Posted: 9/23/2012 5:15:20 AM EDT
This came up in the Mars colony thread. It's a machine I pondered ever since I heard of a Lofstrom Loop and grossly misinterpreted how it works.
The cable is essentially a large, metallic watch band. It's spun at a velocity that causes it to expand into a circle and stand up. The cars are able to roll along the cable on parallel tracks. They use electromagnets to grab the cable to climb. The magnets resist the upward motion to brake the car during descent. The cable would be wide enough to accommodate multiple cars. It could have doors on the sides of each car so that the cars can be grouped to transport something that wouldn't fit in a single car. Obviously the power consumption would be insane. I think it would have to have fusion as a power source. Arfcom, tell me why it sucks. |
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I drew it to accommodate the same payload as the space shuttle cargo bay. 60' x 18' and 54,000 pounds. It would have three cars each rated for 18,000 pounds and 18' across. The sides of each car can be removed so a 60' long object can be carried if all three cars line up. With three cables supporting each car, it needs 2,835 feet of chain.
Screw the magnets, the cars can move on a roller braking system. The rollers allow the chain to pass through unless friction is reduced. Then they transfer a percentage of the chain velocity to the cars. They can accelerate gently to ascend. When they descend, the brakes control the descent velocity. The base station would have to be able to provide the initial acceleration for the cars. It would also save wear on the system if the base station controlled the final braking. The chain could be made of Kevlar or carbon fiber. It would be light, synthetic, and very strong. Since the chains are linked like a gigantic bicycle chain, they can be easily synthesized. Also it could be built by first raising an small and lightweight chain, then attaching heavier links to the sides, replacing the center, etc. Watch me convince myself this is not a totally stupid idea. 
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Centripetal acceleration is tangential velocity squared divided by the radius. Radius is 50 miles, 80,470 meters give or take. Gravitational acceleration on Mars is 3.69 m/s2 . So using the centripetal acceleration, the velocity would be ~540 m/s. 1780 ft/s. Now, how would you start such a belt in motion? |
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It would have to start as a smaller, lighter belt. It's essentially a large bicycle chain. Mobile tensioners would move closer to the base station as the chain got moving and formed a circle. The trouble is, it was intended to reach LEO, so 890 m/s.
Suppose each link is 20", made of about 5 pounds of Kevlar. There are separators between each chain. I designed it to be 60' across, so it has 9 chains, eight separators. Separators alternate left and right with each link. There are 24 separators, each one 77.625" given the links are 3" thick. I guesstimated 5# per 20" link based on the weight of a level IIIA vest. The separators are 4 times that length, so there are 24 x 4 units, 480# and 225# for the links. Round up to 1000# per 10 feet section, 54' wide. 166,320 sections = 166,320,000#, 75441483 kg. Only 8.3 gigawatts, assuming 100% efficiency. 
Definitely needs fusion. |