can have the best engineering design in the world, but if you don't have the political 1692 01:57:09,869 --> 01:57:13,500 support in a program like this it doesn't matter. 1693 01:57:13,500 --> 01:57:19,469 How does political influence come into a systems engineering thing, kind of like the crew escape 1694 01:57:19,469 --> 01:57:19,780 system? 1695 01:57:19,780 --> 01:57:20,080 Thank you. 1696 01:57:20,080 --> 01:57:34,150 [APPLAUSE] Well, that was just super. 1697 01:57:34,150 --> 01:57:38,440 This is hopefully the first of many lectures which will take us to a much greater depth 1698 01:57:38,440 --> 01:57:39,700 [then when we did the shuttle system?].