sounds like they're off by an order of magnitude and the wrong units: 25,000 MILES is the distance to Geosynchronous orbit: an orbit at 250,000 kilometers would lag behind earths rotation, wrapping the cable around the equator...

Well, Ptah, they have to put the center of gravity at 25,000 miles (actually, a little less, because of drag on the cable in the earth's atmosphere), so they need mass beyond 25,000 miles to balance the mass that's between the earth's surface and geosynchronous orbit.

And the answer to Ptah's question is the answer to oj's: They can't run the cable all the way to the moon because it would wrap around the earth as the moon orbits. So, 250,000 km is the farthest they can put it out while maintaining the center of gravity in geosynchronous orbit.

Basically, they have a space elevator out to 25,000 km, then use the counterweight to the space elevator as a catapult to the moon.

As long as you're dreaming, might as well dream big.

A pretty good, though incomplete, explaination of why 'space elevator' should be listed next to 'cold fusion' in the dictionary.

They should site the first one in Hyannisport.

"We bow to no one in our respect for scientific vision, but can any of you clever boffos explain why grown men and women would dream of building a 250,000 km catapault to send something 384,400 km?"

You're probably thinking of it as a single, linear cable stretching directly toward the moon. The article doesn't make the proposed design very clear, but it would seem that it actually involves multiple cables that twist in potentially complex patterns in earth orbit.

Of course, the basic reason is that although the numbers may seem mind-boggling, such a system is likely cheaper than sending cargo to the moon in rockets. Left unanswered is exactly what we're supposed to be sending to the moon.

Chris B:

Re: the space elevator and cold fusion, one is an engineering problem that, even on the site to which you linked, doesn't seem intractable. The other was a set of unreproducible observations of a phenomenon for which no one had an explanation.

In the interests of continuing the geekfest, try this riposte to Den Beste's speculations:

http://www.aoe.vt.edu/~cdhall/Space/archives/000550.html

And there's a lot more out there.

As a general rule, so long as you aren't dealing with violations of physical laws, you really don't want to be the one telling everyone that something can't be done.

" ... can any of you clever boffos explain why grown men and women would dream of building a 250,000 km catapault to send something 384,400 km?"

Yes, Peter. Gravity. That's the real problem. Getting your stuff into LEO (low earth orbit) is not easy. But that first 200 km of the journey is 99.99 percent of the problem. Once you have escaped earth's gravity well, getting to the moon is a stroll in the park. The catapult is to escape the gravity well. Recommend you watch documentaries on Apollo 11. It's obvious what colossal amounts of energy were expended to escape earth gravity and how little was needed in remainder of mission.

Will we finally be able to harvest all that cheese?

i didn't know kurt vonnegut had moved to scotland.

nasa should have been working on new ways of getting payloads into space, from day one. instead of wasting all their budget on the space shuttle. they didn't and now are being left behind by private companies.

Pepe -- actually, the catapult doesn't address the problem of escaping the Earth's gravity well, that's what the space elevator is for. Basically, an object placed loosely on the cable below geosynchronous orbit will naturally fall to earth; an object placed loosely on the cable above geosynchronous orbit will naturally fly out along the cable with increasing velocity and ultimately, if it never hits a stop, fly off the end. Thus, you can use the elevator to bring something out to 25,000 miles, then nudge it out along your catapult to the moon, and it will fly off of its own accord.

But your main point, that value of such a catapult is trivial compared to the value of the space elevator that gets you the first 25,000 miles, is correct. Rockets could do what the catapult does at relatively low cost. The objects on the catapult would still have to have rockets, to make a controlled landing on the moon, so the catapult would only save half the fuel. And all that catapulting might disturb the space elevator.

Orrin at least ought to be pleased that a 250,000 km 'slingshot' would be a wonderful weapon. A working space elevator would make it cheap and easy to drop giant rocks at hypersonic speeds on any point on the planet.

And, yes, you would like to have a 250,000km structure to reach 380,000km for the same reason you'ld like a 6 foot ladder to reach 9 feet; it's a lot easier than jumping the whole way.

The site noted by M. Bulger has a good partial reply to den Beste's objections. I've never tried to calculate the tensile forces on the space elevator, which I'd imagine would be quite large, but I'll take the word of those who have looked into it that there are materials that can handle it.

The bigger problem will be building the thing. You'd have to build downward from geosynchronous orbit, simultaneously pushing the elevator downward toward earth while pushing the counterweight out away from the earth. It seems a 25,000 mile construction job that would make working on the Golden Gate Bridge an acrophobic's dream.

The biggest problem would probably be ensuring safety when the cable snaps. I understand they would build this in the middle of the Pacific Ocean, to reduce the risk.

build it over nyc or sf.

Gigantic sligshot? What's the problem people? BUILD IT!!!! End Of Story!! Good Lord!!! Are we no longer men? Need I remind you of the prime directive? Once an idea, ANY IDEA, about explosions, digging, jumping over things or slingshots gets put on the table we have to do it(especially if the proposed idea has the word giant or gigantic in it).

What, are you guys chicken?