In article ,
says...
(Henry Spencer) wrote in message ...
The old Luna sample-return missions maxed out the Proton -- in fact, they
needed Proton performance enhancements and reduction of safety margins --
to return a few hundred grams of sample. Yeah, the hardware was pretty
crude stuff and we could do better, but it's a demanding mission, and
trying to squeeze maximum payload out of a mass-limited system will get
expensive fast.

If you use an ion-drive to get to lunar orbit and back and a tether to
collect samples, you don't need to be so mass-limited in your design
and you could bring back much more lunar mass. The difficulty of having
the end of the tether pickup some samples seems much less than having
a couple more rocket stages. An easy mass margin design should be much
easier on R&D money. A Falcon-V would be plenty of LEO launch capacity.
Yes, you would still need to plan on some failures. Having a few backup
winch/tether/scoop modules seems easy. Even loosing all your tether lift
ability after lifting only 1/10th of your expected 10,000 Kg would still
have you well ahead of the non-tether design. So if your goal is to make
a profit returning lunar samples, using a tether to pickup samples from
orbit seems a less demanding mission that will return far more product.

I think you're *really* underestimating the difficulty of designing and
building a tether that can hold up to the conditions it would encounter,
as well as the difficulty in operating a scoop at the end of such a
tether on what are predominantly rolling and hummocky terrains.

Remember, our one and only attempt to deploy a long tether in LEO met
with failure and near-disaster. I'm aware that the conditions in lunar
orbit are different than in LEO, but still, it seems to me that until we
demonstrate something as simple as deploying a 20km tether in LEO, we're
talking out of our asses when speaking of 100km tethers pulling up lunar
materials from orbit.

I'd really like to see a materials engineer chime in on this one...

Doug