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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 3/6/00:
Q:
At a whopping 18.95 grams per cubic centimeter, uranium
is a very heavy element. Depleted uranium, defined as having
a smaller fraction of the uranium 235 isotope than
naturally occurring uranium, is roughly sixty percent as
radioactive, has approximately the same density, and is somewhat
safer to handle than ordinary uranium. Interestingly,
depleted uranium is often built right into the structure
of many aircraft. Aren't aircraft designers usually concerned
about excessive weight? Why would it be used on aircraft?
A:
For years, the material of choice for control surface balance
weights was Depleted Uranium (DU). The journal of the American Society
for Metals explains that DU counterweights "are used in the aerodynamic
controls of planes, rockets and helicopters to maintain the aircraft's
center of gravity ... in many civil and military aircraft."
The type of radiation emitted by depleted uranium is called Alpha
radiation and is not unusually hazardous. It doesn't travel far
and it won't penetrate anything including clothing or skin.
You have to somehow ingest it by mouth, nose or through an opening
in the skin for it to be dangerous. However, despite its name, DU
contains residual amounts of radioactive U235, along with less
radioactive U238 and trace amounts of U236.
Congratulations to Michael Dawidowicz.
Despite its handling difficulties, depleted uranium often
finds its way aboard aircraft as a balancing counterweight.
Both military and commercial aircraft use it for balancing
ailerons and other control surfaces, rotorcraft rotor tips,
and for overall aircraft balancing. (See
12/15/97's quiz question for an explanation of why weights
are added to rotor tips!) Because of its high density, depleted
uranium can add a significant mass to a small volume. And in
the world of aircraft, a reduction in volume often translates to a
reduction in drag.
- The Aeroquiz Editor.
Week of 3/13/00:
Q:
Riddle me this: When is a blackbird a bluebird?
No one got the right answer! The question stands another week!
- The Aeroquiz Editor.
Week of 3/20/00:
Q:
Riddle me this: When is a blackbird a bluebird?
A:
The SR-71 appears to be blue because of viscous heating effects at
high Mach numbers.
Congratulations to Kyle Daun.
The Mach 3+ SR-71 spyplane is nicknamed "Blackbird."
Its black exterior paint is highly sophisticated and specially formulated
to radiate excess heat while at the same time disrupting incoming
radar energy. At operating speeds and temperatures, it changes color
to blue.
- The Aeroquiz Editor.
Week of 3/27/00:
Q:
Antarctica is the world's best hunting ground for meteorites.
So much so that NASA and Carnegie Mellon University have constructed
Nomad: an experimental meteorite-hunting robot vehicle. The Nomad
rover evaluates images taken by its high resolution cameras, and
it even has a metal detector and a spectrometer to chemically
analyze the rocks that it finds. But why search the inhospitable,
frigid polar ice cap at the bottom of the world? What makes
Antarctica such an appealing meteorite hunting ground?
No one got the right answer! The question stands another week!
- The Aeroquiz Editor.
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