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ATO #118 - September 16, 2000

PART 1: Upcoming Chats

PART 2: New Projects for Fall

PART 3: An Experiment Failure but a Happy Ending



QuestChats require registration. You can register at http://quest.arc.nasa.gov/aero/chats/

-Tuesday, September 19, 2000, 10 AM Pacific

Aerospace Team Online QuestChat with George Raiche

George Raiche studies how spacecraft perform as they enter a planet's atmosphere, in order to improve their designs.Read his bio at http://quest.nasa.gov/aero/team/raiche.html

-Wednesday, October 18, 2000, 10 AM Pacific

Virtual Skies QuestChat with Jim McClenahen

Jim McClenahen is an air traffic control analyst in the Future Flight Central Facility.He is very familiar with air traffic management. You can read his profile at http://quest.nasa.gov/aero/team/mcclenahen.html

-Wednesday, November 8, 2000, 11 AM Pacific

Planetary Flight Chat with Andy Hahn

Andy Hahn is a conceptual airplane designer. He has worked on some conceptual designs for planetary planes. Read his profile at http://quest.nasa.gov/aero/team/hahn.html


Expect some changes soon... NASA Quest's Web site redesign is almost done!

We hope you'll find our new look easy to navigate and attractive.


Virtual Skies is an air traffic management project for students and teachers in Grades 9-12. It will be a "project based learning activity" with hands on multimedia to enhance student decision making and problem solving skills. Topics to be covered include Aviation Navigation, Aviation Weather, Communication Air Traffic Management, Airport Design, and Air Traffic Research. Materials will be tied to the National Standards in Mathematics, Science, Technology, Geography and Language Arts. We are scrambling for a Oct. 1, 2000 start date.

Planetary Flight is an aerospace project for Grades 4-8. We know how to fly on Earth but what will it take to fly on Mars. This will be an inquiry based learning project to design an airplane to fly on Mars. The stuff dreams are made of!! We hope to start by October 1, 2000.


[Editor's Note: George Raiche is a research scientist. He studies how a spacecraft performs as it enters a planet's atmosphere. Read his profile at http://quest.nasa.gov/aero/team/raiche.html ]

A Failed Experiment but Happy Ending

by George Raiche

August 22, 2000

One of the most interesting things that can happen to a scientist is running an experiment that doesn't work. One of my recent experiments has been a complete "failure", and I couldn't be happier.

For very high-speed atmospheric entries, heat shields are designed to ablate. Ablation, the controlled decomposition of the heat shield during entry, is a very effective means of dissipating entry heating (of course, the heatshield could not be re-used); energy absorbed in breaking the physical and chemical bonds that hold the ablator together is unavailable for heating the vehicle.

But one of the questions we still don't understand is: what happens to the material that ablates away? Most ablators are hydrocarbon resin composites, which have very complex thermal decomposition chemistry. The decomposition products include everything from diatomic radicals to soot.

From a vehicle design perspective, why do we care where the products go? Because, as in the rest of nature, no waste product ever really goes away. These ablation products enter the shock layer and may effect the heating of the vehicle.

We simulate entry in the arcjets by forming a hot shock layer over test models. My experiment was an attempt to detect the presence of the decomposition products in that shock layer during an ablator test. Since we use air to form the shock layer, I expected the chemistry to resemble hydrocarbon combustion chemistry; in a combustor, two common combustion products are C2 and CH radicals. In a high energy environment, both these molecules strongly emit visible light with characteristic properties.. My experiment was designed to detect that light. Since the properties of that light are well known, my data would give me a good insight about the ablation chemistry. But I didn't see any of this light. What I did see was even more interesting: a broad yellow background glow. What causes this glow? How might it effect the amount of heat that falls on the test model, or onto a real heatshield during entry? We are trying to answer those questions now. Stay tuned!


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