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July 25, 2000
QuestChat with Grant Palmer

Computational Fluid Dynamics Engineer
NASA Ames Research Center, Moffett Field, CA


Tue Jul 25 14:12:02 2000

[ Oran/NASAChatHost - 2 - 12:44:30 ]
Hello to our early arriving chat participants. Today's Aerospace/Space Team Online chat with Grant Palmer will begin in approximately 15 minutes. Be sure you have read Grant's profile at http://quest.nasa.gov/aero/team/palmer.html to prepare your questions.

[ Oran/NASAChatHost - 3 - 12:45:01 ]
During the chat, we will post a few questions in the chat room every few minutes. This will help Grant keep up with our questions. You only need to submit your questions once, and they will be posted shortly thereafter.

[ Oran/NASAChatHost - 4 - 12:45:22 ]
At the conclusion of today's chat, be sure to visit our NASA QuestChat Information Center at http://quest.nasa.gov/qchats. Use our online surveys to send us your comments. We look forward to hearing from you!

[ Oran/NASAChatHost - 10 - 13:01:21 ]
Hello and welcome to today's Aerospace/Space Team Online chat with Grant Palmer. When a spacecraft such as the Space Shuttle returns to Earth from space, the friction caused by the air rushing past the surface of the vehicle causes it to heat up. Grant Palmer writes computer programs that predict how hot these vehicle surfaces will get.

[ Oran/NASAChatHost - 11 - 13:01:40 ]
And now, here is Grant Palmer to answer your questions.

[ Oran/NASAChatHost - 15 - 13:02:55 ]
RE: [Ryan] Hi from Alaska.
Welcome, Ryan. Grant Palmer has just joined and is ready for our questions. Please send yours in and we will post them shortly.

[ GrantPalmer/ARC - 16 - 13:03:15 ]
RE: [Jim] Something to think about before the session begins: JimL/SebringFL would like to know as a programmer himself, if you do basic programming or use object oriented programming to develop your work. I find the object oriented programming gives me more time to think about the problem and minimum time on testing and making my program work. How do you apply your programming expertise and what type of results do you Produce?
These days I like to program in Java. I'm an old FORTRAN/C guy, so it took me a while to get into object oriented programming. Now I think it's the only way to do things.

[ GrantPalmer/ARC - 18 - 13:05:22 ]
RE: [Jim] Two SECRETS I would love to get from Grant before he closes the session today: JimL/SebringFL would like to know if you have found the secret for the computer programmers mental block as you develop the impossible.....namely scratching Bailey'9s ear? and JimL/SebringFL would like to know the secret that allows you to call a swim from Alcatraz Island to San Francisco a simple "race", when only one attempt at an escape is on record and they drowned.
My secret to programming is to do things step-by-step. Don't try to do too much at once and test everything before you move on. Every time I've tried to write a whole code at once it hasn't worked right. A mile and a half isn't that far to swim, and they do it when the currents are at their weakest. The prisoners had no wetsuits and were able to train before their swim. There was no workout pool at Alcatraz.

[ GrantPalmer/ARC - 20 - 13:07:27 ]
RE: [Jim] JimL/SebringFL would like to know if your work in CFD programming has given you any insight into the most effective shape of a re-entry vehicle? GeorgeRaiche/ARC in the Reacting Flow Environments Branch has stated: "You want a blunt surface forward, because the shock wave over a blunt surface stands off more than a shock wave over a sharp surface." Thus reentry is cooler.
George is in my branch and he's right. The heating rate is a function of the nose radius of the vehicle. The smaller the nose, the higher the heating. One thing sharp-nosed vehicles give you is better maneuverability. One research activity going on at NASA Ames right now is to develop materials that could stand temperatures high enough to allow a sharp-nosed entry vehicle.

[ GrantPalmer/ARC - 21 - 13:08:59 ]
RE: [Joy] Hi! I was wondering which effects the heat gained by reentry of a spacecraft more, weight or size?
I think the shape of the vehicle is more important. A heavier vehicle will have more energy when it comes back down and therefore will experience higher heating, but I think the shape effect is greater.

[ GrantPalmer/ARC - 23 - 13:11:02 ]
RE: [GrantPalmer/ARC] I think the shape of the vehicle is more important. A heavier vehicle will have more energy when it comes back down and therefore will experience higher heating, but I think the shape effect is greater.
I should explain the size effect. If you have two vehicles the same shape but different sizes, the smaller vehicle will heat up more. This gets back to that nose radius effect I wrote about earlier.

[ GrantPalmer/ARC - 25 - 13:12:53 ]
RE: [Ryan] How hot does the craft's surface get during re-entry?
It depends how much energy the space vehicle has when it enters the atmosphere. I think the Shuttle surface gets up to 2000 degrees in some places.

[ GrantPalmer/ARC - 26 - 13:14:42 ]
RE: [Joy] Is the temperature a constant? If the shuttle carries different weights of payloads during descent will it affect the temperature of the shuttle?
The temperature depends on a lot of things, like the trajectory the shuttle takes (its descent angle) and how heavy it is when it comes down. The designers and people like me calculate the types of trajectories the shuttle can fly based on the limits of the heat shield material.

[ GrantPalmer/ARC - 30 - 13:18:55 ]
RE: [Jim] JimL/SebringFL would like to know how problems are presented to you. Do you have all your formulae preconceived requiring only modifications with Differing vehicles or do they give you the re-entry path versus weight etc.?
I work on two types of projects, planetary probe design and future concept vehicles. The planetary probes tend to be similar to other probes that worked in the past. You want to be as sure as you can that the probe will get where it is supposed to be so the designers tend to be conservative. The future vehicles sometimes are shapes or concepts that have never been used before. That's when we use our computer programs to calculate what type of heat shield the vehicle will need or even it the concept will work at all.

[ GrantPalmer/ARC - 32 - 13:20:35 ]
RE: [Ryan] How many of the heat shield tiles does the shuttle normally lose during or after re-entry?
You probably know that there are thousands of tiles and they are all glued on to the skin of the space shuttle. The descent can be very bumpy. There is a lot of vibration and the tiles can get very hot. This is what causes the tiles to fall off. I honestly don't know what the number is, but considering what they go through it's surprising more don't fall off.

[ GrantPalmer/ARC - 33 - 13:23:08 ]
RE: [Joy] Is there a specific formula you use to calculate velocity, mass, etc and the friction/heat it creates? Kind of like Einstein'9s E=mc2. :-)
Yes. We solve what are called the Navier-Stokes equations, the conservation of mass, momentum and energy. We solve these equations around the vehicle and this gives us the conditions on the vehicle surface. The equations themselves are pretty simple. Basically, what comes in has to either go out or accumulate.

[ GrantPalmer/ARC - 37 - 13:27:34 ]
RE: [Ryan] What is the status on the X-33 testing & design? Also where is it being tested?
The X-33 is being designed and tested at the Lockheed Skunk Works in Palmdale, CA. They had some trouble with the liquid oxygen fuel tank. They were trying to use a composite material that had never been used before, but the tank wouldn't stay together. They had to switch to a more conventional aluminum tank and this pushed the schedule back. I think the first flight is now scheduled for early next year.

[ GrantPalmer/ARC - 38 - 13:29:19 ]
RE: [Jim] JimL/SebringFL would like to know if laminar flow is considered in your formulae Or is it oriented almost entirely to the heat equations?
The computations I do usually assume laminar flow. Turbulence is one of those things that no one has really figured out how to model correctly over a wide range of conditions. If we want to model turbulent flow, we usually add some terms to our laminar equations.

[ Oran/NASAChatHost - 39 - 13:30:41 ]
As a reminder, please send us your comments about today's chat at http://quest.nasa.gov/qchats. Thanks in advance!

[ GrantPalmer/ARC - 41 - 13:34:20 ]
RE: [Jim] JimL/SebringFL would like to know what you consider to be your best work over the years. Is it a new formula, new approach, or just a different way of looking at things? With object oriented coding I often sit back and marvel at what I have just done!!
I really like doing things that no one has done before. I'm more project oriented now, but a few years ago I did a lot of code development and basic research. I really liked that. One time I was able to show computationally for the first time that a magnetic field will push a shock wave away from a blunt body. That may have been my best work.

[ GrantPalmer/ARC - 47 - 13:44:28 ]
RE: [Ryan] Thanks, Grant. I am going to be in Lancaster (very close to Palmdale) this winter, visiting my grandparents. Is there somewhere I could go and learn more about Ames and especially the X-33? Is the public allowed to tour Lockheed? :0)
You can visit NASA Dryden which is close to Palmdale. They do a lot of flight testing work and I think you can take a tour there. I'm not sure about Lockheed. A lot of it is probably off-limits, but they do have a gift shop and you could always go in and ask them about a tour. NASA Ames is located in Moffett Field, CA [in northern California - Silicon Valley/San Francisco Bay Area]. You could learn more about it by visiting their Web site.

[ Oran/NASAChatHost - 48 - 13:45:35 ]
RE: [GrantPalmer/ARC] You can visit NASA Dryden which is close to Palmdale. They do a lot of flight testing work and I think you can take a tour there. I'm not sure about Lockheed. A lot of it is probably off-limits, but they do have a gift shop and you could always go in and ask them about a tour. NASA Ames is located in Moffett Field, CA. You could learn more about it by visiting their Web site.
Ryan, the NASA Ames Research Center web site is available at http://www.arc.nasa.gov.

[ GrantPalmer/ARC - 49 - 13:45:43 ]
RE: [Joy] Is it difficult to learn Java?
Java is nice because it gives you the power of object-oriented programming but it's a lot easier to learn than C++. Java is not that hard to learn. I've actually written a book on Java.

[ GrantPalmer/ARC - 51 - 13:47:22 ]
RE: [Jim] JimL/SebringFL your best work was marvelous and still not being properly handled. I have been working the reason for flat galaxies rather than spherical attractions to the black hole centers. Were you able to find any magnetic affect on other than ferrite material? A shock wave has Ions, is that what the magnetic field was working against?
The work I did was with an internally generated magnetic field. The spacecraft itself was generating it. At very high speeds, there will be a weak magnetic field generated in the shock wave due to the presence of ionized species. I'm afraid I don't know much about the effects of magnetism on galaxies.

[ GrantPalmer/ARC - 52 - 13:49:10 ]
RE: [Joy] I've seen you're book! I was wondering if it would be easy enough for someone with no computer programming skills to use.
What you should do (excuse the plug for my book) is to get a beginning Java book and also mine. The beginning books are good for someone who has never programmed, but they don't take you very far. My book has the complete details but not a whole lot of the basics. Once you kind of had the feel for Java programming, you could use my book to learn about the really fun stuff.

[ GrantPalmer/ARC - 54 - 13:53:28 ]
RE: [Jim] JimL/SebringFL would like to know if you determined the most effective orientation or Polarity of that repulsive magnetic field?
The only way I could do the calculation was to assume axially symmetric flow and an axially symmetric magnetic field. The equations simplify considerably and that made the computer requirements something I could handle. So I only used one orientation of the magnetic field.

[ GrantPalmer/ARC - 57 - 13:56:03 ]
RE: [Jim] JimL/SebringFL would like to know the title of your book?
It's Java Programmer's Reference, but be careful because there are two other books by that name. Mine has a red cover with my picture on it and is published by Wrox Press.

[ GrantPalmer/ARC - 58 - 13:57:26 ]
RE: [GrantPalmer/ARC] The only way I could do the calculation was to assume axially symmetric flow and an axially symmetric magnetic field. The equations simplify considerably and that made the computer requirements something I could handle. So I only used one orientation of the magnetic field.
A little more detail on the magnetic calculation. What made it difficult is that you have to solve both the fluid equations and the magnetic equations and couple the two sets of equations together. It was a messy process.

[ Oran/NASAChatHost - 60 - 13:58:52 ]
RE: [Joy-stojoy] Thanks for your time Grant and Oran. And thanks for answering my questions.
Joy, thank you very much for joining us today. We hope to hear from you again.

[ Oran/NASAChatHost - 61 - 13:58:59 ]
This concludes today's Aerospace/Space Team Online chat with Grant Palmer. We would like to thank everyone for their great questions. Our very special thanks to Grant Palmer for sharing his time and career expertise with us today. THANK YOU, Grant!

[ GrantPalmer/ARC - 62 - 13:59:07 ]
RE: [Joy-stojoy] Thanks for your time Grant and Oran. And thanks for answering my questions.
Thanks for stopping by, Joy.

[ Oran/NASAChatHost - 64 - 13:59:37 ]
As a final reminder, please send us your comments about today's chat at http://quest.nasa.gov/qchats.

[ GrantPalmer/ARC - 66 - 14:00:19 ]
RE: [Jim-JimL/SebringFL] JimL/SebringFL as you said earlier, it takes one step at a time and much patience. Many thanks for your words and time.
It was nice talking with you Jim.

[ Oran/NASAChatHost - 67 - 14:00:55 ]
An archive of this chat will be available soon. We hope you can join us for our next chat with Chuck Cornelison on Tuesday, August 8 at 10:00 a.m. PDT. Check our online schedule at http://quest.nasa.gov/common/events for more information.

[ GrantPalmer/ARC - 68 - 14:01:09 ]
RE: [Ryan-Ryan/Homeschool] My thanks also go to Grant and Oran. :)
Good luck, Ryan.

[ Oran/NASAChatHost - 69 - 14:01:18 ]
RE: [Ryan-Ryan/Homeschool] My thanks also go to Grant and Oran. :)
Thank you, Ryan. Please join us again.

[ Oran/NASAChatHost - 70 - 14:02:27 ]
Thank you again for joining us today. Have a great day!

[ Ryan - 71 - 14:02:58 ]
You too!

 
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