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UPDATE #16 - March 20, 1998

PART 1: Why the Internet is different than books
PART 2: Prizes for Early Contest Entries
PART 3: Smart Filters Needed
PART 4: Turn Down that Noise
PART 5: Subscribing & Unsubscribing: How to do it


Sometimes teachers say they don't want to teach with
computers because they want students to know the joy of
curling up with a book.  This we all know is a wonderful
pleasure no child should be denied.

Computers connected to the Internet offer children different
and new pleasures - the opportunity to interact with NASA
experts and other children. This is a wonderful way to
reinforce their reading and writing skills with the added
the excitement of talking to real NASA experts.  This may
stimulate and challenge young minds to unimaginably great
endeavors. Certainly many of the Aerospace Team Experts
credit television coverage of the Apollo missions as their
initial inspiration.

We've asked several Aerospace Team members to be available
to interact with your classrooms.
So here's your chance to participate.

Tuesday, March 24, 10:00 a.m.- 11:00 a.m. Pacific Time:
Stephen Jaeger, Aeroacoustics Engineer

Stephen develops tools for measuring aircraft noise. He also
conducts acoustics research on wind tunnel models of supersonic
jets, airliners and aircraft engines. In fact his latest journal
contains pictures of some of the tools he uses during
test and in another journal you can hear the recorded sounds
of his test and see a video interview of Stephen in the 7 x 10'
wind tunnel. http://quest.arc.nasa.gov/aero/team/fjournals/jaeger/

Registration information is at
Read his biography prior to joining this chat.

Tuesday, March 31, 10:00 a.m.- 11:00 a.m. Pacific Time:
Andrew Hahn, Conceptual Aircraft Designer

Andrew designs aircraft concepts. He uses
physics every day in his job.

Registration information is at
Read his biography prior to joining this chat.

Thursday, April 2, 1998 11:00 a.m.- 12:00 p.m. Pacific Time:
Rabi Mehta, Senior Project Scientist,

Rabi is an expert in the aerodynamics of sports balls from cricket balls
to golf balls.

Registration information is at
Read his biography prior to joining this chat.

Tuesday, April 14, 10:00 a.m.- 11:00 a.m. Pacific Time:
Dave Korsmeyer, Senior Project Scientist

Dave is a project manager who develops advanced information
technology and systems like near real time remote access
to wind tunnel data.

Registration information is at
Read his biography prior to joining this chat.

Thursday, April 30, 1:00 p.m.- 2:00 p.m. Pacific Time:
Estela Hernandez, Flight Simulation Engineer

Estela is a flight simulation engineer. She uses math
to build computer models that simulate flying airplanes.
This chat will be in English and Spanish.

Registration information is at
Read her biography prior to joining this chat.


As you know we are holding two contests: "Draw a Picture of an
Airplane" and "Write an Essay Describing the Airplane You
Would Like to Design",

An early bird prize will be awarded to entries received
by March 30, 1998.


As part of Aerospace Team Online, NASA experts answer
personal email questions from students and teachers. Since
these experts are very busy, we use volunteers (called
Smart Filters) to help minimize the expert work load.

These Smart Filters read the incoming mail and determine
if the answer to the question already exists. (This is where
the smart part comes in!)  If so they respond with that answer.
If not, they send the question onto experts; once the
experts reply, the Smart Filter does some minor editing
and then forwards to the original questioner and also
places the answer online for all to see.(It's exciting
to be the first person to see the answer!)

The job of a Smart Filter requires certain skills,
  - good written communication abilities
  - an ability to follow detailed directions
  - an ability to navigate the Internet to find information
  - a self-directed nature to continue to follow through
        quickly to new messages

Our current and past Smart Filters have had fun helping NASA
provide this service.  While participating, they've learned a
lot about the aeronautics and planes.

We need to identify several new Smart Filters for Aerospace Team Online. If you would like to join our team,
please send a note to Barb Weimann at

[Editor's Note: Robert Jercinovich is an instrumentation engineer in the 12' Wind Tunnel. He knows how to make instruments take measurements in the wind tunnel. Read his bio at http://quest.arc.nasa.gov/aero/team/jercinovich.html ]


by Robert Jercinovich

This may sound like a familiar command to some of us. Not only does this
word apply to some forms of music, but it also can be a reference to
electromagnetic interference. As an Instrumentation Engineer you may be
called upon to turn down the noise, but that won't mean adjusting the
volume. An Instrumentation Engineers job during a wind tunnel test is to
insure the customer gets the best quality data attainable.  Our secondary
goal is to ensure that the instrumentation measuring the phenomena
operates reliably and consistently. Immediately after the installation of
the Technology Concept Aircraft model in the test section, problems arose.
A preliminary look at the data reveals that the Rolling Moment gage is
showing a standard deviation of 140 counts over a 0.7 sec span of acquired
data. This is the equivalent of 37 ft-lbs for a gage with a maximum
capacity of 2000 ft-lbs, or a 1.85% error band. This is not music to the
researchers ears. With errors this large it would be pointless to
continue. The Instrumentation team springs into action.

We commence the search for the source of our problems. Instrumentation
engineers get to use lots of electronic equipment. We are used a
spectrum analyzer in an attempt to characterize the noise. Again we see
the rolling moment gage of the balance, only this time it's in the
frequency domain. The balance is used to measure the forces and moments
the model is experiencing. What we see from the graph is 165 mVp @ every
10 Khz. This is riding atop a channel that has a  maximum output of 1.6
mV/V. So, the noise has a magnitude of a hundred of the desired signal.
Now we eliminate the institutional data system, and continue the search
with our own toys.  As we delve deeper for the source of the noise,
reaching into the belly of the tunnel, the wiring looks like intestines
down here.

We have isolated the culprit, a digital stepper motor used to control the
model position. We need the motor to position the model, but we can't
tolerate this level of EMI.  So, we unleash the weapons of
Instrumentation: by-pass capacitors, an external power source, and
shielding and grounding. The capacitors alone reduce the level of noise to
60 mVp. The test team test is happy again, and the test can continue.


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