Let's do a back of the envelope calculation: https://www.google.com/search?q=(pi%20*%20(radius%20of%20the...

If a satellite in low-earth orbit has a cross-section of 10 meters, then the timescale for hitting the space elevator is about 300 years.

Given that there are about 3600 satellites in orbit (http://en.wikipedia.org/wiki/Satellite), a satellite would crash into the space elevator about once a month.

2. What's the cost of building and maintaining a space elevator?

3. What's the cost of having a satellite climb the tether to an altitude of 35,000km? That's a lot of energy.

Taking this into consideration, is it tantalizingly cheap compared to strapping on a rocket? SpaceX has run tests with a reusable Falcon 9 rocket. Cost of fuel for a launch is $200,000. I'm skeptical the space elevator would be much cheaper.

The magic of SpaceX...

http://www.youtube.com/watch?v=9ZDkItO-0a4

Downside of a rocket, it's heavy, and most of the energy is wasted lifting the rocket, and not the payload. Advantage, you don't have to pay to maintain cables that are long enough to wrap around the entire Earth.

Or just an up line and a down line like most cable cars.

Orbits are quite predictable, and moving the tether around isn't all that bad--after all, it makes getting fuel to LEO altitudes cheap. Also, I would expect active sats to avoid the tether, and the presence of a tether will make removal of dead sats both desirable and much easier.

One would also expect the tether to be multi stranded (which is not so hard once you already have one). You would want at least two, up and down. If erosion or collision in LEO looks problematic, you could run even more stands in that area. It's only a few hundred miles.

My main concern is the lack of a good market to justify investing in a tether. It's only a good deal if there are enough trips to amortize the cost. Hopefully we'll see rockets become cheap enough to help develop larger uses in space that will justify something like a tether.

If it just destroys the satellite, I'm kind of tempted to say "who cares", because by then we will have other solutions, or satellites out past the counterweight, or we can easily launch more now that we have the fancy elevator, or whatever... but then we'd have the problem of an unimaginable amount of space junk orbiting the earth.

I almost wrote "nothing man made", which is true for anything we can do now. But if you think scifi enough there's little that can't be done. Turning the Earth inside out is quite possible for certain levels of civilization.

The Moon is yanking the Earth around, but even something that stupendously massive doesn't do much damage (the tidal forces are nothing to sneeze at.. but the 'wobble' caused by the difference between the Earths center of mass and the Earth-Moon barycenter (the point that the Earth and Moon both orbit) is negligible in nearly every consideration).

This would absolutely not be a concern.

You say that now, but I remember that years ago, when nanotubes were hailed as the material that would make the space elevator possible, people quickly pointed out that nanotubes were still not strong enough to carry their own weight over such a tremendous distance.

What changed? Why are nanotubes now strong enough?

If launching satellite becomes cheap with space elevators. You are going to have absolute mad rush to launch satellites, any way. In any such situation, you will have a lot of satellite traffic up there and merely managing that traffic among satellites itself is going to be difficult.

But even if you discount space elevators, if cost of launching satellites gets cheaper by the day. At some point you have to worry about this satellite traffic problem.

Services that need to be done away from the equator (monitoring of the surface, communications at high latitudes) would still need orbits like todays LEO sats. The same model of discrete satellites may prevail, but you might also see larger platforms housing multiple services.

We might see a tether vastly increase the amount of orbital activity, but decrease the number of discrete objects.

The value of the tether would be so high that it would be worth the cost of keeping every satellite diverted around it.

The best option energy wise would be to have the satellite adjust its obit however that would deplete its energy reserves a lot quicker then not having an elevator to avoid colliding with.

Then again satellites should never have energy problems ever again since the can just be refueled cheaply via the elevator.

The best option is to do the math first and plot an orbit that will avoid all the existing known objects for the given satellite's entire active period. And maybe a built-in decommissioning mechanism that will throw it back to the ground afterwards.

Lets say the cable is 1m2 thick: 1m2 * 100000m (Kármán line) = 100000m3. Maybe this doesn't sound like a lot until you check the prices of nanotube-like materials.

2 cm^2 * 10^8 m = 20000 m^3. Yes, it's a lot of nanotubes, but the price of nanotubes per unit mass has dropped exponentially for a long while now, and the economies of scale involved in building a space elevator will lower the prices even more.

Of course, it would prove harder to build it in those cold regions.

Edit: http://gassend.net/publications/NonEquatorialUniformStressSp...

There's a continuum between guns and rockets: you can fire a projectile with a motor on board. That lets you launch with a lower speed, but you have to lift fuel along with your payload. It's a tradeoff.

Space elevators step outside the tradeoff because they add energy to the payload during the trip, to avoiding the drag cost, but don't have to lift the energy as fuel, so avoiding the weight cost.

Iraq (with a Canadian scientist) almost made an artillery piece capable of putting material into orbit. Obviously, international sanctions gummed up the project a tad and it was basically over when the scientist was assassinated. Still, it was within the realm of possibility. Only recently have rail-guns started to usurp chemically propelled artillery in some roles, so it's not out of the question that rail-guns could put material into orbit. Even if the associated forces are too extreme for most equipment to survive, it could provide a way of getting raw materials into orbit at the very least.

I think that it poses an interesting engineering problem, not unlike the space elevator. If given enough velocity, a projectile with retractable wings could be launched into an atmospheric gradient and generate lift after leaving the accelerator.

Whether or not we have materials used on the craft could survive the acceleration to escape velocity is the big question. It would take some serious testing.