C-9 Microgravitational Laboratory
How does a parabolic arc work during a 'weightless' flight (like NASA's KC-135 'vomit comet'? A previous post stated (incorrectly I believe) that weightlessness comes when the plane is 'nose-down', falling from the crest to the trough of the curve. On NASA's web site however (http://jsc-aircraft-ops.jsc.nasa.gov/Reduced_Gravity/trajectory.html), it shows that the weightlessness actually comes at the top of the curve. How is this possible?
I have flown in the C-9a (successor to the KC-135) Weightless Laboratory
(the "weightless wonder"). Weightlessness is the lack of support force.
The flight that I was on had a weightless portion of the parabola begin
just before hitting the peak and ending on the down slope. The graph in
the web site you quote is close, with perhaps a bit more time on the descent.
On our flight, we ranged about 25 - 32 seconds per parabola. The graphic
quoted shows 25 seconds. Was each of the 40 parabolas I experienced exactly
like the graphic? No, but it was a close approximation.
Toss a ball. The entire time it is in the air it is weightless. The trajectory
of the plane is designed so that it is like a tossed ball. The "non-powered"
part of the trajectory begins before going over the top.
---Nathan A. Unterman
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Update: June 2012