I really hadn't thought this out very much. My thought was that you could combine two elevators: a tapered elevator and a loop elevator. The taper would provide the extra strength needed since the CNT is unlikely to be strong enough for loop elevators.This would be hard to do. Perhaps seperating the two laterally would work.I'm not quite sure what your getting at. Coriolis would affect every part of the SE. If this pulls the loop away from the main ribbon, wouldn't that prevent tangling?I was calculating the mass of a loop that had the same cross section as the bottom of the ribbon, but you are right, it is much too small.

The pictured loop is suspended from an attachment on the south side of the ribbon at GEO. It is not tapered and masses about 4680kg. Much of the weight does not cause strain on the SE because it is near GEO. The loop provides a link for direct mechanical energy to GEO as well as eliminating the need for lasers, photovoltaic arrays, motors, and wheels on the climbers. The problem of heat dissipation is greatly reduced. The overall energy efficiency is above the 2% expected for the laser system.

For some reason, I don't think this would work. I can't quite put my finger on it. Too tired to think, going to sleep.

Correction:
If you only send one transient at a time, the climber speed is limited by the speed transients propagate because the transients take longer and longer to reach the climber the further the climber is from the anchor station (assuming the transients originate at the anchor station). However, if you send multiple transients at a time, the climber speed is limited by the frequency and amplitude of the transients. The frequency of transients would depend on the danger of tangling.

It makes sense to have the transients originate at the anchor because you are fighting gravity on that side and it would be easier to control and supply power to transients on the ground.

How about rocking the counterweight back and forth to make the ribbons slide past each other? Or moving the anchor station back and forth? How about having 2 anchor stations that move independently? It seems however you do it you are limited by the speed at which transients can propagate. Moving the base station to avoid satellites and weather would also cause transients that may interrupt climber movement.

Well, if lightning does damage the ribbon, then the entire SE wouldn't be destroyed - just the bottom 1% or so. I would not give that portion of ribbon a great lifespan anyway. Despite repairs, micrometeors would likely destroy that section if it is not replaced after 20 years. There will probably be at least a hundred atmosphere tests of CNT threads before SE1 goes up. These would be long endurance tests and climber tests. If the threads are only about 59kg then you could test several at once at low cost.

One of the proposed uses of the space elevator is a GEO station that would allow research to be done in micro-gravity and space environments, as well as other uses. One requirement of such a station would be dependable transportation between the station and earth. The mechanics of moving people and equipment between GEO and earth would depend largely on the mode of transfer between the station and the SE. There are at least three modes of transfer that we can consider. The first is to have the station attached to the SE, where close physical proximity allows for direct docking. The second is to have the station separated, and design climbers capable of maneuvering the distance between the SE and the station. The third is to have the station separated, but use a docking arm to extend from the station to the climber.

A station attached to the ribbon may dampen transients and increase tensions near GEO. There would also be the problem of allowing outward-bound climbers to pass on the ribbon. Climber designs that encircles the ribbon 360 degrees may require the station to momentarily unattach from the ribbon to allow the climber to pass, or have a dual attachment system (lock system).

The second mode involves maneuvering the payload between the SE and a station. This would require fuel and a propulsion system. It would both lower the maximum payload to a GEO station and risk damage to the ribbon when attaching and unattaching. The climber models produced by Liftport Group show 360-degree enclosure of the ribbon. This is because they are designed to be reused and not to be unattached. The solution, in this mode, is to leave the climber attached to the ribbon, while the payload unattaches from the climber and maneuvers to the station.

Lastly, there is the docking arm, which may be the best mode of transfer. There is still some risk to the SE if the extended arm were to severe the ribbon, but this possibility could be avoided with sufficient safeguards. The attachment may also cause adverse tension on the ribbon if the velocity of the station is not matched precisely with that of the SE. However, safeguards could be designed to prevent that possibility as well.

If I understand you correctly, you are suggesting a propulsion vehicle attached to the ribbon, designed to create and remove transcients in order to move the climber through the atmosphere. The main problem is that the added weight of the vehicle would reduce the maximum payload of the ribbon. You would also have to ensure that the propulsion mechanism did not damage the ribbon. Finally, you would want to use laser power instead of sun power as a more direct form of energy.

Is this what you are suggesting?

Oh! I see what you mean: use balloons to lift sections with protective coating so that less strength is required of the rest of the cable. I hadn't thought of that. Balloons may be useful (or necessary).

No - because the every point on the cable (below GEO) needs to be able to support all the weight below it (hence the taper). Suppose that half of the weight of the cable in the atmosphere were protective coating, lights, conduits, etc. That would require the cable above that section to have twice the strength required to lift a pure CNT ribbon. This results in the upper section being more massive per meter. On the bright side, if balloons could reduce the weight at the bottom, the required strength (and mass) would be reduced all the way up to GEO. However, I suspect that the savings are too small to be worth the effort. (especially considering that the distance to GEO is only 1/3 the length of the ribbon)

The climber needs to travel slow enough through the atomosphere that it doesn't burn up. I think if a climber could go 200km/h in a vacuum, then it should be possible to gear it down while it's in the atmosphere.

Boron is the 5th element. Bruce Willis was looking all over for that.  :smile:

a pound an hour - how about making ashtrays?

I always figured that eventually someone would put a laser in LEO and just zap the stuff.

I was finally able to post. It seems that the quote tags were causing it to freeze.

quote (A_M_SWallow):
As part of the now cancelled Project Prometheus NASA was developing more powerful thrusters. Unfortunately I do not have the mass, thrust, energy and propellent usage details needed to model them. /end quote

http://gltrs.grc.nasa.gov/reports/2004/TM-2004-213194.pdf
http://www.google.com/search?hl=en&q=HiPEP+site%3Ahttp%3A%2F%2Fgltrs.grc.nasa.gov
http://www.google.com/search?hl=en&lr=&q=NEXT+ion+site%3Ahttp%3A%2F%2Fgltrs.grc.nasa.gov
http://trs-new.jpl.nasa.gov/dspace/bitstream/2014/38251/1/04-0452.pdf

HiPEP
Energy Required: 20-50kw (derated at 25kW)
Specific Impulse: 6000-9000s
Exhaust Velocity: 60000-80000m/s
Thrust-to-power ratio: 100kg/kW
Thruster Efficiency: >65%
System specific mass: 30kg/kW
(more info included in the above paper)

Methods of Electromagnetic Thrust
+Ion Thrusters
-+Electrostatic ion thrusters
-+Field Emission Electric Propulsion (FEEP)
-+Pulsed plasma thruster (PPT)
-+Hall effect thrusters (HET)
--+Stationary Plasma Thruster (SPT)
--+Thruster with Anode Layer (TAL)
-+Helicon Double Layer Thruster
-+Electrodeless plasma thruster
-+Pulsed inductive thruster (PIT)
+Magnetoplasmadynamic thruster (MPD)
+Variable specific impulse magneto rocket (VASIMR)

Developed/Proposed Systems
High Power Electric Propulsion (HiPEP)
Dual-Stage 4-Grid European Space Agency
Xenon Ion Propulsion System (XIPS) Boeing Company
NASA's Solar Electric Propulsion Application Readiness (NSTAR)
NASA's Evolutionary Xenon Thruster (NEXT)
Nuclear Electric Xenon Ion System (NEXIS) JPL
Plasma Contactor Unit (PCU) Boeing Company