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4 comments 2004-04-25 Space elevators [isr.us]
Bra teknisk introduktion till rymdhissar. "This manuscript is the result of a six-month investigation I conducted for NASA under the NASA Institute for Advanced Concepts (NIAC) program"

2004-04-25 17:28 pt95vma
Många roliga saker på schemat :-)


2004-04-25 17:22 pt95vma
Severed Cables

If a cable is severed the lower segment will fall back to Earth while the upper portion floats outward. The worst case would be if the countermass breaks off the far end of the cable and the entire 91,000 km of cable falls back to Earth.

Depending on the location of the break, the epoxy used, the dynamics of the fall, etc. the cable will re-enter the Earth's atmosphere at a velocity sufficient to heat the cable above several hundred degrees Celsius (figure 10.9.1). If the cable is designed properly, the epoxy in the cable composite will disintegrate at this temperature. This means the cable above a certain point will re-enter Earth's atmosphere in small segments or carbon nanotube / epoxy dust. About 3000 kg of 2 square millimeter crosssection cable (20 ton capacity) may fall to Earth intact and east of the anchor. Detailed simulations will be required to determine the possible sizes of segments that will survive and the health risks associated with carbon nanotube and epoxy dust. In terms of the mass of dust and debris that will be deposited, we can compare what will happen to what naturally happens now. Each year 10,000 tons of dust accrete onto Earth from space, the additional 750 tons of the first cable will increase that year's infall by 7.5%. A larger 1000-ton capacity cable would have a mass of 30,000 tons or roughly equivalent to 3 years of normal global dust accretion. Further investigations are required to determine the environmental impact of depositing this much dust along the Earth's equator.

2004-04-25 17:16 pt95vma
1x106 => 1x10 upphöjt till 6

2004-04-25 17:15 pt95vma
[..]. At this rate a 20,000 kg capacity cable can be built in 2.3 years or a 1x106 kg in 5.1 years.

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