Is there air resistance in space?

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Ben Luckie

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Is there air resistance in space?
« on: 08/05/2011 17:01:02 »
Ben Luckie  asked the Naked Scientists:
Hi guys, got a melon scratcher for you,

If I was in a spacecraft and it was motoring along at say 50,000kms/hr in space and I stuck my arm out the window (assuming I could) would there be any resistance?  Like when you stick your arm out the window of a  moving car. 


Ben Luckie

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« Last Edit: 08/05/2011 17:01:02 by _system »


Offline Phractality

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Is there air resistance in space?
« Reply #1 on: 08/05/2011 21:51:25 »
The higher you go the thinner the air. At 50 km elevation, the pressure is nearly zero; space officially begins at 100 km.

In a circular low Earth orbit, you would be going about 29,000 km/hr, and you would feel enough drag to make your orbit decay; within a few days or weeks, you would burn up in the atmosphere. To be going 50,000 km/hr in the upper atmosphere, you would need to be near perigee of a very long elliptical orbit, and the air drag depends on how close to sea level you come at closest approach.

The ISS orbits about 350 to 400 km above sea level. Up there, the air drag is negligible. Without firing any rockets, the ISS orbit decays by about 135 meters per day. If you watch videos of astronauts working outside the space station, you might occasionally see a sheet of paper-thin material flapping in the breeze, but that's about it.
Imagination is more important than knowledge. Einstein