Get propellant from athmosphere

[DarkenedOne]

I have seen a number of ideas about producing propellant in space. Practically all of them that I have seen involve actually landing on a celestrial object.

My question is whether or not there is a way to gather propellant from the atmosphere of a planet or moon without actually landing on it. Could you do it while flying though the upper atmosphere?

What I am thinking is that you have have a spacecraft skim the atmosphere of a planet the same way they do in aero-braking. While it skims it could collect the atmosphere. Once it is done it can simply rocket back into space. Since the spacecraft would maintain most of your velocity during this maneuver, the spacecraft should not have a problem rocketing back off into space.

If such technology is developed it would provide us with a relatively cheap supply of propellant. Oxygen and nitrogen could be harvested directly from Earth atmosphere.

 

[JonClarke]

It has been thought of, back in the 50s, it was called PROFAC. http://www.bisbos.com/rocketscience/spa ... rofac.html

 

[kelvinzero]

We have started a few threads on this here. I know I started one as well.

I think particles at that height are often ionised. I think the efficiency could be improved by slowing the ions magnetically to produce some electricity instead of with impacts, that just produce waste heat.

Also I think it would be possible to create a sort of potential barrier that would only collect slower moving particles (relative to the orbiter) also increasing efficiency. The reason this doesnt violate the second law of thermodynamics is because it is only useful due to the incoming particles being fairly directional.

Note im only talking about increasing efficiency, not a perpetual motion machine!