Re: Gun launched orbital systems

From: Doug Jones (
Date: Tue Oct 23 2001 - 11:02:57 MDT

Spike Jones wrote:
> Adrian Tymes wrote:
> > ...One could imagine RC maintenance bots, drifting from solar sat to solar
> > sat, skimming reaction mass from the atmosphere for ion engines powered
> > by its own PV system...
> The breakeven point for a system skimming reaction mass from
> the upper atmosphere would require exhaust velocities in excess
> of 8km/sec. This is at the limit of current space based ion engines.
> Perhaps Doug will comment on this. spike

Unless you combined the trolling collector with an electrodynamic
tether, which requires only power and no reaction mass to do drag
makeup. This would allow putting the solar collectors way up where drag
is low, yet keep the air collector down in the soup where it belongs.
It might be possible to extract useful power from a molecular turbine
operating in the 8 km/s air stream, which would alos keep temperatures
low in the captured gas.

There's a lot of gadgetry in low orbit whose operators would look dimly
at many large tethers sweeping through their volume routinely, though.
LEO is too damn crowded for tethers.

Doug Jones, Rocket Plumber
XCOR Aerospace

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