Lunar Space Elevator Instead?

koa writes "We have all seen articles on building a Space Elevator on the earth, how about this article about experimenting with the Moon first since the technology we have available to us is sufficient, as the Moon's gravity is 1/6th that of Earth's (the cable weight would require less exotic materials such as carbon nano-tubes). One could make a very good argument for commercialization of Space if getting materials to and from the Moon's surface was vastly cheaper and easier."

Comments

Re:Sure, you could, but...

[ZorbaTHut]

"A lunar space elevator would work differently than one based on Earth. Unlike our own planet, which rotates every 24 hours, the Moon only turns on its axis once every 29 days; the same amount of time it takes to complete one orbit around the Earth. This is why we can only ever see one side of the Moon. The concept of geostationary orbit doesn't really make sense around the Moon.

There are, however, five places in the Earth-Moon system where you could put an object of low mass - like a satellite... or a space elevator counterweight - and have them remain stable with very little energy: the Earth-Moon Lagrange points. The L1 point, a spot approximately 58,000 km above the surface of the Moon, will work perfectly."

In other words, RTFA.

Re:Moonbase would be in the always-lit north

[danila]

RTFA. The logistical problems consist of launching 7 tons of kevlar cable to the L1 point 250 000 km from Earth. I am not saying there are no technological obstacles to overcome, but compared with Cassini probe or Mars rovers this is a piece of cake. There are existing rockets with that launch capacity, it doesn't take long to get there, it's cheap, easy and we get to test the space elevator prototype. There is simply no reason not to do it in the next few years.

Doesn't anyone read the actual article?

[Fraser Cain]

I wrote the article, and now I'm reading through the Slashdot comments, and they're killing me. Didn't anyone actually RTFA?!?

Let me clear these up...

1. The cable would be 58,000 km long. This is the distance from the Moon to the L1 point, which is the balance point of gravity between the Earth and Moon. The Earth pulls the elevator straight using its gravity. If you looked at the Moon from the Earth, the space elevator would always be at exactly the same place on the Moon, always pointed directly at us, like we're tugging at it with the Earth's gravity. This has nothing to do with centrifigal force, like an Earth-based elevator where the counterweight keeps the cable taut.

2. Because of low gravity on the Moon, you could build the elevator with commercially available materials on the market today, like Kevlar or M5. The cable would be light enough that it could be launched on a single heavy lift rocket available from Arianespace, Boeing or Lockheed Martin.

One launch = one lunar space elevator

3. You could connect a second cable to the Moon's south pole, so the two cables form a V, and then bring up water ice from the south pole. This would put water, air and rocket fuel into high Earth orbit at a fraction of the price of bringing it up from Earth.

4. As you make the cable longer, it allows you to kick objects into high-Earth orbit. You could transfer materials from the Moon into orbit for relatively little fuel.

what resources?

[dspeyer]

Mining the moon is of very limited value.

Almost the entire highlands surface is composed of plagioclase. You can extract glass and maybe aluminum from that. You might be able to create dopes silicates for electronics, but you'd probably need to bring trace elements from earth. The Mare are a little better: they're basalt. You can probably get Iron there, maybe some other metals as well. Maybe not. In general, there won't be much in the may of heavy metals, because the moon doesn't have mantle convection and volcanism to make them accessible. It certainly doesn't have hydrocarbons, which we need a lot of.

We could probably mine the moon for a few things, but most of our materials would still come from Earth.