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Author: Chapman208 Big gold star, 5000 posts Old School Fool Add to my Favorite Fools Ignore this person (you won't see their posts anymore) Number: of 27  
Subject: Space elevators Date: 2/17/2006 2:16 PM
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AP: Sounds like an interesting board. I've always been fascinated by science and I've been a SF buff since I was an adolescent (the melding of fiction and future science, I guess). Over the last few years, I've taken a stab at writing SF myself. My second novel is largely centered around a space elevator (a topic that has nearly reached the point of progressing from SF into science fact).

Space elevators are interesting for a number of reasons:

1) They offer a cheap way to move cargo between Earth and orbit--once you get past the large initial start-up costs. (No rockets, just frictionless elevator cars traveling up/down a carbon nanotube ribbon cable.)

2) The far end of the elevator would be a space station in geostationary orbit, which could function as a depot for handling people and things in transit up/down the elevator, as well as a low-gee/zero-gee research and manufacturing facility and as an "air traffic controller" for ships in or near orbit.

3) Because the elevator/station functions like a ball swung around a person's head on the end of a string, the cable actually holds it down, rather than up. (Centrifugal force would cause the station to be hurled into space if the cable broke.) As a result, any ships docked to the station would be subject to the same centrifugal force as the station itself. By simply undocking from the station, the ship would be hurled away from Earth by that centrifugal force, getting a free boost toward its destination (assuming the undocking was timed correctly). How much of a boost? Using a 78,000 km cable between Earth and the station, the boost would be on the order of 20,000 kph! (I verified these calculations with the acknowledged expert on the subject, Dr. Brad Edwards, who wrote the NASA-sponsored proposal on the subject.)

Pretty impressive stuff! This "slingshot" approach also offers the potential for unpowered/uncrewed "space trains". These would be cargo containers hurled by centrifugal force between Earth and, say, Mars, where they would be captured by space tugs and towed to another space elevator for lowering to the planet's surface. Then Mars could in turn hurl cargo (refined ores, perhaps) back to Earth.

I talk about a lot of this stuff in my novel. It's called "Lichen or Not". (Still looking for a publisher.)

Here's a link to Dr. Edwards' study, for anyone interested in reading about space elevators. (I disagree with some of his conclusions, however, such as having floating "anchors" for the tethers to attach to. He suggests moving them around to keep the tethers out of the way of orbiting debris, which I think is impractical. Just how much could you move a floating platform the size of a drilling rig on a daily basis? Not only that, but to make the elevator commercially viable, you'd need a large shipping infrastructure around it--wharfs, warehouses, etc.--which would be impractical with a base that constantly moves around.)

http://www.spaceelevator.com/docs/521Edwards.pdf

The advantage I have over Dr. Edwards is that my novel is set 170 years from now, so I've had time to work out all the bugs in the system.... <grin>, such as including Gravitic Field Generators on the space stations, so that everyone has a nice 1G gravity to work in, and using superconductor-powered maglev elevator cars, instead of the laser-powered cars he envisions (with the lasers on Earth, firing at the underside of the cars as they rise through and beyond the atmosphere, in all weather conditions--sounds unrealistic to me).

Anyone, if anyone wants to discuss space elevators/trains, I think that would be an interesting topic.

Mark.
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