The Space Elevator Thread

[tnphysics]

This thread is for any discussion about space elevators.

They would provide CATS IMO.

[A_M_Swallow]

We could build a Space Elevator on the Moon with current materials such as Kevlar and M5.
http://en.wikipedia.org/wiki/Lunar_space_elevator
Lifting many tons of carbon will be very expensive.  A stronger version of glass fiber (silicon) that can be manufactured from regolith would be nice.

Mars's moons get in the way of building a space elevator on Mars.  However attaching a long tether to Deimos would be nearly as good.  A say 5 mile flight to the surface could be used.  Alternatively the tether could be winched up and down.  Rotovators have also be suggested.

The Earth Space Elevator needs a very strong material inventing.  Carbon nanotubes have sufficient theoretical strength but materials currently on sale are an order of magnitude too weak.  The coming power beaming challenge may reveal a stronger material.

[coach]

http://physorg.com/news110727530.html

Here's some brand new stuff regarding nanotubes and the matrix material they would be bonded into.  The major hurdle in building the SE is that the material doesn't yet exist.  The good news is that carbon nanotubes are theoretically strong enough so we have a path to follow.  


Coach

[tnphysics]

That's good.

Now, what is the optimum trajectory for an elevator extended beyond GEO being used for lunar missions?

[PurduesUSAFguy]

This is the kind of high-risk, high pay-off technology that NASA should be pursuing through an arm dedicated to such advanced research, like there own version of DARPA, maybe they could call it the NASA Institute for Advanced Concepts, or NIAC for short.


...oh wait...

[tnphysics]

Good idea.

[BarryKirk]

Well, I like the idea of a Space Elevator... but.  As a first step, a rotovator would be far easier to build and could make a huge dent in the CATS problem.

With a proper rotovator, true re-usable cheap SSTO would become a possibility.  Once we've got rotovators operational and the bugs worked out, then and only then should we be looking to see if the next step, a true space elevator is viable.

[khallow]

Barry, I don't see a rotovator working from Earth's surface due to a combination of air resistance losses (both in winding up to speed and operating at speed) and just the physical space that the rotovator would operate in. If you were speaking of using this on the Moon, then that would be a different story.

[chazmataz]

khallow - 19/10/2007  7:46 PM

Barry, I don't see a rotovator working from Earth's surface due to a combination of air resistance losses (both in winding up to speed and operating at speed) and just the physical space that the rotovator would operate in. If you were speaking of using this on the Moon, then that would be a different story.

Nobody is suggesting that a rotovator that lifts payloads all the way from the Earth's surface to LEO would be practical with current technology.

What I believe Barry was suggesting is a rotovator which captures and lifts fast-moving payloads from the high stratosphere, at least 50 miles up, and gives them a boost of between two and four km/sec to place them in LEO.  See tethers.com for more details.  It is much technologically easier than a space elevator, and could be built with current materials.

[BarryKirk]

I was referring to a rotovator in LEO.  It would reduce the delta v required for a rocket to acheive to reach LEO.  Small reductions in required delta v to acheive orbit make for massive increases in payload mass fraction.

And if the delta V is decreased enough ( read that large and capable rotovator in LEO ), SSTO re-usable becomes economical.  The rotovator can also reduce the heat shield requirements on the trip down as well as using downmass to help reboost.

The rotovator can be re-boosted by any number of methods including EM against the earth's magnetic field or high ISP electric rockets.

The whole point is that a rotovator could substantially reduce cost to acheive LEO and would be cheaper and technically easier to build than a full blown elevator.

[colbourne]

Once we have rotorvators working successfully, and I believe they will be made to work, there will be almost no area in which a true SE will offer any real advantage.
Space elevators are going to be slow, limited to low mass loads and due to their extreme size very costly to build.

The problem that both the SE and rotovator will suffer from is that they will both interfere with existing satallite orbits and some kind of active avoidance will have to be allowed for .
It should be possible to build a series of rotorvators that will pass loads from one to another to launch loads towards other planets and support colonies.


If we do decide to go ahead with a sunshield to prevent global warming , some kind of cheap access to space could be very useful, and the rotorvator would provide this.