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UPDATE # 3 - December 4, 1997

PART 1: Student Stumpers
PART 2: Web Chat with Brent Wellman
PART 3: A Catastrophic Structural Failure
PART 4: Subscribing and Unsubscribing


STUDENT STUMPERS: AN EASY ACTIVITY

Here is a simple activity that will work on the communication skills of
your students while challenging them to think creatively. The basic idea is this: kids make riddles for other kids to solve. Students will create a question about the shuttle that they think will be difficult but fun to answer. Pose that question (we'll put it online in the Kids' Corner of the Web), and others will email their responses directly back. The question creator gets to decide if the respondent is right. Then, we'd love to see the results if you'd like to share. We expect the result to be a bunch of kid-kid email exchanges which heat up the Internet. An example question might be: Where is the world's largest motion simulator? That question isn't too tough; we know you can do better than that! Send your original Student Stumpers to Susan at slee@mail.arc.nasa.gov. Also, visit the web at http://quest.arc.nasa.gov/aero/kids/stumpers.html

WEB CHAT WITH BRENT WELLMAN


The best part of chats is being in touch LIVE with an expert, so
JOIN US for an exciting hour of give and take about helicopters and
related subjects.  Our upcoming chat will be:

Wednesday, December 10, 10:00-11:00 a.m. Pacific Time
Brent Wellman, Deputy Project Manager, 2GCHAS Brent is a project manager
for a computer program that makes it easier to design helicopters and
similar aircraft. Please read Brent's biography and journal prior to
joining this chat.
http://quest.arc.nasa.gov/aero/team/wellman.html

To participate (ask questions), you will need to pre-register for the
 chats. Go to:  http://quest.arc.nasa.gov/aero/chats


A CATASTROPHIC STRUCTURAL FAILURE

Brent Wellman's Field Journal

October 29, 1997 

This morning I called an engineer for one of the major helicopter
companies (Maybe you have heard of them -- Sikorsky) to check on a problem
he had been having with the new release of our computer program for
helicopter analysis, 2GCHAS (pronounced "TOO-GEE-CHARLEY). His problem had
evaporated, so I set out for more pressing matters... 

I wrote a section of a report on an incident that occurred in one of our
wind tunnels. A major aerospace company (perhaps you've heard of them --
but you didn't hear it from me!) had been testing a stopped rotor concept
(the rotor stops spinning to become a [fixed] wing!). Without warning, the
rotor experienced a catastrophic structural failure and disintegrated,
sending debris in every direction. I was named to an investigating board
and had to use my knowledge of physics, and engineering materials to piece
together what had occurred. This report section pretty well puts my
participation to rest, but I remain on call (as long as we push the limits
of technology, we will have accidents). 

Back to computer stuff...I worked on a persistent problem with an upgrade
to 2GCHAS that I have been working on. It is a mainstay of modern physics
that physical laws do not depend on whether the physicist stands on his
feet or his head (we say the laws are independent of observer's reference
frames). It is rather handy for engineers to use special reference frames
(usually X-Y-Z coordinate systems, if you've had that much math) to
describe the items he is working with. To do this in our program, one must
define the reference frame with respect to a standard one, by defining a
"direction cosine matrix." It is complicated to do (and frought with
errors for all but the simplest transformations), but, once done, the
computer-generated "physics" in one coordinate system immediately
translate into [consistent] "physics" in the reference coordinate system. 

My improvement would allow an engineer to say to the program, "slide the
reference coordinate system to *here,* then turn it so, twist it so, roll
it so," and the computer figures it all out. It is provable that ANY
transformation, no matter how cockeyed, can be specified this way. Trouble
is, the computer keeps dropping out a step and improperly transforming
some of the various reference frames. I figured out why the program was
dropping out the extra step and cured the program sections I had been
working on. A little more testing and I'll be able to put this to bed. 

A problem came up with one of the versions of the most recent software.
The code was compiled with the DEBUG option turned on. As a result, the
code worked fine, but the computer was spending so much time keeping track
of what it was doing, that it only spent a little time actually doing it.
So the program runs about four times slower. I notified the affected
customers by phone and had the systems operator generate new code (with
DEBUG off). 

After lunch and a workout (whew!), I looked into safety concerns over a
new rotor test in one of our wind tunnels. This is an all-government test,
so I can talk to the project persons directly. 

I contacted the principal investigator of the wind tunnel test following
that one about my acting as backup pilot for him. Rotors in wind tunnels
have to be "flown." They can't just spin in the wind. They need someone to
control their collective (which governs the amount of lift a rotor
develops) and cyclic (which governs the propulsive force generated)
controls. Anyway, this project's pilot is nearing retirement, and he may
need to be replaced. 

I hopped back to the computer and checked up on one of our programmer's
work. Each of us on the team checks (we say "certifies") the programming
changes that are made by the others. In this way, we look over each
other's shoulders, so to speak. I actually found an error in her work (a
change she said she made which was overlooked), brought it to her
attention, and had her correct it. I documented my certification of the
software units and went on to other things. 

I set up a visit by an engineering VP for a small technology company (no,
you haven't heard of them) to Ames Research Center to see me and our chief
scientist about a -- umm, ...device he is developing for us. I can't say a
lot about that project, except that it is part of the "peace dividend" you
may have heard about and it will REVOLUTIONIZE vertical flight if it
works. I act as technical monitor for the contract, and conduct "technical
surveilance" of the work. 

Incidentally, I was able to set up the clearance for his visit all on our
new, secure Web site (no, you may NOT have the URL!). Cool. 

That's the day. I'm off to the day care center to pick up the tyke, and to
have dinner, bye.

SUBSCRIBING & UNSUBSCRIBING: HOW TO DO IT!


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