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Today Dr. Robert Ried, Bob Ried, is going to
talk to us about aerothermodynamics.

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He got a bachelor's in Mechanical Engineering
here at MIT a few years ago, and then went

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on to get a doctorate at Rice University.

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And he has done a lot of things.

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You all have the biographies on the website
so I hope you've looked at that.

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And, like I say, it is better for you to read
it rather than me to take five minutes at

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the beginning just going through it.

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But he has played an important role in developing
both the theory and the practice of atmospheric

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reentry both for Apollo and the Shuttle.

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And, in fact, in many ways the experience
gained through Apollo allowed us to design

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the systems for the Shuttle.

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And so he is actually going to talk about
both Apollo and the Shuttle, comparing and

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contrasting.

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And I think it is going to be a very interesting
opportunity for all of us.

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And I am going to let Professor Cohen say
one or two more words.

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What I want to say is that Dr.

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Ried has done a fantastic job in understanding
aerothermodynamics.

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If you look back on Apollo that was one of
the technologies we really didn't understand.

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Coming in at 36,000 feet per second from the
moon in various atmospheres, what was going

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to happen?

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And, in that era, we had to do a lot of research
and development to understand the methodology

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of doing aerodynamic heating.

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The systems engineering comes in as you heard
Bass Redd talk about the aerodynamics, you

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heard Tom Moser talk about the tile system
or the thermal protection system, and Dr.

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Ried sort of tied that together.

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Because he actually came up with based on
the trajectory you were flying, based on the

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atmosphere, based on the materials that you
had, what the surface temperatures were going

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to be and how you designed the thermal protection
system to withstand those temperatures and

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still maintain the back-face temperature at
a suitable level.

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I have a couple of displays for you, and if
you can start looking at them.

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The first is a specimen that came out of Apollo
10.

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That was a Lunar orbital mission, and it is
a core sample out of an ablative heat shield.

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It shows you the thickness of a thermal protection
system was about two inches, and the depth

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of the char layer is about an inch.

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And we always used to give Dr.

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Ried a hard time, why couldn't we take some
weight out of the heat shield?

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But he always said he never flew the Design
Reference Mission.

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And he will talk about that a little bit.

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So, that is one specimen.

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The other specimen is a tile that flew on
the 102 mission four times, I believe, that

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it got to 2800 degrees Fahrenheit.

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The ablator got to 42,000 degrees Fahrenheit.

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These will give you some examples of what
the results of Dr.

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Ried's work was in terms of designing the
ablator for the Apollo vehicle and the tiles

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for the Shuttle vehicle.

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That is really a systems engineering job.

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I hope you can appreciate understanding the
aerodynamics, understanding the guidance,

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navigation and control trajectory that you
fly and understanding the materials that you're

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going to use.

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That is really a systems engineering problem.

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Let me now turn it over to Dr.

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Ried to put all the details together for you.

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Thank you.

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Good morning.

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We are going to try to cover an awful lot
of ground here in short order.

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First, I am going to try to go through aerothermodynamics
in terms of the discipline and give you an

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understanding.

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I am going to try to relate to what you've
had in your basic heat transfer and fluid

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mechanics courses to actual application and
where the technology is today.

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I am also going to, as Aaron said, go back
to Apollo which is really where the rubber

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hit the road in terms of being able to enter
things at those types of velocities.

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And then I will get into how that affected
the Shuttle.

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And the Shuttle is a revolutionary system
in many ways, but particularly in terms of

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the technology associated with aerothermodynamics,
computational fluid dynamics in particular.

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And I am really going to talk about three
levels of aerothermodynamics which I will

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explain as I get into it.

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And then I will try to get into the systems
engineering, as Aaron mentioned.

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And, in fact, one of the major differences
between Apollo and Shuttle, which we had to

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accomplish, is a significant accomplishment
in systems engineering which I hope to get

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into.

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First, I don't think people generally appreciate
the perimeters of what we're working with.

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Traveling at orbital velocity due east 25,000
feet per second, that is about five miles

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a second.

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And the Orbiter is about a quarter of a million
pounds.

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And, I am sorry, I am going to use a lot of
English units.

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A quarter of a million pounds is a pretty
good sized system.

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Picture that at Logan Airport and one second
later in this classroom.

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That is five miles a second.

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Another way of looking at it is that is about
125 tons.

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If you take a supertanker, about a half a
million ton, and just convert the energy,

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that supertanker would be traveling at 250
knots.

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That is the energy that we have to dissipate.

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Norm Augustine introduced the concept of rocket
scientist.

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Our job was to dissipate that energy.

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If I was coming back from the moon that supertanker,
which is about a billion pounds, a half million

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ton, would be traveling about 400 knots.

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Almost twice the amount of energy.

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Actually, the whole problem was relatively
simple.

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Basic parameters are first free stream density
of the air that you're flowing into, the velocity

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that you're moving at and unit area that the
mass flux is just density times velocity.

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The momentum that that air has relative to
you per unit mass is the velocity, so this

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is the momentum flux which basically is the
pressure to a very high accuracy.

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The energy that the gas has relative to you
is one-half V squared.

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And so we're looking at an energy flux
coming to the vehicle one-half rho VQ.

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Those are very important parameters.

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Now, I am going to focus on accuracy and not
on precision.

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People have gotten lost in details in terms
of getting parameters.

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If you've got density and velocity, you basically
have the gas parameters with some major exceptions

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which I will get into.

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And that is relative to the equation of state,
if you want, the constitutive relations.

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The other thing is the geometry which is the
major difference between the Apollo and the

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Shuttle.
All right.

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Now, let's go back to the Apollo system, a
nice, simple system flying at angle-of-attack.

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One of the first problems that I was introduced
to was a newspaper publication saying this

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system is going to burn up.

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It is going to burn up from the thermal radiation
from the gas cap.

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Now, let's consider coming back initially
at 36,000 feet per second.

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Peak heating is around 33,000 feet per second,
10 kilometers per second if you want.

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We've got a shock free stream density.

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At some point, we get to ideally equilibrium
air.

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Out here you're basically at ambient temperature
of ten to the minus four, ten to the minus

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three atmosphere density.

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Here, once you get to equilibrium, you're
operating at a temperature of about ten to

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the fourth degrees ranking.

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The effective black-body radiation from the
sun is 10,000 degrees ranking.

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The distribution in terms of the spectrum.

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That is the temperature of the gas at equilibrium.

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At the wall of the vehicle perhaps 6,000 degrees
ranking.

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And we will get into that a little bit.

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But what happened was there were experiments
done in shock tubes indicating some very intense

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radiation.

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This gas is hot enough to radiate.

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And, in fact, at the peak heating about half
of the heating is from the gas radiation.

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The gas is ten centimeters thick, four inches,
and yet it is hot enough and radiates enough

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that the heat transfer from that radiation
is almost comparable to the convective heating.

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The load is another matter.

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But what happened is out here you've got molecular
oxygen and nitrogen just sitting there at

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ambient temperature bouncing along.

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All of a sudden it is swept up by this snowplow.

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The degrees of freedom basically two rotation,
three translation, five degrees of freedom,

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the gamma of 1.4.

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Go through a shock, the density ratio is only
a factor of six.

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Here the density is 15 to 20 times free strain
density.

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And the temperature goes to 100,000 degrees
ranking if it just stayed as a molecular gas.

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Now, in fact, that temperature has no meaning
other than if all the energy went into translation

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and rotation that would be the temperature.

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Let me just plot temperature as a function
of distance.

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And these were monitored in shock tubes.

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We worked predominantly at AFCO with an electric
wired discharge in helium.

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And we could get to ten kilometers per second
or 33,000 feet per second.

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Conceptually, what happens is if you plot
temperate as a function of distance here,

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ambient temperature is negligible.

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Initially, theoretically, you've got this
ten to the fifth, so your translational temperature

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comes down to ten to the fourth.

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And I will talk about the dimensions here
after a while.

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But the initial collisions, I mean basically
the molecules are piling up into other molecules.

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Quickly, you have collisions that give rise
to vibration, ionize the electronic energy

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levels in the molecule.

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Once it is vibrating it will also dissociate,
so then you've got ionized atoms as well.

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And we have characterized these as basically
temperatures, a vibrational temperature.

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Again, this is a very non-equilibrium situation
so the concept of temperature really goes

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away, but it is sort of a measure of energy
to equate, for example, vibrational and electronic.

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Now, what happened was I mentioned how significant
the radiation was from the equilibrium.

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In the shock tube, the radiation in this region
where the energy has not distributed itself

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into an equilibrium level was two orders of
magnitude higher.

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That led to the publication you cannot bring
people back from the moon.

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That radiation is just going to vaporize the
capsule.

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Now, things were with us.

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The time to relax and the measurements of
radiation, if you want, were extremely intense

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and then they relaxed to equilibrium levels.

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It turned out that we used what was termed
a binary scaling.

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This relaxation distance depended on how many
collisions you had.

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Collisions depended on the pressure.

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The pressure depended on the density.

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The velocity is fixed coming in from lunar
conditions.

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It gives you the pressure.

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In the shock tubes, we couldn't quite get
to the low pressures that we had on Apollo.

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And I will show that in my first chart, actually.

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But what happened is at the pressures that
we experienced, this distance came to be very

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small.

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And that increased the rate so that even though
we had two orders of magnitude higher radiation

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intensity, it was two orders of magnitude
smaller in radiating volume.

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And so the non-equilibrium radiation actually
turned out to be a little less important than

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the equilibrium radiation.

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Now, the point is that before we went to the
moon we didn't have the foggiest idea of what

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was going on.

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We knew that you couldn't use ideal gas, we
knew that you had to go to equilibrium, and

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everybody was worried about trying to calculate
equilibrium accurately.

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All sorts of charts and tables.

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We didn't have the computer capability that
we have today.

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Everybody was focused on equilibrium, but
then initial results in one of the major facilities

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for aerothermodynamics which is basically
a shock tube.

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Does everybody understand a shock tube and
how it functions?

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Basically, it is a one-dimensional situation,
just like I've described here, but the way

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it is generated is you have a driver section
and a driven section.

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In the driver, you try to get extremely high
pressure with a high speed of sound.

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Here you have a diaphragm.

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Here you have, if you want, rho infinity.

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This is the density that you're trying to
test in.

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What we had was an electric wire that exploded,
got into the helium, went to tremendous pressures.

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Basically, these were all battleship guns,
if you want.

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And we had to go to a two-inch diameter tube
in order to get close enough to the Apollo.

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Basically, you start with a pressure distribution
that looks like this.

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This is pressure as a function of distance.

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Once you discharge there is a diaphragm here.

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The diaphragm cannot take that pressure.

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The diaphragm blasts and you get an expansion
wave coming back here and a shockwave traveling

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in that direction.

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The reason we had to go to two feet is you
get a boundary layer building up.

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And if you want some test gas -- I've kind
of go this reversed here.

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In here you've got the shock, you've got a
boundary layer building up and, if you have

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two small tubes, the boundary layer will suck
up the gas and you don't really have a test

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condition.

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But AFCO worked everything out very nicely
and we had a very nice test condition.

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We basically had this condition going by,
a little higher pressure than we experienced

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on Apollo, and we could measure the radiation.

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The challenge at that time was the instrumentation
and a quick response capability to measure

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all that.

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We learned an awful lot.

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We went from ideal gas like you get in Shapiro
to real gas equilibrium.

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In fact, James Fay, in course two, had done
some real pioneering work looking at stagnation

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point heating and a gas dynamics.

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I am getting kind of lost in that detail,
but basically this was the phenomenological

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aspect that we had to understand in order
to work with Apollo.

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This was not why we had twice as much ablator
as we needed, and I will get to that later.

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Second area, what I'm talking about here basically
is fluid convection and some chemistry or

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physical chemistry.

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The next significant item is diffusion.

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The simplest case, obviously, is thermal diffusion.

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The first thing you learn in unsteady heat
transfer, you have a one-dimensional situation,

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temperature initially, and you have a heat
input.

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You end up with a distribution of temperature
which diffuses out.

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The functional form of that, if you recall,
T is proportional to an exponential, let's

224
00:18:41,010 --> 00:18:48,010
call this X squared over four thermal diffusivity
times time, and there is the square root.

225
00:18:53,390 --> 00:19:00,120
Think of it as a one-dimensional normal distribution.

226
00:19:00,120 --> 00:19:07,120
Except instead of two variant squared here
you've got four times the diffusivity time.

227
00:19:07,280 --> 00:19:14,280
The significant thing is when we talk about
ablators, when we talk about tiles or thermal

228
00:19:15,050 --> 00:19:18,920
protection systems, this is the significant
parameter.

229
00:19:18,920 --> 00:19:23,020
We have an extremely high temperature at the
surface.

230
00:19:23,020 --> 00:19:27,430
The job is to keep that from the structure.

231
00:19:27,430 --> 00:19:31,300
Thermal diffusivity is prime parameter.

232
00:19:31,300 --> 00:19:38,300
It is also, not thermal diffusivity, but if
you now consider simplest fluid mechanics,

233
00:19:42,080 --> 00:19:46,720
flat plate, the first thing you learn about
in terms of viscous flow.

234
00:19:46,720 --> 00:19:48,490
You've got some velocity coming along here.

235
00:19:48,490 --> 00:19:52,220
You've got a boundary layer that builds up.

236
00:19:52,220 --> 00:19:59,220
The boundary layer compared to X varies as
one over square root of Reynolds number.

237
00:19:59,860 --> 00:20:06,860
Where does that come from?

238
00:20:08,370 --> 00:20:10,110
The same diffusion.

239
00:20:10,110 --> 00:20:17,110
It is a diffusion of the shear of this wall
against the undisturbed flow, whether it be

240
00:20:19,790 --> 00:20:24,470
the thermal diffusion associated with heat
transfer, the diffusion associated with the

241
00:20:24,470 --> 00:20:29,630
shear, the same phenomena.

242
00:20:29,630 --> 00:20:35,340
When I first found this in fluid mechanics,
I was told that was empirical.

243
00:20:35,340 --> 00:20:41,150
And it basically is, but it really goes back
to the fact that if you approximate the Navier-Stokes

244
00:20:41,150 --> 00:20:47,180
Equations in this one-dimensional situation
you basically have a convection in this direction

245
00:20:47,180 --> 00:20:51,760
and a diffusion in the [UNINTELLIGIBLE] [Unthougtable]direction.

246
00:20:51,760 --> 00:20:57,380
This is extremely important, not just in terms
of boundary layer but also in terms of the

247
00:20:57,380 --> 00:21:03,210
Stanton number which is approximately heat
transfer divided by one-half rho infinity

248
00:21:03,210 --> 00:21:06,940
V infinity cubed for the case of a sphere.

249
00:21:06,940 --> 00:21:11,810
Now, this is a one-dimensional, obviously,
flat plat.

250
00:21:11,810 --> 00:21:13,760
A sphere is also one-dimensional.

251
00:21:13,760 --> 00:21:20,250
If you look at a stagnation point on a sphere,
this is a singularity.

252
00:21:20,250 --> 00:21:24,380
If you go to spherical coordinates you've
got basically the same phenomena.

253
00:21:24,380 --> 00:21:29,790
The diffusion from the wall gives you characteristic
dimensions.

254
00:21:29,790 --> 00:21:35,160
It is very important because heat transfer
is basically inversely proportional to the

255
00:21:35,160 --> 00:21:37,950
square root of the Reynolds number.

256
00:21:37,950 --> 00:21:41,300
We have square roots showing up in the thermal
diffusion.

257
00:21:41,300 --> 00:21:43,130
We have square roots showing up in the heat
transfer.

258
00:21:43,130 --> 00:21:50,130
Now, when you put in the effects of real viscosity
and everything else there is a little variation.

259
00:21:50,480 --> 00:21:54,330
But first order is the behavior that we are
looking for.

260
00:21:54,330 --> 00:21:58,400
And that I will illustrate now.

261
00:21:58,400 --> 00:22:05,400
If we go into a wind tunnel and we measure,
well, let's just basically go to fly.

262
00:22:07,700 --> 00:22:14,700
Let me do local heating over the energy flux.

263
00:22:14,890 --> 00:22:21,890
I am going to do a logarithm of that as a
function of log of what I'm going to call

264
00:22:23,870 --> 00:22:27,550
a normal shock Reynolds number.

265
00:22:27,550 --> 00:22:32,790
All I do, as I go across the shock, the density
of velocity -- The mass flux is conserved,

266
00:22:32,790 --> 00:22:33,270
obviously.

267
00:22:33,270 --> 00:22:38,400
The viscosity is what changes.

268
00:22:38,400 --> 00:22:45,400
I am going to use the normal shock equilibrium
air viscosity because that is more characteristic

269
00:22:47,820 --> 00:22:54,820
of everything going on in what the Russians
call a protective shock layer.

270
00:22:56,940 --> 00:23:02,180
If I looked at either the wind tunnel data
or flight data in the region of prime concern,

271
00:23:02,180 --> 00:23:08,160
I've got that minus one-half slope from that
square root Reynolds number.

272
00:23:08,160 --> 00:23:15,160
I will also have a bound up here that my heat
transfer cannot exceed the energy flux.

273
00:23:16,570 --> 00:23:19,760
And, obviously, if you go all the way to orbit
you're basically one.

274
00:23:19,760 --> 00:23:25,040
The molecules are coming in at orbital velocity,
going into the material, releasing all their

275
00:23:25,040 --> 00:23:29,580
energy and then eventually coming off.

276
00:23:29,580 --> 00:23:34,690
We actually do have that limit, although we
never really worry about it too much.

277
00:23:34,690 --> 00:23:41,690
The significant heating is in this laminar
regime.

278
00:23:50,780 --> 00:23:56,290
I feel like, because I understand Navier-Stokes
Equations, because I understand the diffusion

279
00:23:56,290 --> 00:24:02,710
process and that limit of the Navier-Stokes,
I sort of understand that flow.

280
00:24:02,710 --> 00:24:09,710
However, we also have turbulent heating which
incompressible flow has its slope on the order

281
00:24:09,850 --> 00:24:10,540
of [minus fifth?].

282
00:24:10,540 --> 00:24:14,280
I don't really understand stand that, and
do not claim to understand that.

283
00:24:14,280 --> 00:24:21,280
It is a combination of the diffusion and the
convection, all sorts of things going on.

284
00:24:21,640 --> 00:24:24,360
And then we have transition from one to the
other.

285
00:24:24,360 --> 00:24:28,690
Theoretically, this would come out and come
out lower.

286
00:24:28,690 --> 00:24:35,690
Now, this is extremely important in the shuttle
design, as I will get to when I get the charts.

287
00:24:36,410 --> 00:24:42,710
But basically we go into a wind tunnel and
can measure this on a particular configuration.

288
00:24:42,710 --> 00:24:43,440
We got to flight.

289
00:24:43,440 --> 00:24:50,440
And let me mention heat transfer and aerothermodynamics
has been a field of study for many years.

290
00:24:53,670 --> 00:25:00,230
People have built models, have done wind tunnel
tests, shock tube tests, flown vehicles.

291
00:25:00,230 --> 00:25:07,230
And there was a lot of money spent trying
to fly vehicles to verify our understanding.

292
00:25:07,340 --> 00:25:10,820
The difficulty, certainly with ablators, is
measuring the environment.

293
00:25:10,820 --> 00:25:15,600
Did you really have the right heat transfer
or did the material just start to degrade?

294
00:25:15,600 --> 00:25:18,640
What is really going on?

295
00:25:18,640 --> 00:25:25,640
When we flew the Shuttle, we had a reusable
thermal protection system which is the tile

296
00:25:27,440 --> 00:25:33,440
that is being passed around with a real thin
coating and very low thermal diffusivity.

297
00:25:33,440 --> 00:25:36,770
What better instrument could you have to measure
heat transfer than that?

298
00:25:36,770 --> 00:25:43,770
And the data from the Shuttle configuration
is absolutely fantastic from a technological

299
00:25:44,110 --> 00:25:46,980
standpoint, from an aerothermodynamics standpoint.

300
00:25:46,980 --> 00:25:47,630
Unbelievable.

301
00:25:47,630 --> 00:25:53,090
So much better than anything that was done
in the past with vehicles that were dedicated

302
00:25:53,090 --> 00:26:00,090
to try to get that information.

303
00:26:01,180 --> 00:26:08,180
Let me say a couple words about, well, first
let me address the facilities.

304
00:26:10,170 --> 00:26:15,120
I mentioned the shock tube and went through
that briefly.

305
00:26:15,120 --> 00:26:20,170
And the value of the shock tube was to look
at phenomena just like this.

306
00:26:20,170 --> 00:26:27,170
You also can, which is where Professor Fay
got his information, put a model in the shock

307
00:26:28,190 --> 00:26:32,350
tube.

308
00:26:32,350 --> 00:26:34,290
Right here.

309
00:26:34,290 --> 00:26:39,710
And all of a sudden you've got the flow at
the right enthalpy and closer conditions to

310
00:26:39,710 --> 00:26:41,540
flight than anywhere else.

311
00:26:41,540 --> 00:26:45,700
Getting to these energy levels is extremely
difficult.

312
00:26:45,700 --> 00:26:49,810
There are three facilities you can get to.

313
00:26:49,810 --> 00:26:51,610
One is in a shock tube.

314
00:26:51,610 --> 00:26:55,880
Second is a ballistic facility where you fire
a projectile that looks like what you're going

315
00:26:55,880 --> 00:26:57,260
to fly.

316
00:26:57,260 --> 00:27:00,970
And that does a good simulation job, except
it is very small.

317
00:27:00,970 --> 00:27:04,340
And getting any measurements is very difficult.

318
00:27:04,340 --> 00:27:09,750
If you go into a wind tunnel you can get great
measurements but you cannot get the energy.

319
00:27:09,750 --> 00:27:16,750
The shock tube and ballistic facility, I will
just put this down here, it has the difficulty

320
00:27:19,960 --> 00:27:21,970
of measuring things.

321
00:27:21,970 --> 00:27:24,900
The other place you can get the energy is
in an arc jet.

322
00:27:24,900 --> 00:27:31,900
Now, an arc jet is a continuous electrical
discharge, sort of like the shock tube, where

323
00:27:37,570 --> 00:27:44,570
you're discharging an arc along a tube about
the length of these tables, a very high current

324
00:27:47,730 --> 00:27:52,910
continuous for a significant period of time
into nitrogen.

325
00:27:52,910 --> 00:27:59,260
And then you're expanding this and you're
introducing a supersonic flow.

326
00:27:59,260 --> 00:28:06,260
And you test materials like tiles or the ablator
in as close to the environment as you can

327
00:28:06,890 --> 00:28:07,880
get on the ground.

328
00:28:07,880 --> 00:28:10,350
That is for the times that are required.

329
00:28:10,350 --> 00:28:13,160
Entry times are like 20 minutes.

330
00:28:13,160 --> 00:28:18,450
You need something that has the energy and
runs for 20 minutes.

331
00:28:18,450 --> 00:28:21,600
Now, this is a continuous flow of electrons.

332
00:28:21,600 --> 00:28:24,800
The thermodynamics here is not well-characterized.

333
00:28:24,800 --> 00:28:26,040
People have studied it like mad.

334
00:28:26,040 --> 00:28:27,450
This is very non-equilibrium.

335
00:28:27,450 --> 00:28:30,020
You've got a very high density of electrons.

336
00:28:30,020 --> 00:28:32,730
The temperature is immense in here.

337
00:28:32,730 --> 00:28:34,740
It is not at all in equilibrium.

338
00:28:34,740 --> 00:28:41,170
But, as you expand through a jet, collisions
drop because the pressure goes down and it

339
00:28:41,170 --> 00:28:43,070
pretty much freezes.

340
00:28:43,070 --> 00:28:50,070
But this is where we do research on ablators
and research on service catalysis which I

341
00:28:50,150 --> 00:28:55,470
will talk about in a little bit which really
can affect the heating, particularly on the

342
00:28:55,470 --> 00:28:55,790
Shuttle.

343
00:28:55,790 --> 00:28:57,700
And I will show you some results there.

344
00:28:57,700 --> 00:29:04,620
But, in any event, the arc jet is the other
major facility from a TPS materials standpoint.

345
00:29:04,620 --> 00:29:06,350
TPS being thermal protection system.

346
00:29:06,350 --> 00:29:09,350
Wind tunnels are classic.

347
00:29:09,350 --> 00:29:11,610
That's where NASA came from, NAC came from.

348
00:29:11,610 --> 00:29:18,610
Aerothermodynamics is my field, spelling is
another area.

349
00:29:25,190 --> 00:29:26,430
Wind tunnels you're all familiar with.

350
00:29:26,430 --> 00:29:32,480
And, on Apollo, we tested in every facility
you could think of because we didn't know

351
00:29:32,480 --> 00:29:34,590
what we were doing.

352
00:29:34,590 --> 00:29:39,310
And whatever the different facilities told
us we tried to understand.

353
00:29:39,310 --> 00:29:46,310
What we learned was energy is extremely important,
the enthalpy.

354
00:29:46,440 --> 00:29:52,500
And, frankly, going beyond mach 8, which is
what everybody tried to do, get to the higher

355
00:29:52,500 --> 00:29:57,400
mach number, really doesn't work too well
in a ground facility when you're talking about

356
00:29:57,400 --> 00:29:58,400
heating distribution.

357
00:29:58,400 --> 00:30:02,140
It does give you mach number effects.

358
00:30:02,140 --> 00:30:05,520
But the gas is not at all like what you have
in flight.

359
00:30:05,520 --> 00:30:10,710
And so on the shuttle we didn't really do
much aerothermodynamic testing beyond mach

360
00:30:10,710 --> 00:30:13,320
eight.

361
00:30:13,320 --> 00:30:20,320
That gave us the right normal shock Reynolds
number region, it was closer to, on the Shuttle,

362
00:30:20,850 --> 00:30:26,270
the actual flight environment than if we had
gone to a mach 12, a mach 16, a mach 18, a

363
00:30:26,270 --> 00:30:28,120
mach 20 facility.

364
00:30:28,120 --> 00:30:34,820
Because the way they get the mach number there
is to get the temperature very, very low.

365
00:30:34,820 --> 00:30:40,000
It is very valuable information, but you really
need to understand what you're doing with

366
00:30:40,000 --> 00:30:40,250
that.

367
00:30:40,180 --> 00:30:43,230
You cannot just take mach number as the major
parameter.

368
00:30:43,230 --> 00:30:46,870
It is a significant parameter but you need
to get the Reynolds number.

369
00:30:46,870 --> 00:30:49,210
And, fundamentally, you need to get the enthalpy
of the gas.

370
00:30:49,210 --> 00:30:53,280
And there is not really a good dimensionalist
number for the enthalpy of the gas.

371
00:30:53,280 --> 00:31:00,280
Too much going on for that.

372
00:31:04,370 --> 00:31:11,370
The other significant source of information
is flight test.

373
00:31:13,640 --> 00:31:20,260
In the early days with the capsules, and certainly
with Apollo, we did a lot more testing, invested

374
00:31:20,260 --> 00:31:24,830
a lot more on testing than we do now.

375
00:31:24,830 --> 00:31:30,430
For example, on the Apollo, I talked about
this radiation, we had very good test results

376
00:31:30,430 --> 00:31:31,330
in a shock tube.

377
00:31:31,330 --> 00:31:32,870
We thought we really knew what was going on.

378
00:31:32,870 --> 00:31:39,870
NASA Langley went and built a small scale
Apollo about so big to measure the radiation

379
00:31:45,530 --> 00:31:49,620
in flight because the shock tubes are operating
at little higher pressures than we were going

380
00:31:49,620 --> 00:31:53,910
to fly the Apollo.

381
00:31:53,910 --> 00:31:59,890
It basically had three brilliant heat shields
with a quartz window in it.

382
00:31:59,890 --> 00:32:06,890
It comes in zero angle-of-attack and gets
to a given point where the window basically

383
00:32:07,010 --> 00:32:07,760
starts to melt.

384
00:32:07,760 --> 00:32:12,220
You cannot see through it, you cannot make
a measurement, it sheds that.

385
00:32:12,220 --> 00:32:19,040
And ideally the second heat shield comes about
right at peak heating simulating Apollo entry.

386
00:32:19,040 --> 00:32:20,550
And then a third.

387
00:32:20,550 --> 00:32:23,850
Well, we were really excited about that because
the shock tube was great.

388
00:32:23,850 --> 00:32:26,060
And we thought we understood everything.

389
00:32:26,060 --> 00:32:27,490
Well, we flew Fire 1.

390
00:32:27,490 --> 00:32:28,370
It was called Fire.

391
00:32:28,370 --> 00:32:32,130
I don't remember what the acronym stood for,
but it was basically a small Apollo coming

392
00:32:32,130 --> 00:32:33,580
in.

393
00:32:33,580 --> 00:32:40,190
We got the data and it wasn't anything like
what we expected.

394
00:32:40,190 --> 00:32:40,780
What had happened?

395
00:32:40,780 --> 00:32:46,520
Well, it turned out that in order to get the
high speed, we launched the fire vehicle,

396
00:32:46,520 --> 00:32:52,380
and then we fired a rocket down back into
the atmosphere to simulate lunar return.

397
00:32:52,380 --> 00:32:53,180
Everything went well.

398
00:32:53,180 --> 00:33:00,010
There was a spring between the capsule and
the boost stage and they separated by design.

399
00:33:00,010 --> 00:33:01,050
Fine.

400
00:33:01,050 --> 00:33:07,850
But what happened was the booster lined up
with the wake of the incoming test vehicle

401
00:33:07,850 --> 00:33:12,050
and just road the wake because there was a
lot less resistance where the air has been

402
00:33:12,050 --> 00:33:17,030
sucked along, clobbered the back of the vehicle
and it mutated.

403
00:33:17,030 --> 00:33:19,070
And so we weren't looking at the stagnation
point.

404
00:33:19,070 --> 00:33:20,760
We were looking off at 30 degrees.

405
00:33:20,760 --> 00:33:23,060
Not only that but the radiation was doing
this.

406
00:33:23,060 --> 00:33:30,060
Figured out the problem, sorted it out and
had the second flight test which worked beautifully.

407
00:33:31,240 --> 00:33:38,240
It turned out at altitude the radiation did
not agree with the binary scaling that I mentioned,

408
00:33:40,540 --> 00:33:47,270
and basically the radiation profile here,
as I said, was like two hours magnitude higher

409
00:33:47,270 --> 00:33:50,100
characteristically.

410
00:33:50,100 --> 00:33:54,110
But at high altitudes it just wasn't there.

411
00:33:54,110 --> 00:33:56,200
At peak heating it was.

412
00:33:56,200 --> 00:34:00,510
But, prior to that, which was a significant
heat load, it was not.

413
00:34:00,510 --> 00:34:07,510
There were not adequate collisions to excite
the radiators before the gas came to equilibrium.

414
00:34:07,890 --> 00:34:14,889
Now, as I mentioned before, at peak heating
conditions on Apollo the shock, I cannot draw

415
00:34:17,330 --> 00:34:23,820
it very accurately to scale, was on the order
of about ten centimeters or four inches here

416
00:34:23,820 --> 00:34:24,409
at peak heating.

417
00:34:24,409 --> 00:34:28,780
[Q]: Is that the thickness of the shock or
the standoff distance?

418
00:34:28,780 --> 00:34:29,820
The standoff distance, thank you.

419
00:34:29,820 --> 00:34:31,520
Standoff distance.

420
00:34:31,520 --> 00:34:35,159
The shock is relatively thin, a few mean free
paths.

421
00:34:35,159 --> 00:34:42,159
And some people might call this effective
shock thickness, but I term the transition

422
00:34:42,710 --> 00:34:48,590
to higher temperature of the shock thickness
and then a relaxation distance.

423
00:34:48,590 --> 00:34:55,590
Any altitudes above that the flow could be
completely out of equilibrium.

424
00:34:55,760 --> 00:35:01,800
It hasn't gotten back to equilibrium because
this characteristic time is directly proportional

425
00:35:01,800 --> 00:35:03,460
pressure.

426
00:35:03,460 --> 00:35:04,140
And I erased it.

427
00:35:04,140 --> 00:35:08,390
It is directly proportional to free strain
density.

428
00:35:08,390 --> 00:35:12,050
So at higher altitudes it out of equilibrium.

429
00:35:12,050 --> 00:35:18,470
As you will see shortly, Shuttle is much higher
altitudes than Apollo.

430
00:35:18,470 --> 00:35:19,360
And I will explain why.

431
00:35:19,360 --> 00:35:26,360
At lower altitudes this compresses and is
predominantly at equilibrium radiation.

432
00:35:27,560 --> 00:35:31,000
And that we were able to characterize.

433
00:35:31,000 --> 00:35:32,340
OK.

434
00:35:32,340 --> 00:35:37,790
Back to ways of getting information.

435
00:35:37,790 --> 00:35:44,790
Numerical simulation.

436
00:35:47,830 --> 00:35:52,690
This is a significant revolution that you're
probably more familiar with than I am, but

437
00:35:52,690 --> 00:35:57,190
it really occurred right through the development
of the Shuttle.

438
00:35:57,190 --> 00:36:04,190
And frankly -- Well, I will show this in charts
in terms of the design approach to getting

439
00:36:04,380 --> 00:36:10,080
the aerothermodynamic environment at flight,
used the same technology that we used in Apollo.

440
00:36:10,080 --> 00:36:14,180
And that was we take a scale model, go into
a wind tunnel.

441
00:36:14,180 --> 00:36:21,180
Now, this is a blunt vehicle, and so if you
look at it as an inviscid flow, the close

442
00:36:21,340 --> 00:36:27,140
to normal shock entropy is basically the entropy
of the entire body inviscidly.

443
00:36:27,140 --> 00:36:34,000
And so the normal shock or strong shock gas
dominates the flow around the vehicle.

444
00:36:34,000 --> 00:36:38,240
As you go low angle-of-attack you get into
an entirely different situation.

445
00:36:38,240 --> 00:36:44,220
In any event, what happens in terms of the
wind tunnel, the heating here compared to

446
00:36:44,220 --> 00:36:47,180
different distributions, is all pretty much
proportionate.

447
00:36:47,180 --> 00:36:49,570
And that is fundamentally what we used.

448
00:36:49,570 --> 00:36:51,970
And that included even the wake region back
here.

449
00:36:51,970 --> 00:36:58,970
And I will talk more about that when we get
into the charts.

450
00:37:02,110 --> 00:37:07,180
On the Shuttle we get into far more complicated
geometries.

451
00:37:07,180 --> 00:37:11,960
And the major challenge on Shuttle was that
three-dimensional geometry.

452
00:37:11,960 --> 00:37:15,320
And we did a bunch of numerical simulation
development.

453
00:37:15,320 --> 00:37:21,960
We had focused on the subsonic region on Apollo
which basically is most of the front side

454
00:37:21,960 --> 00:37:24,590
here, is basically subsonic.

455
00:37:24,590 --> 00:37:26,890
About the middle of the vehicle down is supersonic.

456
00:37:26,890 --> 00:37:31,710
And then, of course, you get into the wake
here.

457
00:37:31,710 --> 00:37:37,220
This was our flow field interest on Apollo
primarily because of this radiation.

458
00:37:37,220 --> 00:37:41,820
We had to understand the flow field in order
to be able to compute the radiation.

459
00:37:41,820 --> 00:37:47,050
About half of that radiation is optically
thick from the ultraviolet deionization radiation

460
00:37:47,050 --> 00:37:49,990
and also line radiation from atoms.

461
00:37:49,990 --> 00:37:51,350
Optically thick.

462
00:37:51,350 --> 00:37:57,420
The other half, the radiation is basically
optically thin, the molecular band radiation

463
00:37:57,420 --> 00:37:59,300
and other things.

464
00:37:59,300 --> 00:38:01,360
We needed to understand the flow field.

465
00:38:01,360 --> 00:38:06,250
We did some pretty crude engineering calculations
in order to get that flow field, but we were

466
00:38:06,250 --> 00:38:12,490
focused on getting to a numerical simulation
of the subsonic region in particular.

467
00:38:12,490 --> 00:38:17,030
Now, in those days the computer was our real
limitation.

468
00:38:17,030 --> 00:38:19,330
And, of course, it was sort of embryonic.

469
00:38:19,330 --> 00:38:26,330
We have collectively just become orders of
magnitude beyond where we are today.

470
00:38:27,600 --> 00:38:34,600
However, the design approach that I would
recommend now is basically what we would like

471
00:38:36,120 --> 00:38:38,310
to have used on the Shuttle.

472
00:38:38,310 --> 00:38:39,650
And, to an extent, we did.

473
00:38:39,650 --> 00:38:43,850
Before we actually flew the Shuttle we had
confidence as a result of numerical simulation.

474
00:38:43,850 --> 00:38:50,520
It is a combination of these facilities and
numerical simulation.

475
00:38:50,520 --> 00:38:56,710
This problem of non-equilibrium is kind of
beyond numerical simulation, in my opinion.

476
00:38:56,710 --> 00:39:01,870
Now, you can correlate things, but I would
like to point out the limitations.

477
00:39:01,870 --> 00:39:05,500
You don't just go get a computer program and
you calculate everything because there are

478
00:39:05,500 --> 00:39:09,900
some very fundamental things missing.

479
00:39:09,900 --> 00:39:16,490
The way one gets reaction rates, for example,
dissociation rates or recombination rates

480
00:39:16,490 --> 00:39:18,650
is to go into a shock tube.

481
00:39:18,650 --> 00:39:23,220
As you approach equilibrium, the concept of
temperature, the equilibrium constant makes

482
00:39:23,220 --> 00:39:23,800
sense.

483
00:39:23,800 --> 00:39:26,950
So you can relate forward and backward rates.

484
00:39:26,950 --> 00:39:32,230
And you do diagnostics spectroscopically on
a concentration and you get rates.

485
00:39:32,230 --> 00:39:33,850
And it gets to be kind of complicated.

486
00:39:33,850 --> 00:39:39,170
There was a lot of stuff back in the early
Apollo days said in terms of coupling between

487
00:39:39,170 --> 00:39:42,870
the different modes of vibration, the electronic
excitation.

488
00:39:42,870 --> 00:39:44,850
It is a pretty complex problem.

489
00:39:44,850 --> 00:39:51,850
But, coming to equilibrium, is where we get
our reaction rates for high temperature gases.

490
00:39:53,560 --> 00:39:58,230
Coming back here, we're not close to equilibrium.

491
00:39:58,230 --> 00:39:58,840
Temperature doesn't work.

492
00:39:58,840 --> 00:40:05,840
Unless you start with an end body problem
and Schroedinger's equation, you're not going

493
00:40:06,310 --> 00:40:08,820
to really be able to compute this.

494
00:40:08,820 --> 00:40:15,820
Now, what is used in the field right now is
the basic data and a jump condition in terms

495
00:40:17,869 --> 00:40:20,560
of what matches the relaxation condition.

496
00:40:20,560 --> 00:40:23,030
I am not knocking it.

497
00:40:23,030 --> 00:40:27,440
All I am saying is there are limitations to
numerical simulation, whether it be in physical

498
00:40:27,440 --> 00:40:30,680
chemistry or just about anything you work
with.

499
00:40:30,680 --> 00:40:37,480
At the same time, it is invaluable in terms
of relating what happens in a wind tunnel

500
00:40:37,480 --> 00:40:41,920
and what happens in flight or what happens
in an arc jet and the phenomena.

501
00:40:41,920 --> 00:40:47,430
I will say a little bit more about that as
we get into the charts.

502
00:40:47,430 --> 00:40:54,190
Before we flew, in regions of the vehicle,
I made statements which I still would make,

503
00:40:54,190 --> 00:41:00,280
we could compute the heating on a wind tunnel
model about as accurately as you could measure

504
00:41:00,280 --> 00:41:01,960
it in regions.

505
00:41:01,960 --> 00:41:03,990
Not over the entire region.

506
00:41:03,990 --> 00:41:08,530
Not over the separated region.

507
00:41:08,530 --> 00:41:14,590
Not over conditions where the flow was turbulent.

508
00:41:14,590 --> 00:41:19,180
But, in the laminar environment, we could
compute it as well as you could measure it.

509
00:41:19,180 --> 00:41:24,800
That is outstanding because now if I say I've
got a program, I can tell you what the heating

510
00:41:24,800 --> 00:41:29,450
is, I can tell you all about the aerodynamics,
I can tell you everything.

511
00:41:29,450 --> 00:41:29,800
Good.

512
00:41:29,800 --> 00:41:31,150
Run it on a wind tunnel test.

513
00:41:31,150 --> 00:41:38,150
I will take the data, you run it on the wind
tunnel test and we will see if we agree.

514
00:41:38,180 --> 00:41:43,990
You've got a validation of numerical simulation
in terms of the geometry in wind tunnel, in

515
00:41:43,990 --> 00:41:49,820
terms of the chemistry in shock tubes or ballistic
facilities for that matter and certainly in

516
00:41:49,820 --> 00:41:51,300
terms of flight test.

517
00:41:51,300 --> 00:41:56,100
And you've got Shuttle data and a lot of code
validation for that Shuttle data.

518
00:41:56,100 --> 00:41:58,430
Now, this is just from the heating standpoint.

519
00:41:58,430 --> 00:42:02,310
I haven't talked very much yet about the thermal
protection system or the structure and the

520
00:42:02,310 --> 00:42:04,390
rest of the things.

521
00:42:04,390 --> 00:42:11,390
Let me say just a few things about configuration
and then I will say a few things about the

522
00:42:13,619 --> 00:42:18,080
thermal protection system and then we will
go to some charts that has some real information

523
00:42:18,080 --> 00:42:21,869
on it instead of just a hand-waving that I'm
doing right now.

524
00:42:21,869 --> 00:42:24,730
Configuration.

525
00:42:24,730 --> 00:42:26,840
I mentioned dissipating this energy.

526
00:42:26,840 --> 00:42:33,380
George Truhall [SP?] was in charge of the
thermal protection system on Apollo.

527
00:42:33,380 --> 00:42:38,460
And I used to come to him and say, wow, we
take care of 98% of that energy by putting

528
00:42:38,460 --> 00:42:39,530
it into the air.

529
00:42:39,530 --> 00:42:42,530
We compress the air, heat the air.

530
00:42:42,530 --> 00:42:45,800
You only have 2% to deal with, a small percentage.

531
00:42:45,800 --> 00:42:50,350
And he used to come right back to me and say
I do the same thing.

532
00:42:50,350 --> 00:42:55,420
I get rid of 98% of it and only 2% gets to
the structure.

533
00:42:55,420 --> 00:42:56,590
And, in fact, that it is true.

534
00:42:56,590 --> 00:43:03,000
By design, if you look at a meteor coming
in, the surface will vaporize.

535
00:43:03,000 --> 00:43:08,100
And, depending on the angle of momentum, if
it rotates it will vaporize all the way around

536
00:43:08,100 --> 00:43:09,110
on the outside.

537
00:43:09,110 --> 00:43:10,360
And some of it will come in.

538
00:43:10,360 --> 00:43:16,010
In fact, Professor Fay wrote a wonderful paper
about meteors, what become meteorites and

539
00:43:16,010 --> 00:43:17,470
what are meteors.

540
00:43:17,470 --> 00:43:19,080
An excellent paper.

541
00:43:19,080 --> 00:43:20,310
Put it in a real perspective.

542
00:43:20,310 --> 00:43:25,900
Broad range, much broader than what I'm talking
about here.

543
00:43:25,900 --> 00:43:32,900
The way George was able to get rid of this
heat was by re-radiating.

544
00:43:40,470 --> 00:43:45,780
And this has been kind of unique to manned
vehicles.

545
00:43:45,780 --> 00:43:52,780
Fundamentally, you've got a vehicle coming
in, you've got a surface with the capsules

546
00:43:52,869 --> 00:43:56,000
far exceeding the material capability.

547
00:43:56,000 --> 00:44:01,080
The heat flux coming in here gets you to temperatures
that are far above any material capability.

548
00:44:01,080 --> 00:44:08,080
And so what happens is the material degrades
and is called an ablator.

549
00:44:08,690 --> 00:44:13,040
And the initial concept and application for
ablators is, as the material vaporizes, it

550
00:44:13,040 --> 00:44:17,200
basically pushes the air away to reduce the
heat.

551
00:44:17,200 --> 00:44:19,970
And this is sort of what happens in meteors
if you want.

552
00:44:19,970 --> 00:44:22,290
So, you lose some of the initial material.

553
00:44:22,290 --> 00:44:26,240
And that sample that Aaron passed around,
that black material, well, it was a little

554
00:44:26,240 --> 00:44:30,369
thicker when it started than the sample that
he has.

555
00:44:30,369 --> 00:44:37,369
But you see this what we call char layer where
the material is decomposed?

556
00:44:37,920 --> 00:44:43,780
That generates a gas which at high pressures
and high heating rates basically tends to

557
00:44:43,780 --> 00:44:48,480
absorb the energy that is coming in through
the chemical reactions primarily, and also

558
00:44:48,480 --> 00:44:51,890
due to the blowing.

559
00:44:51,890 --> 00:44:58,180
But a fair more effective way of getting rid
of that heat, for us in Manned Spaceflight,

560
00:44:58,180 --> 00:45:01,930
at the higher altitudes was to re-radiate
it.

561
00:45:01,930 --> 00:45:05,180
How do you draw re-radiation?

562
00:45:05,180 --> 00:45:09,430
I guess sort of a wavy line.

563
00:45:09,430 --> 00:45:12,960
Radiation is always a wave, right?

564
00:45:12,960 --> 00:45:19,960
And so first order, 98% of this energy goes
into heating the air which flows around the

565
00:45:20,910 --> 00:45:22,810
vehicle.

566
00:45:22,810 --> 00:45:29,810
The other 2% that gets to the vehicle, George
re-radiated 98% away with a high-emissivity,

567
00:45:31,440 --> 00:45:32,550
high-temperature surface.

568
00:45:32,550 --> 00:45:39,550
Now, in the ablator, that char, think of it
as a charcoal briquette.

569
00:45:41,350 --> 00:45:45,520
You start with some material.

570
00:45:45,520 --> 00:45:49,020
It degrades and all sorts of chemical reactions
go.

571
00:45:49,020 --> 00:45:55,170
If you've got a good ablator for our application
what happens is you're left with a residual

572
00:45:55,170 --> 00:45:58,520
char which is black and very high-emissivity.

573
00:45:58,520 --> 00:45:59,920
It is pure carbon, if you want.

574
00:45:59,920 --> 00:46:06,920
That is the challenge, is to get a carbon
surface or a high-emissivity, high-temperature

575
00:46:07,180 --> 00:46:08,990
surface that can re-radiate.

576
00:46:08,990 --> 00:46:14,190
Just to remind the class, what is the most
efficient radiator?

577
00:46:14,190 --> 00:46:17,619
Black-body, there you go.

578
00:46:17,619 --> 00:46:22,280
Thank you.

579
00:46:22,280 --> 00:46:26,940
High-emissivity, black-body radiation, get
rid of all that energy before it ever has

580
00:46:26,940 --> 00:46:32,840
to diffuse through the tile or through the
ablator to get to the structure.

581
00:46:32,840 --> 00:46:38,400
That is fundamentally what we use to protect
the vehicle.

582
00:46:38,400 --> 00:46:45,290
Now, while I'm on that, the ablators were
developed for capsules.

583
00:46:45,290 --> 00:46:49,740
And we kept getting lower and lower density
because we wanted to minimize the diffusion

584
00:46:49,740 --> 00:46:51,040
of energy from the surface.

585
00:46:51,040 --> 00:46:56,170
There needed to be a substant enough surface
to hang together.

586
00:46:56,170 --> 00:47:01,610
I mean if you just have charcoal and blow
on it, it's not going to stay there.

587
00:47:01,610 --> 00:47:08,310
With the early capsule, with the Apollo, we
had a fiberglass structure in there that basically

588
00:47:08,310 --> 00:47:12,960
retarded the ablator from flowing away.

589
00:47:12,960 --> 00:47:19,540
Now, everybody tells us we were twice too
heavy on the ablator on a capsule.

590
00:47:19,540 --> 00:47:21,690
And I will explain that in a bit.

591
00:47:21,690 --> 00:47:25,700
It's a systems engineering problem, we got
away from it on Shuttle, so pay attention

592
00:47:25,700 --> 00:47:27,420
when I get to that problem.

593
00:47:27,420 --> 00:47:34,420
In any event, we were a factor too high over
most of the vehicle but not in this region.

594
00:47:37,020 --> 00:47:40,859
On that region, we were right on.

595
00:47:40,859 --> 00:47:42,810
Not by knowing what we were doing, just by
luck.

596
00:47:42,810 --> 00:47:49,810
When you say right on, what you're saying
is that the char layer went essentially all

597
00:47:51,930 --> 00:47:58,930
the way into -- We hit our temperature requirement
on the structure.

598
00:47:59,260 --> 00:48:06,260
If I blow that up a little bit, I've got a
surface here of ablator which is [paralysizing?]

599
00:48:07,380 --> 00:48:08,910
[he actually said that! there's no reference
in aerothermodynamics that refers to that

600
00:48:08,910 --> 00:48:10,930
term] and charing.

601
00:48:10,930 --> 00:48:13,220
And I've got a flow over the vehicle.

602
00:48:13,220 --> 00:48:15,960
I've got one heck of a pressure grid.

603
00:48:15,960 --> 00:48:17,450
And I just described this char.

604
00:48:17,450 --> 00:48:20,270
It's a nice porous carbon like a charcoal
briquette.

605
00:48:20,270 --> 00:48:21,609
Ever blow on a charcoal briquette?

606
00:48:21,609 --> 00:48:26,300
You can blow your air right through it and
it flames up.

607
00:48:26,300 --> 00:48:27,609
That's exactly what happened here.

608
00:48:27,609 --> 00:48:29,980
We had flow through.

609
00:48:29,980 --> 00:48:33,470
The honeycomb wasn't as a high a temperature
as the carbon.

610
00:48:33,470 --> 00:48:36,840
That was just there to hold it as the system
degraded.

611
00:48:36,840 --> 00:48:42,040
So, the combination of the two-dimensional
flow which we really hadn't simulated on the

612
00:48:42,040 --> 00:48:49,040
ground, all we could do, in the arc jet, was
basically little pucks to test the ablator.

613
00:48:49,310 --> 00:48:56,310
You're dealing with an awful lot of energy,
and if you spread that energy over a large

614
00:48:56,390 --> 00:48:59,460
surface the enthalpy basically goes down.

615
00:48:59,460 --> 00:49:01,890
The heating on the surface goes down.

616
00:49:01,890 --> 00:49:07,140
We were testing six inch specimens characteristically.

617
00:49:07,140 --> 00:49:08,369
We really didn't get the flow through.

618
00:49:08,369 --> 00:49:11,840
In fact, we eliminated the flow through because
we had one-dimensional models and we wanted

619
00:49:11,840 --> 00:49:13,810
to understand the process of one-dimensional.

620
00:49:13,810 --> 00:49:20,609
But, in flight, fortunately we were a factor
or two over just in that region.

621
00:49:20,609 --> 00:49:23,560
Over this region, and I will show you a chart,
we were way over.

622
00:49:23,560 --> 00:49:26,090
And, again, I will try to address that.

623
00:49:26,090 --> 00:49:30,180
And, again, the Shuttle has really helped
us in understanding the leeside flow.

624
00:49:30,180 --> 00:49:32,010
Configuration.

625
00:49:32,010 --> 00:49:39,010
Everybody has got their own requirements for
configurations.

626
00:49:39,330 --> 00:49:46,330
From a heating standpoint, I want to put all
that energy into the air so I want a maximum

627
00:49:46,710 --> 00:49:48,900
drag configuration.

628
00:49:48,900 --> 00:49:55,790
I just want a flat plat normal to the flow.

629
00:49:55,790 --> 00:49:56,330
Well, that's wonderful.

630
00:49:56,330 --> 00:49:59,980
It's high drag but it's not stable at all.

631
00:49:59,980 --> 00:50:03,060
Let's go to a sphere.

632
00:50:03,060 --> 00:50:08,609
Now, the center pressure, no matter where
the pressure is on the vehicle, no matter

633
00:50:08,609 --> 00:50:13,400
what the pressure is, it goes right to the
center.

634
00:50:13,400 --> 00:50:17,720
And that is probably also about the center
of gravity if I flew a sphere.

635
00:50:17,720 --> 00:50:22,880
Certainly if it was solid, but if I build
a spherical spacecraft it would be neutrally

636
00:50:22,880 --> 00:50:23,500
stable.

637
00:50:23,500 --> 00:50:24,080
Well, that would be great.

638
00:50:24,080 --> 00:50:28,190
I could spin it and distribute the heating
over the entire thing.

639
00:50:28,190 --> 00:50:30,380
As they enter, that happens to some meteors.

640
00:50:30,380 --> 00:50:33,450
Well, it's not too comfortable and I don't
have control and I also generate a little

641
00:50:33,450 --> 00:50:33,700
left.

642
00:50:33,540 --> 00:50:37,130
There are all kinds of problems with that.

643
00:50:37,130 --> 00:50:42,470
One other problem, if I use just a section
of a flat plate, if I look at the heating

644
00:50:42,470 --> 00:50:48,810
distribution, if I plot the heat transfer
in this direction from ground test, not from

645
00:50:48,810 --> 00:50:51,430
flight, from ground test, you have some level
of heating.

646
00:50:51,430 --> 00:50:55,080
But then, when you get to the corner, it really
goes up because of pressure gradient.

647
00:50:55,080 --> 00:51:00,290
The same thing that we experienced on Apollo
in terms of the ablator.

648
00:51:00,290 --> 00:51:05,130
So, you want to give it some curvature, not
only from the standpoint of stability but

649
00:51:05,130 --> 00:51:09,900
also from the standpoint of the heating distribution.

650
00:51:09,900 --> 00:51:14,470
And, indeed, if you look at the Apollo at
zero angle of attack it pretty much has almost

651
00:51:14,470 --> 00:51:15,880
a uniform heating distribution.

652
00:51:15,880 --> 00:51:17,369
That is very efficient.

653
00:51:17,369 --> 00:51:22,800
I can design my thermal protection system
to be so thick and I manufacture it, produce

654
00:51:22,800 --> 00:51:26,020
it over the entire surface exactly the same.

655
00:51:26,020 --> 00:51:30,630
That is wonderful, except I still have the
corner problem.

656
00:51:30,630 --> 00:51:37,420
And so I round the corners a bit.

657
00:51:37,420 --> 00:51:39,790
This is only from an aerothermodynamic standpoint
now.

658
00:51:39,790 --> 00:51:44,230
And so I don't have this corner edge heating
problem nearly as much.

659
00:51:44,230 --> 00:51:51,230
Well, that's fine, except a zero L/D vehicle
gets kind of high Gs coming in and you don't

660
00:51:52,760 --> 00:51:53,609
have much control.

661
00:51:53,609 --> 00:51:58,550
And I will address a little bit of that, and
you've probably already heard about the flight

662
00:51:58,550 --> 00:51:58,880
mechanics control.

663
00:51:58,880 --> 00:52:03,530
In any event, I need some L/D so I got to
angle-of-attack.

664
00:52:03,530 --> 00:52:09,340
In order to go to angle-of-attack, I have
to take the center pressure, which is basically

665
00:52:09,340 --> 00:52:14,930
the point about which the aerodynamic forces,
if I put a string and pulled on that, that's

666
00:52:14,930 --> 00:52:18,330
how the aerodynamic forces are acting on that.

667
00:52:18,330 --> 00:52:22,619
And I want the center of gravity ahead of
that.

668
00:52:22,619 --> 00:52:26,230
And now I've got a nice stable configuration.

669
00:52:26,230 --> 00:52:31,470
Not too stable because the control people
want to do things with it but stable from

670
00:52:31,470 --> 00:52:35,800
the standpoint of not having to fire RCS jets
or have control surfaces and all that type

671
00:52:35,800 --> 00:52:36,260
of thing.

672
00:52:36,260 --> 00:52:38,030
That is how we designed Apollo.

673
00:52:38,030 --> 00:52:41,650
It worked very well.

674
00:52:41,650 --> 00:52:48,650
And, in fact, if you look at the Shuttle at
angle-of-attack
with some liberties -- Son of a gun.

675
00:52:55,340 --> 00:52:57,390
In two-dimensions.

676
00:52:57,390 --> 00:53:01,220
In three-dimensions it is significantly different.

677
00:53:01,220 --> 00:53:07,369
I think I'm about ready to go to the charts
now.

678
00:53:07,369 --> 00:53:07,970
OK.

679
00:53:07,970 --> 00:53:10,900
Why don't we take a two-minute break.

680
00:53:10,900 --> 00:53:13,450
We usually break about 10:00.

681
00:53:13,450 --> 00:53:13,960
Great.

682
00:53:13,960 --> 00:53:17,790
And I will get the charts set up.

683
00:53:17,790 --> 00:53:18,359
Good.

684
00:53:18,359 --> 00:53:19,109
Quick stretch.

685
00:53:19,109 --> 00:53:19,900
Turn around.

686
00:53:19,900 --> 00:53:22,320
I didn't ask if there were any questions.

687
00:53:22,320 --> 00:53:26,590
I expected everybody to just raise their hands
and start asking questions.

688
00:53:26,590 --> 00:53:30,930
But, since there are no 8:00 classes, this
is the first class of the day, maybe that's

689
00:53:30,930 --> 00:53:37,290
why we're not getting any questions.

690
00:53:37,290 --> 00:53:38,490
That was my hand-waving.

691
00:53:38,490 --> 00:53:40,990
I am going to get into specifics here after
the break.

692
00:53:40,990 --> 00:53:47,990
I have a series of charts.

693
00:54:36,760 --> 00:54:42,850
Most of these came from a technical conference
that Professor Cohen had after the Shuttle

694
00:54:42,850 --> 00:54:43,310
test flights.

695
00:54:43,310 --> 00:54:50,310
We had five test flights, just for information.

696
00:54:53,230 --> 00:55:00,040
We had 17 flights in Mercury before we put
a man in the vehicle.

697
00:55:00,040 --> 00:55:06,930
On Apollo, we never put a man on the vehicle
or did anything before we had a test of the

698
00:55:06,930 --> 00:55:11,140
systems in the vehicle, before we'd put a
man in it, with one exception, and that was

699
00:55:11,140 --> 00:55:12,080
the actual Lunar landing.

700
00:55:12,080 --> 00:55:14,530
We couldn't really simulate that very well.

701
00:55:14,530 --> 00:55:16,230
We couldn't test that.

702
00:55:16,230 --> 00:55:23,230
On the Shuttle, we did as much testing as
we could, but the design constraints forced

703
00:55:30,420 --> 00:55:35,170
us to go with men in the system initially.

704
00:55:35,170 --> 00:55:39,450
And that was the least riskiest thing to do
considering everything.

705
00:55:39,450 --> 00:55:39,700
That's a whole different subject.
All right.

706
00:55:42,640 --> 00:55:49,640
This first chart is altitude in thousands
of feet and velocity in feet per second.

707
00:55:52,130 --> 00:55:59,130
What I've shown here is, first of all, this
is one atmosphere total pressure.

708
00:56:01,470 --> 00:56:08,470
This is a tenth of an atmosphere total pressure.

709
00:56:08,619 --> 00:56:15,619
And first I would like to focus on the Apollo
orbital return, and I am going to show data

710
00:56:15,750 --> 00:56:18,420
from actually one of these flights.

711
00:56:18,420 --> 00:56:21,410
These bands are to show the flight regime.

712
00:56:21,410 --> 00:56:28,109
And this is the Lunar return coming back 36,000
feet per second and then essentially going

713
00:56:28,109 --> 00:56:30,359
through an orbital entry.

714
00:56:30,359 --> 00:56:33,320
You can see there is an order of magnitude
difference here.

715
00:56:33,320 --> 00:56:34,470
I'm sorry.

716
00:56:34,470 --> 00:56:36,220
Here is the Shuttle.

717
00:56:36,220 --> 00:56:42,119
This was the design coming from a polar orbit
at 265,000 feet per second.

718
00:56:42,119 --> 00:56:45,780
And these are the orbital flight tests, the
five flight tests.

719
00:56:45,780 --> 00:56:51,660
They are all laid together here, and you cannot
really see much of a difference.

720
00:56:51,660 --> 00:56:57,660
Now, this is the heating boundary.

721
00:56:57,660 --> 00:57:03,740
If we went beyond that the tiles degrade.

722
00:57:03,740 --> 00:57:08,510
Now, I mentioned three levels of aerothermodynamics.

723
00:57:08,510 --> 00:57:11,609
The design level, well, I'll get into the
design level a little bit later.

724
00:57:11,609 --> 00:57:15,080
The first level was basically the Apollo technology.

725
00:57:15,080 --> 00:57:22,080
That was we went to the wind tunnel, we correlated
the distribution of heating on the Shuttle

726
00:57:23,680 --> 00:57:29,540
relative to a reference, and we used the one
foot sphere as a reference.

727
00:57:29,540 --> 00:57:36,540
And I gave that to the flight mechanics people
and said do not violate these constraints.

728
00:57:37,130 --> 00:57:43,660
So they developed the flight mechanics control
and everything else to fly right along here.

729
00:57:43,660 --> 00:57:47,859
Now, what isn't shown is we anticipated transition.

730
00:57:47,859 --> 00:57:49,530
And I will show that in time histories.

731
00:57:49,530 --> 00:57:52,910
There is another boundary for heating that
actually comes along here.

732
00:57:52,910 --> 00:57:59,890
These trajectories are very tight relative
to having a re-usable thermal protection system

733
00:57:59,890 --> 00:58:03,580
and not having to completely refurbish the
vehicle.

734
00:58:03,580 --> 00:58:04,420
That was the target.

735
00:58:04,420 --> 00:58:09,580
If we wanted a reusable system, we could turn
around and fly again.

736
00:58:09,580 --> 00:58:16,580
You've seen the ablator from Apollo and you've
seen tile that really had some severe environment

737
00:58:22,340 --> 00:58:23,960
from the Shuttle.

738
00:58:23,960 --> 00:58:27,250
But basically here we have a simple configuration.

739
00:58:27,250 --> 00:58:30,190
Here we had a much more complex configuration.

740
00:58:30,190 --> 00:58:37,190
We had capability to fly it and we had capability
to avoid excessive heating.

741
00:58:38,690 --> 00:58:41,060
It takes about 20 minutes to enter.

742
00:58:41,060 --> 00:58:47,510
Ten minutes along this heating boundary where
basically your heating rate comes up and you

743
00:58:47,510 --> 00:58:48,859
are on a plateau.

744
00:58:48,859 --> 00:58:54,690
And you will see that in just a minute.

745
00:58:54,690 --> 00:58:58,970
That contrasts the Apollo and the Shuttle.

746
00:58:58,970 --> 00:59:04,010
And I mentioned on Apollo we did a lot of
shock tube testing trying to get into this

747
00:59:04,010 --> 00:59:09,300
environment, about 33,000 feet per second
for peak heating, when this thing comes down

748
00:59:09,300 --> 00:59:13,480
to also about max pressure on this chart anyway.

749
00:59:13,480 --> 00:59:19,900
But Shuttle was significantly higher altitude,
significantly more out of equilibrium, which

750
00:59:19,900 --> 00:59:21,380
is the bad news.

751
00:59:21,380 --> 00:59:25,720
The good news is the radiation was not that
significant.

752
00:59:25,720 --> 00:59:32,160
In fact, when we calculated what the astronauts
would see coming in -- On Apollo, when they

753
00:59:32,160 --> 00:59:36,800
were looking out the windows on the wake,
it was extremely bright.

754
00:59:36,800 --> 00:59:43,090
This is just in the wake which is orders of
magnitude down from the radiation on the front

755
00:59:43,090 --> 00:59:44,810
side.

756
00:59:44,810 --> 00:59:51,380
On the Shuttle, we suggested a 100 watt light
bulb behind a table.

757
00:59:51,380 --> 00:59:55,990
It worked beautifully in the simulator.

758
00:59:55,990 --> 01:00:02,810
Significant change in environment from Apollo
at 33,000 to 36,000 feet per second to orbital

759
01:00:02,810 --> 01:00:03,880
environment.

760
01:00:03,880 --> 01:00:07,010
The heating basically increases.

761
01:00:07,010 --> 01:00:10,500
In this direction, I don't show [UNINTELLIGIBLE
PHRASE].[question about mars, that i miss

762
01:00:10,500 --> 01:00:16,880
to catch due to the cough some other person
enters] Mars return is like 45,000 feet per

763
01:00:16,880 --> 01:00:18,460
second.

764
01:00:18,460 --> 01:00:22,920
The convective heating goes up as velocity
cubed.

765
01:00:22,920 --> 01:00:27,040
The radiation probably goes up by two orders
of magnitude.

766
01:00:27,040 --> 01:00:30,119
The radiation is very, very sensitive.

767
01:00:30,119 --> 01:00:35,680
Some of the people at Ames did correlations
with velocity and with temperature.

768
01:00:35,680 --> 01:00:38,970
And there were numbers like a temperature
to the eighth power, a temperature to the

769
01:00:38,970 --> 01:00:44,030
twelfth power because it is not limited by
black-body over a lot of the spectrum.

770
01:00:44,030 --> 01:00:47,940
And, as the temperature goes up, there are
more and more radiated degrees of freedom.

771
01:00:47,940 --> 01:00:50,830
It gets much closer to a black-body.

772
01:00:50,830 --> 01:00:57,830
Radiation becomes dominant on a Mars return.

773
01:00:59,200 --> 01:01:03,430
On Lunar return it is a problem.

774
01:01:03,430 --> 01:01:09,680
However, if you look at the radiative heating,
it is first order proportional to two-dimension.

775
01:01:09,680 --> 01:01:13,380
Whereas, a convective heating is just the
opposite, it is inversely proportional square

776
01:01:13,380 --> 01:01:14,190
root.

777
01:01:14,190 --> 01:01:19,730
As you go up in dimension, your convective
heating is less important, as we did with

778
01:01:19,730 --> 01:01:20,119
the Shuttle.

779
01:01:20,119 --> 01:01:21,380
And I will try to address that.

780
01:01:21,380 --> 01:01:25,640
So we don't really have an ablator type of
material that would work for Mars return?

781
01:01:25,640 --> 01:01:27,910
I think we could develop an ablator.

782
01:01:27,910 --> 01:01:32,840
But we would have to do it in an environment
that gets as close as we can to simulating

783
01:01:32,840 --> 01:01:35,080
the radiation.

784
01:01:35,080 --> 01:01:40,740
And these days there is a lot more capability
there than there was in Apollo days.

785
01:01:40,740 --> 01:01:42,730
But that is a real challenge.

786
01:01:42,730 --> 01:01:43,030
Yes.

787
01:01:43,030 --> 01:01:44,520
I have a couple questions.

788
01:01:44,520 --> 01:01:44,770
Sure.
[all/among the lines Why do they come backup]
That was the basic flight mechanics that dissipate

789
01:01:54,830 --> 01:01:56,310
the energy.

790
01:01:56,310 --> 01:02:01,570
And, actually, I will get into this a little
bit more on the next chart and then go through

791
01:02:01,570 --> 01:02:02,050
an entry.

792
01:02:02,050 --> 01:02:07,540
You wanted to not exceed the deceleration.

793
01:02:07,540 --> 01:02:13,300
Actually, from an ablator standpoint, one
of the most efficient ways to come in is hot

794
01:02:13,300 --> 01:02:15,589
and heavy.

795
01:02:15,589 --> 01:02:17,700
Go to max heating rate but keep that time
down.

796
01:02:17,700 --> 01:02:22,810
You remember I mentioned the square root of
time on the diffusion of the energy in.

797
01:02:22,810 --> 01:02:24,410
You want to keep that time down.

798
01:02:24,410 --> 01:02:29,130
And you're better off taking your lumps on
heating rate.

799
01:02:29,130 --> 01:02:31,540
Heat load is really what designs.

800
01:02:31,540 --> 01:02:34,650
Did that answer your question?

801
01:02:34,650 --> 01:02:41,210
[UNINTELLIGIBLE PHRASE] [i'm sorry enviroment
noise plus air condition] This is the flight

802
01:02:41,210 --> 01:02:48,160
mechanics, and I'm not an expert on that,
but basically this portion was designed to

803
01:02:48,160 --> 01:02:50,400
capture.

804
01:02:50,400 --> 01:02:54,930
If you don't capture you're gone for another
two weeks.

805
01:02:54,930 --> 01:03:01,930
And so you didn't want to get beyond 20 Gs
because nothing would take beyond 20 Gs obviously.

806
01:03:02,640 --> 01:03:05,710
You didn't want to skip out.

807
01:03:05,710 --> 01:03:06,730
This is a linear plot.

808
01:03:06,730 --> 01:03:10,940
You're looking at an atmosphere and you're
coming in at high speed.

809
01:03:10,940 --> 01:03:16,339
I want to make sure you capture it.

810
01:03:16,339 --> 01:03:22,770
Not too steep or you're blown apart, but if
you miss you're gone for another two weeks.

811
01:03:22,770 --> 01:03:23,630
First thing is capture.

812
01:03:23,630 --> 01:03:24,859
Dissipate that energy.

813
01:03:24,859 --> 01:03:29,720
Then we worry about getting down to a landing
point.

814
01:03:29,720 --> 01:03:36,720
In terms of corridor, they term that corridor,
the Apollo vehicle had about a 27 mile corridor

815
01:03:37,540 --> 01:03:38,000
at 400,000 feet.

816
01:03:38,000 --> 01:03:41,119
If you were too shallow then you would skip
out.

817
01:03:41,119 --> 01:03:47,200
If you were too steep in that corridor you
would go in too deep and exceed the G level.

818
01:03:47,200 --> 01:03:54,200
Coming back from the moon, 240,000 miles away,
you basically had to a corridor about 27 miles

819
01:03:54,430 --> 01:03:59,460
in the earth's atmosphere.

820
01:03:59,460 --> 01:04:04,760
And that was really what the guidance navigation
system did for us.

821
01:04:04,760 --> 01:04:08,220
And with the mid-course correction, of course
you've got a lot of leverage, but it is a

822
01:04:08,220 --> 01:04:12,280
very tight corridor that you've got to hit.

823
01:04:12,280 --> 01:04:13,250
Well, I can talk about it now.

824
01:04:13,250 --> 01:04:19,520
No, I will wait until the next chart in terms
of the systems engineering and everything.

825
01:04:19,520 --> 01:04:26,520
When I
was here, the computers were in the electrical
engineering department and occupied an entire

826
01:04:34,740 --> 01:04:35,260
room.

827
01:04:35,260 --> 01:04:41,690
Mechanical engineers like me, I mean we didn't
understand all that stuff.

828
01:04:41,690 --> 01:04:43,920
Generations.

829
01:04:43,920 --> 01:04:46,420
Design and flight test environments, a lot
of points I want to make here.

830
01:04:46,420 --> 01:04:53,420
This is a log maximum heating rate and this
is the maximum integrated heat load at design

831
01:04:55,500 --> 01:04:56,270
conditions.

832
01:04:56,270 --> 01:05:00,190
Now, the numbers are not so important.

833
01:05:00,190 --> 01:05:01,589
Apollo is triangles.

834
01:05:01,589 --> 01:05:05,180
Shuttle is circles.

835
01:05:05,180 --> 01:05:08,050
Filled is design.

836
01:05:08,050 --> 01:05:10,450
Open is actual.

837
01:05:10,450 --> 01:05:12,230
Let's start with the Apollo.

838
01:05:12,230 --> 01:05:17,119
Our design is up here coming back from the
moon.

839
01:05:17,119 --> 01:05:18,900
Actually, there were two design points.

840
01:05:18,900 --> 01:05:22,550
This was the maximum load which was the thickness
of the ablator.

841
01:05:22,550 --> 01:05:23,400
That is the weight.

842
01:05:23,400 --> 01:05:25,040
We picked the material.

843
01:05:25,040 --> 01:05:26,950
We got the best material we could.

844
01:05:26,950 --> 01:05:28,320
Now the question is how thick do we make it?

845
01:05:28,320 --> 01:05:29,950
And that's the weight.

846
01:05:29,950 --> 01:05:31,690
Here is the design condition.

847
01:05:31,690 --> 01:05:37,000
The heat load I mentioned before relative
to the question.

848
01:05:37,000 --> 01:05:41,810
We didn't have the trajectories of flight
mechanics when we started the design.

849
01:05:41,810 --> 01:05:47,119
We had to start to design the capsule, the
ablator and everything else in parallel with

850
01:05:47,119 --> 01:05:50,750
the development of the computer capability
and the flight mechanics and being able to

851
01:05:50,750 --> 01:05:53,029
actually fly this thing.

852
01:05:53,029 --> 01:05:55,130
What happened?

853
01:05:55,130 --> 01:05:58,430
We knew we couldn't exceed 20 Gs.

854
01:05:58,430 --> 01:06:01,510
And so give me a trajectory that comes in
and hits 20 Gs.

855
01:06:01,510 --> 01:06:03,839
I've got to be able to handle that heating
rate.

856
01:06:03,839 --> 01:06:06,470
We also needed to capture.

857
01:06:06,470 --> 01:06:13,470
If we skipped out and went another two weeks,
that was kind of tough on the crew, so give

858
01:06:13,630 --> 01:06:15,930
me a trajectory that just stays in.

859
01:06:15,930 --> 01:06:18,770
They are miles apart.

860
01:06:18,770 --> 01:06:22,010
That point is up here on that chart.

861
01:06:22,010 --> 01:06:27,380
For clarity and trying to illustrate other
things, it is way up here in heating rate.

862
01:06:27,380 --> 01:06:34,380
And there is sort of a range of entry of Apollo
in terms of -- That's the maximum you could

863
01:06:36,040 --> 01:06:36,290
get.
All sorts of things in between.

864
01:06:39,339 --> 01:06:40,320
This is an actual flight.

865
01:06:40,320 --> 01:06:44,540
This is log paper.

866
01:06:44,540 --> 01:06:46,310
A significant difference.

867
01:06:46,310 --> 01:06:48,660
A factor of two.

868
01:06:48,660 --> 01:06:55,660
Square root of that, 40% of that ablator that
we didn't need is in the trajectory difference.

869
01:06:56,260 --> 01:07:02,770
But now here is the systems engineering point.

870
01:07:02,770 --> 01:07:08,010
When we started the Shuttle, we looked at
Apollo and said how do we get this heat shield

871
01:07:08,010 --> 01:07:08,260
down?

872
01:07:08,029 --> 01:07:14,529
Well, if you look at the aerospace industry
or NASA you have specialists.

873
01:07:14,529 --> 01:07:16,599
Everybody does their own little thing.

874
01:07:16,599 --> 01:07:17,599
I am aerothermodynamicist.

875
01:07:17,599 --> 01:07:21,599
George Truhall was the thermal protection
system guy.

876
01:07:21,599 --> 01:07:23,160
Tom Moser was a structures guy.

877
01:07:23,160 --> 01:07:24,490
Then there was a materials guy.

878
01:07:24,490 --> 01:07:28,589
All these different people, they all do their
thing and work together as a team.

879
01:07:28,589 --> 01:07:32,089
We're designing a system to go to the moon
and come back.

880
01:07:32,089 --> 01:07:36,640
Boy, I sure don't want to put too low a heating
rate in.

881
01:07:36,640 --> 01:07:43,640
I mean I don't want to be the cause of a failure,
so I think the heating rate is going to be

882
01:07:45,869 --> 01:07:48,080
right here or whatever.

883
01:07:48,080 --> 01:07:55,080
Well, I don't have that level of confidence,
I've got some uncertainty, so I will put 10%

884
01:07:55,279 --> 01:07:58,830
or 20% at least in on my heating.

885
01:07:58,830 --> 01:08:05,830
The ablator guy, he is testing on arc jets,
and he does exactly the same thing.

886
01:08:06,070 --> 01:08:08,920
The structures guy says, well, we want to
do this and that.

887
01:08:08,920 --> 01:08:14,180
Well, on the Shuttle, for example, our guideline
was 100 missions, a structure that would take

888
01:08:14,180 --> 01:08:15,200
100 cycles.

889
01:08:15,200 --> 01:08:22,200
Well, if I don't exceed this temperature,
you know, how well do I know that, what is

890
01:08:22,569 --> 01:08:26,839
the stress level, all the different variables,
you know, this is what I expect but I better

891
01:08:26,839 --> 01:08:27,788
put a little pad in.

892
01:08:27,788 --> 01:08:30,029
There is nothing wrong with that.

893
01:08:30,029 --> 01:08:35,198
What was wrong is we didn't have communication
with all these people.

894
01:08:35,198 --> 01:08:40,318
Somebody gives me a trajectory and I calculate
heat and I say, boy, this is what I think

895
01:08:40,318 --> 01:08:40,799
it's going to be.

896
01:08:40,799 --> 01:08:44,488
And I'm going to show you some of that, in
all honesty, which you won't see in journal

897
01:08:44,488 --> 01:08:46,238
articles.

898
01:08:46,238 --> 01:08:52,988
But I better put a little bit of pad on that
because I don't know this that well.

899
01:08:52,988 --> 01:08:53,759
They compound.

900
01:08:53,759 --> 01:08:57,068
We call it compound conservatism.

901
01:08:57,068 --> 01:09:03,139
Everybody puts their 10% in and you get your
factor of two.

902
01:09:03,139 --> 01:09:09,999
Now, you just lost significant, if not half
the payload on the Shuttle by doing that.

903
01:09:09,999 --> 01:09:11,880
We did not do that on the Shuttle.

904
01:09:11,880 --> 01:09:15,078
Now, let me very honest.

905
01:09:15,078 --> 01:09:18,618
In the early days, when we recognized that,
because we were getting beat on.

906
01:09:18,618 --> 01:09:21,670
You don't need all that TPS.

907
01:09:21,670 --> 01:09:26,328
When we realized where it really came from,
we would go back to the management and say

908
01:09:26,328 --> 01:09:26,849
this is what you need to do.

909
01:09:26,849 --> 01:09:30,618
You need a system where you have all this
communication.

910
01:09:30,618 --> 01:09:33,499
Well, that's going to be expensive.

911
01:09:33,499 --> 01:09:35,529
We did it, but we did it informally.

912
01:09:35,529 --> 01:09:39,488
We did it by communicating informally everybody
understanding.

913
01:09:39,488 --> 01:09:44,759
And we actually did a statistical assessment
before we flew the Shuttle to give us confidence

914
01:09:44,759 --> 01:09:49,299
that things would work.

915
01:09:49,299 --> 01:09:49,749
Extremely important.

916
01:09:49,749 --> 01:09:54,179
I mean when you talk about systems engineering
it is communication, different disciplines,

917
01:09:54,179 --> 01:09:56,829
different requirements, different everything.

918
01:09:56,829 --> 01:09:59,079
Communication between people is very important.

919
01:09:59,079 --> 01:09:59,650
All right.

920
01:09:59,650 --> 01:10:01,010
Where was I?

921
01:10:01,010 --> 01:10:08,010
Here is the orbital entry on Apollo, the two
flight tests that we did, 201 and 202.

922
01:10:08,179 --> 01:10:11,699
And, I'm sorry, I don't remember why we called
them one, three, four.

923
01:10:11,699 --> 01:10:14,170
This was a design, there's another design
up here.

924
01:10:14,170 --> 01:10:15,229
That was a conservative.

925
01:10:15,229 --> 01:10:15,959
All right.

926
01:10:15,959 --> 01:10:22,959
Here are the five OFT flights on Shuttle,
heat rate and heat load, and there is the

927
01:10:23,239 --> 01:10:25,760
design.

928
01:10:25,760 --> 01:10:29,219
We do not have a whole lot of margin.

929
01:10:29,219 --> 01:10:34,119
But, as you saw from the previous chart, we
can fly it.

930
01:10:34,119 --> 01:10:38,179
We're obviously able to do it as long as the
TPS and the structure are intact, obviously.

931
01:10:38,179 --> 01:10:38,429
Any questions?

932
01:10:38,400 --> 01:10:38,650
Yes.

933
01:10:38,510 --> 01:10:39,539
How much does your ability to control the
trajectory play into that?

934
01:10:39,539 --> 01:10:46,539
I mean it seems like you'd be able to control
the trajectory of the Shuttle a lot more precise

935
01:10:49,039 --> 01:10:56,039
than you would Apollo.

936
01:10:56,300 --> 01:10:56,719
Yes.

937
01:10:56,719 --> 01:10:57,139
Absolutely.

938
01:10:57,139 --> 01:11:01,619
You've got a body flap on there, in particular,
to trim angle-of-attack.

939
01:11:01,619 --> 01:11:06,130
We also have RCS engines which we'd use if
we would have to.

940
01:11:06,130 --> 01:11:08,489
And, in some cases, we have to.

941
01:11:08,489 --> 01:11:11,969
And you've got aileron settings which primarily
are used later.

942
01:11:11,969 --> 01:11:13,780
But, yes, crucial.

943
01:11:13,780 --> 01:11:20,329
In terms of getting this level of precision
you need control.

944
01:11:20,329 --> 01:11:27,329
But isn't the most important factor the flight
path angle, the angle between the velocity

945
01:11:29,139 --> 01:11:30,579
vector and the local horizontal at [400,000?]
feet?

946
01:11:30,579 --> 01:11:30,940
Initially yes.

947
01:11:30,940 --> 01:11:34,199
On Shuttle you could modulate that.

948
01:11:34,199 --> 01:11:34,749
Yes.

949
01:11:34,749 --> 01:11:40,150
And, actually, you see some of these wiggles,
you know, we have highs and lows.

950
01:11:40,150 --> 01:11:47,150
We have hurricanes and high pressure areas,
but the atmosphere is an exponential decay.

951
01:11:48,190 --> 01:11:54,820
And any waves, any ripples, by the time you
get to the tail end of the whip it can get

952
01:11:54,820 --> 01:11:57,289
very significant.

953
01:11:57,289 --> 01:12:01,769
And so there are density variations that you
really don't know about until you hit them.

954
01:12:01,769 --> 01:12:05,840
And being able to control is sort of crucial
there.

955
01:12:05,840 --> 01:12:11,829
Coming back from the moon right on, that initial
angle is crucial, and the de-orbit from orbit

956
01:12:11,829 --> 01:12:12,679
obviously the same thing.

957
01:12:12,679 --> 01:12:19,679
Any other questions on this before we go to
the next chart?

958
01:12:19,820 --> 01:12:20,590
OK.

959
01:12:20,590 --> 01:12:22,150
All right.

960
01:12:22,150 --> 01:12:26,780
I mentioned three levels of aerothermodynamic
methodology.

961
01:12:26,780 --> 01:12:32,090
One is to correlate in the wind tunnel and
relate everything to reference heating or

962
01:12:32,090 --> 01:12:38,479
stagnation point heating, which is what we
did on the capsules which are good blunt vehicles.

963
01:12:38,479 --> 01:12:43,340
The real technology challenge on the Shuttle
was the geometry.

964
01:12:43,340 --> 01:12:49,889
It was a lot more complicated than just the
shock and a stagnation point and flow around

965
01:12:49,889 --> 01:12:52,340
a blunt vehicle.

966
01:12:52,340 --> 01:12:55,599
You name it, you've got it, in terms of flow
on this thing.

967
01:12:55,599 --> 01:13:02,130
Now, the way this was modeled in terms of
-- When we started, we didn't have computational

968
01:13:02,130 --> 01:13:03,920
fluid dynamics.

969
01:13:03,920 --> 01:13:10,179
The design methodology that was used to actually
design the system was to model the flow.

970
01:13:10,179 --> 01:13:14,579
Obviously, up front here looks kind of like
a sphere.

971
01:13:14,579 --> 01:13:16,780
And so I calculate the heating on a sphere.

972
01:13:16,780 --> 01:13:21,510
I go into a wind tunnel and look at the actual
data and relate that and say, well, that's

973
01:13:21,510 --> 01:13:25,260
kind of like a sphere of two foot radius.

974
01:13:25,260 --> 01:13:26,550
So that's my heating there.

975
01:13:26,550 --> 01:13:33,199
I look at flow down the center line -- And,
I'm sorry, this wedge isn't supposed to be

976
01:13:33,199 --> 01:13:35,829
wedge or a flat platted angle-of-attack.

977
01:13:35,829 --> 01:13:37,949
This flat surface down here looks kind of
like a wedge.

978
01:13:37,949 --> 01:13:44,599
Well, I can calculate [a boundary?] on a wedge
given the pressure which Newtonian would work

979
01:13:44,599 --> 01:13:45,179
fine.

980
01:13:45,179 --> 01:13:49,900
Certainly, in the blunt regions and on a wedge,
I can do that flow.

981
01:13:49,900 --> 01:13:55,729
I can do a swept cylinder for the leading
edge and I can do a comb for the boundary

982
01:13:55,729 --> 01:13:55,979
layer.
I can take diagnostics in a wind tunnel, look
at the boundary layer path and say, boy, this

983
01:14:02,690 --> 01:14:05,630
thing is spreading kind of like a cone.

984
01:14:05,630 --> 01:14:07,229
This is the design methodology.

985
01:14:07,229 --> 01:14:12,059
These are all one-dimensional flows for the
boundary layer.

986
01:14:12,059 --> 01:14:16,619
These are geometric flow models where the
boundary layer is basically one-dimensional.

987
01:14:16,619 --> 01:14:20,999
And even though, for example, on a cone, the
boundary layer is spreading, it's still a

988
01:14:20,999 --> 01:14:22,349
one-dimensional flow.

989
01:14:22,349 --> 01:14:29,349
So I calculated in a wind tunnel what the
heating would be at this particular condition.

990
01:14:29,900 --> 01:14:34,369
I calculate, for example, flat plate.

991
01:14:34,369 --> 01:14:38,860
This heating rate has a function of distance
from the nose to the tail if you want.

992
01:14:38,860 --> 01:14:45,860
This is what I calculate, here is what I measure,
a little factor in there.

993
01:14:46,159 --> 01:14:51,320
But I assume whatever I don't know in the
wind tunnel, I don't know in flight, too.

994
01:14:51,320 --> 01:14:58,320
But I take this analysis which can include
the chemistry, all the nice things that go

995
01:14:59,139 --> 01:15:00,789
on in flight.

996
01:15:00,789 --> 01:15:06,690
So I calibrate it to wind tunnel which is
basically an empirical flow field now and

997
01:15:06,690 --> 01:15:07,559
I take that to flight.

998
01:15:07,559 --> 01:15:08,369
It works pretty well.

999
01:15:08,369 --> 01:15:11,510
It really does.

1000
01:15:11,510 --> 01:15:18,159
Better than my normal shock Reynolds number
that I gave to the trajectory guys.

1001
01:15:18,159 --> 01:15:22,449
Actually, there are areas where there is significant
disagreement.

1002
01:15:22,449 --> 01:15:29,130
But mostly they are pretty consistent because
they're reflecting the basic diffusion of

1003
01:15:29,130 --> 01:15:34,079
the boundary layer and the basic physics that
I tried to talk about in the beginning here.

1004
01:15:34,079 --> 01:15:38,999
It is very important to normalize what you're
doing to something fundamental.

1005
01:15:38,999 --> 01:15:42,869
If you cannot do it on the back of the envelope,
have a question about it.

1006
01:15:42,869 --> 01:15:48,119
If you cannot back it up with the back of
the envelope, have a question about it.

1007
01:15:48,119 --> 01:15:50,550
So this is the design methodology.

1008
01:15:50,550 --> 01:15:57,550
I mentioned the Apollo methodology which was
used for quick numbers and for trajectories.

1009
01:15:58,219 --> 01:16:02,489
The third level is a computational fluid dynamics.

1010
01:16:02,489 --> 01:16:09,489
I'm only going to show results from the technology
that we had at the time we flew the Shuttle.

1011
01:16:12,269 --> 01:16:18,559
Since then computers have done so much, we
can do so much more, but I want to compare

1012
01:16:18,559 --> 01:16:25,559
what we expected and what we actually got
with the technology we had at the time.

1013
01:16:26,530 --> 01:16:27,880
Boundary layer transition.

1014
01:16:27,880 --> 01:16:34,880
I talked about the boundary between the turbulent
and laminar heating.

1015
01:16:35,489 --> 01:16:39,489
Characteristically, and in the Shuttle level,
your heating goes up by about a factor of

1016
01:16:39,489 --> 01:16:40,619
three.

1017
01:16:40,619 --> 01:16:45,489
If you go to higher Reynolds numbers it can
get significantly higher, so you want to avoid

1018
01:16:45,489 --> 01:16:48,369
that factor of three.

1019
01:16:48,369 --> 01:16:53,179
Our initial estimate on the effect of roughness,
I have to say, was not as good as it should

1020
01:16:53,179 --> 01:16:56,090
have been, but the technology wasn't really
there.

1021
01:16:56,090 --> 01:16:56,999
This is the logic.

1022
01:16:56,999 --> 01:16:59,570
And I won't go through in intimate detail.

1023
01:16:59,570 --> 01:17:05,800
Just to point out the complexity to recognize
the level of effort that goes into getting

1024
01:17:05,800 --> 01:17:07,840
a basic database to design vehicles.

1025
01:17:07,840 --> 01:17:12,920
This is all in that document in that conference
report.

1026
01:17:12,920 --> 01:17:13,429
And there are two copies, I think.

1027
01:17:13,429 --> 01:17:14,469
I brought a copy, and I think there is a copy
in the library that Dr.

1028
01:17:14,469 --> 01:17:16,979
Hoffman has on reserve, but this is all documented
in there.

1029
01:17:16,979 --> 01:17:17,999
Yes.

1030
01:17:17,999 --> 01:17:24,999
And I won't spend much time other than to
say we first looked at smooth body transition.

1031
01:17:25,499 --> 01:17:27,590
This is heating rate versus distance.

1032
01:17:27,590 --> 01:17:29,110
Smooth body.

1033
01:17:29,110 --> 01:17:31,630
And then we put roughness in.

1034
01:17:31,630 --> 01:17:37,170
We actually went to cryogenic models with
simulated tiles to get that boundary layer

1035
01:17:37,170 --> 01:17:40,849
to suck down to be a little better simulation
of flight.

1036
01:17:40,849 --> 01:17:46,269
The alternative was to put bowling balls on
the surface of the thing to try to trip the

1037
01:17:46,269 --> 01:17:48,800
flow, and that didn't have anything to do
with physical reality.

1038
01:17:48,800 --> 01:17:51,369
So a lot of work there.

1039
01:17:51,369 --> 01:17:58,369
We related and took the simulations for the
transition and came up with an effective roughness

1040
01:17:59,809 --> 01:18:01,940
relative to smooth body transition.

1041
01:18:01,940 --> 01:18:06,860
Again, I don't claim to understand turbulence,
I certainly don't claim to understand transition

1042
01:18:06,860 --> 01:18:09,099
and certainly on a complex configuration.

1043
01:18:09,099 --> 01:18:12,070
So then we correlated that and we had predictions.

1044
01:18:12,070 --> 01:18:14,510
And you will see some of that in a few minutes.

1045
01:18:14,510 --> 01:18:18,699
On the tile problem on the last mission when
those little gap fillers came out, do you

1046
01:18:18,699 --> 01:18:20,860
think that it tripped the boundary layer?

1047
01:18:20,860 --> 01:18:22,510
No, I don't.

1048
01:18:22,510 --> 01:18:27,340
On the other hand, some of the people that
had been correlating the various missions

1049
01:18:27,340 --> 01:18:28,889
felt that we would.

1050
01:18:28,889 --> 01:18:31,510
And the problem is it was the first time we
had a picture.

1051
01:18:31,510 --> 01:18:32,389
Yeah, I understand.

1052
01:18:32,389 --> 01:18:37,329
We had tile gaps after we landed and we said
oh, gee, this is the relationship.

1053
01:18:37,329 --> 01:18:43,119
There was a lot of correlation, but I'm not
sure it was that valid.

1054
01:18:43,119 --> 01:18:50,119
I really don't think so.

1055
01:18:50,499 --> 01:18:52,099
Now, this is the surface catalysis.

1056
01:18:52,099 --> 01:18:53,309
I haven't really talked about that.

1057
01:18:53,309 --> 01:19:00,309
I talked about the gas going from molecular
to dissociated, ionized to weekly ionized.

1058
01:19:01,070 --> 01:19:05,780
When you get back to the surface conditions,
you're back to a molecule again.

1059
01:19:05,780 --> 01:19:07,820
Now, I am simplifying things here.

1060
01:19:07,820 --> 01:19:12,510
But I think the way I look at it is you start
out with a molecule, you blast it apart, you

1061
01:19:12,510 --> 01:19:17,050
have atoms, you get back to the surface of
the vehicle.

1062
01:19:17,050 --> 01:19:19,800
And at equilibrium now you're back to a microstate.

1063
01:19:19,800 --> 01:19:20,050
Yes.

1064
01:19:19,809 --> 01:19:20,059
In the whole design process, was the shape
of the wings and the underbelly designed first

1065
01:19:19,880 --> 01:19:20,130
and then you calculated properties?

1066
01:19:19,900 --> 01:19:23,010
Or, did you have to go back and say no, this
redesign is impossible?

1067
01:19:23,010 --> 01:19:30,010
Because of the heating do it this way.

1068
01:19:38,170 --> 01:19:38,420
Was there a [cyclic process?

1069
01:19:38,219 --> 01:19:38,469
(check)] or was it one way?
It was primarily one way.

1070
01:19:39,429 --> 01:19:43,570
Here is the aerodynamic requirement in order
to come in.

1071
01:19:43,570 --> 01:19:49,659
The biggest exception of that was on boundary
layer transition.

1072
01:19:49,659 --> 01:19:56,449
That classic if the structures guys design
an airplane or if the electronics guys design

1073
01:19:56,449 --> 01:20:02,769
an airplane or the aerodynamic guys, they
all come out to be different airplanes.

1074
01:20:02,769 --> 01:20:08,539
The prime thing was the aerodynamics, to be
able to control it and bring it in.

1075
01:20:08,539 --> 01:20:13,170
We did alter it relative to where the thermal
protection system was.

1076
01:20:13,170 --> 01:20:16,900
The other thing we did is don't fool with
Mother Nature.

1077
01:20:16,900 --> 01:20:21,679
The structures guys like to make things nice
and flat or cylindrical.

1078
01:20:21,679 --> 01:20:26,469
And the flow is a continuous radius curvature
type phenomenon.

1079
01:20:26,469 --> 01:20:31,030
And that difference is very, very important,
particularly for boundary layer transition.

1080
01:20:31,030 --> 01:20:38,030
So we did fair the geometry to keep the boundary
layer transition essentially two orders of

1081
01:20:38,760 --> 01:20:41,229
magnitude lower than it might have been.

1082
01:20:41,229 --> 01:20:44,510
But overall I would say predominantly it is
aerodynamics.

1083
01:20:44,510 --> 01:20:47,739
And we tried to calculate the heating to the
configuration that we had.

1084
01:20:47,739 --> 01:20:48,760
[UNINTELLIGIBLE PHRASE] [would you change?

1085
01:20:48,760 --> 01:20:55,760
< 3 or 4 of this type of question ] The only
thing I would have preferred to have done

1086
01:21:10,939 --> 01:21:16,409
is fly higher angle-of-attack which could
have reconfigured the thermal protection system.

1087
01:21:16,409 --> 01:21:22,059
The tiles are a very efficient system.

1088
01:21:22,059 --> 01:21:27,459
They are fragile but are very efficient from
[an entry?] standpoint.

1089
01:21:27,459 --> 01:21:33,739
The carbon nose and leading edge are heavy
and they don't insulate worth a darn.

1090
01:21:33,739 --> 01:21:39,059
I mean that's a layer of carbon.

1091
01:21:39,059 --> 01:21:43,159
When it gets hot it radiates out, but it also
radiates in.

1092
01:21:43,159 --> 01:21:46,760
And so you have to have an insulation behind
that.

1093
01:21:46,760 --> 01:21:52,420
And, in fact, the way we're able to reconcile
the environment with the temperature capability

1094
01:21:52,420 --> 01:21:56,699
of the carbon is it's sort of like an oven.

1095
01:21:56,699 --> 01:22:03,699
And it's easier to illustrate on a leading
edge.

1096
01:22:06,269 --> 01:22:11,639
Just picture a two-dimensional air foil at
angle-of-attack.

1097
01:22:11,639 --> 01:22:17,070
And a carbon section, if you want, covers
from here to here.

1098
01:22:17,070 --> 01:22:22,760
Now, if I look at the heating distribution,
here the heating is quite high, still high

1099
01:22:22,760 --> 01:22:25,439
over here, still high over here, still high
over here.

1100
01:22:25,439 --> 01:22:27,610
Boy, it drops off very quickly over here.

1101
01:22:27,610 --> 01:22:34,610
Well, if I can radiate this energy over here,
this basically becomes a uniform temperature

1102
01:22:35,280 --> 01:22:36,119
oven first order.

1103
01:22:36,119 --> 01:22:39,999
And insulation is back here.

1104
01:22:39,999 --> 01:22:43,349
I don't know how you illustrate insulation.

1105
01:22:43,349 --> 01:22:47,189
Insulation is back here to keep the lower
temperature structure from getting too hot.

1106
01:22:47,189 --> 01:22:52,590
I don't think a lot of people realize that,
but behind the carbon-carbon, on the leading

1107
01:22:52,590 --> 01:22:57,630
edge of the wing and the nose, there are actually
tiles in there just like on the outside of

1108
01:22:57,630 --> 01:22:59,420
the rest of the Shuttle.

1109
01:22:59,420 --> 01:23:04,789
So this is sort of a staged thermal protection
system.

1110
01:23:04,789 --> 01:23:10,349
And if we didn't do that, if we put the tiles
right up here then this temperature could

1111
01:23:10,349 --> 01:23:15,689
exceed the carbon capability.

1112
01:23:15,689 --> 01:23:20,499
By flying at high angle of attack, I could
reduce the amount of carbon.

1113
01:23:20,499 --> 01:23:25,809
What was the problem going to a higher angle
of attack?

1114
01:23:25,809 --> 01:23:26,599
You said there was a conflict.

1115
01:23:26,599 --> 01:23:26,849
Yeah.

1116
01:23:26,739 --> 01:23:30,719
The problem was one of the requirements was
long cross-range, and you don't get that at

1117
01:23:30,719 --> 01:23:31,300
high angle of attack.

1118
01:23:31,300 --> 01:23:34,360
I mean high angle of attack just comes in
ballistically, if you want.

1119
01:23:34,360 --> 01:23:39,030
You roll around the velocity vector so you
get a little L/D.

1120
01:23:39,030 --> 01:23:43,329
But, if you want to go range, you need more
lift so you need to drop your angle of attack.

1121
01:23:43,329 --> 01:23:47,249
A very significant design parameter for Shuttle.

1122
01:23:47,249 --> 01:23:52,769
And if you recall the trajectories, it was
primarily needed from a polar orbit where

1123
01:23:52,769 --> 01:23:56,110
you're trying to get to a particular runway.

1124
01:23:56,110 --> 01:24:03,110
You don't have as much capability coming from
polar orbit as you do from equatorial or lower

1125
01:24:03,159 --> 01:24:05,239
inclinational orbits.

1126
01:24:05,239 --> 01:24:12,239
You remember we were talking about energy
management, and I talked about how if you

1127
01:24:12,789 --> 01:24:19,789
end up low on energy you actually have to
decrease your angle-of-attack even more and

1128
01:24:20,039 --> 01:24:22,959
no S turns or anything, just straight in.

1129
01:24:22,959 --> 01:24:26,429
But there is a thermal boundary.

1130
01:24:26,429 --> 01:24:32,260
I don't remember whether it was 38 degrees
or 37, but 40 degrees was nominal.

1131
01:24:32,260 --> 01:24:34,679
And you really didn't have a whole lot to
play with.

1132
01:24:34,679 --> 01:24:41,099
If you drop your angle-of-attack in order
to increase your lift so that you can stretch

1133
01:24:41,099 --> 01:24:46,249
your trajectory to make the runway, at some
point you're going to violate thermal constraints

1134
01:24:46,249 --> 01:24:49,420
and start melting your thermal protection.

1135
01:24:49,420 --> 01:24:56,420
There were years of concepts and vehicles
that were developed and flown, test vehicles

1136
01:24:58,800 --> 01:25:02,909
with different emphasis.

1137
01:25:02,909 --> 01:25:05,880
And there were some aerothermodynamic vehicles
nice and smooth.

1138
01:25:05,880 --> 01:25:07,369
I mean it just looked beautiful.

1139
01:25:07,369 --> 01:25:11,860
It looked like something an architect would
come up with, if you want.

1140
01:25:11,860 --> 01:25:13,590
And, from a heating standpoint, they worked
well.

1141
01:25:13,590 --> 01:25:18,880
But the structures guys, it was very heavy
from a structures standpoint to get all these

1142
01:25:18,880 --> 01:25:21,800
compound curvatures, this, that and the other
thing.

1143
01:25:21,800 --> 01:25:25,309
There were also vehicles that were designed
specifically from a structures standpoint.

1144
01:25:25,309 --> 01:25:26,610
And I'm not knocking the structure people.

1145
01:25:26,610 --> 01:25:27,889
I do a lot of structure work, too.

1146
01:25:27,889 --> 01:25:34,449
But there was one that had discontinuous two
flat surfaces to be able to handle all kinds

1147
01:25:34,449 --> 01:25:34,969
of good stuff.

1148
01:25:34,969 --> 01:25:39,059
And that was a terrible configuration from
an aerothermodynamic standpoint.

1149
01:25:39,059 --> 01:25:43,150
So there actually was a heritage of all kinds
of attempts.

1150
01:25:43,150 --> 01:25:46,059
The big challenge was how do you land some
of these things?

1151
01:25:46,059 --> 01:25:51,739
A nice hypersonic aerothermodynamic configuration
and aerodynamic configuration, OK, now you

1152
01:25:51,739 --> 01:25:53,659
try to put it down the runway and it is hot.

1153
01:25:53,659 --> 01:26:00,320
A lot of test pilots had some problems with
some of these vehicles.

1154
01:26:00,320 --> 01:26:04,610
There are all kinds of heritage of people
pursuing this, that and the other thing.

1155
01:26:04,610 --> 01:26:06,949
And one of them was aerothermodynamic design.

1156
01:26:06,949 --> 01:26:11,650
And it didn't have these big wings that we
have on Shuttle, but it was hot as can be

1157
01:26:11,650 --> 01:26:12,360
coming in.

1158
01:26:12,360 --> 01:26:17,760
I think the Shuttle frankly, I mean I don't
look at it just from an aerothermodynamic

1159
01:26:17,760 --> 01:26:18,010
standpoint.

1160
01:26:17,889 --> 01:26:23,239
If I look at it overall, we needed all the
lift we could get on landing.

1161
01:26:23,239 --> 01:26:28,909
And, as it was, we had to build a pretty special
runway to do that or go to the dessert.

1162
01:26:28,909 --> 01:26:31,300
So, from an aerodynamic standpoint, we would
like a lot higher lift.

1163
01:26:31,300 --> 01:26:37,019
In fact, that is a nice area for innovation.

1164
01:26:37,019 --> 01:26:42,079
Some of the earlier concepts for vehicles,
you're probably with familiar with, capsules

1165
01:26:42,079 --> 01:26:45,130
with rotogyros on them that power up as you
come down.

1166
01:26:45,130 --> 01:26:51,260
Boosters, if you wanted a cylindrical configuration
with a straight wing on it that swings out.

1167
01:26:51,260 --> 01:26:57,969
Now you've got to lift an airplane when it
comes in to land, but there are problems with

1168
01:26:57,969 --> 01:26:58,219
all of them.
In that case, the weight estimate for all
the hardware and all that kind of good stuff

1169
01:27:02,689 --> 01:27:03,559
was excessive.

1170
01:27:03,559 --> 01:27:06,429
Anyway, that is a real challenge for design.

1171
01:27:06,429 --> 01:27:10,719
I understand you folks are going to come up
with a better design, some real innovative

1172
01:27:10,719 --> 01:27:14,340
thoughts in terms of how to marry all these
different requirements.

1173
01:27:14,340 --> 01:27:21,340
In my opinion, the mindset for hypersonic
vehicles was [UNINTELLIGIBLE] [fibercups]

1174
01:27:22,510 --> 01:27:24,530
have straight wings.

1175
01:27:24,530 --> 01:27:28,979
Supersonics like this and, boy, hypersonic
ought to be like this.

1176
01:27:28,979 --> 01:27:30,249
I mean that's just kind of the mindset.

1177
01:27:30,249 --> 01:27:32,639
And it kind of works.

1178
01:27:32,639 --> 01:27:35,880
But an entry vehicle is a whole different
vehicle.

1179
01:27:35,880 --> 01:27:38,099
Capsules work fine for their requirements.

1180
01:27:38,099 --> 01:27:42,099
Shuttle has been a fantastic marriage of different
requirements.

1181
01:27:42,099 --> 01:27:46,179
The challenge today, and I think the reason
for the class, is how about some new and better

1182
01:27:46,179 --> 01:27:46,709
ideas.

1183
01:27:46,709 --> 01:27:51,979
It's not going to be easy but there's a big
need.

1184
01:27:51,979 --> 01:27:52,749
OK.

1185
01:27:52,749 --> 01:27:56,599
Surface catalysis.

1186
01:27:56,599 --> 01:28:00,729
First order, start with molecules in a free
strain.

1187
01:28:00,729 --> 01:28:01,689
Atoms.

1188
01:28:01,689 --> 01:28:03,909
Some ionized.

1189
01:28:03,909 --> 01:28:10,909
And then I get to a surface back here at equilibrium,
I am back to molecules again.

1190
01:28:12,159 --> 01:28:14,840
They're pretty hot but they are still molecules.

1191
01:28:14,840 --> 01:28:20,719
Well, Professor Fay did a wonderful job in
looking at a stagnation point on a sphere

1192
01:28:20,719 --> 01:28:22,159
and saying, well, we've got limits.

1193
01:28:22,159 --> 01:28:27,860
If we're at equilibrium, that is the chemistry
is fast enough that you're always at equilibrium,

1194
01:28:27,860 --> 01:28:32,059
all the way through to the boundary layer,
you get this amount of heating.

1195
01:28:32,059 --> 01:28:36,989
And that amount of heating included not just
the conduction but the chemistry changes going

1196
01:28:36,989 --> 01:28:43,989
from dissociated atoms, if you want, and putting
that energy back into translation and rotation

1197
01:28:44,360 --> 01:28:46,889
into molecules.

1198
01:28:46,889 --> 01:28:53,889
Or the other limit is completely out of equilibrium
where all you get is the translational energy.

1199
01:28:56,729 --> 01:29:03,729
And what happens there, however, is if the
surface is catalytic -- That is I
have atoms coming into the surface
and they are, if you want for discussion,

1200
01:29:17,280 --> 01:29:18,729
absorbed on the surface.

1201
01:29:18,729 --> 01:29:23,780
And then another atom comes in, recombines
and forms a molecule that releases that energy.

1202
01:29:23,780 --> 01:29:26,119
That is a catalytic surface.

1203
01:29:26,119 --> 01:29:32,840
So you have sort of two limits, a completely
catalytic surface and a non-catalytic surface

1204
01:29:32,840 --> 01:29:34,360
in a non-equilibrium environment.

1205
01:29:34,360 --> 01:29:37,639
And that is very significant on Shuttle, and
you will see that in some data I am going

1206
01:29:37,639 --> 01:29:43,329
to show here in a short while.

1207
01:29:43,329 --> 01:29:47,849
This is just the concept which, again, as
Aaron mentioned is in the report.

1208
01:29:47,849 --> 01:29:52,650
We had to go to arc jets and spectroscopic
diagnostics and flow models of what is going

1209
01:29:52,650 --> 01:29:58,590
on in the arc jet to understand the surface
catalysis of tiles and carbon.

1210
01:29:58,590 --> 01:30:04,320
We had to model the flow and model the chemistry
to come up with an efficiency.

1211
01:30:04,320 --> 01:30:08,139
Then we go to flight with similar analysis
and predict, and I will show some predictions

1212
01:30:08,139 --> 01:30:08,559
of this.

1213
01:30:08,559 --> 01:30:15,559
This is a significant phenomenon at the high
altitudes, low density for the Shuttle.

1214
01:30:17,380 --> 01:30:18,849
Any questions on surface catalysis?

1215
01:30:18,849 --> 01:30:25,849
I always found it amazing that you don't think
of designing a space vehicle that you have

1216
01:30:28,349 --> 01:30:29,389
to worry about chemistry.

1217
01:30:29,389 --> 01:30:33,349
There are lots of things you have to worry
about, but chemistry I had never thought about.

1218
01:30:33,349 --> 01:30:40,099
But when I first heard about the surface catalysis
problem, there are just so many things you

1219
01:30:40,099 --> 01:30:42,380
have to take into account.

1220
01:30:42,380 --> 01:30:46,679
This is the flow field.

1221
01:30:46,679 --> 01:30:53,679
At the time of this conference and the OFT
flights, again, the design was the methodology

1222
01:30:55,789 --> 01:31:00,999
that I explained where you use simple configurations,
model it and extrapolate the flight.

1223
01:31:00,999 --> 01:31:06,639
This is sort of the level of the technology,
and this is at 20% of the vehicle length.

1224
01:31:06,639 --> 01:31:11,570
If the vehicle length is 1.0, it is 0.2, 0.4,
0.5 cross-sections.

1225
01:31:11,570 --> 01:31:14,849
And it's just the cross flow speed contours.

1226
01:31:14,849 --> 01:31:21,849
The only point I'm trying to make here is
this is kind of the level of CFD that we had

1227
01:31:22,579 --> 01:31:24,219
at the time.

1228
01:31:24,219 --> 01:31:27,340
Since then, boy, we've gone gangbusters.

1229
01:31:27,340 --> 01:31:30,780
But this kind of the level.

1230
01:31:30,780 --> 01:31:33,619
We did not have the finite rate chemistry
in this.

1231
01:31:33,619 --> 01:31:37,039
That is a lot more computer than we could
handle.

1232
01:31:37,039 --> 01:31:41,869
At this point, we were trying to develop algorithms
and grids.

1233
01:31:41,869 --> 01:31:48,829
And, as I said, we could, in certain regions
of the body, compute the heat transfer as

1234
01:31:48,829 --> 01:31:50,800
accurately as we could measure it in the wind
tunnel.

1235
01:31:50,800 --> 01:31:52,199
But that's not at flight.

1236
01:31:52,199 --> 01:31:56,729
That is just sort of a picture of where we
were, and that is where I'm focusing in terms

1237
01:31:56,729 --> 01:32:03,729
of comparing what we expected from what we
actually got.

1238
01:32:04,820 --> 01:32:11,090
Now I'm going to show results in terms of
temperature as a function of time.

1239
01:32:11,090 --> 01:32:16,499
This is the entry time from about 400 to 1,000
seconds.

1240
01:32:16,499 --> 01:32:18,459
You notice this plateau.

1241
01:32:18,459 --> 01:32:25,110
You're talking about 20 minutes entry and
ten minutes of flying it so you don't exceed

1242
01:32:25,110 --> 01:32:27,630
the thermal protection system.

1243
01:32:27,630 --> 01:32:29,360
I am going to show three locations.

1244
01:32:29,360 --> 01:32:35,659
Right up here at the nose, just behind the
carbon, mid body and aft body.

1245
01:32:35,659 --> 01:32:41,289
Now, the flow field technology, we had a heck
of a time getting from our starting solution,

1246
01:32:41,289 --> 01:32:46,590
subsonic flow, which used one particular algorithm
[to match?] supersonically down the vehicle.

1247
01:32:46,590 --> 01:32:49,570
We succeeded in doing that prior to flying.

1248
01:32:49,570 --> 01:32:55,849
And we were able to compute up to the point
where the shocks from the wing intersect the

1249
01:32:55,849 --> 01:32:56,989
shock from the fuselage.

1250
01:32:56,989 --> 01:33:00,219
And then we had another subsonic region and
we weren't able to handle it.

1251
01:33:00,219 --> 01:33:01,079
Now we can do that.

1252
01:33:01,079 --> 01:33:06,079
But at the time we flew, we could only compute
up to about here.

1253
01:33:06,079 --> 01:33:08,979
Now, this is not what you'd see in a journal.

1254
01:33:08,979 --> 01:33:11,920
I will show you one you'd see in a journal
here in the middle.

1255
01:33:11,920 --> 01:33:13,699
This is right behind the carbon.

1256
01:33:13,699 --> 01:33:19,360
Now, what we did is we computed at different
times through the trajectory and then there

1257
01:33:19,360 --> 01:33:24,729
were correlations to get the history.

1258
01:33:24,729 --> 01:33:26,769
This is JSC prediction right here.

1259
01:33:26,769 --> 01:33:30,590
Now, we didn't worry about exceeding Stanton
number one.

1260
01:33:30,590 --> 01:33:35,959
That is we didn't worry about the heat transfer
being higher than the energy flux to the vehicle

1261
01:33:35,959 --> 01:33:39,739
up here because it doesn't, I mean it is,
if you look at these numbers, we should have

1262
01:33:39,739 --> 01:33:44,070
accounted for that, but it's not that important
so don't worry about that portion of the curve.

1263
01:33:44,070 --> 01:33:44,829
Up here is very important.

1264
01:33:44,829 --> 01:33:46,429
Now, this is temperature.

1265
01:33:46,429 --> 01:33:50,699
And I just mentioned epsilon sigma T to the
fourth.

1266
01:33:50,699 --> 01:33:55,849
That means the heat transfer is four times
a bad.

1267
01:33:55,849 --> 01:33:59,559
We did a terrible job up here, and I will
get back to that.

1268
01:33:59,559 --> 01:34:04,479
Now over here what happens is I've tried to
stay laminar.

1269
01:34:04,479 --> 01:34:05,119
I come down.

1270
01:34:05,119 --> 01:34:07,829
And this was really a stretch.

1271
01:34:07,829 --> 01:34:11,420
We never got turbulence heating up on the
nose.

1272
01:34:11,420 --> 01:34:16,228
Way beyond wind tunnel, way beyond our experience
base, but the model just went up there.

1273
01:34:16,228 --> 01:34:17,478
So we really didn't expect that.

1274
01:34:17,478 --> 01:34:20,280
That was a pretty conservative boundary layer
transition.

1275
01:34:20,280 --> 01:34:26,519
And then, son of a gun, the actual temperature
is higher than turbulent even though it would

1276
01:34:26,519 --> 01:34:30,709
appear to be laminar.

1277
01:34:30,709 --> 01:34:33,559
What is really going on here?

1278
01:34:33,559 --> 01:34:35,340
This is right behind a carbon.

1279
01:34:35,340 --> 01:34:38,619
The carbon is an oven.

1280
01:34:38,619 --> 01:34:42,550
As the service temperature of the tile drops,
which drops very quickly because it re-radiates.

1281
01:34:42,550 --> 01:34:43,639
Not because it diffuses.

1282
01:34:43,639 --> 01:34:45,699
We control that.

1283
01:34:45,699 --> 01:34:48,119
It re-radiates so, as soon as the heating
drops, the temperature drops.

1284
01:34:48,119 --> 01:34:51,900
I mean this is almost identical to reflecting
what the heating is.

1285
01:34:51,900 --> 01:34:54,659
It is dropping like mad.

1286
01:34:54,659 --> 01:34:56,449
And, indeed, we're agreeing quite well.

1287
01:34:56,449 --> 01:35:00,150
We're kind of out of the real bad chemistry
and surface catalysis which is part of the

1288
01:35:00,150 --> 01:35:02,909
problem here.

1289
01:35:02,909 --> 01:35:08,249
And here, all of a sudden, the laminar is
higher than the turbulent.

1290
01:35:08,249 --> 01:35:09,760
The carbon is this oven.

1291
01:35:09,760 --> 01:35:10,900
It doesn't cool down.

1292
01:35:10,900 --> 01:35:13,349
Even sitting on a runway it is as hot as can
be.

1293
01:35:13,349 --> 01:35:16,789
If you think about it, it's got this oven.

1294
01:35:16,789 --> 01:35:19,999
It can only radiate out of surface and inside
it is still radiating.

1295
01:35:19,999 --> 01:35:24,619
Just like when you turn your oven off at home,
it takes a while for it to cool down.

1296
01:35:24,619 --> 01:35:29,340
The flow is going across the nose and actually
heating the air.

1297
01:35:29,340 --> 01:35:32,719
At least changing the boundary layer profile
so that the heating is higher.

1298
01:35:32,719 --> 01:35:34,030
How do I know that?

1299
01:35:34,030 --> 01:35:37,610
[Here is your tank?

1300
01:35:37,610 --> 01:35:38,510
yup].

1301
01:35:38,510 --> 01:35:44,570
Over here there can be a little bit of that
effect also, and it takes a while to preheat

1302
01:35:44,570 --> 01:35:46,380
the oven, if you want, if you're doing any
cooking.

1303
01:35:46,380 --> 01:35:48,519
There is a little bit of that.

1304
01:35:48,519 --> 01:35:50,929
But, predominantly, this is the chemistry.

1305
01:35:50,929 --> 01:35:56,539
See, we come much closer together here in
time.

1306
01:35:56,539 --> 01:35:59,179
This is predominantly the chemistry.

1307
01:35:59,179 --> 01:36:06,179
At this time, this non-equilibrium relaxation
distance is about six inches.

1308
01:36:06,900 --> 01:36:10,840
Now, we're not into radiating gas but we're
certainly not into equilibrium.

1309
01:36:10,840 --> 01:36:16,590
That is also a factor and that is not well-included,
even today in my opinion, other than through

1310
01:36:16,590 --> 01:36:20,789
correlations of the shock in what's going
on here.

1311
01:36:20,789 --> 01:36:24,679
You won't see that on paper because we did
a terrible job there.

1312
01:36:24,679 --> 01:36:28,189
We did not exceed design material requirements.

1313
01:36:28,189 --> 01:36:33,809
And I don't think I put anything in there
about -- Well, when I get to the thermal protection

1314
01:36:33,809 --> 01:36:39,669
system, I will go through the philosophy of
having confidence to fly.

1315
01:36:39,669 --> 01:36:43,570
And, obviously, with our predictions, we would
not exceed the top capabilities so we could

1316
01:36:43,570 --> 01:36:44,530
fly.

1317
01:36:44,530 --> 01:36:47,439
But we were off here badly.

1318
01:36:47,439 --> 01:36:51,179
But at least you were off in the conservative
direction.

1319
01:36:51,179 --> 01:36:55,978
Well, that's the way we tried to be.

1320
01:36:55,978 --> 01:36:57,809
This I will get into.

1321
01:36:57,809 --> 01:37:01,469
This is really what we expected, to the best
of our understanding.

1322
01:37:01,469 --> 01:37:07,639
Yes, I was surprised at this also.

1323
01:37:07,639 --> 01:37:13,889
We did consider service catalysis, which I
will show here after a while, but we did not

1324
01:37:13,889 --> 01:37:18,978
really include the nonequilibrium flow in
the inviscid, what I've been talking here

1325
01:37:18,978 --> 01:37:19,599
about Apollo.

1326
01:37:19,599 --> 01:37:26,599
That was beyond our capability to do finite
rate chemistry in the inviscid flow field.

1327
01:37:26,739 --> 01:37:30,978
Why don't we go to mid body now?

1328
01:37:30,978 --> 01:37:31,239
All right.

1329
01:37:31,239 --> 01:37:36,840
Here is something you might see in a journal.

1330
01:37:36,840 --> 01:37:39,030
Right where we wanted it.

1331
01:37:39,030 --> 01:37:40,478
And that's where we had the most confidence,
too.

1332
01:37:40,478 --> 01:37:45,760
We got away from the subsonic, supersonic
condition.

1333
01:37:45,760 --> 01:37:47,239
We were into a marching solution.

1334
01:37:47,239 --> 01:37:51,400
That is as good as we could do it those days.

1335
01:37:51,400 --> 01:37:58,400
And we knew that transition was going to be
later than what we predicted because wind

1336
01:37:58,409 --> 01:37:59,889
tunnels, you've got walls.

1337
01:37:59,889 --> 01:38:02,570
You've got all kinds of reflected noise.

1338
01:38:02,570 --> 01:38:08,070
And wind tunnels are notoriously conservative
relative to boundary layer transition.

1339
01:38:08,070 --> 01:38:15,070
But, amazingly, the turbulent heating correlated
quite well.

1340
01:38:16,949 --> 01:38:19,559
And that even works with normal shock Reynolds
numbers.

1341
01:38:19,559 --> 01:38:26,300
I mean when you go back and look at all of
the Shuttle data with a crude back of the

1342
01:38:26,300 --> 01:38:33,300
envelope normal shock local heating to reference
heating, including turbulence, it is amazing.

1343
01:38:34,030 --> 01:38:36,228
It really is.

1344
01:38:36,228 --> 01:38:40,709
First order physics seems to hang in there,
in spite of all the complications of chemistry

1345
01:38:40,709 --> 01:38:42,419
and all the kinds of things that can happen.

1346
01:38:42,419 --> 01:38:46,139
You have to be careful, but overall things
usually work for you.

1347
01:38:46,139 --> 01:38:48,499
Again, that is academic there.

1348
01:38:48,499 --> 01:38:52,679
If we put in a constraint it would look a
lot better.

1349
01:38:52,679 --> 01:38:57,110
That is good stuff, but we can do even better
now.

1350
01:38:57,110 --> 01:39:01,329
And, as you can see, when I said we could
do a wind tunnel as accurately as we could

1351
01:39:01,329 --> 01:39:04,349
measure, in flight basically we could do the
same thing.

1352
01:39:04,349 --> 01:39:04,869
Mid body.

1353
01:39:04,869 --> 01:39:08,889
Everything is just right for the CFD folks.

1354
01:39:08,889 --> 01:39:15,889
Now we'll go to the rear where we go past
CFD and more to the wind tunnel correlations,

1355
01:39:17,429 --> 01:39:18,829
and we're not doing as well.

1356
01:39:18,829 --> 01:39:23,719
Certainly on transition we knew we'd be very
conservative.

1357
01:39:23,719 --> 01:39:25,939
This is ideally how we design the vehicle.

1358
01:39:25,939 --> 01:39:32,749
Fly to temperature capability of the tile.

1359
01:39:32,749 --> 01:39:39,269
And on this STS-3 that's what we were trying
to do.

1360
01:39:39,269 --> 01:39:43,800
Now, if we exceeded this that's all right,
but we don't want to exceed the material capability.

1361
01:39:43,800 --> 01:39:47,070
And we obviously don't want to exceed the
structural capability.

1362
01:39:47,070 --> 01:39:48,289
Let's see.

1363
01:39:48,289 --> 01:39:51,478
I want to talk about surface catalysis.

1364
01:39:51,478 --> 01:39:52,539
Then we will get into the thermal protection
system.

1365
01:39:52,539 --> 01:39:59,539
I've got one chart I am going to spend a lot
of time on.

1366
01:39:59,949 --> 01:40:02,860
This is distance down the vehicle from the
nose.

1367
01:40:02,860 --> 01:40:05,380
I mean it is linear distance.

1368
01:40:05,380 --> 01:40:08,309
There is 50%.

1369
01:40:08,309 --> 01:40:12,840
This is surface heat flux at one particular
time in the entry.

1370
01:40:12,840 --> 01:40:14,119
The circles are flight data.

1371
01:40:14,119 --> 01:40:17,619
These are catalysis experiments.

1372
01:40:17,619 --> 01:40:23,179
This is a fully catalytic or equilibrium heat
transfer.

1373
01:40:23,179 --> 01:40:29,179
This is a zero catalysis non-equilibrium,
boundary layer non-equilibrium.

1374
01:40:29,179 --> 01:40:32,150
The reactions are not occurring in the boundary
layer.

1375
01:40:32,150 --> 01:40:34,869
This is the flight data that opens circles.

1376
01:40:34,869 --> 01:40:37,769
I don't remember what the measurement problem
here was.

1377
01:40:37,769 --> 01:40:42,199
And here is this point way up front you can
see again.

1378
01:40:42,199 --> 01:40:47,300
Now, this is a viscous flow field where we
could do the chemistry but we couldn't do

1379
01:40:47,300 --> 01:40:49,550
the fluid mechanics real accurately.

1380
01:40:49,550 --> 01:40:52,199
This is still a mix and match.

1381
01:40:52,199 --> 01:40:54,929
Look at the difference between the measurement
and the prediction.

1382
01:40:54,929 --> 01:41:01,228
The same thing as before only I eased it by
showing temperature instead of heat flux.

1383
01:41:01,228 --> 01:41:05,209
The surface catalysis is a predominant factor.

1384
01:41:05,209 --> 01:41:11,880
Now, there is some rambling in the data here,
depending on particular location, et cetera.

1385
01:41:11,880 --> 01:41:18,429
But our friends at Ames developed a catalytic
coding, and they coded tiles.

1386
01:41:18,429 --> 01:41:24,939
And they said we're going to demonstrate service
catalysis, so they put these tiles at these

1387
01:41:24,939 --> 01:41:26,820
particular locations.

1388
01:41:26,820 --> 01:41:29,978
If the whole vehicle was like that, the heating
would have been up here.

1389
01:41:29,978 --> 01:41:34,739
But since there was just the tile, the boundary
layer comes along here and all of a sudden,

1390
01:41:34,739 --> 01:41:36,760
boom, it gets hit with a different boundary
condition.

1391
01:41:36,760 --> 01:41:43,760
We've got all those atoms and they see this
catalytic surface, the heating goes way up

1392
01:41:44,499 --> 01:41:45,189
and then relaxes.

1393
01:41:45,189 --> 01:41:51,820
This is the computation and there is the measurement.

1394
01:41:51,820 --> 01:41:58,639
Indeed, here is a demonstration that chemistry
can be important in this flight regime.

1395
01:41:58,639 --> 01:42:03,228
If you come down in altitude where everything
starts going to equilibrium, it's not that

1396
01:42:03,228 --> 01:42:04,239
important.

1397
01:42:04,239 --> 01:42:10,059
You're going to get this because the chemistry
is going to, the gas is going to react.

1398
01:42:10,059 --> 01:42:17,059
But where we are, up in altitude trying to
maintain conditions so we can be reusable,

1399
01:42:17,349 --> 01:42:22,260
that chemistry is significant.

1400
01:42:22,260 --> 01:42:25,959
Now, I think the next one is probably the
thermal protection system.

1401
01:42:25,959 --> 01:42:27,369
No, one more measurement.

1402
01:42:27,369 --> 01:42:29,340
This is the leeside.

1403
01:42:29,340 --> 01:42:34,519
This is normal shock versus film heat transfer
coefficient.

1404
01:42:34,519 --> 01:42:35,489
Basically heat transfer.

1405
01:42:35,489 --> 01:42:36,889
Log.

1406
01:42:36,889 --> 01:42:38,300
Log.

1407
01:42:38,300 --> 01:42:44,689
This is the heating shown here as a function
of normal shock Reynolds number.

1408
01:42:44,689 --> 01:42:51,280
Now, remember I said we designed the trajectories
so we went up here and spent 10 minutes and

1409
01:42:51,280 --> 01:42:54,189
then came down as normal a normal shock Reynolds
number.

1410
01:42:54,189 --> 01:43:00,880
And here are three trajectories with a heating
on one location of the leeside.

1411
01:43:00,880 --> 01:43:06,880
By the way, Max Faget told me to burn a hole
some place on the leeside.

1412
01:43:06,880 --> 01:43:10,070
He didn't want too much tile there.

1413
01:43:10,070 --> 01:43:13,360
The only thing I was able to do was we exceeded
heating here because we didn't simulate the

1414
01:43:13,360 --> 01:43:14,709
flow very well in the wind tunnel.

1415
01:43:14,709 --> 01:43:17,429
We had to put tiles there after first flight.

1416
01:43:17,429 --> 01:43:19,650
So I told him that was as close as we came.

1417
01:43:19,650 --> 01:43:26,499
In any event, this is heating on three trajectories
through normal shock history.

1418
01:43:26,499 --> 01:43:29,579
It's sort of like time.

1419
01:43:29,579 --> 01:43:31,849
Three different vehicles.

1420
01:43:31,849 --> 01:43:34,449
This is to reference heat.

1421
01:43:34,449 --> 01:43:38,579
This is our old Apollo level technology.

1422
01:43:38,579 --> 01:43:43,760
It works quite well all the way through to
peak heating, and then it starts to change

1423
01:43:43,760 --> 01:43:49,130
as the Reynolds number picks up and the weight
characteristic changes.

1424
01:43:49,130 --> 01:43:56,130
In ballistic facilities, if you have a vehicle
traveling at high speed, eventually your weight

1425
01:43:57,409 --> 01:43:59,650
goes transitional and turbulent.

1426
01:43:59,650 --> 01:44:01,989
As you increase the Reynolds number that moves
forward.

1427
01:44:01,989 --> 01:44:04,489
As that moves forward, you get more mixing.

1428
01:44:04,489 --> 01:44:08,489
As you get more mixing the gas in the wake
gets hotter.

1429
01:44:08,489 --> 01:44:11,070
And I believe that is fundamentally what's
going on.

1430
01:44:11,070 --> 01:44:12,630
It is very repeatable.

1431
01:44:12,630 --> 01:44:18,070
We cannot get this in the wind tunnel.

1432
01:44:18,070 --> 01:44:19,610
Now we'll go to TPS.

1433
01:44:19,610 --> 01:44:22,119
No, one more on the leeside heating.

1434
01:44:22,119 --> 01:44:27,699
On the Shuttle we had thermal couples located
here, there, as many places as the aerothermodynamics

1435
01:44:27,699 --> 01:44:31,280
could put them, the TPS guys, but we couldn't
put them anywhere.

1436
01:44:31,280 --> 01:44:35,689
This is the 201 vehicle and it's on its side.

1437
01:44:35,689 --> 01:44:37,829
I apologize because of my chartmanship.

1438
01:44:37,829 --> 01:44:41,239
The vehicle is coming in angle-of-attack on
here.

1439
01:44:41,239 --> 01:44:45,059
This is the windward side where there was
charring.

1440
01:44:45,059 --> 01:44:46,449
This is white paint down here.

1441
01:44:46,449 --> 01:44:48,789
And, I'm sorry, it is a terrible photograph.

1442
01:44:48,789 --> 01:44:55,419
Because of some of the protrusions we had
on the first vehicle, we also got some charring

1443
01:44:55,419 --> 01:44:56,050
on this side.

1444
01:44:56,050 --> 01:44:57,010
This is not charring.

1445
01:44:57,010 --> 01:44:58,030
This is some charring.

1446
01:44:58,030 --> 01:45:02,260
And it is blown up here in the way the chart
was made.

1447
01:45:02,260 --> 01:45:03,919
One point.

1448
01:45:03,919 --> 01:45:07,059
This is the first entry heating.

1449
01:45:07,059 --> 01:45:08,849
And the leeside was extremely important.

1450
01:45:08,849 --> 01:45:10,010
How well did we do?

1451
01:45:10,010 --> 01:45:11,809
How hot is it?

1452
01:45:11,809 --> 01:45:16,070
We got the data and it was all over the place.

1453
01:45:16,070 --> 01:45:18,400
It was down where we thought it probably should
be.

1454
01:45:18,400 --> 01:45:21,619
And it was like an order of magnitude higher.

1455
01:45:21,619 --> 01:45:22,760
We thought that data is no good.

1456
01:45:22,760 --> 01:45:29,749
Well, then we went back and realized what
happened is when the control system fired

1457
01:45:29,749 --> 01:45:35,260
jets, a lot more dynamic pressure than the
airflow.

1458
01:45:35,260 --> 01:45:37,169
A lot cooler.

1459
01:45:37,169 --> 01:45:43,119
So, when I fired a jet, all of a sudden it
is like putting a big wing out there.

1460
01:45:43,119 --> 01:45:45,360
Tremendous disturbance.

1461
01:45:45,360 --> 01:45:50,679
And, indeed, we were able to correlate firing
RCS jets with when the heating was way up

1462
01:45:50,679 --> 01:45:52,570
here.

1463
01:45:52,570 --> 01:45:58,300
And flow times you're talking milliseconds
for reaction time back then when we weren't

1464
01:45:58,300 --> 01:46:00,099
firing a jet.

1465
01:46:00,099 --> 01:46:00,570
Unbelievable.

1466
01:46:00,570 --> 01:46:04,478
We went to learning something.

1467
01:46:04,478 --> 01:46:06,709
Again, interaction of systems.

1468
01:46:06,709 --> 01:46:12,590
Now, finally, this is my one and only chart
on the thermal protection system which is

1469
01:46:12,590 --> 01:46:16,610
the real hardware stuff.

1470
01:46:16,610 --> 01:46:22,780
This is temperature versus time at a mid body
location.

1471
01:46:22,780 --> 01:46:25,880
Now, this is from STS-1.

1472
01:46:25,880 --> 01:46:29,459
We didn't have data until this time on that
flight, which is why I haven't shown much

1473
01:46:29,459 --> 01:46:30,510
aerothermodynamic today.

1474
01:46:30,510 --> 01:46:33,829
We only had late time data.

1475
01:46:33,829 --> 01:46:39,260
This is the design trajectory coming in from
polar orbit.

1476
01:46:39,260 --> 01:46:44,369
Our design condition was we do not exceed
350 degrees Fahrenheit if we want to have

1477
01:46:44,369 --> 01:46:47,419
a hundred flight life with this aluminum.

1478
01:46:47,419 --> 01:46:51,150
Aluminum is great stuff because it is a good
conductor but it is low temperature and it

1479
01:46:51,150 --> 01:46:51,419
expands.

1480
01:46:51,419 --> 01:46:55,550
[Bond line?] that means at the [hahahahahaha]
bottom, just so that everybody understands.

1481
01:46:55,550 --> 01:46:56,869
Yes, thank you.

1482
01:46:56,869 --> 01:47:01,320
Those temperatures are much lower than you
see on the surface of the tiles.

1483
01:47:01,320 --> 01:47:05,090
That's after the heat has diffused.

1484
01:47:05,090 --> 01:47:05,340
Right.

1485
01:47:05,139 --> 01:47:08,429
I think Tom probably talked about the SIP,
the strain isolation pad.

1486
01:47:08,429 --> 01:47:11,030
I'm sure he did.

1487
01:47:11,030 --> 01:47:16,019
This is after you diffuse through the clouds
and through the RTV bonds through the SIP.

1488
01:47:16,019 --> 01:47:19,110
This is the actual aluminum temperature.

1489
01:47:19,110 --> 01:47:22,179
Now I'm talking predictions.

1490
01:47:22,179 --> 01:47:27,909
This is what the vehicle was designed to experience.

1491
01:47:27,909 --> 01:47:32,329
Now, the design prediction was right here.

1492
01:47:32,329 --> 01:47:36,459
That was purposefully a little conservative.

1493
01:47:36,459 --> 01:47:40,389
The guy who is building it doesn't want to
lose the vehicle.

1494
01:47:40,389 --> 01:47:45,969
He is not going to get paid, plus much bigger
problems, but this is what we expected.

1495
01:47:45,969 --> 01:47:50,249
This is our best estimate.

1496
01:47:50,249 --> 01:47:54,179
And, again, if you recall, I showed you where
we really knew where the heating was.

1497
01:47:54,179 --> 01:47:56,199
This is really a TPS test right now.

1498
01:47:56,199 --> 01:48:01,039
If you read the TPS section in that report,
those guys with the heating, they were just

1499
01:48:01,039 --> 01:48:02,280
way too hot.

1500
01:48:02,280 --> 01:48:04,159
Right here we were right on.

1501
01:48:04,159 --> 01:48:10,300
This is a purely TPS test, except it turns
out it was my fault here.

1502
01:48:10,300 --> 01:48:12,340
In any event, here comes the data.

1503
01:48:12,340 --> 01:48:19,340
This is the prediction for this particular
flight STS-1 right here.

1504
01:48:19,519 --> 01:48:21,389
This is what we predicted for STS-1.

1505
01:48:21,389 --> 01:48:24,989
This is what we would have predicted for design.

1506
01:48:24,989 --> 01:48:31,749
And this is the design technology prediction
which has a little conservatism in it, obviously,

1507
01:48:31,749 --> 01:48:33,179
and on purpose.

1508
01:48:33,179 --> 01:48:35,689
This is yes you can fly the vehicle with confidence.

1509
01:48:35,689 --> 01:48:38,179
We're flying this STS-1 no problem.

1510
01:48:38,179 --> 01:48:43,150
And we're pretty sure we can fly a design
but things have to go right for us.

1511
01:48:43,150 --> 01:48:46,978
We did a pretty good job along here.

1512
01:48:46,978 --> 01:48:50,260
And this structure is intricate and everything.

1513
01:48:50,260 --> 01:48:53,419
The thermal modeling has to take into account
all kinds of geometry, materials, et cetera.

1514
01:48:53,419 --> 01:49:00,389
And all of a sudden right here, boom, what
happened?

1515
01:49:00,389 --> 01:49:06,169
I admit to overlooking this.

1516
01:49:06,169 --> 01:49:12,570
What happened is we opened the vents, we let
some air in.

1517
01:49:12,570 --> 01:49:14,459
I mean you're up in a vacuum.

1518
01:49:14,459 --> 01:49:16,900
You do not want to let air in when it's hot.

1519
01:49:16,900 --> 01:49:21,939
The best way of burning a hole right through
the vehicle is open a front and back door.

1520
01:49:21,939 --> 01:49:26,050
The absolutely worst thing that could happen
to you.

1521
01:49:26,050 --> 01:49:27,199
You cannot radiate the energy.

1522
01:49:27,199 --> 01:49:28,369
You don't get rid of that 98%.

1523
01:49:28,369 --> 01:49:34,228
It was just like a blowtorch.

1524
01:49:34,228 --> 01:49:41,228
But, once you get down, if you don't do something,
you've got this vacuum vehicle and you're

1525
01:49:41,280 --> 01:49:44,139
getting atmospheric pressure coming up on
you.

1526
01:49:44,139 --> 01:49:45,389
And all of a sudden you're going to be crushed.

1527
01:49:45,389 --> 01:49:46,800
At some point, OK, it's all right.

1528
01:49:46,800 --> 01:49:47,619
We open the door.

1529
01:49:47,619 --> 01:49:48,439
We open a vent.

1530
01:49:48,439 --> 01:49:52,949
This particular location, not all locations,
could experience that.

1531
01:49:52,949 --> 01:49:57,409
And, not only that, but the air is expanding
so it is chilled as it comes in from outside.

1532
01:49:57,409 --> 01:50:00,919
Still cold compared to what we've been working
with.

1533
01:50:00,919 --> 01:50:04,699
I overlooked that.

1534
01:50:04,699 --> 01:50:08,469
Now, in fairness, there are a lot of areas
where there is insulation, you don't get that

1535
01:50:08,469 --> 01:50:12,340
cold air and so you cannot use it in many
places.

1536
01:50:12,340 --> 01:50:17,999
But the point is, looking at the overall system
and the kinds of things that could happen,

1537
01:50:17,999 --> 01:50:24,999
you could take advantage of those in designs
if you're cleaver, if you're innovative.

1538
01:50:25,519 --> 01:50:32,409
And so there was, not 100 degrees, a significant
difference there.

1539
01:50:32,409 --> 01:50:37,329
You could take advantage of that if you design
a vehicle that you pop it at the right time

1540
01:50:37,329 --> 01:50:44,329
and get some cold air in there because that's
what we're trying to control, this temperature,

1541
01:50:44,679 --> 01:50:46,239
from a temperature standpoint.

1542
01:50:46,239 --> 01:50:53,239
The other thing in the Shuttle, which I'm
sure Tom discussed, was the thermal stress.

1543
01:50:54,219 --> 01:51:01,219
I mean if the belly gets heated and the wings
don't, the whole wings will pop up.

1544
01:51:02,728 --> 01:51:07,610
That is one big integrated problem which gave
us a lot of difficulty.

1545
01:51:07,610 --> 01:51:11,039
Again, with the simulation and computational
capability we have today, I think we can do

1546
01:51:11,039 --> 01:51:12,469
a much better job of that.

1547
01:51:12,469 --> 01:51:19,469
And also just understanding the importance
of it.

1548
01:51:20,280 --> 01:51:22,329
I think those are all my charts.

1549
01:51:22,329 --> 01:51:23,249
No, I'm sorry.

1550
01:51:23,249 --> 01:51:30,249
I have one more which is not a Shuttle chart.

1551
01:51:31,119 --> 01:51:38,119
We were looking at an experimental orbital
transfer vehicle, a [low WOCDA?] vehicle running

1552
01:51:38,728 --> 01:51:43,860
from geosynchronous to low earth orbit, and
then we use the Shuttle to go from low earth

1553
01:51:43,860 --> 01:51:45,110
orbit to the ground.

1554
01:51:45,110 --> 01:51:49,249
We were trying to make that reusable because
you don't want to go up and put an ablator

1555
01:51:49,249 --> 01:51:51,919
on a vehicle in orbit on a space station.

1556
01:51:51,919 --> 01:51:53,329
And we thought we could do that.

1557
01:51:53,329 --> 01:51:54,898
Now, this is not coming back from the moon.

1558
01:51:54,898 --> 01:51:55,939
This is coming back from geosynchronous.

1559
01:51:55,939 --> 01:51:58,739
It's not quite as bad.

1560
01:51:58,739 --> 01:52:00,228
We had a design.

1561
01:52:00,228 --> 01:52:04,329
And, to prove the concept, we had a little
model we were going to build and fly.

1562
01:52:04,329 --> 01:52:06,849
This came from a paper I gave discussing that.

1563
01:52:06,849 --> 01:52:13,489
Basically, this is the analysis and testing
from research to an actual real hardware system,

1564
01:52:13,489 --> 01:52:18,659
from the fundamental equations down to numerical
simulation.

1565
01:52:18,659 --> 01:52:24,469
Back of the envelope or perspective fundamentals,
that's kind of the fun part that I enjoy.

1566
01:52:24,469 --> 01:52:31,050
Then modeling as we do, for example, in the
design approach on Apollo.

1567
01:52:31,050 --> 01:52:34,550
Correlations of data, numerical computation
and then numerical simulation where you're

1568
01:52:34,550 --> 01:52:38,610
trying to do as good as we understand with
the equations.

1569
01:52:38,610 --> 01:52:39,659
Fundamental research.

1570
01:52:39,659 --> 01:52:43,579
The technology development which is where
NASA's major emphasis is.

1571
01:52:43,579 --> 01:52:45,449
Component development of systems.

1572
01:52:45,449 --> 01:52:48,439
And finally subsystem, model and system testing.

1573
01:52:48,439 --> 01:52:51,110
You need all that stuff.

1574
01:52:51,110 --> 01:52:54,739
You would like to go right down the matrix
here, have a good, firm foundation so you

1575
01:52:54,739 --> 01:52:57,059
really understand what you're doing.

1576
01:52:57,059 --> 01:52:58,519
Therefore, you have confidence in doing it.

1577
01:52:58,519 --> 01:53:00,249
And, therefore, you develop capability.

1578
01:53:00,249 --> 01:53:03,849
There are no shortcuts.

1579
01:53:03,849 --> 01:53:09,699
Shuttle has done a fantastic job in both these
areas all the way down to computational fluid

1580
01:53:09,699 --> 01:53:09,949
dynamics.
It is not limited just to NASA Shuttle people
or aerospace people.

1581
01:53:14,570 --> 01:53:18,780
And certainly in this area, in Apollo, but
all the human space flight.

1582
01:53:18,780 --> 01:53:20,709
We've got a lot of experience.

1583
01:53:20,709 --> 01:53:24,719
That needs to be taken advantage of for our
future systems.

1584
01:53:24,719 --> 01:53:28,530
It is not just it looks like this or it looks
like that, it's going to use this system,

1585
01:53:28,530 --> 01:53:29,579
it's going to use that system.

1586
01:53:29,579 --> 01:53:33,469
It's an overall integrated take advantage
of the experience in what we've learned.

1587
01:53:33,469 --> 01:53:33,749
Yes.

1588
01:53:33,749 --> 01:53:35,639
I just have a question about the chart.

1589
01:53:35,639 --> 01:53:40,030
I'm just wondering if the inner section points
on those lines correspond to a particular

1590
01:53:40,030 --> 01:53:41,499
path or something like that?

1591
01:53:41,499 --> 01:53:46,119
I used this from the standpoint of we were
trying to do a flight test model.

1592
01:53:46,119 --> 01:53:51,269
We were going to predict what happened to
an aero braking vehicle coming in, and so

1593
01:53:51,269 --> 01:53:56,169
I was focused on this and also on the numerical
aspect.

1594
01:53:56,169 --> 01:54:00,630
Marrying those two, at this point, which was
the reason for this flight test.

1595
01:54:00,630 --> 01:54:07,630
But I just thought that is applicable today
in terms of where we're going in general.

1596
01:54:11,409 --> 01:54:12,929
I didn't get very many questions.

1597
01:54:12,929 --> 01:54:15,289
It must be because it's the first class of
the day.

1598
01:54:15,289 --> 01:54:17,630
Well, you were going at a mile a minute.

1599
01:54:17,630 --> 01:54:21,019
I think we got a few in there.

1600
01:54:21,019 --> 01:54:28,019
But, yeah, the content of what we've been
exposed to today has been tremendous.

1601
01:54:28,349 --> 01:54:31,409
We really want to thank you.

1602
01:54:31,409 --> 01:54:38,409
If they want to do some simple calculations,
what reference would you give them?

1603
01:54:39,419 --> 01:54:43,999
Are there any simple calculations they could
do?

1604
01:54:43,999 --> 01:54:45,709
[Faye and Rodell?

1605
01:54:45,709 --> 01:54:48,510
yes] has the boundary layer activity.

1606
01:54:48,510 --> 01:54:50,340
That is a crucial reference.

1607
01:54:50,340 --> 01:54:56,389
In the paper that they have, the Shuttle Technology
Conference, I have a list of references that

1608
01:54:56,389 --> 01:55:02,630
were to date in the various areas, whether
it be service catalysis, TPS, you name it.

1609
01:55:02,630 --> 01:55:05,478
And those were the best references at the
time.

1610
01:55:05,478 --> 01:55:09,749
And the individuals named, many of them have
gone on and done much better work.

1611
01:55:09,749 --> 01:55:11,829
Plus, there are lots of younger people, too.

1612
01:55:11,829 --> 01:55:13,800
I think that would be the best source.

1613
01:55:13,800 --> 01:55:14,300
OK, Bob.

1614
01:55:14,300 --> 01:55:15,630
Thank you very much.

1615
01:55:15,630 --> 01:55:16,269
Thank you.

1616
01:55:16,269 --> 01:55:16,599
[APPLAUSE]