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cjackson
2014-Mar-17, 05:27 AM
Where do scientists and engineers stand with regards to space elevators at the present time?

Should space elevators prove unfeasible is it possible that single stage to orbit access to space could be achieved frequently and economically by systems like Skylon?

Will there ever be an alternative to conventional staged rockets to reach orbit, or will this prove to be the only way to get off the surface of the planet?

Van Rijn
2014-Mar-17, 09:33 AM
The space elevator was just discussed in another thread here:

http://cosmoquest.org/forum/showthread.php?149446-Has-space-elevator-s-time-arrived

The first space elevator may be built on Ceres. Ceres has low mass and fast rotation, so current materials would be sufficient. I suspect Ceres will be a good source of material for space habitats, though we'll get a much better idea when Dawn gets there.

For Earth, rotovators or similar schemes are much easier. In that case, the tether is a momentum bank. The good thing is that a lift tether can be very useful even if it only handles 10% of the velocity change. And if it handles 50%, it would be easy to build single stage suborbital rockets to do the other 50%.

Here's an interesting paper on a cislunar tether system:

http://www.tethers.com/papers/LDC00Cislunar.pdf

In this case, there's one tether orbiting Earth and another orbiting the Moon. Here, mass sent from the Moon could offset the momentum lost by lifting a spacecraft from Earth. Alternately, the Earth tether could use electrodynamic propulsion (no fuel needed, and solar panels would provide the energy).

That could change the economics of Earth-moon transport substantially, and would give an incentive to bring back lunar or astroidal material. But this would be a "railroad" scheme - it is the sort of thing you'd probably not try until you already have fairly robust space infrastructure.

cjameshuff
2014-Mar-17, 12:16 PM
The first space elevator may be built on Ceres. Ceres has low mass and fast rotation, so current materials would be sufficient. I suspect Ceres will be a good source of material for space habitats, though we'll get a much better idea when Dawn gets there.

My bet would be a moon...either our moon or Phobos. Both are much easier to get to than Ceres.

A small near-Earth or captured asteroid is another possibility.

publiusr
2014-Mar-17, 11:30 PM
SLS? Too expensive.

22,300 mile tall Space elevators? Yeah--that'll be cheap.

Garrison
2014-Mar-17, 11:52 PM
Where do scientists and engineers stand with regards to space elevators at the present time?

Should space elevators prove unfeasible is it possible that single stage to orbit access to space could be achieved frequently and economically by systems like Skylon?

Will there ever be an alternative to conventional staged rockets to reach orbit, or will this prove to be the only way to get off the surface of the planet?

Well firstly yes a Skylon type vehicle could achieve frequent cheap flights but we are too far out from a working vehicle to say whether it will. Secondly don't dismiss conventional rockets; their costs can be reduced and work is ongoing to do so. That in fact is probably the biggest bar to the development of a space elevator; it simply won't be able to compete on cost per kilo basis.