Building a space elevator would stimulate the economy

Indeed, you can hang a counterweight on the space side and make the cable shorter. However, the idea only works if you are in a geostationary orbit, which means that you need to be at least 22,236 miles above the surface of the Earth. You also have to lift a massive counterweight into orbit. (In fact, the center of mass needs to be above geosynchronous orbit, so it’s actually longer than that…)

Who says it will cost $50 billion dollars? The Apollo program cost $25 billion dollars back in the 60’s and 70’s. That’s $125B dollars in today’s money.

The mass of the cable is extremely sensitive to the density and the strength of the material you build it out of. Even if you have magically strong and light buckytubes, you’re still looking at around 13,000,000 kg of the stuff. And the smallest cost I’ve seen for a gram of the stuff is $25. So we’re talking about $300B just for the raw materials.
Worrying about what happens when it breaks is actually a fool’s game, because if you can build it, you already have an army of wizards on your payroll. Just have one of them magic it back together the same way they magicked it into being in the first place.

It’s because the orbit it’s in isn’t stable.

Another problem to solve are the thermal issues. It’s an enormous cable which is spending part of its time in sunshine and part of its time in the dark.

Oh, and oxygen tends to destroy the nanotubes.

NASA estimate from 2003 was ~$10 billion to build one over 15 years, with technical costs around ~$6.5 billion.

And Japan thinks it’s doable. And here’s a list of cost estimates.

There is a company floating the project but it ain’t doing so well.

Just my semi-technical opinion…

The cable breaking presents no real danger to anyone, besides of course the people very close to it or on it.

It would be quite spectacular visually and one hell of a disaster financially, but as any kind of threat to the general population? …meh…next worry please…

There is a megadistaster scenario plausibly portrayed in Ben Bova’s novel Mercury.

One thing to remember about a space elevator is you do not need the entire mass of the cable up at once. Remember to build a suspension bridge… Shoot a small cable over to the other side, then pull the rest of the cable across… Now, likely it would be impossible to pull the cable up with a smaller one, but construction materials could be pulled up.

So you don’t need to get a lot of the millions of kg of material into space right off the bat using normal, innefficient rockets.
Personally though, I think a launch loop is a much more feasible idea.

How hard would it be to destroy this thing? Could a single madman/terrorist bring the whole thing down with a small plane? Or would the strength of the cable be sufficient to withstand that kind of impact?

The cable doesn’t have to be a massive thick structure. In fact the proposals for the first generation cables are for a cellophane-thin ribbon which can still hoist several tons at a time. The mass to be boosted to geosync orbit thus becomes workable. If it broke, what didn’t burn up on impact with the Earth’s atmosphere would float down like confetti. In that sense, the concept is scalable- you can start with a small one and only expand once the bugs are worked out.

The “NASA Report” is a study that was apparently funded by NASA through a child organization meant to showcase big ideas for the future. The budget rundown was made by the same guy, Brad Edwards. The estimate on the spaceelevatorwiki and in the 2003 report seem to use the same data. I call your attention to the part of the table where he accounts for the cost of the cable itself at $75M. This figure is arrived at by taking 750,000 kg of CNTs at $100/kg. Where does the $100/kg figure come from? In 2003, someone at the Mitsui corporation told Dr. Edwards that Mitsui would be producing 10 tons of CNTs per month at a cost of $100/kg.

Of course, the lowest actual price yet recorded is $25 per gram. Using this as our cost for the cable (not of actually building the cable, just collecting the stuff we’re going to build it out of) we have a cost of around $19B for the cable. The rest of the numbers also appear to be just stuff he pulled out of the sky.

It’s not really an issue. The average person would have to eat a couple of hundred space elevators before they’d get cancer.

I rather favor the Space Fountain concept, anyhow. Probably safer in the long run.

The cost today is totally irrelevant. Clearly lots of work has to be done on the material, and on manufacturing. We can expect some significant economies of scale, to put it mildly. Who uses this now? If it is made in a lab, $25 a gram is pretty cheap. But saying this is a limiting factor is like saying the Web is impossible because of the cost of mainframe computers in 1964.

You also might have to move it to keep things from crashing into it. Not far, but the possibility exists.

True, but you’d have to get the construction infrastructure up there. Look how much the space station has cost. The base for this operation is going to cost a lot more, be bigger, and include a lot more people.

Probably wouldn’t be hard, but from what I’ve read it would be built out in the ocean, along the equator away from hurricanes and normal aircraft flight paths. It’d probably require some security but hey, we’ve got a Coast Guard and Air Force, among other things.

The cost today does matter if you’re claiming, as Edwards is, that this is a project which can and should be undertaken within the next few years. Also, he doesn’t appear to explain where any of his figures come from. What is his justification for a cable mass of 750,000 kg? If you build the cable without a counterweight it works out to, best case scenario, 13,000,000 kg (w/ a density of 1.3 g/cm[sup]3[/sup]). Cutting this cable in half an attaching a whopping big counterweight, you get 7.5 million kg, which is only an order of magnitude off of Edwards’ number. Of course, where did his figures come from? Who knows.

By the way, I’m getting my numbers from here. The original language was croation, but he at least has the right equations. I haven’t checked them all myself, but the things he says are reasonable. By contrast, Edwards just makes grandiose proclamations about powering the thing using space lasers beaming power back and forth. :rolleyes:

As to part of the OPs questio, No there are no funds in the stimulus bil directly for a space elevator. In fact there are no funds for any specific projects at all. However, there are research funds for various broader categories that potentially a space elevator could compete for and get on its merits.

Outside of it being really cool, what exactly is the point of a space elevator? Do we really need to put that much stuff in orbit (and is there even room) to justify the massive cost of a space elevator when we have a proven technology already capable of the same task.

Well, yes and no.

We could take the whatever billion we spend each year putting a few people into orbit and few really light probes to other planets and instead put many more people into orbit, go to the moon, asteroids, mars, and send some hefty and much more capable probes to other planets.

REALLY big telescopes in orbit would probably be the most “concrete” benefit.

If you can get the cost per pound WAY down from how we do it now, solar power in orbit might be possible.