With all the talk of space elevators, I had to bring up what I think is a better approach. The space pulley is basically two elevators, one going up while one goes down. When you need to launch something into orbit, you put your satellite on the elevator at the bottom, and someone up at the space station puts something even heavier on the elevator at the top. Gravity pulls the heavy object down and the pulley lifts your object up. We use friction to keep the speeds reasonable.

What would we want to bring down?

The first thing is space junk. There's lots of it up there, and you can sell it on eBay.

The second thing, once you've exhausted space junk, is asteroids. With these, you can lift up really heavy satellites (which will become the space junk of the future), and you can bring down some raw materials which will be worth plenty in the commodities markets.

The third thing, which might be harder to find, is comets. You can bring some comets down in Egypt to provide fresh water to irrigate the rest of the country.

You might also want to bring things down to harness the gravitational energy. As with hydroelectric dams, you can generate energy when things fall.

Don't tell me it's impractical. The description of my blog is Amit has crazy thoughts, so I'm required to post things like this!

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Unknown wrote at Monday, May 28, 2007 at 3:09:00 AM PDT

gravitational force = G * m1 * m2 / (d ^ 2)

How do you get something which is orbiting the earth to fall toward it?

I'm not saying that a dual elevator system isn't possible, I'd just like an example of how one would work. For instance, how would you put one of those tungsten rod clusters into orbit?

Amit wrote at Saturday, June 2, 2007 at 9:54:00 PM PDT

The space elevator is not stationary relative to orbiting objects; you'd need to catch one as it goes by, which will decrease its velocity enough that it will no longer be able to stay in orbit. Once its speed matches that of the stationary object (the space elevator/pulley), then you can use it as a weight.