The construction of a space elevator is considered to be a large project. Like other historical large projects it entails technical risk: some advances in engineering, manufacture and physical technology are required. Once a first space elevator is built, the second one and all others would have the use of the previous ones to assist in construction, making their costs considerably cheaper. Such follow-on space elevators would also benefit from the great reduction in technical risk achieved by the construction of the first space elevator.
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David Smitherman of NASA has published a paper that identifies "Five Key Technologies for Future Space Elevator Development":[1]
Two different ways to deploy a space elevator have been proposed.
One early plan involved lifting the entire mass of the elevator into geostationary orbit, and simultaneously lowering one cable downwards towards the Earth's surface while another cable is deployed upwards directly away from the Earth's surface.
Tidal forces (gravity and centrifugal force) would naturally pull the cables directly towards and directly away from the Earth and keep the elevator balanced around geostationary orbit. As the cable is deployed, Coriolis forces would pull the upper portion of the cable somewhat to the West and the lower portion of the cable somewhat to the East; this effect can be controlled by varying the deployment speed.
However, this approach requires lifting hundreds or even thousands of tons on conventional rockets, an expensive proposition.
Bradley C. Edwards, former Director of Research for the Institute for Scientific Research (ISR), based in Fairmont, West Virginia proposed that, if nanotubes with sufficient strength could be made in bulk, a space elevator could be built in little more than a decade, rather than the far future. He proposed that a single hair-like 20-ton 'seed' cable be deployed in the traditional way, giving a very lightweight elevator with very little lifting capacity. Then, progressively heavier cables would be pulled up from the ground along it, repeatedly strengthening it until the elevator reaches the required mass and strength. This is much the same technique used to build suspension bridges.[2]
This is a less well developed design, but offers some other possibilities.
If the cable provides a useful tensile strength of about 62.5 GPa or above, then a constant width cable can reach beyond geostationary orbit without breaking under its own weight. The far end can then be turned around and passed back down to the Earth forming a constant width loop, which would be kept spinning to avoid tangling. The two sides of the loop are naturally kept apart by coriolis forces due to the rotation of the Earth and the loop. By increasing the thickness of the cable from the ground a very quick (exponential) build-up of a new elevator may be performed (it helps that no active climbers are needed, and power is applied mechanically.) However, because the loop runs at constant speed, joining and leaving the loop may be somewhat challenging, and the carrying capacity of such a loop is lower than a conventional tapered design.[3]
Current technological status:
| Parameter | Required | Achieved | Year | Notes |
|---|---|---|---|---|
| Tether | ||||
| Strength | 100,000 kN/(kg/m)[4] | 7,100 N | 2010 | House-tether.[5] |
| Climber | ||||
| Speed | 83 m/s (300 km/h) a | 18.3 m/s (66 km/h) 4 m/s (14 km/h) |
2010 2009 |
Battery-powered climber to a distance of 300m, Second Japan Space Elevator Technical & Engineering Competition.[6] Beam-powered climber to an altitude of 1km, Space Elevator Games 2009.[7] |
| Altitude | 36,000 km[4] | 1km | 2009 | Speed over 4 m/s (14 km/h).[7] |
| Payload | 10kg | 2009 | Estimated - climber dragged bottom stop about 30m up, with speed over 6 m/s (22 km/h), during the Space Elevator Games 2009.[7] | |
| Laser power beaming | ||||
| Power beam | 1 kW | 2009 | Distance greater than 300 meters.[7] | |
a) It would take 5 days to reach a geostationary altitude of 36,000 km with this speed.[8]
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