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Multidisciplinary
Design, Analysis, and
Optimization Branch
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EDUCATIONAL ACTIVITIES: THE NASA AEROQUIZ
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Week of 2/1/99:
Q:
New evidence suggests that around the year 1250 AD, light from a
supernova explosion reached the Earth. This supernova was closer to
the Earth than any other now known, and, except for the sun and moon,
it should have been the brightest object in the sky for weeks. Even
today, the gas cloud remains twice as hot as our sun's core and it
stretches up to 25 light years across. Yet it was never recorded in
any historical records at the time. Why?
A:
There are several explanations. Europe at that time was in medieval
times, and records there were poorly kept. Even the great astronomers of
old China may have had their records disrupted by the Mongol rule of
the time. It's also possible that the view of the supernova may have been
blocked by the sun.
And although the sight should have been spectacular if it
were an ordinary supernova, there may be evidence that it was one of a
class of previously unknown "subluminous" supernovas. The explosion
of superheated gas and radiation in these supernovas may not emit much
visible light.
No one got the correct answer!
- The Aeroquiz Editor.
Week of 2/8/99:
Q:
In April, 1951, the US Air Force began flight testing the X-7:
an unpiloted, supersonic ramjet test bed missile built by Lockheed.
The X-7s, equipped with dummy warheads, were dropped from a carrier aircraft,
flown, and recovered at the White Sands Missile Range. At the end of their
missions, the missiles deployed parachutes, and their sharp, aerodynamic nose
spikes buried themselves vertically into the ground. Later on, this flight
test program suffered its only casualty. Thankfully, it was not serious.
What happened?
A:
There were cattle nearby White Sands in those days. The aerospike
nose of an X-7 skewered a steer.
Congratulations to Walter Curlett.
Week of 2/15/99:
Q:
In a jet engine, the amount of clearance between the compressor blade tips
and the case that surrounds them is an important variable in determining the
compressor's overall performance. Tip gap design requires a complex
consideration of many effects, but in general, the smallest safe gap distance
results in the lowest losses and the best thrust. During takeoff, when the
engine spins to high shaft speeds, the tip gaps tend to close due to the
centrifugal forces acting on the compressor blades and the thrust improves.
Just moments later, however, something often causes the tip gaps to widen
again. This can reduce thrust slightly during the aircraft rotation and
liftoff -- just when it's needed most. What is happening?
A:
The engine heats up under full throttle conditions and the engine case expands.
Since the case has a lower thermal mass than the relatively
dense compressor rotor disks, it expands at a faster rate.
This differential expansion causes tip clearances to open
up and performance to suffer temporarily.
Congratulations to Daniel Shedd.
Week of 2/22/99:
Q:
What segment of aviation uses the arcane slang terms "shrimp boats,"
"upside-down wedding cakes," and "ground clutter"?
A:
Air Traffic Controllers.
Upside-down wedding cakes refer to the shape of controlled
airspace. Ground clutter is radar reflections from buildings, etc.
Not sure what shrimp boats are (but I didn't have to answer
that to get the question right, did I?).
Congratulations to Dale J. Martin.
Class B Airspace is generally the airspace from the surface to 10,000 feet.
This airspace is normally around the busiest airports
such as Chicago or Los Angeles. Class B airspace is individually
designed to meet the needs of a particular airport and consists of a
surface area and two more layers. Most Class B airspace resembles an "upside
down wedding cake." Pilots must contact air traffic control to receive a
clearance to enter such airspace. Once a pilot
receives an air traffic control clearance, they receive separation services
from other aircraft within the airspace.
As for the "shrimp boats," early air traffic control systems used tiny
pieces of paper stuck onto radar screens to identify the radar blips. Computers
now label the blips with flight number, altitude, speed, and other
vital information. Even today, controllers still "get out the boats" when
air traffic computers crash.
- The Aeroquiz Editor.
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