The effect of vertical UCM on weight

Is it possible to fly a plane in just the right way to make the force between the pilot and his seat completely disappear? Yes!



  Q:  If the plane continues to fly in the same circle
      of radius 800 m, what speed will lead to
      weightless conditions at the top of the circle?

           A. about 150 mph
           B. about 175 mph
           C. about 200 mph
           D. about 225 mph


      How long will this period of "weightlessness" last?

A simple circular path is easy to analyze, but turns out to be impractical: the duration of weightlessness is too short. In order to create weightless conditions for useful periods of more than a second or two, one must fly a more complicated trajectory. For many years, NASA pilots have flown planes on parabolic paths which give researchers inside 20 to 30 seconds of weightless conditions; that's long enough to run simple experiments.

Image courtesy of Apollo 13: Behind the Scenes

NASA's Reduced Gravity Research Program

If one moves in a very big circle, very fast, then one can experience weightless conditions for a very long time ...

Thanks to the Canadian Space Agency!

Another way to run experiments under weightless conditions is to drop the apparatus down a mine shaft: as long as it is falling (and as long as we neglect air resistance), the materials experience weightlessness.



  Q:  How deep a shaft is required to yield 
      30 seconds of weightlessness?

Examples of some real "drop towers" are

Marshall Space Flight Center Low-gravity Drop Tower Facility (alas, this appears to have been taken out of service)
Queensland University of Technology Drop Tower which is about 20 meters tall.
The ZARM Drop Tower in Germany provides an evacuated shaft of about 110 meters. Look at a picture of the tower.

This example of measurements from QUT shows good news and bad news.