Thinking random thoughts about our space program (which, as a religion, makes this automatically a GD issue) and considering the Moon Base and a Space Elevator, it struck me that nobody seems to be seriously considering a Lunar Space Elevator (aka a moonstalk).
All the impediments to an Earth Space Elevator are non-existent on a moonstalk. It is well within the reach of our current technology; it would open half of the moon surface for exploitation; it would make lunar exploration cheaper, simpler and less risky; it would make a great testing facility not only for an ESE but also for a Martian SE. I just don’t see any reason not to get going on it.
I would just like to open this thread for any thoughts about such a project.
I doubt that’s true. Conservation of angular momentum springs immediately to mind, plus many of the sheer difficulties of engineering don’t completely vanish.
The whole thing still sounds like something out of Civilization IV, but I think it could work- basically, a lift to a Space Station, whereupon you board your Pan Am Clipper/Space Shuttle and then head for that hotel on the Moon we were all promised back in the '60s and '70s.
We may even see it in our lifetimes, especially if we can get the various Space Agencies to stop bickering and co-operate with each other…
It seems from my Pierian-sipping perspective that there are no real technological barriers to a LSE the way there are to the ESE. I would welcome an explanation or link to the issues you find. Wiki mentions the matter of angular momentum as an issue to consider more than as an impediment.
And I am not even thinking of human transport. Imagine dropping mining robots anywhere on the surface of the moon at no cost and having the results put back in orbit by a conveyor belt. Sending them back to Earth orbit would also be a minimum cost operation. Remember that transit time is not really an issue if there are no humans involved.
You may be right, but it seems to be the case that the whole article does that. As with interstellar travel, this particular topic does seem to generate the kind of massive optimism that results in people saying “Yeah, but that’s just a minor engineering problem, I expect they’ll just solve that” to any and every obstacle, no matter how difficult.
A Moonstalk would provide a quick, cheap way to get things from the Lunar surface into Lunar orbit – but lack of that isn’t the main reason why we don’t have a Moonbase yet, is it? The big hurdles are at the Earth end of the trip.
Yes but if you could mine the fuel for a Mars trip on the Moon and not have to lift it from the Earth, that would be a great time saver. If you didn’t have to worry about taking off from the moon, that increases your usable payload when you take off from the Earth.
It may not be the only hurdle but it is a serious one that needed to be solved at some point or another.
The biggest objection to a Moonstalk that I can see is that it doesn’t do anything a lunar mass driver wouldn’t do, and we have a much better idea of how to build them than we do a Moonstalk. (The second external link from Wikipedia is pretty good reading!)
To get to Moon orbit, you have to get up there from its surface and you have to get up to orbital speed, and the potential energy and kinetic energy required have to come from somewhere. As something climbs the Moonstalk it gains PE directly from the lifting mechanism, but the KE comes from the rotating Moon, so your energy bill is smaller than with a mass driver. Whether energy is likely to be a scarce commodity on the Moon, where sunlight is hellish strong and you can set up very flimsy focusing mirrors without worrying about the wind, may be the determining factor.
Earth based mass drivers have that pesky atmosphere thing to contend with, but that hasn’t stopped people from thinking about it.
At first glance, I thought the OP was describing an actual Earth-Moon tether, stretching a line 250,000 miles long presumably with a mobile base on Earth the size of an aircraft carrier sailing around the globe every 29.5 days.
Compared to that, a lunar elevator is practically a LEGO project. Seems to me a much easier way to lift objects off the lunar surface is with some kind of mag-lev deal, shooting a payload along rails until it reaches escape velocity. With no atmosphere providing friction, acceleration should be easy enough. Power it with a Helium-3 fusion reactor and you’re good to go.
If the numbers in the Wikipedia article are correct, it seems that the length of the cable needed would be a problem.
and
So to offset a 1kg mass at the surface, there would need to be a 1,000kg mass 82,000km off the surface on the Earth side, or 187,000km off the L2 point. With the average distance between the Earth and the Moon of about 384,000 km, that’s a moomstalk that stretchs 21% of the way from the Moon to the Earth.
I think that would be an argument AGAINST using it.
At any rate, a mass driver is just as good as a moonstalk. The net result is the same, lifting stuff without having to ship the fuel needed for take off all the way there. That is, of course, on the wild assumption that there is something there that we wan’t here.
The stalk has small advantage at setting stuff down but if a mass drive is so much easier, then that’s just a tradeoff that needs to be calculated
The question remains, though. If we are seriously talking about a moon base, whay aren’t we thinking of better ways to move stuff back and forth? Why are we still thinking in terms of super inefficient rocket engines?
Heck, even with just two half decent orbital stations at both ends you already open the door to ion drives to move the stuff from here to there. Just about anything is better than rockets.
The only real players in the space game have been NASA and the old Soviet Union. The Soviet Union doesn’t exist any more and couldn’t afford it when it did, whereas NASA lost its pioneering spirit somewhere along the way.
There was a BBC series and associated book Spaceship’s of the Mind that documented a lot of exciting ideas generated in the sixties and seventies - ion drives, solar sails, lunar mass drivers, Earth-based laser launchers, space-based solar power, nuclear heat-exchanger rockets (NERVA - got as far as a working test unit with an ISP of 1100), nuclear pulse drives (project Orion, killed by a nuke-limiting treaty) and more. Pournelle’s Step Further Out has similar material. But it takes huge investment for such projects, and while the potential returns are similarly tremendous, politicians lack vision and courage. Without the Cold War to stimulate them into international dick-waving, there just isn’t the motivation for much more than publicity stunts.
The OP is talking about a moon-based space elevator, not a tether linking the earth and the moon (although I admit, I made the same misunderstanding when I first came across this thread).
