From: Jeff Davis (jdavis@socketscience.com)
Date: Fri Dec 10 1999 - 12:31:03 MST
On Wed, 08 Dec 1999 18:58:23 -0800
Doug Jones <random@qnet.com> writes:
>The tradeoffs are not immediately obvious. I think the moon's south pole
>
>might be best *if* volatiles can be extracted, since it would have frequent
>
>launch windows, short travel times, and reliable power (if only in limited
>
>geographical locations). While the delta-V for landing is high, the short
>
>trip time allows use of high performance cryo stages.
At the risk of seeming crackpottish, I have an exploratory suggestion re
the lunar landing delta v problem and the scarcity of water, etc.
(hydrogen, oxygen, and carbon) problem. Since, sans atmosphere, it is
possible to orbit the moon mere millimeters above the surface, might it not
be possible to set up a "landing system", ie, a moonport equipped with a
mechanism to catch and decelerate inbound vehicles? Vis the system
employed on aircraft carriers.
If the inbound vehicle was, at the same time, equipped with a
"conventional" liquid oxygen and liquid hydrocarbon fuel rocket
braking/landing system, for backup/safety/redundancy, then, when the
vehicle lands by "capture" the rocket fuel becomes cargo, which can be used
first as fuel, and then as water and a source of carbon.
This might kill two birds with one stone,... or at least scare the hell out
of them.
I did some math last night to figure out the lunar orbital velocity. Came
up with 3725 mph. If earth orbital velocity is 17,500, then a lander
inbound from lunar orbit has a "mere"
( 3725 / 17,500 )^2 = 0.0453
of the kenetic energy of the same item inbound from earth orbit.
Now if the capture cable was bungi cord, with the other end attached to an
outbound vehicle, you could catch one and launch one at the same time. :-)
Hmmm. A bungi cord launch system? Setting aside the excessive complexity
of a simultaneous capture and launch arrangement, I wonder if this has any
merit. It certainly is elegant in its simplicity. I like elegant. I'll
have to do some calcs. In fact, I'm thinking that a mass driver may be a
bit more tech than is needed (though I'd be delighted to here of the
elegance available in mass driver designs). I wonder what other low tech
options are available for getting a lunar vehicle up to the
not-very-intimidating-speed of 3745 mph. Suggestions, anyone?
Best, Jeff Davis
"Everything's hard till you know how to do it."
Ray Charles
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