Anti-mass-driver

Subj: RE: [ssi_list] Anti-mass-driver
Date: Fri, 6 Apr 2001 11:51:32 AM Eastern Daylight Time
What dol you think of the closed cycle momentum exchange tether system for delivering payloads to the surface of Luna, and carrying payloads to Earth ? It would cost a lot less than a mass driver based system. The investment would pay for itself versus a rocket based system after 17 missions.

I think it all depends on what your mission is. If you are exchanging large payloads at infrequent intervals,
and there's two-way traffic which is pretty close to being balanced, then a tether system is obviously
better. If you instead are trying to get lunar resources out of the moon's gravity well, then I think the
mass-driver is better, because instead of launching a several ton payload every few hours, you're launching
kilogram payloads every second. The latter can form a kind of "mass-pipeline" streaming up from the
moon.

In that case one would expect the total mass sent up from the moon to outweigh the equipment we
sent down to the lunar surface by a substantial ratio.

Regards,

Wow I had thought the problem would be the reverse, a severe shortage of delivering terrestrial equipment to the surface because of the high cost of doing so. This is whether the tether is very attractive.

Using "regenerative braking" to capture payloads on to Luna is a possibility, but does require some very
Precise engineering because of the high closing velocity. The tether system actually soft lands the payload in a gradually decelerating profile with a final closing velocity of zero.

To reduce the mission interval requires increasing the number of tethers, there is no theoretical limit. But there could be practical problems of interference between the tethers if they are too close together.

As for balancing the mass landed on the Moon versus the mass launched: this is fairly easy to do :- Ballast.

Fill the moonbound containers with carbon, nitrogen and hydrogen bearing items, e.g. organic materials, and water - we can never get too much of that on Luna, there will always be a market for it.