Space Elevators - Some perplexing questions.

C M Edwards · 2002-05-17 12:50:07

I did some work as a volunteer researcher/net-miner for Allen Meece?s Virtual Beanstalk Project,

members.aol.com/beanstalkr/project

and we discussed this very issue in some depth. He?s currently addressing the issue using models to simulate tether ascents in the lower atmosphere.

The ideas basically came down to various electric winches ? electric motors yield more torque at low speeds than other motors ? but we ultimately had to agree to disagree on the ultimate source of power for the motor. Allen favors solar electric because of its greater range and lower likelihood of breakdown. I preferred modifying good old-fashioned reciprocating gasoline generators to run on nitrous oxide, because they offer more power and no time pressure (i.e., they run at night). We didn?t touch the problem of dealing with more than a few millimeters variation in the size of the tether because it didn?t concern us; however, it will be a major problem for an ascent to orbit. Allen is also seriously considering the idea of using wind for lift in the lower troposphere.

I don't know about using towers to ascend to meet a descending tether, but we've given serious consideration to using balloons to do the same job.

CME

Phobos · 2002-05-17 14:53:00

It's funny that you mention steering an asteriod into the place
where you want to place the space elevator. I was thinking
that it might be cool to build a space station around the space
elevator and an asteroid could make for nice shielding not
to mention the materials it would supply . As for whether
to power the winch by fuel or solar power, I wonder if
it might be good to use both? You could probably reduce your operating costs by only using the fuel at night and
solar by day.

C M Edwards · 2002-05-18 18:55:47

Actually, Lars, try this one:

http://members.aol.com/beanstalkr/eleva … orclub.htm

This page is also accessible via the chart page by clicking on the blinking star in the middle of the chart.

The information here is incomplete. The site hasn't been updated much since most of the work results weren't posted to the web. But it should be enough to give the general idea.

As for stationkeeping, we opted not to use any for the initial incarnation, as guy lines are too heavy and a single tether will keep the platform inside a desirable radius. As for wires running up the tether for power, 25km of wire is ultimately quite massive, so we dropped that idea.

CME

C M Edwards · 2002-05-19 07:50:48

Hello Lars.

If you would like to provide help with the Beanstalk, you can reach Allen Meece at:

Navigaiter2002@aol.com

He can probably tell you all sorts of things that need doing.

(The Beanstalkr@aol.com address you may find listed at the site is likely to be ignored due to excessive spam.)

Currently, IMHO, the project status is somewhere below "sure thing" and somewhere above "glorified research paper." The dynamics have all been largely worked out by Allen, myself and others -- it can work, and work well. However, we still have a pressing need for scale models (Allen's elevators, etc.), so that we can find the best ways to do things. At this point, we are still operating without funding, so we're having problems with some basic milestones: realistic market surveys, getting people to take us seriously enough to give us quotes, etc. There are also numerous engineering details that have yet to be settled, many of them only valid below the freezing point of propane.

However, despite remaining obstacles, I think that this can be done. For example, for less than US $3000000, a largely automated platform with a simple repeater station could be put up near San Juan and take cell phone calls from the Virgin Islands. And that's just one of the purposes you could use systems like this for. Anything a high altitude station-keeping aircraft can do, a stratospheric beanstalk can do, without a drop of fuel or even a single turn of a motor.

A beanstalk could even be made to launch orbital payloads. We estimate that the largest cargo one could carry on its way up is about 40T to 60T, large enough to carry small rockets like the old Scout series. The main limitation to cargo capacity is the effect of midlevel winds on the balloon, but if you can get one to work, you can get two or more. Thus, loads larger than 60T can be lifted. The ability to raise multiple beanstalks also means that a stable "tower" could be constructed to receive a descending space tether.

CME

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#1 2002-05-17 12:50:07

Re: Space Elevators - Some perplexing questions.

#2 2002-05-17 14:53:00

Re: Space Elevators - Some perplexing questions.

#3 2002-05-18 18:55:47

Re: Space Elevators - Some perplexing questions.

#4 2002-05-19 07:50:48

Re: Space Elevators - Some perplexing questions.

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