Comments on: Ep. 144: Space Elevators

By: Jerry Fox

Jerry Fox — Thu, 13 Aug 2009 21:49:58 +0000

There's an interesting Wikipedia entry on Tether Propulsion which covers the use of flexible tethers. Dr Robert L Forward set up a company called Tethers Unlimited Inc to develop some of these ideas. Arthur C Clarke explored some of the problems of a Space Elevator in "The Fountains of Paradise".
Another related concept is the Space Fountain – again, try the Wiki entry.

By: rarchimedes

rarchimedes — Tue, 04 Aug 2009 06:08:51 +0000

The danger of a cable breaking is not it falling on the Earth, as it is extremely light, and it is unlikely to break close to GSO, but someplace in the first 1,000 km or so. What is dangerous is that the counterbalance is likely to be moving at almost 100,000 km/hr, which will, lacking major countermeasures, yank the rest of the tether up through GSO along a very long arc, potentially damaging hundreds of billions of dollars of other satellites that are and will be in GSO. And, I would say that it is almost certain that any elevator will break at some point, because even theoretically, the load is close to the limit of materials. Every object, from the smallest to the largest, orbiting below GSO is likely to cross the path of a space elevator at some point in their orbital life, and many of them will be smaller than we can currently detect. We cannot even find all NEO's larger than 1 km in size, so it seems unlikely that we will be able to even know about, much less track, all the tiny particles that could cut a space elevator with the greatest of ease.

And Mitch, even if it were to take the same amount of energy(which it does not), it does not require rocket fuel or major fairing, nor does it require that the energy be expended in a matter of minutes. Most elevator writeups say that it is unlikely that the elevator will move at more than 200 km/hr and will require somewhere upwards of 200 hours to climb the elevator. With power that is not onboard the climber, you don't have to lift the body of a rocket anywhere, only the load and the weight of the climber. And, by the time you reach the altitude of one radius, gravity will be approximately one fourth Earth normal, and at GSO, it will be less than one part in twenty-five of Earth normal. The major issue is the horizontal force on the station at GSO and on the counterbalance out further. That must be compensated.

By: muz

muz — Wed, 29 Jul 2009 10:10:51 +0000

Mitch, they are looking at nuclear and solar power for it.

This is partly what the climber xprize is for.

By: Mitch

Mitch — Tue, 28 Jul 2009 03:03:04 +0000

Maybe I missed something — wouldn't it take as much energy to lift an object along the cable as it does to push the object with rocket engines? Is the advantage of the elevator just that we don't need to use rockets? What energy source could be used to lift the objects?

By: MattFenwick

MattFenwick — Sat, 25 Jul 2009 04:40:09 +0000

Thats really scary to think about. The cable being long enough that if it breaks it could wrap around earth causing heaps of destruction. O.o I don't think it would burn up in the atmosphere because weren't they going to make the cable out of some really crazy material, like carbon something i don't know.