(Vincent Cate) wrote in message . com...
(Charles F. Radley) wrote in message
. com...
Nice idea, but not original. Hoyt, Forward and Moravec have each
proposed using tethers for lunar landing and sample return some
years ago.

I realize that they proposed tethers for the Moon; however, I have
not seen them point out that you could pick up samples without any
infrastructure in place on the Moon. The thing that might be
original is that a single probe, with no advance landing on the moon,
could use a tether to scoop up samples.


The Hoyt/Forward proposals do not need infrastructure on the Moon.
A bit of infrastructure might be nice to collect the specimens ahead
of time and make them ready for pick-up, but that is not essential.


If we use an ion drive of 10,000 seconds ISP, it is throwing xenon
out the back at about 98 km/sec. To pick up something from the
Moon we need to give it 1.6 km/sec of momentum. So 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.


OK. Whether that is better than zero momentum exchange depends on
whether you are interested in putting payloads on the lunar surface.
Since soft landing on the Moon using rockets is extremely expensive,
the tether method of depositing payloads is much cheaper. It would
open up new markets for lunar development.

Adding an ion drive has the advantage of lowering the amount of mass
which must be launched from Earth, but it loses the opportunity
benefit of soft-landing lots of payloads on to the Moon.

For the details, take a look at these web links:

http://www.tethers.com/MXTethers3.html

http://www.tethers.com/MXTethers.html

When I say "lunar sample return" I mean that there is nothing already
in place on the Moon. I have not seen anything in these or any
others papers I have read that indicates they were thinking of a
sample return type mission. Sure people have looked at Lunar

True, their paradigm is rather the inverse, soft landing high-value
payloads on to the Moon. They did not recognize collecting lunar
samples as a significant market.

You have taken the precise opposite viewpoint, going for the lunar
samples, and ignoring the oppportunity to soft-land payloads.

Perhaps reality will be somewhere in between.

tethers. And I do think that two way lunar tether traffic would be
*really cool*. In particular once we have lots of tourists going to
the moon and coming back.


In the short term we can soft land lots of infrastructure on to the
Moon basically for free (except for the cost of launch from Earth),
and build hotels ready for the tourists when they come.