Re: retrieving material from asteroids

"Fred J. McCall" <fmccall@xxxxxxxxxxxxx> wrote in message
news:gpv202pm5o5usqj40nb814t70nvqkdajam@xxxxxxxxxx

The big problem with the whole 'mass driver' concept is that you're
spraying rocks at high speed out into orbits which will potentially,
at some future time, intersect some other vehicle. Not sure it's a
great idea even if you grind it up into fine dust first.

True, but interplanetary space is already criss-crossed with small grains of
matter traveling at high speeds. So the only sensible question that needs
to be answered is: Are you increasing an already-existing hazard to a point
where the gains don't justify the increased risk. We might could do a
significant amount of activity in this way before the contribution we're
making to the problem becomes significant.

One way to mitigate this problem entirely would be to ensure that all of
your reaction mass is ejected at a speed in excess of solar escape velocity.
Although I've heard it said that the scenario is a lot more energy efficient
using larger volumes of lower velocity reaction mass.

In the High Frontier proposal, they only recommended using regolith for
reaction mass until the orbital ore refineries were up and running. Past
that point, they recommended switching over to liquid oxygen, which would
vaporize after release (and we'll be producing more of it than we need).

--


Regards,
Mike Combs
----------------------------------------------------------------------
By all that you hold dear on this good Earth
I bid you stand, Men of the West!
Aragorn


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