Posted on 06/25/2004 2:21:35 PM PDT by Junior
It goes flying into space (and likely wipes out a good percentage of geosynchronous comm sattelites in the process). Actually, I would hate to see us put all our eggs in this basket, while it has been discussed by brighter people than my own fine self, in theoretical terms for over a hundred years, a lot of details need yet to be hammered out. Carbon fiber may well be a good start, depending on the structure, carbon makes a fantastically strong molecular bond.
I am just glad to see someone get serious about something besides the overpriced, overly complicated, all too delicate shuttle as a primary Earth to orbit conveyance. The NASA people who are still serious about space as opposed to waiting on their pensions, know full well the shuttle is an overpriced piece of crap.
To space. And back down again. And *VERY* economically; per trip, anyway -- the cable itself might be horrendously expensive to build). But once it's operational it makes traveling to/from space vastly cheaper (and less complicated) than any rocket launch. Rocket launches are shockingly inefficient on energy, and wasteful of expensive components, and require armies of ground technicians for each launch.
Actually, this is just a special case of the more general "space tether" problem, in which the entire system moves at the orbital rate of the center of mass. Things below the CM travel slower than they should, and things above the CM travel faster than they should.
The whole key to the space elevator is to maintain the Center of Mass of the entire system at GEO. If you lower something down, something else has to go up, in order to keep the whole system at GEO.
If you drop something off the elevator, you've essentially moved the CM of the system down. The bigger the thing you drop off, the farther down the CM drops. The new CM will be travelling more slowly than it should, so I believe the whole tether will begin to sag, until the CM can be brought back to GEO.
Likewise, anything latching on to the tether will raise the CM, and the tension on the tether should increase some, until the counterweight can be moved to compensate.
I think in practice the mass of the tether will be vastly greater than anything being dropped off of it, so the net effect may not be that large.
The in-plane location of the CM would be somewhat controlled by adjusting the CM. Out-of-plane position would require the use of thrusters.
The question of lunisolar gravitational perturbations (Don Joe's "tidal forces") are serious -- if nothing else, they represent a significant periodic tension variation on the tether.
It's older than that. It's only recently that materials science has advanced to the point where the design might be actually possible.
Of course there is.
You don't really believe that a geostationary satellite is really "stationary", do you?
It's "spinning" too, at a rate that has it travelling (oh, hell, someone look up the numbers) a fantastic number of miles around the Earth in every 24 hour "spin cycle".
If you stand on the equator, you're "spinning" at roughly a thousand miles an hour.
If your satellite "stands still" at thousands of miles above the equator, it's travelling at a hell of a lot higher velocity than the 1,000 MPH that you're traveling on the equator.
Aim a spotlight up at the clouds. Now move it a few feet, to sweep the spot across the clouds. For every foot the light moves in its gimbals, the spot moves several miles.
So, you have that object moving at tens of thousands of miles per hour -- sideways -- and, you want to lower it to ground level.
Well, that sideways velocity has to go somewhere -- and the only place to put it is to sink it into the "elevator" ribbon.
Someone suggested that if you move it slow enough, it won't matter.
I got a chuckle out of that, because all the pictures I've seen of proposed "elevators" show things moving pretty darned fast. The NASA page linked above in this thread shows what looks like a rocket -- a very streamlined "shuttle"-looking cab. I can't picture that thang slowly inching along the ribbon.
A piece of lead weighing only a few grains will wreak havoc if it hits something made of meat (or wood, or metal, or...) at a few thousand feet per second. Visualize the forces involved in sinking the energy carried in a mass of a few tons, traveling at miles per second.
I could see the beanstalk requiring counterweights, but I don't see what your skater has to do with anything.
*groan*
Forget I said anything, OK?
(Still, if you find yourself at the Ice Capades, keep a keen eye on the skater-lady when she starts spinning, and then pulls in her arms, OK?)
I wonder what the electrical potential would be between the top and the bottom...
Yup. And airplanes, too. :)
It's a great idea, but there's a lot of stuff that needs to happen before this can be made to work. This guy's shading the truth, which is too bad.
And you claim to have as much or more knowledge than Bradley Edwards who has been researching the project for years. BTW, he won't need government funding as there are more than enough venture capitalists which is what Edwards is counting on. That said, venture capitalists don't waste money like governments though they do risk capital. For the vast majority they're not fool hardy, lacking due diligence. Least wise not since the dot com bubble burst.
Have you ever read the continuation of 2001? I believe it was called 3001 a space oddessy. Really an interesting book.
It will stabilize wherever the base is anchored even as far north as the continental US. You can be pretty far off the equator and still get the thing to work.
"But did you know that the first concept originated in the world of science fiction? In 1945, Arthur C. Clarke hit on the idea of using this sort of satellite as a 'booster station without a pole' and published this in the October issue of the magazine Wireless World. ("Extra Terrestrial Relays", By Arthur C. Clarke) However, even the powers of the SF prophets fail at times. Twelve years before the launch of Sputnik, Clarke was not very optimistic about the probability of his idea being realised in the near future. In fact, he says he did not expect to live to see the arrival of communication satellites in space. Now he is sorry that he did not patent his idea. It would have made him a billionaire. Only INTELSAT, the International Telecommunication Satellite Organisation, does not forget the original inventor. This organisation always refers to the 'geostationary orbit' as the 'Clarke orbit'."
As I recall, Arthur C. Clark's novel had an elevator from an equitorial site, attached to a platform in space in geocentric orbit. Sounded plausible. This would be exciting.
About 5500 mph. Don't let real numbers interfere with the plan, though.
Suppose the rocket could do a sideways thrust as it descends. Would that help?
No -- you've just got to move something up at the same time, so that the CM of the system remains at GEO. What that essentially means is, you've got to launch twice the mass of the cable in order to get the cable to the ground.
They did an experiment a few years back, lowering a tether from a Shuttle, I think it was a couple of hundred yards.
They weren't able to measure the potential, but fortunately, they didn't lose the Shuttle when it blew up from the current it had generated.
The radius of the Earth is about 4000 miles (roughly).
So the radius of this orbit would be 4000 + 62000 = 66000 miles.
The circumference of this orbit would be 2 * pi * 66000 = 415000 miles.
in one day, it travels 415000 miles - that's a speed of 17270 MPH.
Oh man, and it would attract lightning from 100 miles away.
A space elevator is a ridiculous idea. I will NEVER work. Now, a space escalator...Ahh. That's a very reasonable idea.
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