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January 7, 1998
QuestChat with Grant Palmer

[ Grant/Ames - 9 - 10:02:20 ]
RE: [Susan/NASAChatHost] What are you working on now?
Right now I am doing some computer simulations on what is known as the Mars2001 program. This is a spacecraft (actually two spacecraft) that will fly to Mars. I am helping to calculate how much thermal protection (the heatshield) the vehicle will need.

[ Grant/Ames - 12 - 10:04:37 ]
RE: [Susan/NASAChatHost] Is the heatshield like the tiles on the space shuttle?
Yes. The heatshield is what protects the spacecraft when it re-enters an atmosphere. Air (or CO2 for Mars) friction heats up the skin of the vehicle as it flies through the atmosphere. If it gets too hot, it can damage or destroy the vehicle

[ Grant/Ames - 14 - 10:05:39 ]
RE: [Susan/NASAChatHost] Can you use any information from the Pathfinder mission?
We always use information from past projects to help us with what we are doing now. A lot of computer simulation was done for Pathfinder and we are using it for Mars2001 and other Mars missions

[ Grant/Ames - 15 - 10:06:01 ]
RE: [Carl/homeschooled] Hi Susan and bill
Hi, Carl. My name is Grant

[ Susan/NASAChatHost - 16 - 10:06:18 ]
Hi Carl do you have a question for Grant?

[ Bill-Bill/FCCDNASAAmes - 18 - 10:07:40 ]
hi Carl and Good Morning

[ Grant/Ames - 19 - 10:07:55 ]
RE: [Bill-Bill/FCCDNASAAmes] I know that there are many materials that these can be made of. What are the most recent shields consturcted of?
There are two basic types, ceramic and metallic. The ceramic are similar to the type of thing you might find in baking dishes (but can stand a much higher temperature). The metallics tend to be exotic mixtures of various metals. There is also ceramic blanket insulation

[ Grant/Ames - 22 - 10:12:00 ]
RE: [Susan/NASAChatHost] When you write a CFD program then what are you calculating? Heat generated by friction, are you also looking at drag and other aero concerns?
Actually the CFD program is based on the conservation (what goes in, comes out) of mass, momentum, and energy, so these are the things actually calculated. From these quantities you can calculate everything else (temperature, pressure, density, drag, etc.)

[ Grant/Ames - 25 - 10:14:43 ]
RE: [Bill-Bill/FCCDNASAAmes] I is amazing that they can use metals for this purpose. Is the blanket insulation on the outside of the craft or is this only used for insulaiton inside the outer walls?
For really high temperatures, the metallic heatshield material is put on top of a blanket insulation. The metallic panels have a honeycomb structure very much like a car radiator. This dissipates heat very well. As far as the blankets go, blanket insulation is used on the outside of the Space Shuttle. It is pretty durable stuff.

[ Grant/Ames - 27 - 10:15:57 ]
RE: [Kelly/PioneerSchool-Kelly/PioneerSchool] Hi everybody. I was surprised that Mr. Palmer is working on Mars. I thought everybody here was an aeronautics person.
Hi, Kelly. NASA does just about everything you can think of as far as air and space goes. We have people who are working on biology, astronomy, and physiology as well as in aeronautics and space

[ Susan/NASAChatHost - 28 - 10:16:28 ]
RE: [Kelly/PioneerSchool-Kelly/PioneerSchool] Hi everybody. I was surprised that Mr. Palmer is working on Mars. I thought everybody here was an aeronautics person.
Welcome Kelly, Grant is a specialist in Computational Fluid Dynamics, some space transportation is aerodynamics too!

[ Grant/Ames - 29 - 10:17:36 ]
RE: [Carl/homeschooled] Ofcourse Do you use diffrent CFD programs for aircraft and spacecraft?
Yes. There are basically two types of CFD codes. Low speed codes and high speed codes. The low speed ones use a simpler set of governing equations. The codes that compute high speed flows (like the flow over spacecraft) have much more complex physics built in, stuff like chemistry, radiation, etc.

[ Grant/Ames - 32 - 10:19:11 ]
RE: [Kelly/PioneerSchool] Did Mr. Palmer work on the Mars projects from this past summer?
Mars 2001 is my first Mars project. Before this I worked on experimental vehicles for Earth orbit like the X-33 vehicle. The X-33 is that smooth, diamond-shaped spacecraft that you might have seen at the Ames open house

[ Grant/Ames - 33 - 10:20:16 ]
RE: [Bill-Bill/FCCDNASAAmes] which atmosphere causes more friction, The CO2 atmosphere of Mars or the mixed atmosphere of Earth?
Earth has a much denser atmosphere than Mars, so for a given velocity Earth's atmosphere will generate more friction (and therefore heat) than Mars.

[ Grant/Ames - 35 - 10:21:31 ]
RE: [Kelly/PioneerSchool] So how long does it take to make a computer program for a Mars heat shield. Do you do this by yourself? And what kind of computer language do you use?
I sometimes write my own codes. But the more complex codes are the work of many people. The one we are using for Mars was first written by a company called Aerosoft. We took it and made changes to it to suit our needs

[ Grant/Ames - 37 - 10:22:49 ]
RE: [Kelly/PioneerSchool] What is an Ames open house?
Last September (was it September) NASA Ames invited the public to visit our complex and find out what we do. There were a lot of displays on the various projects we work on.

[ Grant/Ames - 39 - 10:24:43 ]
RE: [Kelly/PioneerSchool] Maybe this is silly, but I read from Mr. Palmer's biography that he swam off of Alcatrz island. I thought there were sharks and stuf that made it too dangerous, so that is why they lept prisoners there. Was is safe to do that swim, and how long did that take?
They do this race every year. There are sharks out there. They have spotter boats but I think you just have to hope for the best. I don't think anyone has ever been attacked during the race. The 1.5 mile swim took me about 36 minutes and it was cold. One thing I didn't answer before, most of the programming for CFD codes is done in FORTRAN and C. C is becoming more and more popular.

[ Grant/Ames - 42 - 10:26:07 ]
RE: [Carl/homeschooled] Grant why dont they make layers of hard rock proof metal and soft super heat resistant ceramics in an interlocking honey comb like they do with new tanks?
One big reason is weight. Unlike a tank that just rolls along the ground, you have to lift a spacecraft or rocket off the ground and into space. Thermal protection systems (heatshields) have to withstand high temperatures and be very lightweight

[ Grant/Ames - 43 - 10:28:07 ]
RE: [Kelly/PioneerSchool] So how much longer will it take to do the Mars heat shield. Oh yeah, what is that Mars mission about. Will it have a rover too?
The calculations I'm doing for the Mars heatshield will take about 1700 hours on a Cray C90 supercomputer. That is currently the world's largest computer. The Mars2001 mission is just one of a series of Mars missions. This one has two spacecraft. One will land on the surface and take soil samples. The other will orbit the planet and study the atmosphere. I'm not sure about the rover.

[ Grant/Ames - 45 - 10:29:27 ]
RE: [Carl/homeschooled] Grant why C and not C
C is being used more and more to write codes because of its very efficient memory management capabilities. C++ is more of a visual language. You don't see it as much with the CFD codes, but you do see it a lot in the programs people use to look at their CFD results.

[ Grant/Ames - 47 - 10:30:50 ]
RE: [Kelly/PioneerSchool] So do you also design the heat shiled material or do you just use computers to say how the design will do?
The group that I work with is mostly involved with CFD. There is another group of people next door who do design and develop new heatshield materials. They also do a lot of ground testing of materials by blowing very hot air at it.

[ Grant/Ames - 49 - 10:33:31 ]
RE: [Kelly/PioneerSchool] Wow. 1700 hours seems like alot of time. So you have to be thinking about the project all of that time. Or do you just send it in and then you are done?
The hardest part about CFD is generating your grids. You have to take some representation (picture, geometry file) of the spacecraft and you have to divide it up into very small squares. This is called a surface grid. The CFD code needs to know the x,y,z coordinates of each your grid. Then you can start running the code. After that, I always check my solution, look at it on my workstation, and make any changes I have to.

[ Grant/Ames - 52 - 10:35:13 ]
RE: [Kelly/PioneerSchool] After you test the heat shield design on a computer, does it get built and tested in a windtunnel before it is made part of the spacecraft?
Yes. The thing about CFD codes is that it is very easy to make a mistake. The code may run and give you an answer, but if you are not very careful that everything was set up right the answer may be wrong. To check the CFD, it is always best to run an experiment in a wind tunnel to make sure the data looks consistent

[ Grant/Ames - 54 - 10:37:02 ]
RE: [Carl/homeschooled] What kind of operating system does a CFD run in?
A CFD code is just a FORTRAN or C program. It can run pretty much anywhere. I have run codes on my SGI workstation. I know of people who run them on PC's. The Cray C90 is just the biggest and fastest machine I have access to. The operating system on the Cray is something called UNICOS, on the SGI workstation it is called IRIX.

[ Grant/Ames - 55 - 10:37:51 ]
RE: [Susan/NASAChatHost] Is it hard to get time on the Cray computer do you run into scheduling projects?
There is a lot of competition for time. Some of the time is given away free to worthwhile projects. For people who don't get the free time, they can but time.

[ Grant/Ames - 57 - 10:39:11 ]
RE: [Kelly/PioneerSchool] What was the spacecraft you worked on before Mars. I think you said X-32 or 33? What does that one do?
The X-33 is a scale model of a spacecraft that may someday take the place of the Space Shuttle. The Space Shuttle works great but it is very expensive to fly and maintain. The idea is that with new technology we should be able to get satellites and other payloads into orbit a lot cheaper.

[ Grant/Ames - 58 - 10:41:19 ]
RE: [Kelly/PioneerSchool] In the grid, it sounds like you have to know the exact shape you are testing. Is that right? How can you know the exact shape...wouldn't it depend on what the heatshield is made out of?
The heatshield is usually placed on top of a metal skin. You know the metal skin shape exactly. This was an excellent question, because you don't know the exact shape of the heatshield before you do the CFD because the CFD is supposed to tell you how thick the heatshield should be. What we do is based on past experience we guess at the heatshield thickness, run the CFD, and make changes to the thickness we guessed.

[ Grant/Ames - 61 - 10:42:10 ]
RE: [Grant/Ames] There is a lot of competition for time. Some of the time is given away free to worthwhile projects. For people who don't get the free time, they can but time.
I meant they could buy time

[ Grant/Ames - 63 - 10:42:46 ]
RE: [Sarah-AndersonElemSchool] Sorry we are late, did you bring Bailey to work today?
No, I thought it might rain today. I'll bring Bailey in tomorrow. He would come in every day if he had his way.

[ Grant/Ames - 65 - 10:44:31 ]
RE: [Kelly/PioneerSchool] So will there be people on the X-33
No, the X-33 will be remote-controlled. The full-scale version of it, called the Reusable Launch Vehicle (RLV) may be manned. When you put people on a rocket, it becomes a lot more expensive and you have to be much more careful with the design. The idea behind the X-33 is to build it quickly and as cheaply as possible to demonstrate the new technology.

[ Grant/Ames - 67 - 10:45:43 ]
RE: [Carl/homeschooled] My Watcom 10.0 C compiler can optimize C code to be faster and more memory efficient than ASCII and standard C. So do you use some special C90 super compiler to make your C code?
One nice thing about the Cray computers is they have very good compilers. I just use the Cray standard C compiler. I'm not sure what the specifics of it are.

[ Grant/Ames - 70 - 10:46:47 ]
RE: [Kelly/PioneerSchool] About making changes to the heatshield thickness. Does every change mean that you have to run another 1700 hours on the computer?
No. The CFD gives you a general idea of the surface temperature during the spacecraft's mission. You assume that small changes to the shape of it won't change the surface temperature that much.

[ Grant/Ames - 71 - 10:47:38 ]
RE: [Bill-Bill/FCCDNASAAmes] would the X-33 be able to take off and land on its own accord?
yes. The X-33 will take off like a rocket and land like an airplane. The entire thing will be remote controlled. The first flight is scheduled for next year. It should be really cool.

[ Grant/Ames - 72 - 10:49:05 ]
RE: [Sarah-AndersonElemSchool] When you get your results are they displayed in color? The colors are so great when you look at CFD images?
We use graphics programs that take the CFD data and express whatever quantity you want (temperature, pressure, etc.) as color contours. Then you can view the results on your screen. If you haven't seen any before, CFD can generate some really cool pictures.

[ Grant/Ames - 75 - 10:50:07 ]
RE: [Kelly/PioneerSchool] When is NASa going to build a real X-33 that can take cargo into space?
That's the idea. Actually, NASA won't build it just help design it. The X-33 is being built by Lockheed Martin. The X-33 won't take cargo into space, but the full-sized version will.

[ Grant/Ames - 77 - 10:50:57 ]
RE: [Sarah-AndersonElemSchool] Will you get to go to the Launch?
I'm hoping to get to go to the launch. It is taking off from Edwards Air Force Base in Southern California

[ Grant/Ames - 78 - 10:51:20 ]
RE: [Kelly/PioneerSchool] I am going to have to go to my next class. This was great. I learned a lot and my teacher will be happy when I show her what I did. Thanks you so much Mr. Palmer for answering so many questions. Bye.
Bye, Kelly

[ Grant/Ames - 79 - 10:52:33 ]
RE: [Bill-Bill/FCCDNASAAmes] How large will the remote controlled version be? Will the full scale version be remote controlled?
the X-33 will be pretty large. I don't have the exact number on the top of my head, but I think it will be 70-80 feet long and about 60 feet wide, a little smaller than the Space Shuttle.

[ Grant/Ames - 81 - 10:53:47 ]
RE: [Grant/Ames] the X-33 will be pretty large. I don't have the exact number on the top of my head, but I think it will be 70-80 feet long and about 60 feet wide, a little smaller than the Space Shuttle.
They haven't decided if the full-scale version will be piloted or remote-controlled.

[ Grant/Ames - 83 - 10:55:12 ]
RE: [Carl/homeschooled] Do you know of a web page about cray computers Grant?
I'm sure if you do a search for cray you could find it. Cray was bought by SGI so you might search their websites too. Also, you might be able to find out something from the NASA Ames Information Technology division website.

[ Grant/Ames - 84 - 10:56:01 ]
RE: [Sarah-AndersonElemSchool] I guess the landing will be exciting to will you get to go to that too?
The first landing I think is in Utah. I have a better chance of going to the launch. I'm sure both will be on TV.

[ Grant/Ames - 88 - 10:58:21 ]
RE: [Carl/homeschooled] Does the X-33 have a helper rocket like the shuttle or does it take off from a runway like an air plane?
The X-33 is completely self-contained. The whole idea behind it is to make it fully re-usable, so it has no external tanks. It takes off vertically and lands like an airplane, just like the Shuttle.

[ Grant/Ames - 91 - 11:01:25 ]
RE: [Sarah-AndersonElemSchool] When the x-33 lands is it flying or more like a glider? Thanks for the answers!
It uses up all of its fuel on ascent, so it is essentially a glider. It can maneuver around a little bit, but once it is coming down it is coming down.

[ Grant/Ames - 92 - 11:01:42 ]
RE: [Carl/homeschooled] Thank you Grant this has been a fun chat... See you later
Bye, Carl.

[ Grant/Ames - 94 - 11:02:19 ]
RE: [Susan/NASAChatHost] Thank you Grant and everyone for all the great questions !! I learned lots I hope you all enjoyed it!
Bye everybody. This was fun.


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