In article ,
Vincent Cate wrote:
You can do it entirely with zero momentum exchange, you simply
deposit payloads on to the lunar surface whose mass equals that of
the samples you remove.

...with the momentum
from 1 Kg of xenon we can pick up 98 kps / 1.6 kps or about 61 Kg
of regolith. If you simply deposited equal mass on the lunar surface
you would only pick up 1 Kg for every 1 Kg you put down. So this way
is cheaper for a probe on a sample return type mission.

Yes and no and maybe. It uses less fuel, but that does not necessarily
equate to "cheaper". The issue is not fuel cost -- xenon is one of the
few fuels whose cost actually *is* comparable to LEO launch costs, but
even so, that's a relatively minor issue here -- but hardware costs and
complexity and reliability.
--
MOST launched 30 June; first light, 29 July; 5arcsec | Henry Spencer
pointing, 10 Sept; first science, early Oct; all well. |