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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.

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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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00:18:27.570 --> 00:18:32.620
You end up with a distribution of temperature
which diffuses out.

224
00:18:32.620 --> 00:18:39.620
The functional form of that, if you recall,
T is proportional to an exponential, let's

225
00:18:41.010 --> 00:18:48.010
call this X squared over four thermal diffusivity
times time, and there is the square root.

226
00:18:53.390 --> 00:19:00.120
Think of it as a one-dimensional normal distribution.

227
00:19:00.120 --> 00:19:07.120
Except instead of two variant squared here
you've got four times the diffusivity time.

228
00:19:07.280 --> 00:19:14.280
The significant thing is when we talk about
ablators, when we talk about tiles or thermal

229
00:19:15.050 --> 00:19:18.920
protection systems, this is the significant
parameter.

230
00:19:18.920 --> 00:19:23.020
We have an extremely high temperature at the
surface.

231
00:19:23.020 --> 00:19:27.430
The job is to keep that from the structure.

232
00:19:27.430 --> 00:19:31.300
Thermal diffusivity is prime parameter.

233
00:19:31.300 --> 00:19:38.300
It is also, not thermal diffusivity, but if
you now consider simplest fluid mechanics,

234
00:19:42.080 --> 00:19:46.720
flat plate, the first thing you learn about
in terms of viscous flow.

235
00:19:46.720 --> 00:19:48.490
You've got some velocity coming along here.

236
00:19:48.490 --> 00:19:52.220
You've got a boundary layer that builds up.

237
00:19:52.220 --> 00:19:59.220
The boundary layer compared to X varies as
one over square root of Reynolds number.

238
00:19:59.860 --> 00:20:06.860
Where does that come from?

239
00:20:08.370 --> 00:20:10.110
The same diffusion.

240
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

241
00:20:19.790 --> 00:20:24.470
the thermal diffusion associated with heat
transfer, the diffusion associated with the

242
00:20:24.470 --> 00:20:29.630
shear, the same phenomena.

243
00:20:29.630 --> 00:20:35.340
When I first found this in fluid mechanics,
I was told that was empirical.

244
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

245
00:20:41.150 --> 00:20:47.180
Equations in this one-dimensional situation
you basically have a convection in this direction

246
00:20:47.180 --> 00:20:51.760
and a diffusion in the [UNINTELLIGIBLE] [Unthougtable]direction.

247
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

248
00:20:57.380 --> 00:21:03.210
Stanton number which is approximately heat
transfer divided by one-half rho infinity

249
00:21:03.210 --> 00:21:06.940
V infinity cubed for the case of a sphere.

250
00:21:06.940 --> 00:21:11.810
Now, this is a one-dimensional, obviously,
flat plat.

251
00:21:11.810 --> 00:21:13.760
A sphere is also one-dimensional.

252
00:21:13.760 --> 00:21:20.250
If you look at a stagnation point on a sphere,
this is a singularity.

253
00:21:20.250 --> 00:21:24.380
If you go to spherical coordinates you've
got basically the same phenomena.

254
00:21:24.380 --> 00:21:29.790
The diffusion from the wall gives you characteristic
dimensions.

255
00:21:29.790 --> 00:21:35.160
It is very important because heat transfer
is basically inversely proportional to the

256
00:21:35.160 --> 00:21:37.950
square root of the Reynolds number.

257
00:21:37.950 --> 00:21:41.300
We have square roots showing up in the thermal
diffusion.

258
00:21:41.300 --> 00:21:43.130
We have square roots showing up in the heat
transfer.

259
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.

260
00:21:50.480 --> 00:21:54.330
But first order is the behavior that we are
looking for.

261
00:21:54.330 --> 00:21:58.400
And that I will illustrate now.

262
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.

263
00:22:07.700 --> 00:22:14.700
Let me do local heating over the energy flux.

264
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

265
00:22:23.870 --> 00:22:27.550
a normal shock Reynolds number.

266
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,

267
00:22:32.790 --> 00:22:33.270
obviously.

268
00:22:33.270 --> 00:22:38.400
The viscosity is what changes.

269
00:22:38.400 --> 00:22:45.400
I am going to use the normal shock equilibrium
air viscosity because that is more characteristic

270
00:22:47.820 --> 00:22:54.820
of everything going on in what the Russians
call a protective shock layer.

271
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,

272
00:23:02.180 --> 00:23:08.160
I've got that minus one-half slope from that
square root Reynolds number.

273
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.

274
00:23:16.570 --> 00:23:19.760
And, obviously, if you go all the way to orbit
you're basically one.

275
00:23:19.760 --> 00:23:25.040
The molecules are coming in at orbital velocity,
going into the material, releasing all their

276
00:23:25.040 --> 00:23:29.580
energy and then eventually coming off.

277
00:23:29.580 --> 00:23:34.690
We actually do have that limit, although we
never really worry about it too much.

278
00:23:34.690 --> 00:23:41.690
The significant heating is in this laminar
regime.

279
00:23:50.780 --> 00:23:56.290
I feel like, because I understand Navier-Stokes
Equations, because I understand the diffusion

280
00:23:56.290 --> 00:24:02.710
process and that limit of the Navier-Stokes,
I sort of understand that flow.

281
00:24:02.710 --> 00:24:09.710
However, we also have turbulent heating which
incompressible flow has its slope on the order

282
00:24:09.850 --> 00:24:10.540
of [minus fifth?].

283
00:24:10.540 --> 00:24:14.280
I don't really understand stand that, and
do not claim to understand that.

284
00:24:14.280 --> 00:24:21.280
It is a combination of the diffusion and the
convection, all sorts of things going on.

285
00:24:21.640 --> 00:24:24.360
And then we have transition from one to the
other.

286
00:24:24.360 --> 00:24:28.690
Theoretically, this would come out and come
out lower.

287
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.

288
00:24:36.410 --> 00:24:42.710
But basically we go into a wind tunnel and
can measure this on a particular configuration.

289
00:24:42.710 --> 00:24:43.440
We got to flight.

290
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.

291
00:24:53.670 --> 00:25:00.230
People have built models, have done wind tunnel
tests, shock tube tests, flown vehicles.

292
00:25:00.230 --> 00:25:07.230
And there was a lot of money spent trying
to fly vehicles to verify our understanding.

293
00:25:07.340 --> 00:25:10.820
The difficulty, certainly with ablators, is
measuring the environment.

294
00:25:10.820 --> 00:25:15.600
Did you really have the right heat transfer
or did the material just start to degrade?

295
00:25:15.600 --> 00:25:18.640
What is really going on?

296
00:25:18.640 --> 00:25:25.640
When we flew the Shuttle, we had a reusable
thermal protection system which is the tile

297
00:25:27.440 --> 00:25:33.440
that is being passed around with a real thin
coating and very low thermal diffusivity.

298
00:25:33.440 --> 00:25:36.770
What better instrument could you have to measure
heat transfer than that?

299
00:25:36.770 --> 00:25:43.770
And the data from the Shuttle configuration
is absolutely fantastic from a technological

300
00:25:44.110 --> 00:25:46.980
standpoint, from an aerothermodynamics standpoint.

301
00:25:46.980 --> 00:25:47.630
Unbelievable.

302
00:25:47.630 --> 00:25:53.090
So much better than anything that was done
in the past with vehicles that were dedicated

303
00:25:53.090 --> 00:26:00.090
to try to get that information.

304
00:26:01.180 --> 00:26:08.180
Let me say a couple words about, well, first
let me address the facilities.

305
00:26:10.170 --> 00:26:15.120
I mentioned the shock tube and went through
that briefly.

306
00:26:15.120 --> 00:26:20.170
And the value of the shock tube was to look
at phenomena just like this.

307
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

308
00:26:28.190 --> 00:26:32.350
tube.

309
00:26:32.350 --> 00:26:34.290
Right here.

310
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

311
00:26:39.710 --> 00:26:41.540
flight than anywhere else.

312
00:26:41.540 --> 00:26:45.700
Getting to these energy levels is extremely
difficult.

313
00:26:45.700 --> 00:26:49.810
There are three facilities you can get to.

314
00:26:49.810 --> 00:26:51.610
One is in a shock tube.

315
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

316
00:26:55.880 --> 00:26:57.260
to fly.

317
00:26:57.260 --> 00:27:00.970
And that does a good simulation job, except
it is very small.

318
00:27:00.970 --> 00:27:04.340
And getting any measurements is very difficult.

319
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.

320
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

321
00:27:19.960 --> 00:27:21.970
of measuring things.

322
00:27:21.970 --> 00:27:24.900
The other place you can get the energy is
in an arc jet.

323
00:27:24.900 --> 00:27:31.900
Now, an arc jet is a continuous electrical
discharge, sort of like the shock tube, where

324
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

325
00:27:47.730 --> 00:27:52.910
continuous for a significant period of time
into nitrogen.

326
00:27:52.910 --> 00:27:59.260
And then you're expanding this and you're
introducing a supersonic flow.

327
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

328
00:28:06.890 --> 00:28:07.880
get on the ground.

329
00:28:07.880 --> 00:28:10.350
That is for the times that are required.

330
00:28:10.350 --> 00:28:13.160
Entry times are like 20 minutes.

331
00:28:13.160 --> 00:28:18.450
You need something that has the energy and
runs for 20 minutes.

332
00:28:18.450 --> 00:28:21.600
Now, this is a continuous flow of electrons.

333
00:28:21.600 --> 00:28:24.800
The thermodynamics here is not well-characterized.

334
00:28:24.800 --> 00:28:26.040
People have studied it like mad.

335
00:28:26.040 --> 00:28:27.450
This is very non-equilibrium.

336
00:28:27.450 --> 00:28:30.020
You've got a very high density of electrons.

337
00:28:30.020 --> 00:28:32.730
The temperature is immense in here.

338
00:28:32.730 --> 00:28:34.740
It is not at all in equilibrium.

339
00:28:34.740 --> 00:28:41.170
But, as you expand through a jet, collisions
drop because the pressure goes down and it

340
00:28:41.170 --> 00:28:43.070
pretty much freezes.

341
00:28:43.070 --> 00:28:50.070
But this is where we do research on ablators
and research on service catalysis which I

342
00:28:50.150 --> 00:28:55.470
will talk about in a little bit which really
can affect the heating, particularly on the

343
00:28:55.470 --> 00:28:55.790
Shuttle.

344
00:28:55.790 --> 00:28:57.700
And I will show you some results there.

345
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.

346
00:29:04.620 --> 00:29:06.350
TPS being thermal protection system.

347
00:29:06.350 --> 00:29:09.350
Wind tunnels are classic.

348
00:29:09.350 --> 00:29:11.610
That's where NASA came from, NAC came from.

349
00:29:11.610 --> 00:29:18.610
Aerothermodynamics is my field, spelling is
another area.

350
00:29:25.190 --> 00:29:26.430
Wind tunnels you're all familiar with.

351
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

352
00:29:32.480 --> 00:29:34.590
what we were doing.

353
00:29:34.590 --> 00:29:39.310
And whatever the different facilities told
us we tried to understand.

354
00:29:39.310 --> 00:29:46.310
What we learned was energy is extremely important,
the enthalpy.

355
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

356
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

357
00:29:57.400 --> 00:29:58.400
heating distribution.

358
00:29:58.400 --> 00:30:02.140
It does give you mach number effects.

359
00:30:02.140 --> 00:30:05.520
But the gas is not at all like what you have
in flight.

360
00:30:05.520 --> 00:30:10.710
And so on the shuttle we didn't really do
much aerothermodynamic testing beyond mach

361
00:30:10.710 --> 00:30:13.320
eight.

362
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,

363
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

364
00:30:26.270 --> 00:30:28.120
mach 20 facility.

365
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.

366
00:30:34.820 --> 00:30:40.000
It is very valuable information, but you really
need to understand what you're doing with

367
00:30:40.000 --> 00:30:40.250
that.

368
00:30:40.180 --> 00:30:43.230
You cannot just take mach number as the major
parameter.

369
00:30:43.230 --> 00:30:46.870
It is a significant parameter but you need
to get the Reynolds number.

370
00:30:46.870 --> 00:30:49.210
And, fundamentally, you need to get the enthalpy
of the gas.

371
00:30:49.210 --> 00:30:53.280
And there is not really a good dimensionalist
number for the enthalpy of the gas.

372
00:30:53.280 --> 00:31:00.280
Too much going on for that.

373
00:31:04.370 --> 00:31:11.370
The other significant source of information
is flight test.

374
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

375
00:31:20.260 --> 00:31:24.830
a lot more on testing than we do now.

376
00:31:24.830 --> 00:31:30.430
For example, on the Apollo, I talked about
this radiation, we had very good test results

377
00:31:30.430 --> 00:31:31.330
in a shock tube.

378
00:31:31.330 --> 00:31:32.870
We thought we really knew what was going on.

379
00:31:32.870 --> 00:31:39.870
NASA Langley went and built a small scale
Apollo about so big to measure the radiation

380
00:31:45.530 --> 00:31:49.620
in flight because the shock tubes are operating
at little higher pressures than we were going

381
00:31:49.620 --> 00:31:53.910
to fly the Apollo.

382
00:31:53.910 --> 00:31:59.890
It basically had three brilliant heat shields
with a quartz window in it.

383
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

384
00:32:07.010 --> 00:32:07.760
starts to melt.

385
00:32:07.760 --> 00:32:12.220
You cannot see through it, you cannot make
a measurement, it sheds that.

386
00:32:12.220 --> 00:32:19.040
And ideally the second heat shield comes about
right at peak heating simulating Apollo entry.

387
00:32:19.040 --> 00:32:20.550
And then a third.

388
00:32:20.550 --> 00:32:23.850
Well, we were really excited about that because
the shock tube was great.

389
00:32:23.850 --> 00:32:26.060
And we thought we understood everything.

390
00:32:26.060 --> 00:32:27.490
Well, we flew Fire 1.

391
00:32:27.490 --> 00:32:28.370
It was called Fire.

392
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

393
00:32:32.130 --> 00:32:33.580
in.

394
00:32:33.580 --> 00:32:40.190
We got the data and it wasn't anything like
what we expected.

395
00:32:40.190 --> 00:32:40.780
What had happened?

396
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,

397
00:32:46.520 --> 00:32:52.380
and then we fired a rocket down back into
the atmosphere to simulate lunar return.

398
00:32:52.380 --> 00:32:53.180
Everything went well.

399
00:32:53.180 --> 00:33:00.010
There was a spring between the capsule and
the boost stage and they separated by design.

400
00:33:00.010 --> 00:33:01.050
Fine.

401
00:33:01.050 --> 00:33:07.850
But what happened was the booster lined up
with the wake of the incoming test vehicle

402
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

403
00:33:12.050 --> 00:33:17.030
sucked along, clobbered the back of the vehicle
and it mutated.

404
00:33:17.030 --> 00:33:19.070
And so we weren't looking at the stagnation
point.

405
00:33:19.070 --> 00:33:20.760
We were looking off at 30 degrees.

406
00:33:20.760 --> 00:33:23.060
Not only that but the radiation was doing
this.

407
00:33:23.060 --> 00:33:30.060
Figured out the problem, sorted it out and
had the second flight test which worked beautifully.

408
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,

409
00:33:40.540 --> 00:33:47.270
and basically the radiation profile here,
as I said, was like two hours magnitude higher

410
00:33:47.270 --> 00:33:50.100
characteristically.

411
00:33:50.100 --> 00:33:54.110
But at high altitudes it just wasn't there.

412
00:33:54.110 --> 00:33:56.200
At peak heating it was.

413
00:33:56.200 --> 00:34:00.510
But, prior to that, which was a significant
heat load, it was not.

414
00:34:00.510 --> 00:34:07.510
There were not adequate collisions to excite
the radiators before the gas came to equilibrium.

415
00:34:07.890 --> 00:34:14.890
Now, as I mentioned before, at peak heating
conditions on Apollo the shock, I cannot draw

416
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

417
00:34:23.820 --> 00:34:24.409
at peak heating.

418
00:34:24.409 --> 00:34:28.780
[Q]: Is that the thickness of the shock or
the standoff distance?

419
00:34:28.780 --> 00:34:29.820
The standoff distance, thank you.

420
00:34:29.820 --> 00:34:31.520
Standoff distance.

421
00:34:31.520 --> 00:34:35.159
The shock is relatively thin, a few mean free
paths.

422
00:34:35.159 --> 00:34:42.159
And some people might call this effective
shock thickness, but I term the transition

423
00:34:42.710 --> 00:34:48.590
to higher temperature of the shock thickness
and then a relaxation distance.

424
00:34:48.590 --> 00:34:55.590
Any altitudes above that the flow could be
completely out of equilibrium.

425
00:34:55.760 --> 00:35:01.800
It hasn't gotten back to equilibrium because
this characteristic time is directly proportional

426
00:35:01.800 --> 00:35:03.460
pressure.

427
00:35:03.460 --> 00:35:04.140
And I erased it.

428
00:35:04.140 --> 00:35:08.390
It is directly proportional to free strain
density.

429
00:35:08.390 --> 00:35:12.050
So at higher altitudes it out of equilibrium.

430
00:35:12.050 --> 00:35:18.470
As you will see shortly, Shuttle is much higher
altitudes than Apollo.

431
00:35:18.470 --> 00:35:19.360
And I will explain why.

432
00:35:19.360 --> 00:35:26.360
At lower altitudes this compresses and is
predominantly at equilibrium radiation.

433
00:35:27.560 --> 00:35:31.000
And that we were able to characterize.

434
00:35:31.000 --> 00:35:32.340
OK.

435
00:35:32.340 --> 00:35:37.790
Back to ways of getting information.

436
00:35:37.790 --> 00:35:44.790
Numerical simulation.

437
00:35:47.830 --> 00:35:52.690
This is a significant revolution that you're
probably more familiar with than I am, but

438
00:35:52.690 --> 00:35:57.190
it really occurred right through the development
of the Shuttle.

439
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

440
00:36:04.380 --> 00:36:10.080
the aerothermodynamic environment at flight,
used the same technology that we used in Apollo.

441
00:36:10.080 --> 00:36:14.180
And that was we take a scale model, go into
a wind tunnel.

442
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

443
00:36:21.340 --> 00:36:27.140
to normal shock entropy is basically the entropy
of the entire body inviscidly.

444
00:36:27.140 --> 00:36:34.000
And so the normal shock or strong shock gas
dominates the flow around the vehicle.

445
00:36:34.000 --> 00:36:38.240
As you go low angle-of-attack you get into
an entirely different situation.

446
00:36:38.240 --> 00:36:44.220
In any event, what happens in terms of the
wind tunnel, the heating here compared to

447
00:36:44.220 --> 00:36:47.180
different distributions, is all pretty much
proportionate.

448
00:36:47.180 --> 00:36:49.570
And that is fundamentally what we used.

449
00:36:49.570 --> 00:36:51.970
And that included even the wake region back
here.

450
00:36:51.970 --> 00:36:58.970
And I will talk more about that when we get
into the charts.

451
00:37:02.110 --> 00:37:07.180
On the Shuttle we get into far more complicated
geometries.

452
00:37:07.180 --> 00:37:11.960
And the major challenge on Shuttle was that
three-dimensional geometry.

453
00:37:11.960 --> 00:37:15.320
And we did a bunch of numerical simulation
development.

454
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

455
00:37:21.960 --> 00:37:24.590
here, is basically subsonic.

456
00:37:24.590 --> 00:37:26.890
About the middle of the vehicle down is supersonic.

457
00:37:26.890 --> 00:37:31.710
And then, of course, you get into the wake
here.

458
00:37:31.710 --> 00:37:37.220
This was our flow field interest on Apollo
primarily because of this radiation.

459
00:37:37.220 --> 00:37:41.820
We had to understand the flow field in order
to be able to compute the radiation.

460
00:37:41.820 --> 00:37:47.050
About half of that radiation is optically
thick from the ultraviolet deionization radiation

461
00:37:47.050 --> 00:37:49.990
and also line radiation from atoms.

462
00:37:49.990 --> 00:37:51.350
Optically thick.

463
00:37:51.350 --> 00:37:57.420
The other half, the radiation is basically
optically thin, the molecular band radiation

464
00:37:57.420 --> 00:37:59.300
and other things.

465
00:37:59.300 --> 00:38:01.360
We needed to understand the flow field.

466
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

467
00:38:06.250 --> 00:38:12.490
focused on getting to a numerical simulation
of the subsonic region in particular.

468
00:38:12.490 --> 00:38:17.030
Now, in those days the computer was our real
limitation.

469
00:38:17.030 --> 00:38:19.330
And, of course, it was sort of embryonic.

470
00:38:19.330 --> 00:38:26.330
We have collectively just become orders of
magnitude beyond where we are today.

471
00:38:27.600 --> 00:38:34.600
However, the design approach that I would
recommend now is basically what we would like

472
00:38:36.120 --> 00:38:38.310
to have used on the Shuttle.

473
00:38:38.310 --> 00:38:39.650
And, to an extent, we did.

474
00:38:39.650 --> 00:38:43.850
Before we actually flew the Shuttle we had
confidence as a result of numerical simulation.

475
00:38:43.850 --> 00:38:50.520
It is a combination of these facilities and
numerical simulation.

476
00:38:50.520 --> 00:38:56.710
This problem of non-equilibrium is kind of
beyond numerical simulation, in my opinion.

477
00:38:56.710 --> 00:39:01.870
Now, you can correlate things, but I would
like to point out the limitations.

478
00:39:01.870 --> 00:39:05.500
You don't just go get a computer program and
you calculate everything because there are

479
00:39:05.500 --> 00:39:09.900
some very fundamental things missing.

480
00:39:09.900 --> 00:39:16.490
The way one gets reaction rates, for example,
dissociation rates or recombination rates

481
00:39:16.490 --> 00:39:18.650
is to go into a shock tube.

482
00:39:18.650 --> 00:39:23.220
As you approach equilibrium, the concept of
temperature, the equilibrium constant makes

483
00:39:23.220 --> 00:39:23.800
sense.

484
00:39:23.800 --> 00:39:26.950
So you can relate forward and backward rates.

485
00:39:26.950 --> 00:39:32.230
And you do diagnostics spectroscopically on
a concentration and you get rates.

486
00:39:32.230 --> 00:39:33.850
And it gets to be kind of complicated.

487
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

488
00:39:39.170 --> 00:39:42.870
the different modes of vibration, the electronic
excitation.

489
00:39:42.870 --> 00:39:44.850
It is a pretty complex problem.

490
00:39:44.850 --> 00:39:51.850
But, coming to equilibrium, is where we get
our reaction rates for high temperature gases.

491
00:39:53.560 --> 00:39:58.230
Coming back here, we're not close to equilibrium.

492
00:39:58.230 --> 00:39:58.840
Temperature doesn't work.

493
00:39:58.840 --> 00:40:05.840
Unless you start with an end body problem
and Schroedinger's equation, you're not going

494
00:40:06.310 --> 00:40:08.820
to really be able to compute this.

495
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

496
00:40:17.869 --> 00:40:20.560
of what matches the relaxation condition.

497
00:40:20.560 --> 00:40:23.030
I am not knocking it.

498
00:40:23.030 --> 00:40:27.440
All I am saying is there are limitations to
numerical simulation, whether it be in physical

499
00:40:27.440 --> 00:40:30.680
chemistry or just about anything you work
with.

500
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

501
00:40:37.480 --> 00:40:41.920
and what happens in flight or what happens
in an arc jet and the phenomena.

502
00:40:41.920 --> 00:40:47.430
I will say a little bit more about that as
we get into the charts.

503
00:40:47.430 --> 00:40:54.190
Before we flew, in regions of the vehicle,
I made statements which I still would make,

504
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

505
00:41:00.280 --> 00:41:01.960
it in regions.

506
00:41:01.960 --> 00:41:03.990
Not over the entire region.

507
00:41:03.990 --> 00:41:08.530
Not over the separated region.

508
00:41:08.530 --> 00:41:14.590
Not over conditions where the flow was turbulent.

509
00:41:14.590 --> 00:41:19.180
But, in the laminar environment, we could
compute it as well as you could measure it.

510
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

511
00:41:24.800 --> 00:41:29.450
is, I can tell you all about the aerodynamics,
I can tell you everything.

512
00:41:29.450 --> 00:41:29.800
Good.

513
00:41:29.800 --> 00:41:31.150
Run it on a wind tunnel test.

514
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.

515
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

516
00:41:43.990 --> 00:41:49.820
terms of the chemistry in shock tubes or ballistic
facilities for that matter and certainly in

517
00:41:49.820 --> 00:41:51.300
terms of flight test.

518
00:41:51.300 --> 00:41:56.100
And you've got Shuttle data and a lot of code
validation for that Shuttle data.

519
00:41:56.100 --> 00:41:58.430
Now, this is just from the heating standpoint.

520
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

521
00:42:02.310 --> 00:42:04.390
rest of the things.

522
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

523
00:42:13.619 --> 00:42:18.080
thermal protection system and then we will
go to some charts that has some real information

524
00:42:18.080 --> 00:42:21.869
on it instead of just a hand-waving that I'm
doing right now.

525
00:42:21.869 --> 00:42:24.730
Configuration.

526
00:42:24.730 --> 00:42:26.840
I mentioned dissipating this energy.

527
00:42:26.840 --> 00:42:33.380
George Truhall [SP?] was in charge of the
thermal protection system on Apollo.

528
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

529
00:42:38.460 --> 00:42:39.530
it into the air.

530
00:42:39.530 --> 00:42:42.530
We compress the air, heat the air.

531
00:42:42.530 --> 00:42:45.800
You only have 2% to deal with, a small percentage.

532
00:42:45.800 --> 00:42:50.350
And he used to come right back to me and say
I do the same thing.

533
00:42:50.350 --> 00:42:55.420
I get rid of 98% of it and only 2% gets to
the structure.

534
00:42:55.420 --> 00:42:56.590
And, in fact, that it is true.

535
00:42:56.590 --> 00:43:03.000
By design, if you look at a meteor coming
in, the surface will vaporize.

536
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

537
00:43:08.100 --> 00:43:09.110
on the outside.

538
00:43:09.110 --> 00:43:10.360
And some of it will come in.

539
00:43:10.360 --> 00:43:16.010
In fact, Professor Fay wrote a wonderful paper
about meteors, what become meteorites and

540
00:43:16.010 --> 00:43:17.470
what are meteors.

541
00:43:17.470 --> 00:43:19.080
An excellent paper.

542
00:43:19.080 --> 00:43:20.310
Put it in a real perspective.

543
00:43:20.310 --> 00:43:25.900
Broad range, much broader than what I'm talking
about here.

544
00:43:25.900 --> 00:43:32.900
The way George was able to get rid of this
heat was by re-radiating.

545
00:43:40.470 --> 00:43:45.780
And this has been kind of unique to manned
vehicles.

546
00:43:45.780 --> 00:43:52.780
Fundamentally, you've got a vehicle coming
in, you've got a surface with the capsules

547
00:43:52.869 --> 00:43:56.000
far exceeding the material capability.

548
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.

549
00:44:01.080 --> 00:44:08.080
And so what happens is the material degrades
and is called an ablator.

550
00:44:08.690 --> 00:44:13.040
And the initial concept and application for
ablators is, as the material vaporizes, it

551
00:44:13.040 --> 00:44:17.200
basically pushes the air away to reduce the
heat.

552
00:44:17.200 --> 00:44:19.970
And this is sort of what happens in meteors
if you want.

553
00:44:19.970 --> 00:44:22.290
So, you lose some of the initial material.

554
00:44:22.290 --> 00:44:26.240
And that sample that Aaron passed around,
that black material, well, it was a little

555
00:44:26.240 --> 00:44:30.369
thicker when it started than the sample that
he has.

556
00:44:30.369 --> 00:44:37.369
But you see this what we call char layer where
the material is decomposed?

557
00:44:37.920 --> 00:44:43.780
That generates a gas which at high pressures
and high heating rates basically tends to

558
00:44:43.780 --> 00:44:48.480
absorb the energy that is coming in through
the chemical reactions primarily, and also

559
00:44:48.480 --> 00:44:51.890
due to the blowing.

560
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,

561
00:44:58.180 --> 00:45:01.930
at the higher altitudes was to re-radiate
it.

562
00:45:01.930 --> 00:45:05.180
How do you draw re-radiation?

563
00:45:05.180 --> 00:45:09.430
I guess sort of a wavy line.

564
00:45:09.430 --> 00:45:12.960
Radiation is always a wave, right?

565
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

566
00:45:20.910 --> 00:45:22.810
vehicle.

567
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,

568
00:45:31.440 --> 00:45:32.550
high-temperature surface.

569
00:45:32.550 --> 00:45:39.550
Now, in the ablator, that char, think of it
as a charcoal briquette.

570
00:45:41.350 --> 00:45:45.520
You start with some material.

571
00:45:45.520 --> 00:45:49.020
It degrades and all sorts of chemical reactions
go.

572
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

573
00:45:55.170 --> 00:45:58.520
char which is black and very high-emissivity.

574
00:45:58.520 --> 00:45:59.920
It is pure carbon, if you want.

575
00:45:59.920 --> 00:46:06.920
That is the challenge, is to get a carbon
surface or a high-emissivity, high-temperature

576
00:46:07.180 --> 00:46:08.990
surface that can re-radiate.

577
00:46:08.990 --> 00:46:14.190
Just to remind the class, what is the most
efficient radiator?

578
00:46:14.190 --> 00:46:17.619
Black-body, there you go.

579
00:46:17.619 --> 00:46:22.280
Thank you.

580
00:46:22.280 --> 00:46:26.940
High-emissivity, black-body radiation, get
rid of all that energy before it ever has

581
00:46:26.940 --> 00:46:32.840
to diffuse through the tile or through the
ablator to get to the structure.

582
00:46:32.840 --> 00:46:38.400
That is fundamentally what we use to protect
the vehicle.

583
00:46:38.400 --> 00:46:45.290
Now, while I'm on that, the ablators were
developed for capsules.

584
00:46:45.290 --> 00:46:49.740
And we kept getting lower and lower density
because we wanted to minimize the diffusion

585
00:46:49.740 --> 00:46:51.040
of energy from the surface.

586
00:46:51.040 --> 00:46:56.170
There needed to be a substant enough surface
to hang together.

587
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.

588
00:47:01.610 --> 00:47:08.310
With the early capsule, with the Apollo, we
had a fiberglass structure in there that basically

589
00:47:08.310 --> 00:47:12.960
retarded the ablator from flowing away.

590
00:47:12.960 --> 00:47:19.540
Now, everybody tells us we were twice too
heavy on the ablator on a capsule.

591
00:47:19.540 --> 00:47:21.690
And I will explain that in a bit.

592
00:47:21.690 --> 00:47:25.700
It's a systems engineering problem, we got
away from it on Shuttle, so pay attention

593
00:47:25.700 --> 00:47:27.420
when I get to that problem.

594
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.

595
00:47:37.020 --> 00:47:40.859
On that region, we were right on.

596
00:47:40.859 --> 00:47:42.810
Not by knowing what we were doing, just by
luck.

597
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

598
00:47:51.930 --> 00:47:58.930
the way into -- We hit our temperature requirement
on the structure.

599
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?]

600
00:48:07.380 --> 00:48:08.910
[he actually said that! there's no reference
in aerothermodynamics that refers to that

601
00:48:08.910 --> 00:48:10.930
term] and charing.

602
00:48:10.930 --> 00:48:13.220
And I've got a flow over the vehicle.

603
00:48:13.220 --> 00:48:15.960
I've got one heck of a pressure grid.

604
00:48:15.960 --> 00:48:17.450
And I just described this char.

605
00:48:17.450 --> 00:48:20.270
It's a nice porous carbon like a charcoal
briquette.

606
00:48:20.270 --> 00:48:21.609
Ever blow on a charcoal briquette?

607
00:48:21.609 --> 00:48:26.300
You can blow your air right through it and
it flames up.

608
00:48:26.300 --> 00:48:27.609
That's exactly what happened here.

609
00:48:27.609 --> 00:48:29.980
We had flow through.

610
00:48:29.980 --> 00:48:33.470
The honeycomb wasn't as a high a temperature
as the carbon.

611
00:48:33.470 --> 00:48:36.840
That was just there to hold it as the system
degraded.

612
00:48:36.840 --> 00:48:42.040
So, the combination of the two-dimensional
flow which we really hadn't simulated on the

613
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.

614
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

615
00:48:56.390 --> 00:48:59.460
surface the enthalpy basically goes down.

616
00:48:59.460 --> 00:49:01.890
The heating on the surface goes down.

617
00:49:01.890 --> 00:49:07.140
We were testing six inch specimens characteristically.

618
00:49:07.140 --> 00:49:08.369
We really didn't get the flow through.

619
00:49:08.369 --> 00:49:11.840
In fact, we eliminated the flow through because
we had one-dimensional models and we wanted

620
00:49:11.840 --> 00:49:13.810
to understand the process of one-dimensional.

621
00:49:13.810 --> 00:49:20.609
But, in flight, fortunately we were a factor
or two over just in that region.

622
00:49:20.609 --> 00:49:23.560
Over this region, and I will show you a chart,
we were way over.

623
00:49:23.560 --> 00:49:26.090
And, again, I will try to address that.

624
00:49:26.090 --> 00:49:30.180
And, again, the Shuttle has really helped
us in understanding the leeside flow.

625
00:49:30.180 --> 00:49:32.010
Configuration.

626
00:49:32.010 --> 00:49:39.010
Everybody has got their own requirements for
configurations.

627
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

628
00:49:46.710 --> 00:49:48.900
drag configuration.

629
00:49:48.900 --> 00:49:55.790
I just want a flat plat normal to the flow.

630
00:49:55.790 --> 00:49:56.330
Well, that's wonderful.

631
00:49:56.330 --> 00:49:59.980
It's high drag but it's not stable at all.

632
00:49:59.980 --> 00:50:03.060
Let's go to a sphere.

633
00:50:03.060 --> 00:50:08.609
Now, the center pressure, no matter where
the pressure is on the vehicle, no matter

634
00:50:08.609 --> 00:50:13.400
what the pressure is, it goes right to the
center.

635
00:50:13.400 --> 00:50:17.720
And that is probably also about the center
of gravity if I flew a sphere.

636
00:50:17.720 --> 00:50:22.880
Certainly if it was solid, but if I build
a spherical spacecraft it would be neutrally

637
00:50:22.880 --> 00:50:23.500
stable.

638
00:50:23.500 --> 00:50:24.080
Well, that would be great.

639
00:50:24.080 --> 00:50:28.190
I could spin it and distribute the heating
over the entire thing.

640
00:50:28.190 --> 00:50:30.380
As they enter, that happens to some meteors.

641
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

642
00:50:33.450 --> 00:50:33.700
left.

643
00:50:33.540 --> 00:50:37.130
There are all kinds of problems with that.

644
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

645
00:50:42.470 --> 00:50:48.810
distribution, if I plot the heat transfer
in this direction from ground test, not from

646
00:50:48.810 --> 00:50:51.430
flight, from ground test, you have some level
of heating.

647
00:50:51.430 --> 00:50:55.080
But then, when you get to the corner, it really
goes up because of pressure gradient.

648
00:50:55.080 --> 00:51:00.290
The same thing that we experienced on Apollo
in terms of the ablator.

649
00:51:00.290 --> 00:51:05.130
So, you want to give it some curvature, not
only from the standpoint of stability but

650
00:51:05.130 --> 00:51:09.900
also from the standpoint of the heating distribution.

651
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

652
00:51:14.470 --> 00:51:15.880
a uniform heating distribution.

653
00:51:15.880 --> 00:51:17.369
That is very efficient.

654
00:51:17.369 --> 00:51:22.800
I can design my thermal protection system
to be so thick and I manufacture it, produce

655
00:51:22.800 --> 00:51:26.020
it over the entire surface exactly the same.

656
00:51:26.020 --> 00:51:30.630
That is wonderful, except I still have the
corner problem.

657
00:51:30.630 --> 00:51:37.420
And so I round the corners a bit.

658
00:51:37.420 --> 00:51:39.790
This is only from an aerothermodynamic standpoint
now.

659
00:51:39.790 --> 00:51:44.230
And so I don't have this corner edge heating
problem nearly as much.

660
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

661
00:51:52.760 --> 00:51:53.609
have much control.

662
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

663
00:51:58.550 --> 00:51:58.880
mechanics control.

664
00:51:58.880 --> 00:52:03.530
In any event, I need some L/D so I got to
angle-of-attack.

665
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

666
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

667
00:52:14.930 --> 00:52:18.330
how the aerodynamic forces are acting on that.

668
00:52:18.330 --> 00:52:22.619
And I want the center of gravity ahead of
that.

669
00:52:22.619 --> 00:52:26.230
And now I've got a nice stable configuration.

670
00:52:26.230 --> 00:52:31.470
Not too stable because the control people
want to do things with it but stable from

671
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

672
00:52:35.800 --> 00:52:36.260
of thing.

673
00:52:36.260 --> 00:52:38.030
That is how we designed Apollo.

674
00:52:38.030 --> 00:52:41.650
It worked very well.

675
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.

676
00:52:55.340 --> 00:52:57.390
In two-dimensions.

677
00:52:57.390 --> 00:53:01.220
In three-dimensions it is significantly different.

678
00:53:01.220 --> 00:53:07.369
I think I'm about ready to go to the charts
now.

679
00:53:07.369 --> 00:53:07.970
OK.

680
00:53:07.970 --> 00:53:10.900
Why don't we take a two-minute break.

681
00:53:10.900 --> 00:53:13.450
We usually break about 10:00.

682
00:53:13.450 --> 00:53:13.960
Great.

683
00:53:13.960 --> 00:53:17.790
And I will get the charts set up.

684
00:53:17.790 --> 00:53:18.359
Good.

685
00:53:18.359 --> 00:53:19.109
Quick stretch.

686
00:53:19.109 --> 00:53:19.900
Turn around.

687
00:53:19.900 --> 00:53:22.320
I didn't ask if there were any questions.

688
00:53:22.320 --> 00:53:26.590
I expected everybody to just raise their hands
and start asking questions.

689
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

690
00:53:30.930 --> 00:53:37.290
why we're not getting any questions.

691
00:53:37.290 --> 00:53:38.490
That was my hand-waving.

692
00:53:38.490 --> 00:53:40.990
I am going to get into specifics here after
the break.

693
00:53:40.990 --> 00:53:47.990
I have a series of charts.

694
00:54:36.760 --> 00:54:42.850
Most of these came from a technical conference
that Professor Cohen had after the Shuttle

695
00:54:42.850 --> 00:54:43.310
test flights.

696
00:54:43.310 --> 00:54:50.310
We had five test flights, just for information.

697
00:54:53.230 --> 00:55:00.040
We had 17 flights in Mercury before we put
a man in the vehicle.

698
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

699
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

700
00:55:11.140 --> 00:55:12.080
the actual Lunar landing.

701
00:55:12.080 --> 00:55:14.530
We couldn't really simulate that very well.

702
00:55:14.530 --> 00:55:16.230
We couldn't test that.

703
00:55:16.230 --> 00:55:23.230
On the Shuttle, we did as much testing as
we could, but the design constraints forced

704
00:55:30.420 --> 00:55:35.170
us to go with men in the system initially.

705
00:55:35.170 --> 00:55:39.450
And that was the least riskiest thing to do
considering everything.

706
00:55:39.450 --> 00:55:39.700
That's a whole different subject.

707
00:55:39.450 --> 00:55:42.640
All right.

708
00:55:42.640 --> 00:55:49.640
This first chart is altitude in thousands
of feet and velocity in feet per second.

709
00:55:52.130 --> 00:55:59.130
What I've shown here is, first of all, this
is one atmosphere total pressure.

710
00:56:01.470 --> 00:56:08.470
This is a tenth of an atmosphere total pressure.

711
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

712
00:56:15.750 --> 00:56:18.420
from actually one of these flights.

713
00:56:18.420 --> 00:56:21.410
These bands are to show the flight regime.

714
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

715
00:56:28.109 --> 00:56:30.359
through an orbital entry.

716
00:56:30.359 --> 00:56:33.320
You can see there is an order of magnitude
difference here.

717
00:56:33.320 --> 00:56:34.470
I'm sorry.

718
00:56:34.470 --> 00:56:36.220
Here is the Shuttle.

719
00:56:36.220 --> 00:56:42.119
This was the design coming from a polar orbit
at 265,000 feet per second.

720
00:56:42.119 --> 00:56:45.780
And these are the orbital flight tests, the
five flight tests.

721
00:56:45.780 --> 00:56:51.660
They are all laid together here, and you cannot
really see much of a difference.

722
00:56:51.660 --> 00:56:57.660
Now, this is the heating boundary.

723
00:56:57.660 --> 00:57:03.740
If we went beyond that the tiles degrade.

724
00:57:03.740 --> 00:57:08.510
Now, I mentioned three levels of aerothermodynamics.

725
00:57:08.510 --> 00:57:11.609
The design level, well, I'll get into the
design level a little bit later.

726
00:57:11.609 --> 00:57:15.080
The first level was basically the Apollo technology.

727
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

728
00:57:23.680 --> 00:57:29.540
relative to a reference, and we used the one
foot sphere as a reference.

729
00:57:29.540 --> 00:57:36.540
And I gave that to the flight mechanics people
and said do not violate these constraints.

730
00:57:37.130 --> 00:57:43.660
So they developed the flight mechanics control
and everything else to fly right along here.

731
00:57:43.660 --> 00:57:47.859
Now, what isn't shown is we anticipated transition.

732
00:57:47.859 --> 00:57:49.530
And I will show that in time histories.

733
00:57:49.530 --> 00:57:52.910
There is another boundary for heating that
actually comes along here.

734
00:57:52.910 --> 00:57:59.890
These trajectories are very tight relative
to having a re-usable thermal protection system

735
00:57:59.890 --> 00:58:03.580
and not having to completely refurbish the
vehicle.

736
00:58:03.580 --> 00:58:04.420
That was the target.

737
00:58:04.420 --> 00:58:09.580
If we wanted a reusable system, we could turn
around and fly again.

738
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

739
00:58:22.340 --> 00:58:23.960
from the Shuttle.

740
00:58:23.960 --> 00:58:27.250
But basically here we have a simple configuration.

741
00:58:27.250 --> 00:58:30.190
Here we had a much more complex configuration.

742
00:58:30.190 --> 00:58:37.190
We had capability to fly it and we had capability
to avoid excessive heating.

743
00:58:38.690 --> 00:58:41.060
It takes about 20 minutes to enter.

744
00:58:41.060 --> 00:58:47.510
Ten minutes along this heating boundary where
basically your heating rate comes up and you

745
00:58:47.510 --> 00:58:48.859
are on a plateau.

746
00:58:48.859 --> 00:58:54.690
And you will see that in just a minute.

747
00:58:54.690 --> 00:58:58.970
That contrasts the Apollo and the Shuttle.

748
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

749
00:59:04.010 --> 00:59:09.300
environment, about 33,000 feet per second
for peak heating, when this thing comes down

750
00:59:09.300 --> 00:59:13.480
to also about max pressure on this chart anyway.

751
00:59:13.480 --> 00:59:19.900
But Shuttle was significantly higher altitude,
significantly more out of equilibrium, which

752
00:59:19.900 --> 00:59:21.380
is the bad news.

753
00:59:21.380 --> 00:59:25.720
The good news is the radiation was not that
significant.

754
00:59:25.720 --> 00:59:32.160
In fact, when we calculated what the astronauts
would see coming in -- On Apollo, when they

755
00:59:32.160 --> 00:59:36.800
were looking out the windows on the wake,
it was extremely bright.

756
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

757
00:59:43.090 --> 00:59:44.810
side.

758
00:59:44.810 --> 00:59:51.380
On the Shuttle, we suggested a 100 watt light
bulb behind a table.

759
00:59:51.380 --> 00:59:55.990
It worked beautifully in the simulator.

760
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

761
01:00:02.810 --> 01:00:03.880
environment.

762
01:00:03.880 --> 01:00:07.010
The heating basically increases.

763
01:00:07.010 --> 01:00:10.500
In this direction, I don't show [UNINTELLIGIBLE
PHRASE].[question about mars, that i miss

764
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

765
01:00:16.880 --> 01:00:18.460
second.

766
01:00:18.460 --> 01:00:22.920
The convective heating goes up as velocity
cubed.

767
01:00:22.920 --> 01:00:27.040
The radiation probably goes up by two orders
of magnitude.

768
01:00:27.040 --> 01:00:30.119
The radiation is very, very sensitive.

769
01:00:30.119 --> 01:00:35.680
Some of the people at Ames did correlations
with velocity and with temperature.

770
01:00:35.680 --> 01:00:38.970
And there were numbers like a temperature
to the eighth power, a temperature to the

771
01:00:38.970 --> 01:00:44.030
twelfth power because it is not limited by
black-body over a lot of the spectrum.

772
01:00:44.030 --> 01:00:47.940
And, as the temperature goes up, there are
more and more radiated degrees of freedom.

773
01:00:47.940 --> 01:00:50.830
It gets much closer to a black-body.

774
01:00:50.830 --> 01:00:57.830
Radiation becomes dominant on a Mars return.

775
01:00:59.200 --> 01:01:03.430
On Lunar return it is a problem.

776
01:01:03.430 --> 01:01:09.680
However, if you look at the radiative heating,
it is first order proportional to two-dimension.

777
01:01:09.680 --> 01:01:13.380
Whereas, a convective heating is just the
opposite, it is inversely proportional square

778
01:01:13.380 --> 01:01:14.190
root.

779
01:01:14.190 --> 01:01:19.730
As you go up in dimension, your convective
heating is less important, as we did with

780
01:01:19.730 --> 01:01:20.119
the Shuttle.

781
01:01:20.119 --> 01:01:21.380
And I will try to address that.

782
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?

783
01:01:25.640 --> 01:01:27.910
I think we could develop an ablator.

784
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

785
01:01:32.840 --> 01:01:35.080
the radiation.

786
01:01:35.080 --> 01:01:40.740
And these days there is a lot more capability
there than there was in Apollo days.

787
01:01:40.740 --> 01:01:42.730
But that is a real challenge.

788
01:01:42.730 --> 01:01:43.030
Yes.

789
01:01:43.030 --> 01:01:44.520
I have a couple questions.

790
01:01:44.520 --> 01:01:44.770
Sure.

791
01:01:44.520 --> 01:01:51.520
[all/among the lines Why do they come backup]
That was the basic flight mechanics that dissipate

792
01:01:54.830 --> 01:01:56.310
the energy.

793
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

794
01:02:01.570 --> 01:02:02.050
an entry.

795
01:02:02.050 --> 01:02:07.540
You wanted to not exceed the deceleration.

796
01:02:07.540 --> 01:02:13.300
Actually, from an ablator standpoint, one
of the most efficient ways to come in is hot

797
01:02:13.300 --> 01:02:15.589
and heavy.

798
01:02:15.589 --> 01:02:17.700
Go to max heating rate but keep that time
down.

799
01:02:17.700 --> 01:02:22.810
You remember I mentioned the square root of
time on the diffusion of the energy in.

800
01:02:22.810 --> 01:02:24.410
You want to keep that time down.

801
01:02:24.410 --> 01:02:29.130
And you're better off taking your lumps on
heating rate.

802
01:02:29.130 --> 01:02:31.540
Heat load is really what designs.

803
01:02:31.540 --> 01:02:34.650
Did that answer your question?

804
01:02:34.650 --> 01:02:41.210
[UNINTELLIGIBLE PHRASE] [i'm sorry enviroment
noise plus air condition] This is the flight

805
01:02:41.210 --> 01:02:48.160
mechanics, and I'm not an expert on that,
but basically this portion was designed to

806
01:02:48.160 --> 01:02:50.400
capture.

807
01:02:50.400 --> 01:02:54.930
If you don't capture you're gone for another
two weeks.

808
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.

809
01:03:02.640 --> 01:03:05.710
You didn't want to skip out.

810
01:03:05.710 --> 01:03:06.730
This is a linear plot.

811
01:03:06.730 --> 01:03:10.940
You're looking at an atmosphere and you're
coming in at high speed.

812
01:03:10.940 --> 01:03:16.339
I want to make sure you capture it.

813
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.

814
01:03:22.770 --> 01:03:23.630
First thing is capture.

815
01:03:23.630 --> 01:03:24.859
Dissipate that energy.

816
01:03:24.859 --> 01:03:29.720
Then we worry about getting down to a landing
point.

817
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

818
01:03:37.540 --> 01:03:38.000
at 400,000 feet.

819
01:03:38.000 --> 01:03:41.119
If you were too shallow then you would skip
out.

820
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.

821
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

822
01:03:54.430 --> 01:03:59.460
in the earth's atmosphere.

823
01:03:59.460 --> 01:04:04.760
And that was really what the guidance navigation
system did for us.

824
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

825
01:04:08.220 --> 01:04:12.280
very tight corridor that you've got to hit.

826
01:04:12.280 --> 01:04:13.250
Well, I can talk about it now.

827
01:04:13.250 --> 01:04:19.520
No, I will wait until the next chart in terms
of the systems engineering and everything.

828
01:04:19.520 --> 01:04:26.520
When I 
was here, the computers were in the electrical
engineering department and occupied an entire

829
01:04:34.740 --> 01:04:35.260
room.

830
01:04:35.260 --> 01:04:41.690
Mechanical engineers like me, I mean we didn't
understand all that stuff.

831
01:04:41.690 --> 01:04:43.920
Generations.

832
01:04:43.920 --> 01:04:46.420
Design and flight test environments, a lot
of points I want to make here.

833
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

834
01:04:55.500 --> 01:04:56.270
conditions.

835
01:04:56.270 --> 01:05:00.190
Now, the numbers are not so important.

836
01:05:00.190 --> 01:05:01.589
Apollo is triangles.

837
01:05:01.589 --> 01:05:05.180
Shuttle is circles.

838
01:05:05.180 --> 01:05:08.050
Filled is design.

839
01:05:08.050 --> 01:05:10.450
Open is actual.

840
01:05:10.450 --> 01:05:12.230
Let's start with the Apollo.

841
01:05:12.230 --> 01:05:17.119
Our design is up here coming back from the
moon.

842
01:05:17.119 --> 01:05:18.900
Actually, there were two design points.

843
01:05:18.900 --> 01:05:22.550
This was the maximum load which was the thickness
of the ablator.

844
01:05:22.550 --> 01:05:23.400
That is the weight.

845
01:05:23.400 --> 01:05:25.040
We picked the material.

846
01:05:25.040 --> 01:05:26.950
We got the best material we could.

847
01:05:26.950 --> 01:05:28.320
Now the question is how thick do we make it?

848
01:05:28.320 --> 01:05:29.950
And that's the weight.

849
01:05:29.950 --> 01:05:31.690
Here is the design condition.

850
01:05:31.690 --> 01:05:37.000
The heat load I mentioned before relative
to the question.

851
01:05:37.000 --> 01:05:41.810
We didn't have the trajectories of flight
mechanics when we started the design.

852
01:05:41.810 --> 01:05:47.119
We had to start to design the capsule, the
ablator and everything else in parallel with

853
01:05:47.119 --> 01:05:50.750
the development of the computer capability
and the flight mechanics and being able to

854
01:05:50.750 --> 01:05:53.030
actually fly this thing.

855
01:05:53.030 --> 01:05:55.130
What happened?

856
01:05:55.130 --> 01:05:58.430
We knew we couldn't exceed 20 Gs.

857
01:05:58.430 --> 01:06:01.510
And so give me a trajectory that comes in
and hits 20 Gs.

858
01:06:01.510 --> 01:06:03.839
I've got to be able to handle that heating
rate.

859
01:06:03.839 --> 01:06:06.470
We also needed to capture.

860
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

861
01:06:13.630 --> 01:06:15.930
me a trajectory that just stays in.

862
01:06:15.930 --> 01:06:18.770
They are miles apart.

863
01:06:18.770 --> 01:06:22.010
That point is up here on that chart.

864
01:06:22.010 --> 01:06:27.380
For clarity and trying to illustrate other
things, it is way up here in heating rate.

865
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

866
01:06:36.040 --> 01:06:36.290
get.

867
01:06:36.040 --> 01:06:39.339
All sorts of things in between.

868
01:06:39.339 --> 01:06:40.320
This is an actual flight.

869
01:06:40.320 --> 01:06:44.540
This is log paper.

870
01:06:44.540 --> 01:06:46.310
A significant difference.

871
01:06:46.310 --> 01:06:48.660
A factor of two.

872
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.

873
01:06:56.260 --> 01:07:02.770
But now here is the systems engineering point.

874
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

875
01:07:08.010 --> 01:07:08.260
down?

876
01:07:08.030 --> 01:07:14.530
Well, if you look at the aerospace industry
or NASA you have specialists.

877
01:07:14.530 --> 01:07:16.599
Everybody does their own little thing.

878
01:07:16.599 --> 01:07:17.599
I am aerothermodynamicist.

879
01:07:17.599 --> 01:07:21.599
George Truhall was the thermal protection
system guy.

880
01:07:21.599 --> 01:07:23.160
Tom Moser was a structures guy.

881
01:07:23.160 --> 01:07:24.490
Then there was a materials guy.

882
01:07:24.490 --> 01:07:28.589
All these different people, they all do their
thing and work together as a team.

883
01:07:28.589 --> 01:07:32.089
We're designing a system to go to the moon
and come back.

884
01:07:32.089 --> 01:07:36.640
Boy, I sure don't want to put too low a heating
rate in.

885
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

886
01:07:45.869 --> 01:07:48.080
right here or whatever.

887
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%

888
01:07:55.280 --> 01:07:58.830
or 20% at least in on my heating.

889
01:07:58.830 --> 01:08:05.830
The ablator guy, he is testing on arc jets,
and he does exactly the same thing.

890
01:08:06.070 --> 01:08:08.920
The structures guy says, well, we want to
do this and that.

891
01:08:08.920 --> 01:08:14.180
Well, on the Shuttle, for example, our guideline
was 100 missions, a structure that would take

892
01:08:14.180 --> 01:08:15.200
100 cycles.

893
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

894
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

895
01:08:26.839 --> 01:08:27.789
put a little pad in.

896
01:08:27.789 --> 01:08:30.029
There is nothing wrong with that.

897
01:08:30.029 --> 01:08:35.199
What was wrong is we didn't have communication
with all these people.

898
01:08:35.199 --> 01:08:40.319
Somebody gives me a trajectory and I calculate
heat and I say, boy, this is what I think

899
01:08:40.319 --> 01:08:40.799
it's going to be.

900
01:08:40.799 --> 01:08:44.489
And I'm going to show you some of that, in
all honesty, which you won't see in journal

901
01:08:44.489 --> 01:08:46.239
articles.

902
01:08:46.239 --> 01:08:52.989
But I better put a little bit of pad on that
because I don't know this that well.

903
01:08:52.989 --> 01:08:53.759
They compound.

904
01:08:53.759 --> 01:08:57.069
We call it compound conservatism.

905
01:08:57.069 --> 01:09:03.139
Everybody puts their 10% in and you get your
factor of two.

906
01:09:03.139 --> 01:09:09.999
Now, you just lost significant, if not half
the payload on the Shuttle by doing that.

907
01:09:09.999 --> 01:09:11.880
We did not do that on the Shuttle.

908
01:09:11.880 --> 01:09:15.079
Now, let me very honest.

909
01:09:15.079 --> 01:09:18.619
In the early days, when we recognized that,
because we were getting beat on.

910
01:09:18.619 --> 01:09:21.670
You don't need all that TPS.

911
01:09:21.670 --> 01:09:26.329
When we realized where it really came from,
we would go back to the management and say

912
01:09:26.329 --> 01:09:26.849
this is what you need to do.

913
01:09:26.849 --> 01:09:30.619
You need a system where you have all this
communication.

914
01:09:30.619 --> 01:09:33.499
Well, that's going to be expensive.

915
01:09:33.499 --> 01:09:35.529
We did it, but we did it informally.

916
01:09:35.529 --> 01:09:39.489
We did it by communicating informally everybody
understanding.

917
01:09:39.489 --> 01:09:44.759
And we actually did a statistical assessment
before we flew the Shuttle to give us confidence

918
01:09:44.759 --> 01:09:49.299
that things would work.

919
01:09:49.299 --> 01:09:49.749
Extremely important.

920
01:09:49.749 --> 01:09:54.179
I mean when you talk about systems engineering
it is communication, different disciplines,

921
01:09:54.179 --> 01:09:56.829
different requirements, different everything.

922
01:09:56.829 --> 01:09:59.079
Communication between people is very important.

923
01:09:59.079 --> 01:09:59.650
All right.

924
01:09:59.650 --> 01:10:01.010
Where was I?

925
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.

926
01:10:08.179 --> 01:10:11.699
And, I'm sorry, I don't remember why we called
them one, three, four.

927
01:10:11.699 --> 01:10:14.170
This was a design, there's another design
up here.

928
01:10:14.170 --> 01:10:15.229
That was a conservative.

929
01:10:15.229 --> 01:10:15.959
All right.

930
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

931
01:10:23.239 --> 01:10:25.760
design.

932
01:10:25.760 --> 01:10:29.219
We do not have a whole lot of margin.

933
01:10:29.219 --> 01:10:34.119
But, as you saw from the previous chart, we
can fly it.

934
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.

935
01:10:38.179 --> 01:10:38.429
Any questions?

936
01:10:38.400 --> 01:10:38.650
Yes.

937
01:10:38.510 --> 01:10:39.539
How much does your ability to control the
trajectory play into that?

938
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

939
01:10:49.039 --> 01:10:56.039
than you would Apollo.

940
01:10:56.300 --> 01:10:56.719
Yes.

941
01:10:56.719 --> 01:10:57.139
Absolutely.

942
01:10:57.139 --> 01:11:01.619
You've got a body flap on there, in particular,
to trim angle-of-attack.

943
01:11:01.619 --> 01:11:06.130
We also have RCS engines which we'd use if
we would have to.

944
01:11:06.130 --> 01:11:08.489
And, in some cases, we have to.

945
01:11:08.489 --> 01:11:11.969
And you've got aileron settings which primarily
are used later.

946
01:11:11.969 --> 01:11:13.780
But, yes, crucial.

947
01:11:13.780 --> 01:11:20.329
In terms of getting this level of precision
you need control.

948
01:11:20.329 --> 01:11:27.329
But isn't the most important factor the flight
path angle, the angle between the velocity

949
01:11:29.139 --> 01:11:30.579
vector and the local horizontal at [400,000?]
feet?

950
01:11:30.579 --> 01:11:30.940
Initially yes.

951
01:11:30.940 --> 01:11:34.199
On Shuttle you could modulate that.

952
01:11:34.199 --> 01:11:34.749
Yes.

953
01:11:34.749 --> 01:11:40.150
And, actually, you see some of these wiggles,
you know, we have highs and lows.

954
01:11:40.150 --> 01:11:47.150
We have hurricanes and high pressure areas,
but the atmosphere is an exponential decay.

955
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

956
01:11:54.820 --> 01:11:57.289
very significant.

957
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.

958
01:12:01.769 --> 01:12:05.840
And being able to control is sort of crucial
there.

959
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

960
01:12:11.829 --> 01:12:12.679
obviously the same thing.

961
01:12:12.679 --> 01:12:19.679
Any other questions on this before we go to
the next chart?

962
01:12:19.820 --> 01:12:20.590
OK.

963
01:12:20.590 --> 01:12:22.150
All right.

964
01:12:22.150 --> 01:12:26.780
I mentioned three levels of aerothermodynamic
methodology.

965
01:12:26.780 --> 01:12:32.090
One is to correlate in the wind tunnel and
relate everything to reference heating or

966
01:12:32.090 --> 01:12:38.479
stagnation point heating, which is what we
did on the capsules which are good blunt vehicles.

967
01:12:38.479 --> 01:12:43.340
The real technology challenge on the Shuttle
was the geometry.

968
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

969
01:12:49.889 --> 01:12:52.340
a blunt vehicle.

970
01:12:52.340 --> 01:12:55.599
You name it, you've got it, in terms of flow
on this thing.

971
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

972
01:13:02.130 --> 01:13:03.920
fluid dynamics.

973
01:13:03.920 --> 01:13:10.179
The design methodology that was used to actually
design the system was to model the flow.

974
01:13:10.179 --> 01:13:14.579
Obviously, up front here looks kind of like
a sphere.

975
01:13:14.579 --> 01:13:16.780
And so I calculate the heating on a sphere.

976
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

977
01:13:21.510 --> 01:13:25.260
kind of like a sphere of two foot radius.

978
01:13:25.260 --> 01:13:26.550
So that's my heating there.

979
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

980
01:13:33.199 --> 01:13:35.829
wedge or a flat platted angle-of-attack.

981
01:13:35.829 --> 01:13:37.949
This flat surface down here looks kind of
like a wedge.

982
01:13:37.949 --> 01:13:44.599
Well, I can calculate [a boundary?] on a wedge
given the pressure which Newtonian would work

983
01:13:44.599 --> 01:13:45.179
fine.

984
01:13:45.179 --> 01:13:49.900
Certainly, in the blunt regions and on a wedge,
I can do that flow.

985
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

986
01:13:55.729 --> 01:13:55.979
layer.

987
01:13:55.729 --> 01:14:02.690
I can take diagnostics in a wind tunnel, look
at the boundary layer path and say, boy, this

988
01:14:02.690 --> 01:14:05.630
thing is spreading kind of like a cone.

989
01:14:05.630 --> 01:14:07.229
This is the design methodology.

990
01:14:07.229 --> 01:14:12.059
These are all one-dimensional flows for the
boundary layer.

991
01:14:12.059 --> 01:14:16.619
These are geometric flow models where the
boundary layer is basically one-dimensional.

992
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

993
01:14:20.999 --> 01:14:22.349
one-dimensional flow.

994
01:14:22.349 --> 01:14:29.349
So I calculated in a wind tunnel what the
heating would be at this particular condition.

995
01:14:29.900 --> 01:14:34.369
I calculate, for example, flat plate.

996
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.

997
01:14:38.860 --> 01:14:45.860
This is what I calculate, here is what I measure,
a little factor in there.

998
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.

999
01:14:51.320 --> 01:14:58.320
But I take this analysis which can include
the chemistry, all the nice things that go

1000
01:14:59.139 --> 01:15:00.789
on in flight.

1001
01:15:00.789 --> 01:15:06.690
So I calibrate it to wind tunnel which is
basically an empirical flow field now and

1002
01:15:06.690 --> 01:15:07.559
I take that to flight.

1003
01:15:07.559 --> 01:15:08.369
It works pretty well.

1004
01:15:08.369 --> 01:15:11.510
It really does.

1005
01:15:11.510 --> 01:15:18.159
Better than my normal shock Reynolds number
that I gave to the trajectory guys.

1006
01:15:18.159 --> 01:15:22.449
Actually, there are areas where there is significant
disagreement.

1007
01:15:22.449 --> 01:15:29.130
But mostly they are pretty consistent because
they're reflecting the basic diffusion of

1008
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.

1009
01:15:34.079 --> 01:15:38.999
It is very important to normalize what you're
doing to something fundamental.

1010
01:15:38.999 --> 01:15:42.869
If you cannot do it on the back of the envelope,
have a question about it.

1011
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.

1012
01:15:48.119 --> 01:15:50.550
So this is the design methodology.

1013
01:15:50.550 --> 01:15:57.550
I mentioned the Apollo methodology which was
used for quick numbers and for trajectories.

1014
01:15:58.219 --> 01:16:02.489
The third level is a computational fluid dynamics.

1015
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.

1016
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

1017
01:16:18.559 --> 01:16:25.559
what we expected and what we actually got
with the technology we had at the time.

1018
01:16:26.530 --> 01:16:27.880
Boundary layer transition.

1019
01:16:27.880 --> 01:16:34.880
I talked about the boundary between the turbulent
and laminar heating.

1020
01:16:35.489 --> 01:16:39.489
Characteristically, and in the Shuttle level,
your heating goes up by about a factor of

1021
01:16:39.489 --> 01:16:40.619
three.

1022
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

1023
01:16:45.489 --> 01:16:48.369
that factor of three.

1024
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

1025
01:16:53.179 --> 01:16:56.090
have been, but the technology wasn't really
there.

1026
01:16:56.090 --> 01:16:56.999
This is the logic.

1027
01:16:56.999 --> 01:16:59.570
And I won't go through in intimate detail.

1028
01:16:59.570 --> 01:17:05.800
Just to point out the complexity to recognize
the level of effort that goes into getting

1029
01:17:05.800 --> 01:17:07.840
a basic database to design vehicles.

1030
01:17:07.840 --> 01:17:12.920
This is all in that document in that conference
report.

1031
01:17:12.920 --> 01:17:13.429
And there are two copies, I think.

1032
01:17:13.429 --> 01:17:14.469
I brought a copy, and I think there is a copy
in the library that Dr.

1033
01:17:14.469 --> 01:17:16.979
Hoffman has on reserve, but this is all documented
in there.

1034
01:17:16.979 --> 01:17:17.999
Yes.

1035
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.

1036
01:17:25.499 --> 01:17:27.590
This is heating rate versus distance.

1037
01:17:27.590 --> 01:17:29.110
Smooth body.

1038
01:17:29.110 --> 01:17:31.630
And then we put roughness in.

1039
01:17:31.630 --> 01:17:37.170
We actually went to cryogenic models with
simulated tiles to get that boundary layer

1040
01:17:37.170 --> 01:17:40.849
to suck down to be a little better simulation
of flight.

1041
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

1042
01:17:46.269 --> 01:17:48.800
flow, and that didn't have anything to do
with physical reality.

1043
01:17:48.800 --> 01:17:51.369
So a lot of work there.

1044
01:17:51.369 --> 01:17:58.369
We related and took the simulations for the
transition and came up with an effective roughness

1045
01:17:59.809 --> 01:18:01.940
relative to smooth body transition.

1046
01:18:01.940 --> 01:18:06.860
Again, I don't claim to understand turbulence,
I certainly don't claim to understand transition

1047
01:18:06.860 --> 01:18:09.099
and certainly on a complex configuration.

1048
01:18:09.099 --> 01:18:12.070
So then we correlated that and we had predictions.

1049
01:18:12.070 --> 01:18:14.510
And you will see some of that in a few minutes.

1050
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

1051
01:18:18.699 --> 01:18:20.860
think that it tripped the boundary layer?

1052
01:18:20.860 --> 01:18:22.510
No, I don't.

1053
01:18:22.510 --> 01:18:27.340
On the other hand, some of the people that
had been correlating the various missions

1054
01:18:27.340 --> 01:18:28.889
felt that we would.

1055
01:18:28.889 --> 01:18:31.510
And the problem is it was the first time we
had a picture.

1056
01:18:31.510 --> 01:18:32.389
Yeah, I understand.

1057
01:18:32.389 --> 01:18:37.329
We had tile gaps after we landed and we said
oh, gee, this is the relationship.

1058
01:18:37.329 --> 01:18:43.119
There was a lot of correlation, but I'm not
sure it was that valid.

1059
01:18:43.119 --> 01:18:50.119
I really don't think so.

1060
01:18:50.499 --> 01:18:52.099
Now, this is the surface catalysis.

1061
01:18:52.099 --> 01:18:53.309
I haven't really talked about that.

1062
01:18:53.309 --> 01:19:00.309
I talked about the gas going from molecular
to dissociated, ionized to weekly ionized.

1063
01:19:01.070 --> 01:19:05.780
When you get back to the surface conditions,
you're back to a molecule again.

1064
01:19:05.780 --> 01:19:07.820
Now, I am simplifying things here.

1065
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

1066
01:19:12.510 --> 01:19:17.050
have atoms, you get back to the surface of
the vehicle.

1067
01:19:17.050 --> 01:19:19.800
And at equilibrium now you're back to a microstate.

1068
01:19:19.800 --> 01:19:20.050
Yes.

1069
01:19:19.809 --> 01:19:20.059
In the whole design process, was the shape
of the wings and the underbelly designed first

1070
01:19:19.880 --> 01:19:20.130
and then you calculated properties?

1071
01:19:19.900 --> 01:19:23.010
Or, did you have to go back and say no, this
redesign is impossible?

1072
01:19:23.010 --> 01:19:30.010
Because of the heating do it this way.

1073
01:19:38.170 --> 01:19:38.420
Was there a [cyclic process?

1074
01:19:38.219 --> 01:19:38.469
(check)] or was it one way?

1075
01:19:38.219 --> 01:19:39.429
It was primarily one way.

1076
01:19:39.429 --> 01:19:43.570
Here is the aerodynamic requirement in order
to come in.

1077
01:19:43.570 --> 01:19:49.659
The biggest exception of that was on boundary
layer transition.

1078
01:19:49.659 --> 01:19:56.449
That classic if the structures guys design
an airplane or if the electronics guys design

1079
01:19:56.449 --> 01:20:02.769
an airplane or the aerodynamic guys, they
all come out to be different airplanes.

1080
01:20:02.769 --> 01:20:08.539
The prime thing was the aerodynamics, to be
able to control it and bring it in.

1081
01:20:08.539 --> 01:20:13.170
We did alter it relative to where the thermal
protection system was.

1082
01:20:13.170 --> 01:20:16.900
The other thing we did is don't fool with
Mother Nature.

1083
01:20:16.900 --> 01:20:21.679
The structures guys like to make things nice
and flat or cylindrical.

1084
01:20:21.679 --> 01:20:26.469
And the flow is a continuous radius curvature
type phenomenon.

1085
01:20:26.469 --> 01:20:31.030
And that difference is very, very important,
particularly for boundary layer transition.

1086
01:20:31.030 --> 01:20:38.030
So we did fair the geometry to keep the boundary
layer transition essentially two orders of

1087
01:20:38.760 --> 01:20:41.229
magnitude lower than it might have been.

1088
01:20:41.229 --> 01:20:44.510
But overall I would say predominantly it is
aerodynamics.

1089
01:20:44.510 --> 01:20:47.739
And we tried to calculate the heating to the
configuration that we had.

1090
01:20:47.739 --> 01:20:48.760
[UNINTELLIGIBLE PHRASE] [would you change?

1091
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

1092
01:21:10.939 --> 01:21:16.409
is fly higher angle-of-attack which could
have reconfigured the thermal protection system.

1093
01:21:16.409 --> 01:21:22.059
The tiles are a very efficient system.

1094
01:21:22.059 --> 01:21:27.459
They are fragile but are very efficient from
[an entry?] standpoint.

1095
01:21:27.459 --> 01:21:33.739
The carbon nose and leading edge are heavy
and they don't insulate worth a darn.

1096
01:21:33.739 --> 01:21:39.059
I mean that's a layer of carbon.

1097
01:21:39.059 --> 01:21:43.159
When it gets hot it radiates out, but it also
radiates in.

1098
01:21:43.159 --> 01:21:46.760
And so you have to have an insulation behind
that.

1099
01:21:46.760 --> 01:21:52.420
And, in fact, the way we're able to reconcile
the environment with the temperature capability

1100
01:21:52.420 --> 01:21:56.699
of the carbon is it's sort of like an oven.

1101
01:21:56.699 --> 01:22:03.699
And it's easier to illustrate on a leading
edge.

1102
01:22:06.269 --> 01:22:11.639
Just picture a two-dimensional air foil at
angle-of-attack.

1103
01:22:11.639 --> 01:22:17.070
And a carbon section, if you want, covers
from here to here.

1104
01:22:17.070 --> 01:22:22.760
Now, if I look at the heating distribution,
here the heating is quite high, still high

1105
01:22:22.760 --> 01:22:25.439
over here, still high over here, still high
over here.

1106
01:22:25.439 --> 01:22:27.610
Boy, it drops off very quickly over here.

1107
01:22:27.610 --> 01:22:34.610
Well, if I can radiate this energy over here,
this basically becomes a uniform temperature

1108
01:22:35.280 --> 01:22:36.119
oven first order.

1109
01:22:36.119 --> 01:22:39.999
And insulation is back here.

1110
01:22:39.999 --> 01:22:43.349
I don't know how you illustrate insulation.

1111
01:22:43.349 --> 01:22:47.189
Insulation is back here to keep the lower
temperature structure from getting too hot.

1112
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

1113
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

1114
01:22:57.630 --> 01:22:59.420
the rest of the Shuttle.

1115
01:22:59.420 --> 01:23:04.789
So this is sort of a staged thermal protection
system.

1116
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

1117
01:23:10.349 --> 01:23:15.689
exceed the carbon capability.

1118
01:23:15.689 --> 01:23:20.499
By flying at high angle of attack, I could
reduce the amount of carbon.

1119
01:23:20.499 --> 01:23:25.809
What was the problem going to a higher angle
of attack?

1120
01:23:25.809 --> 01:23:26.599
You said there was a conflict.

1121
01:23:26.599 --> 01:23:26.849
Yeah.

1122
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

1123
01:23:30.719 --> 01:23:31.300
high angle of attack.

1124
01:23:31.300 --> 01:23:34.360
I mean high angle of attack just comes in
ballistically, if you want.

1125
01:23:34.360 --> 01:23:39.030
You roll around the velocity vector so you
get a little L/D.

1126
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.

1127
01:23:43.329 --> 01:23:47.249
A very significant design parameter for Shuttle.

1128
01:23:47.249 --> 01:23:52.769
And if you recall the trajectories, it was
primarily needed from a polar orbit where

1129
01:23:52.769 --> 01:23:56.110
you're trying to get to a particular runway.

1130
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

1131
01:24:03.159 --> 01:24:05.239
inclinational orbits.

1132
01:24:05.239 --> 01:24:12.239
You remember we were talking about energy
management, and I talked about how if you

1133
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

1134
01:24:20.039 --> 01:24:22.959
no S turns or anything, just straight in.

1135
01:24:22.959 --> 01:24:26.429
But there is a thermal boundary.

1136
01:24:26.429 --> 01:24:32.260
I don't remember whether it was 38 degrees
or 37, but 40 degrees was nominal.

1137
01:24:32.260 --> 01:24:34.679
And you really didn't have a whole lot to
play with.

1138
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

1139
01:24:41.099 --> 01:24:46.249
your trajectory to make the runway, at some
point you're going to violate thermal constraints

1140
01:24:46.249 --> 01:24:49.420
and start melting your thermal protection.

1141
01:24:49.420 --> 01:24:56.420
There were years of concepts and vehicles
that were developed and flown, test vehicles

1142
01:24:58.800 --> 01:25:02.909
with different emphasis.

1143
01:25:02.909 --> 01:25:05.880
And there were some aerothermodynamic vehicles
nice and smooth.

1144
01:25:05.880 --> 01:25:07.369
I mean it just looked beautiful.

1145
01:25:07.369 --> 01:25:11.860
It looked like something an architect would
come up with, if you want.

1146
01:25:11.860 --> 01:25:13.590
And, from a heating standpoint, they worked
well.

1147
01:25:13.590 --> 01:25:18.880
But the structures guys, it was very heavy
from a structures standpoint to get all these

1148
01:25:18.880 --> 01:25:21.800
compound curvatures, this, that and the other
thing.

1149
01:25:21.800 --> 01:25:25.309
There were also vehicles that were designed
specifically from a structures standpoint.

1150
01:25:25.309 --> 01:25:26.610
And I'm not knocking the structure people.

1151
01:25:26.610 --> 01:25:27.889
I do a lot of structure work, too.

1152
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

1153
01:25:34.449 --> 01:25:34.969
of good stuff.

1154
01:25:34.969 --> 01:25:39.059
And that was a terrible configuration from
an aerothermodynamic standpoint.

1155
01:25:39.059 --> 01:25:43.150
So there actually was a heritage of all kinds
of attempts.

1156
01:25:43.150 --> 01:25:46.059
The big challenge was how do you land some
of these things?

1157
01:25:46.059 --> 01:25:51.739
A nice hypersonic aerothermodynamic configuration
and aerodynamic configuration, OK, now you

1158
01:25:51.739 --> 01:25:53.659
try to put it down the runway and it is hot.

1159
01:25:53.659 --> 01:26:00.320
A lot of test pilots had some problems with
some of these vehicles.

1160
01:26:00.320 --> 01:26:04.610
There are all kinds of heritage of people
pursuing this, that and the other thing.

1161
01:26:04.610 --> 01:26:06.949
And one of them was aerothermodynamic design.

1162
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

1163
01:26:11.650 --> 01:26:12.360
coming in.

1164
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

1165
01:26:17.760 --> 01:26:18.010
standpoint.

1166
01:26:17.889 --> 01:26:23.239
If I look at it overall, we needed all the
lift we could get on landing.

1167
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.

1168
01:26:28.909 --> 01:26:31.300
So, from an aerodynamic standpoint, we would
like a lot higher lift.

1169
01:26:31.300 --> 01:26:37.019
In fact, that is a nice area for innovation.

1170
01:26:37.019 --> 01:26:42.079
Some of the earlier concepts for vehicles,
you're probably with familiar with, capsules

1171
01:26:42.079 --> 01:26:45.130
with rotogyros on them that power up as you
come down.

1172
01:26:45.130 --> 01:26:51.260
Boosters, if you wanted a cylindrical configuration
with a straight wing on it that swings out.

1173
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

1174
01:26:57.969 --> 01:26:58.219
all of them.

1175
01:26:57.969 --> 01:27:02.689
In that case, the weight estimate for all
the hardware and all that kind of good stuff

1176
01:27:02.689 --> 01:27:03.559
was excessive.

1177
01:27:03.559 --> 01:27:06.429
Anyway, that is a real challenge for design.

1178
01:27:06.429 --> 01:27:10.719
I understand you folks are going to come up
with a better design, some real innovative

1179
01:27:10.719 --> 01:27:14.340
thoughts in terms of how to marry all these
different requirements.

1180
01:27:14.340 --> 01:27:21.340
In my opinion, the mindset for hypersonic
vehicles was [UNINTELLIGIBLE] [fibercups]

1181
01:27:22.510 --> 01:27:24.530
have straight wings.

1182
01:27:24.530 --> 01:27:28.979
Supersonics like this and, boy, hypersonic
ought to be like this.

1183
01:27:28.979 --> 01:27:30.249
I mean that's just kind of the mindset.

1184
01:27:30.249 --> 01:27:32.639
And it kind of works.

1185
01:27:32.639 --> 01:27:35.880
But an entry vehicle is a whole different
vehicle.

1186
01:27:35.880 --> 01:27:38.099
Capsules work fine for their requirements.

1187
01:27:38.099 --> 01:27:42.099
Shuttle has been a fantastic marriage of different
requirements.

1188
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

1189
01:27:46.179 --> 01:27:46.709
ideas.

1190
01:27:46.709 --> 01:27:51.979
It's not going to be easy but there's a big
need.

1191
01:27:51.979 --> 01:27:52.749
OK.

1192
01:27:52.749 --> 01:27:56.599
Surface catalysis.

1193
01:27:56.599 --> 01:28:00.729
First order, start with molecules in a free
strain.

1194
01:28:00.729 --> 01:28:01.689
Atoms.

1195
01:28:01.689 --> 01:28:03.909
Some ionized.

1196
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.

1197
01:28:12.159 --> 01:28:14.840
They're pretty hot but they are still molecules.

1198
01:28:14.840 --> 01:28:20.719
Well, Professor Fay did a wonderful job in
looking at a stagnation point on a sphere

1199
01:28:20.719 --> 01:28:22.159
and saying, well, we've got limits.

1200
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,

1201
01:28:27.860 --> 01:28:32.059
all the way through to the boundary layer,
you get this amount of heating.

1202
01:28:32.059 --> 01:28:36.989
And that amount of heating included not just
the conduction but the chemistry changes going

1203
01:28:36.989 --> 01:28:43.989
from dissociated atoms, if you want, and putting
that energy back into translation and rotation

1204
01:28:44.360 --> 01:28:46.889
into molecules.

1205
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.

1206
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,

1207
01:29:17.280 --> 01:29:18.729
absorbed on the surface.

1208
01:29:18.729 --> 01:29:23.780
And then another atom comes in, recombines
and forms a molecule that releases that energy.

1209
01:29:23.780 --> 01:29:26.119
That is a catalytic surface.

1210
01:29:26.119 --> 01:29:32.840
So you have sort of two limits, a completely
catalytic surface and a non-catalytic surface

1211
01:29:32.840 --> 01:29:34.360
in a non-equilibrium environment.

1212
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

1213
01:29:37.639 --> 01:29:43.329
to show here in a short while.

1214
01:29:43.329 --> 01:29:47.849
This is just the concept which, again, as
Aaron mentioned is in the report.

1215
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

1216
01:29:52.650 --> 01:29:58.590
on in the arc jet to understand the surface
catalysis of tiles and carbon.

1217
01:29:58.590 --> 01:30:04.320
We had to model the flow and model the chemistry
to come up with an efficiency.

1218
01:30:04.320 --> 01:30:08.139
Then we go to flight with similar analysis
and predict, and I will show some predictions

1219
01:30:08.139 --> 01:30:08.559
of this.

1220
01:30:08.559 --> 01:30:15.559
This is a significant phenomenon at the high
altitudes, low density for the Shuttle.

1221
01:30:17.380 --> 01:30:18.849
Any questions on surface catalysis?

1222
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

1223
01:30:28.349 --> 01:30:29.389
to worry about chemistry.

1224
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.

1225
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

1226
01:30:40.099 --> 01:30:42.380
have to take into account.

1227
01:30:42.380 --> 01:30:46.679
This is the flow field.

1228
01:30:46.679 --> 01:30:53.679
At the time of this conference and the OFT
flights, again, the design was the methodology

1229
01:30:55.789 --> 01:31:00.999
that I explained where you use simple configurations,
model it and extrapolate the flight.

1230
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.

1231
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.

1232
01:31:11.570 --> 01:31:14.849
And it's just the cross flow speed contours.

1233
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

1234
01:31:22.579 --> 01:31:24.219
at the time.

1235
01:31:24.219 --> 01:31:27.340
Since then, boy, we've gone gangbusters.

1236
01:31:27.340 --> 01:31:30.780
But this kind of the level.

1237
01:31:30.780 --> 01:31:33.619
We did not have the finite rate chemistry
in this.

1238
01:31:33.619 --> 01:31:37.039
That is a lot more computer than we could
handle.

1239
01:31:37.039 --> 01:31:41.869
At this point, we were trying to develop algorithms
and grids.

1240
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

1241
01:31:48.829 --> 01:31:50.800
accurately as we could measure it in the wind
tunnel.

1242
01:31:50.800 --> 01:31:52.199
But that's not at flight.

1243
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

1244
01:31:56.729 --> 01:32:03.729
of comparing what we expected from what we
actually got.

1245
01:32:04.820 --> 01:32:11.090
Now I'm going to show results in terms of
temperature as a function of time.

1246
01:32:11.090 --> 01:32:16.499
This is the entry time from about 400 to 1,000
seconds.

1247
01:32:16.499 --> 01:32:18.459
You notice this plateau.

1248
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

1249
01:32:25.110 --> 01:32:27.630
the thermal protection system.

1250
01:32:27.630 --> 01:32:29.360
I am going to show three locations.

1251
01:32:29.360 --> 01:32:35.659
Right up here at the nose, just behind the
carbon, mid body and aft body.

1252
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,

1253
01:32:41.289 --> 01:32:46.590
subsonic flow, which used one particular algorithm
[to match?] supersonically down the vehicle.

1254
01:32:46.590 --> 01:32:49.570
We succeeded in doing that prior to flying.

1255
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

1256
01:32:55.849 --> 01:32:56.989
shock from the fuselage.

1257
01:32:56.989 --> 01:33:00.219
And then we had another subsonic region and
we weren't able to handle it.

1258
01:33:00.219 --> 01:33:01.079
Now we can do that.

1259
01:33:01.079 --> 01:33:06.079
But at the time we flew, we could only compute
up to about here.

1260
01:33:06.079 --> 01:33:08.979
Now, this is not what you'd see in a journal.

1261
01:33:08.979 --> 01:33:11.920
I will show you one you'd see in a journal
here in the middle.

1262
01:33:11.920 --> 01:33:13.699
This is right behind the carbon.

1263
01:33:13.699 --> 01:33:19.360
Now, what we did is we computed at different
times through the trajectory and then there

1264
01:33:19.360 --> 01:33:24.729
were correlations to get the history.

1265
01:33:24.729 --> 01:33:26.769
This is JSC prediction right here.

1266
01:33:26.769 --> 01:33:30.590
Now, we didn't worry about exceeding Stanton
number one.

1267
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

1268
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

1269
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.

1270
01:33:44.070 --> 01:33:44.829
Up here is very important.

1271
01:33:44.829 --> 01:33:46.429
Now, this is temperature.

1272
01:33:46.429 --> 01:33:50.699
And I just mentioned epsilon sigma T to the
fourth.

1273
01:33:50.699 --> 01:33:55.849
That means the heat transfer is four times
a bad.

1274
01:33:55.849 --> 01:33:59.559
We did a terrible job up here, and I will
get back to that.

1275
01:33:59.559 --> 01:34:04.479
Now over here what happens is I've tried to
stay laminar.

1276
01:34:04.479 --> 01:34:05.119
I come down.

1277
01:34:05.119 --> 01:34:07.829
And this was really a stretch.

1278
01:34:07.829 --> 01:34:11.420
We never got turbulence heating up on the
nose.

1279
01:34:11.420 --> 01:34:16.229
Way beyond wind tunnel, way beyond our experience
base, but the model just went up there.

1280
01:34:16.229 --> 01:34:17.479
So we really didn't expect that.

1281
01:34:17.479 --> 01:34:20.280
That was a pretty conservative boundary layer
transition.

1282
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

1283
01:34:26.519 --> 01:34:30.709
appear to be laminar.

1284
01:34:30.709 --> 01:34:33.559
What is really going on here?

1285
01:34:33.559 --> 01:34:35.340
This is right behind a carbon.

1286
01:34:35.340 --> 01:34:38.619
The carbon is an oven.

1287
01:34:38.619 --> 01:34:42.550
As the service temperature of the tile drops,
which drops very quickly because it re-radiates.

1288
01:34:42.550 --> 01:34:43.639
Not because it diffuses.

1289
01:34:43.639 --> 01:34:45.699
We control that.

1290
01:34:45.699 --> 01:34:48.119
It re-radiates so, as soon as the heating
drops, the temperature drops.

1291
01:34:48.119 --> 01:34:51.900
I mean this is almost identical to reflecting
what the heating is.

1292
01:34:51.900 --> 01:34:54.659
It is dropping like mad.

1293
01:34:54.659 --> 01:34:56.449
And, indeed, we're agreeing quite well.

1294
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

1295
01:35:00.150 --> 01:35:02.909
problem here.

1296
01:35:02.909 --> 01:35:08.249
And here, all of a sudden, the laminar is
higher than the turbulent.

1297
01:35:08.249 --> 01:35:09.760
The carbon is this oven.

1298
01:35:09.760 --> 01:35:10.900
It doesn't cool down.

1299
01:35:10.900 --> 01:35:13.349
Even sitting on a runway it is as hot as can
be.

1300
01:35:13.349 --> 01:35:16.789
If you think about it, it's got this oven.

1301
01:35:16.789 --> 01:35:19.999
It can only radiate out of surface and inside
it is still radiating.

1302
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.

1303
01:35:24.619 --> 01:35:29.340
The flow is going across the nose and actually
heating the air.

1304
01:35:29.340 --> 01:35:32.719
At least changing the boundary layer profile
so that the heating is higher.

1305
01:35:32.719 --> 01:35:34.030
How do I know that?

1306
01:35:34.030 --> 01:35:37.610
[Here is your tank?

1307
01:35:37.610 --> 01:35:38.510
yup].

1308
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

1309
01:35:44.570 --> 01:35:46.380
the oven, if you want, if you're doing any
cooking.

1310
01:35:46.380 --> 01:35:48.519
There is a little bit of that.

1311
01:35:48.519 --> 01:35:50.929
But, predominantly, this is the chemistry.

1312
01:35:50.929 --> 01:35:56.539
See, we come much closer together here in
time.

1313
01:35:56.539 --> 01:35:59.179
This is predominantly the chemistry.

1314
01:35:59.179 --> 01:36:06.179
At this time, this non-equilibrium relaxation
distance is about six inches.

1315
01:36:06.900 --> 01:36:10.840
Now, we're not into radiating gas but we're
certainly not into equilibrium.

1316
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

1317
01:36:16.590 --> 01:36:20.789
correlations of the shock in what's going
on here.

1318
01:36:20.789 --> 01:36:24.679
You won't see that on paper because we did
a terrible job there.

1319
01:36:24.679 --> 01:36:28.189
We did not exceed design material requirements.

1320
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

1321
01:36:33.809 --> 01:36:39.669
system, I will go through the philosophy of
having confidence to fly.

1322
01:36:39.669 --> 01:36:43.570
And, obviously, with our predictions, we would
not exceed the top capabilities so we could

1323
01:36:43.570 --> 01:36:44.530
fly.

1324
01:36:44.530 --> 01:36:47.439
But we were off here badly.

1325
01:36:47.439 --> 01:36:51.179
But at least you were off in the conservative
direction.

1326
01:36:51.179 --> 01:36:55.979
Well, that's the way we tried to be.

1327
01:36:55.979 --> 01:36:57.809
This I will get into.

1328
01:36:57.809 --> 01:37:01.469
This is really what we expected, to the best
of our understanding.

1329
01:37:01.469 --> 01:37:07.639
Yes, I was surprised at this also.

1330
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

1331
01:37:13.889 --> 01:37:18.979
really include the nonequilibrium flow in
the inviscid, what I've been talking here

1332
01:37:18.979 --> 01:37:19.599
about Apollo.

1333
01:37:19.599 --> 01:37:26.599
That was beyond our capability to do finite
rate chemistry in the inviscid flow field.

1334
01:37:26.739 --> 01:37:30.979
Why don't we go to mid body now?

1335
01:37:30.979 --> 01:37:31.239
All right.

1336
01:37:31.239 --> 01:37:36.840
Here is something you might see in a journal.

1337
01:37:36.840 --> 01:37:39.030
Right where we wanted it.

1338
01:37:39.030 --> 01:37:40.479
And that's where we had the most confidence,
too.

1339
01:37:40.479 --> 01:37:45.760
We got away from the subsonic, supersonic
condition.

1340
01:37:45.760 --> 01:37:47.239
We were into a marching solution.

1341
01:37:47.239 --> 01:37:51.400
That is as good as we could do it those days.

1342
01:37:51.400 --> 01:37:58.400
And we knew that transition was going to be
later than what we predicted because wind

1343
01:37:58.409 --> 01:37:59.889
tunnels, you've got walls.

1344
01:37:59.889 --> 01:38:02.570
You've got all kinds of reflected noise.

1345
01:38:02.570 --> 01:38:08.070
And wind tunnels are notoriously conservative
relative to boundary layer transition.

1346
01:38:08.070 --> 01:38:15.070
But, amazingly, the turbulent heating correlated
quite well.

1347
01:38:16.949 --> 01:38:19.559
And that even works with normal shock Reynolds
numbers.

1348
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

1349
01:38:26.300 --> 01:38:33.300
envelope normal shock local heating to reference
heating, including turbulence, it is amazing.

1350
01:38:34.030 --> 01:38:36.229
It really is.

1351
01:38:36.229 --> 01:38:40.709
First order physics seems to hang in there,
in spite of all the complications of chemistry

1352
01:38:40.709 --> 01:38:42.419
and all the kinds of things that can happen.

1353
01:38:42.419 --> 01:38:46.139
You have to be careful, but overall things
usually work for you.

1354
01:38:46.139 --> 01:38:48.499
Again, that is academic there.

1355
01:38:48.499 --> 01:38:52.679
If we put in a constraint it would look a
lot better.

1356
01:38:52.679 --> 01:38:57.110
That is good stuff, but we can do even better
now.

1357
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

1358
01:39:01.329 --> 01:39:04.349
measure, in flight basically we could do the
same thing.

1359
01:39:04.349 --> 01:39:04.869
Mid body.

1360
01:39:04.869 --> 01:39:08.889
Everything is just right for the CFD folks.

1361
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,

1362
01:39:17.429 --> 01:39:18.829
and we're not doing as well.

1363
01:39:18.829 --> 01:39:23.719
Certainly on transition we knew we'd be very
conservative.

1364
01:39:23.719 --> 01:39:25.939
This is ideally how we design the vehicle.

1365
01:39:25.939 --> 01:39:32.749
Fly to temperature capability of the tile.

1366
01:39:32.749 --> 01:39:39.269
And on this STS-3 that's what we were trying
to do.

1367
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.

1368
01:39:43.800 --> 01:39:47.070
And we obviously don't want to exceed the
structural capability.

1369
01:39:47.070 --> 01:39:48.289
Let's see.

1370
01:39:48.289 --> 01:39:51.479
I want to talk about surface catalysis.

1371
01:39:51.479 --> 01:39:52.539
Then we will get into the thermal protection
system.

1372
01:39:52.539 --> 01:39:59.539
I've got one chart I am going to spend a lot
of time on.

1373
01:39:59.949 --> 01:40:02.860
This is distance down the vehicle from the
nose.

1374
01:40:02.860 --> 01:40:05.380
I mean it is linear distance.

1375
01:40:05.380 --> 01:40:08.309
There is 50%.

1376
01:40:08.309 --> 01:40:12.840
This is surface heat flux at one particular
time in the entry.

1377
01:40:12.840 --> 01:40:14.119
The circles are flight data.

1378
01:40:14.119 --> 01:40:17.619
These are catalysis experiments.

1379
01:40:17.619 --> 01:40:23.179
This is a fully catalytic or equilibrium heat
transfer.

1380
01:40:23.179 --> 01:40:29.179
This is a zero catalysis non-equilibrium,
boundary layer non-equilibrium.

1381
01:40:29.179 --> 01:40:32.150
The reactions are not occurring in the boundary
layer.

1382
01:40:32.150 --> 01:40:34.869
This is the flight data that opens circles.

1383
01:40:34.869 --> 01:40:37.769
I don't remember what the measurement problem
here was.

1384
01:40:37.769 --> 01:40:42.199
And here is this point way up front you can
see again.

1385
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

1386
01:40:47.300 --> 01:40:49.550
the fluid mechanics real accurately.

1387
01:40:49.550 --> 01:40:52.199
This is still a mix and match.

1388
01:40:52.199 --> 01:40:54.929
Look at the difference between the measurement
and the prediction.

1389
01:40:54.929 --> 01:41:01.229
The same thing as before only I eased it by
showing temperature instead of heat flux.

1390
01:41:01.229 --> 01:41:05.209
The surface catalysis is a predominant factor.

1391
01:41:05.209 --> 01:41:11.880
Now, there is some rambling in the data here,
depending on particular location, et cetera.

1392
01:41:11.880 --> 01:41:18.429
But our friends at Ames developed a catalytic
coding, and they coded tiles.

1393
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

1394
01:41:24.939 --> 01:41:26.820
particular locations.

1395
01:41:26.820 --> 01:41:29.979
If the whole vehicle was like that, the heating
would have been up here.

1396
01:41:29.979 --> 01:41:34.739
But since there was just the tile, the boundary
layer comes along here and all of a sudden,

1397
01:41:34.739 --> 01:41:36.760
boom, it gets hit with a different boundary
condition.

1398
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

1399
01:41:44.499 --> 01:41:45.189
and then relaxes.

1400
01:41:45.189 --> 01:41:51.820
This is the computation and there is the measurement.

1401
01:41:51.820 --> 01:41:58.639
Indeed, here is a demonstration that chemistry
can be important in this flight regime.

1402
01:41:58.639 --> 01:42:03.229
If you come down in altitude where everything
starts going to equilibrium, it's not that

1403
01:42:03.229 --> 01:42:04.239
important.

1404
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.

1405
01:42:10.059 --> 01:42:17.059
But where we are, up in altitude trying to
maintain conditions so we can be reusable,

1406
01:42:17.349 --> 01:42:22.260
that chemistry is significant.

1407
01:42:22.260 --> 01:42:25.959
Now, I think the next one is probably the
thermal protection system.

1408
01:42:25.959 --> 01:42:27.369
No, one more measurement.

1409
01:42:27.369 --> 01:42:29.340
This is the leeside.

1410
01:42:29.340 --> 01:42:34.519
This is normal shock versus film heat transfer
coefficient.

1411
01:42:34.519 --> 01:42:35.489
Basically heat transfer.

1412
01:42:35.489 --> 01:42:36.889
Log.

1413
01:42:36.889 --> 01:42:38.300
Log.

1414
01:42:38.300 --> 01:42:44.689
This is the heating shown here as a function
of normal shock Reynolds number.

1415
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

1416
01:42:51.280 --> 01:42:54.189
then came down as normal a normal shock Reynolds
number.

1417
01:42:54.189 --> 01:43:00.880
And here are three trajectories with a heating
on one location of the leeside.

1418
01:43:00.880 --> 01:43:06.880
By the way, Max Faget told me to burn a hole
some place on the leeside.

1419
01:43:06.880 --> 01:43:10.070
He didn't want too much tile there.

1420
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

1421
01:43:13.360 --> 01:43:14.709
flow very well in the wind tunnel.

1422
01:43:14.709 --> 01:43:17.429
We had to put tiles there after first flight.

1423
01:43:17.429 --> 01:43:19.650
So I told him that was as close as we came.

1424
01:43:19.650 --> 01:43:26.499
In any event, this is heating on three trajectories
through normal shock history.

1425
01:43:26.499 --> 01:43:29.579
It's sort of like time.

1426
01:43:29.579 --> 01:43:31.849
Three different vehicles.

1427
01:43:31.849 --> 01:43:34.449
This is to reference heat.

1428
01:43:34.449 --> 01:43:38.579
This is our old Apollo level technology.

1429
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

1430
01:43:43.760 --> 01:43:49.130
as the Reynolds number picks up and the weight
characteristic changes.

1431
01:43:49.130 --> 01:43:56.130
In ballistic facilities, if you have a vehicle
traveling at high speed, eventually your weight

1432
01:43:57.409 --> 01:43:59.650
goes transitional and turbulent.

1433
01:43:59.650 --> 01:44:01.989
As you increase the Reynolds number that moves
forward.

1434
01:44:01.989 --> 01:44:04.489
As that moves forward, you get more mixing.

1435
01:44:04.489 --> 01:44:08.489
As you get more mixing the gas in the wake
gets hotter.

1436
01:44:08.489 --> 01:44:11.070
And I believe that is fundamentally what's
going on.

1437
01:44:11.070 --> 01:44:12.630
It is very repeatable.

1438
01:44:12.630 --> 01:44:18.070
We cannot get this in the wind tunnel.

1439
01:44:18.070 --> 01:44:19.610
Now we'll go to TPS.

1440
01:44:19.610 --> 01:44:22.119
No, one more on the leeside heating.

1441
01:44:22.119 --> 01:44:27.699
On the Shuttle we had thermal couples located
here, there, as many places as the aerothermodynamics

1442
01:44:27.699 --> 01:44:31.280
could put them, the TPS guys, but we couldn't
put them anywhere.

1443
01:44:31.280 --> 01:44:35.689
This is the 201 vehicle and it's on its side.

1444
01:44:35.689 --> 01:44:37.829
I apologize because of my chartmanship.

1445
01:44:37.829 --> 01:44:41.239
The vehicle is coming in angle-of-attack on
here.

1446
01:44:41.239 --> 01:44:45.059
This is the windward side where there was
charring.

1447
01:44:45.059 --> 01:44:46.449
This is white paint down here.

1448
01:44:46.449 --> 01:44:48.789
And, I'm sorry, it is a terrible photograph.

1449
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

1450
01:44:55.419 --> 01:44:56.050
on this side.

1451
01:44:56.050 --> 01:44:57.010
This is not charring.

1452
01:44:57.010 --> 01:44:58.030
This is some charring.

1453
01:44:58.030 --> 01:45:02.260
And it is blown up here in the way the chart
was made.

1454
01:45:02.260 --> 01:45:03.919
One point.

1455
01:45:03.919 --> 01:45:07.059
This is the first entry heating.

1456
01:45:07.059 --> 01:45:08.849
And the leeside was extremely important.

1457
01:45:08.849 --> 01:45:10.010
How well did we do?

1458
01:45:10.010 --> 01:45:11.809
How hot is it?

1459
01:45:11.809 --> 01:45:16.070
We got the data and it was all over the place.

1460
01:45:16.070 --> 01:45:18.400
It was down where we thought it probably should
be.

1461
01:45:18.400 --> 01:45:21.619
And it was like an order of magnitude higher.

1462
01:45:21.619 --> 01:45:22.760
We thought that data is no good.

1463
01:45:22.760 --> 01:45:29.749
Well, then we went back and realized what
happened is when the control system fired

1464
01:45:29.749 --> 01:45:35.260
jets, a lot more dynamic pressure than the
airflow.

1465
01:45:35.260 --> 01:45:37.169
A lot cooler.

1466
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.

1467
01:45:43.119 --> 01:45:45.360
Tremendous disturbance.

1468
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

1469
01:45:50.679 --> 01:45:52.570
here.

1470
01:45:52.570 --> 01:45:58.300
And flow times you're talking milliseconds
for reaction time back then when we weren't

1471
01:45:58.300 --> 01:46:00.099
firing a jet.

1472
01:46:00.099 --> 01:46:00.570
Unbelievable.

1473
01:46:00.570 --> 01:46:04.479
We went to learning something.

1474
01:46:04.479 --> 01:46:06.709
Again, interaction of systems.

1475
01:46:06.709 --> 01:46:12.590
Now, finally, this is my one and only chart
on the thermal protection system which is

1476
01:46:12.590 --> 01:46:16.610
the real hardware stuff.

1477
01:46:16.610 --> 01:46:22.780
This is temperature versus time at a mid body
location.

1478
01:46:22.780 --> 01:46:25.880
Now, this is from STS-1.

1479
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

1480
01:46:29.459 --> 01:46:30.510
aerothermodynamic today.

1481
01:46:30.510 --> 01:46:33.829
We only had late time data.

1482
01:46:33.829 --> 01:46:39.260
This is the design trajectory coming in from
polar orbit.

1483
01:46:39.260 --> 01:46:44.369
Our design condition was we do not exceed
350 degrees Fahrenheit if we want to have

1484
01:46:44.369 --> 01:46:47.419
a hundred flight life with this aluminum.

1485
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

1486
01:46:51.150 --> 01:46:51.419
expands.

1487
01:46:51.419 --> 01:46:55.550
[Bond line?] that means at the [hahahahahaha]
bottom, just so that everybody understands.

1488
01:46:55.550 --> 01:46:56.869
Yes, thank you.

1489
01:46:56.869 --> 01:47:01.320
Those temperatures are much lower than you
see on the surface of the tiles.

1490
01:47:01.320 --> 01:47:05.090
That's after the heat has diffused.

1491
01:47:05.090 --> 01:47:05.340
Right.

1492
01:47:05.139 --> 01:47:08.429
I think Tom probably talked about the SIP,
the strain isolation pad.

1493
01:47:08.429 --> 01:47:11.030
I'm sure he did.

1494
01:47:11.030 --> 01:47:16.019
This is after you diffuse through the clouds
and through the RTV bonds through the SIP.

1495
01:47:16.019 --> 01:47:19.110
This is the actual aluminum temperature.

1496
01:47:19.110 --> 01:47:22.179
Now I'm talking predictions.

1497
01:47:22.179 --> 01:47:27.909
This is what the vehicle was designed to experience.

1498
01:47:27.909 --> 01:47:32.329
Now, the design prediction was right here.

1499
01:47:32.329 --> 01:47:36.459
That was purposefully a little conservative.

1500
01:47:36.459 --> 01:47:40.389
The guy who is building it doesn't want to
lose the vehicle.

1501
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.

1502
01:47:45.969 --> 01:47:50.249
This is our best estimate.

1503
01:47:50.249 --> 01:47:54.179
And, again, if you recall, I showed you where
we really knew where the heating was.

1504
01:47:54.179 --> 01:47:56.199
This is really a TPS test right now.

1505
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

1506
01:48:01.039 --> 01:48:02.280
way too hot.

1507
01:48:02.280 --> 01:48:04.159
Right here we were right on.

1508
01:48:04.159 --> 01:48:10.300
This is a purely TPS test, except it turns
out it was my fault here.

1509
01:48:10.300 --> 01:48:12.340
In any event, here comes the data.

1510
01:48:12.340 --> 01:48:19.340
This is the prediction for this particular
flight STS-1 right here.

1511
01:48:19.519 --> 01:48:21.389
This is what we predicted for STS-1.

1512
01:48:21.389 --> 01:48:24.989
This is what we would have predicted for design.

1513
01:48:24.989 --> 01:48:31.749
And this is the design technology prediction
which has a little conservatism in it, obviously,

1514
01:48:31.749 --> 01:48:33.179
and on purpose.

1515
01:48:33.179 --> 01:48:35.689
This is yes you can fly the vehicle with confidence.

1516
01:48:35.689 --> 01:48:38.179
We're flying this STS-1 no problem.

1517
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.

1518
01:48:43.150 --> 01:48:46.979
We did a pretty good job along here.

1519
01:48:46.979 --> 01:48:50.260
And this structure is intricate and everything.

1520
01:48:50.260 --> 01:48:53.419
The thermal modeling has to take into account
all kinds of geometry, materials, et cetera.

1521
01:48:53.419 --> 01:49:00.389
And all of a sudden right here, boom, what
happened?

1522
01:49:00.389 --> 01:49:06.169
I admit to overlooking this.

1523
01:49:06.169 --> 01:49:12.570
What happened is we opened the vents, we let
some air in.

1524
01:49:12.570 --> 01:49:14.459
I mean you're up in a vacuum.

1525
01:49:14.459 --> 01:49:16.900
You do not want to let air in when it's hot.

1526
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.

1527
01:49:21.939 --> 01:49:26.050
The absolutely worst thing that could happen
to you.

1528
01:49:26.050 --> 01:49:27.199
You cannot radiate the energy.

1529
01:49:27.199 --> 01:49:28.369
You don't get rid of that 98%.

1530
01:49:28.369 --> 01:49:34.229
It was just like a blowtorch.

1531
01:49:34.229 --> 01:49:41.229
But, once you get down, if you don't do something,
you've got this vacuum vehicle and you're

1532
01:49:41.280 --> 01:49:44.139
getting atmospheric pressure coming up on
you.

1533
01:49:44.139 --> 01:49:45.389
And all of a sudden you're going to be crushed.

1534
01:49:45.389 --> 01:49:46.800
At some point, OK, it's all right.

1535
01:49:46.800 --> 01:49:47.619
We open the door.

1536
01:49:47.619 --> 01:49:48.439
We open a vent.

1537
01:49:48.439 --> 01:49:52.949
This particular location, not all locations,
could experience that.

1538
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.

1539
01:49:57.409 --> 01:50:00.919
Still cold compared to what we've been working
with.

1540
01:50:00.919 --> 01:50:04.699
I overlooked that.

1541
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

1542
01:50:08.469 --> 01:50:12.340
cold air and so you cannot use it in many
places.

1543
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,

1544
01:50:17.999 --> 01:50:24.999
you could take advantage of those in designs
if you're cleaver, if you're innovative.

1545
01:50:25.519 --> 01:50:32.409
And so there was, not 100 degrees, a significant
difference there.

1546
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

1547
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,

1548
01:50:44.679 --> 01:50:46.239
from a temperature standpoint.

1549
01:50:46.239 --> 01:50:53.239
The other thing in the Shuttle, which I'm
sure Tom discussed, was the thermal stress.

1550
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.

1551
01:51:02.729 --> 01:51:07.610
That is one big integrated problem which gave
us a lot of difficulty.

1552
01:51:07.610 --> 01:51:11.039
Again, with the simulation and computational
capability we have today, I think we can do

1553
01:51:11.039 --> 01:51:12.469
a much better job of that.

1554
01:51:12.469 --> 01:51:19.469
And also just understanding the importance
of it.

1555
01:51:20.280 --> 01:51:22.329
I think those are all my charts.

1556
01:51:22.329 --> 01:51:23.249
No, I'm sorry.

1557
01:51:23.249 --> 01:51:30.249
I have one more which is not a Shuttle chart.

1558
01:51:31.119 --> 01:51:38.119
We were looking at an experimental orbital
transfer vehicle, a [low WOCDA?] vehicle running

1559
01:51:38.729 --> 01:51:43.860
from geosynchronous to low earth orbit, and
then we use the Shuttle to go from low earth

1560
01:51:43.860 --> 01:51:45.110
orbit to the ground.

1561
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

1562
01:51:49.249 --> 01:51:51.919
on a vehicle in orbit on a space station.

1563
01:51:51.919 --> 01:51:53.329
And we thought we could do that.

1564
01:51:53.329 --> 01:51:54.899
Now, this is not coming back from the moon.

1565
01:51:54.899 --> 01:51:55.939
This is coming back from geosynchronous.

1566
01:51:55.939 --> 01:51:58.739
It's not quite as bad.

1567
01:51:58.739 --> 01:52:00.229
We had a design.

1568
01:52:00.229 --> 01:52:04.329
And, to prove the concept, we had a little
model we were going to build and fly.

1569
01:52:04.329 --> 01:52:06.849
This came from a paper I gave discussing that.

1570
01:52:06.849 --> 01:52:13.489
Basically, this is the analysis and testing
from research to an actual real hardware system,

1571
01:52:13.489 --> 01:52:18.659
from the fundamental equations down to numerical
simulation.

1572
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.

1573
01:52:24.469 --> 01:52:31.050
Then modeling as we do, for example, in the
design approach on Apollo.

1574
01:52:31.050 --> 01:52:34.550
Correlations of data, numerical computation
and then numerical simulation where you're

1575
01:52:34.550 --> 01:52:38.610
trying to do as good as we understand with
the equations.

1576
01:52:38.610 --> 01:52:39.659
Fundamental research.

1577
01:52:39.659 --> 01:52:43.579
The technology development which is where
NASA's major emphasis is.

1578
01:52:43.579 --> 01:52:45.449
Component development of systems.

1579
01:52:45.449 --> 01:52:48.439
And finally subsystem, model and system testing.

1580
01:52:48.439 --> 01:52:51.110
You need all that stuff.

1581
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

1582
01:52:54.739 --> 01:52:57.059
really understand what you're doing.

1583
01:52:57.059 --> 01:52:58.519
Therefore, you have confidence in doing it.

1584
01:52:58.519 --> 01:53:00.249
And, therefore, you develop capability.

1585
01:53:00.249 --> 01:53:03.849
There are no shortcuts.

1586
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

1587
01:53:09.699 --> 01:53:09.949
dynamics.

1588
01:53:09.699 --> 01:53:14.570
It is not limited just to NASA Shuttle people
or aerospace people.

1589
01:53:14.570 --> 01:53:18.780
And certainly in this area, in Apollo, but
all the human space flight.

1590
01:53:18.780 --> 01:53:20.709
We've got a lot of experience.

1591
01:53:20.709 --> 01:53:24.719
That needs to be taken advantage of for our
future systems.

1592
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,

1593
01:53:28.530 --> 01:53:29.579
it's going to use that system.

1594
01:53:29.579 --> 01:53:33.469
It's an overall integrated take advantage
of the experience in what we've learned.

1595
01:53:33.469 --> 01:53:33.749
Yes.

1596
01:53:33.749 --> 01:53:35.639
I just have a question about the chart.

1597
01:53:35.639 --> 01:53:40.030
I'm just wondering if the inner section points
on those lines correspond to a particular

1598
01:53:40.030 --> 01:53:41.499
path or something like that?

1599
01:53:41.499 --> 01:53:46.119
I used this from the standpoint of we were
trying to do a flight test model.

1600
01:53:46.119 --> 01:53:51.269
We were going to predict what happened to
an aero braking vehicle coming in, and so

1601
01:53:51.269 --> 01:53:56.169
I was focused on this and also on the numerical
aspect.

1602
01:53:56.169 --> 01:54:00.630
Marrying those two, at this point, which was
the reason for this flight test.

1603
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.

1604
01:54:11.409 --> 01:54:12.929
I didn't get very many questions.

1605
01:54:12.929 --> 01:54:15.289
It must be because it's the first class of
the day.

1606
01:54:15.289 --> 01:54:17.630
Well, you were going at a mile a minute.

1607
01:54:17.630 --> 01:54:21.019
I think we got a few in there.

1608
01:54:21.019 --> 01:54:28.019
But, yeah, the content of what we've been
exposed to today has been tremendous.

1609
01:54:28.349 --> 01:54:31.409
We really want to thank you.

1610
01:54:31.409 --> 01:54:38.409
If they want to do some simple calculations,
what reference would you give them?

1611
01:54:39.419 --> 01:54:43.999
Are there any simple calculations they could
do?

1612
01:54:43.999 --> 01:54:45.709
[Faye and Rodell?

1613
01:54:45.709 --> 01:54:48.510
yes] has the boundary layer activity.

1614
01:54:48.510 --> 01:54:50.340
That is a crucial reference.

1615
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

1616
01:54:56.389 --> 01:55:02.630
were to date in the various areas, whether
it be service catalysis, TPS, you name it.

1617
01:55:02.630 --> 01:55:05.479
And those were the best references at the
time.

1618
01:55:05.479 --> 01:55:09.749
And the individuals named, many of them have
gone on and done much better work.

1619
01:55:09.749 --> 01:55:11.829
Plus, there are lots of younger people, too.

1620
01:55:11.829 --> 01:55:13.800
I think that would be the best source.

1621
01:55:13.800 --> 01:55:14.300
OK, Bob.

1622
01:55:14.300 --> 01:55:15.630
Thank you very much.

1623
01:55:15.630 --> 01:55:16.269
Thank you.

1624
01:55:16.269 --> 01:55:16.599
[APPLAUSE]