The Imminent Arrival of the Space Elevator
In the article author Bradley Carl Edwards describes (with some nifty pictures) the process of building a Space Elevator in the near future - perhaps within 15 years. This guy is no idle dreamer. Edwards received a grant from NASA in 2000 to study the concept.
First, Edwards explains why we should build it:
It all boils down to dollars and cents, of course. It now costs about US $20 000 per kilogram to put objects into orbit. Contrast that rate with the results of a study I recently performed for NASA, which concluded that a single space elevator could reduce the cost of orbiting payloads to a remarkably low $200 a kilogram and that multiple elevators could ultimately push costs down below $10 a kilogram.
Let me make this personal. A kilogram is 2.2 pounds. That means it would cost $1,909,090 to haul my 210-pounds into orbit - never mind the cost of air, food, water or other necessities I would need to have with me. Edwards is talking about lowering that cost to $955. I'll spend that much flying my family to Disney World.
There's also the issue of safety. Riding to earth orbit atop an explosive rocket is a dangerous system that fails far too often to be acceptible for civilian transport.
Edwards explains the engineering challenges of a space elevator. The biggest hurtle has been developing a material strong enough to withstand the extreme forces involved. When I was a kid I read an article that described the building of a space elevator with an unknown material the author called "fictionite." We now know what "fictionite" is:
In 1991, Japanese researcher Sumio Iijima discovered carbon nanotubes. These are long, narrow, cylindrical molecules; the cylinder walls are made of carbon atoms, and the tube is about 1 nanometer in diameter.
In theory, at least, carbon-nanotube-based materials have the potential to be 100 times as strong as steel, at one-sixth the density.
The reduced density over steel is as important as the increased strength. Old space elevator ideas had us parking an asteroid in earth orbit just to support the massive weight of the system. Edwards doesn't think anything near that level of mass will be necessary.
And at this lower density the space elevator material would only have to be about 33 times the strength of steel.
This strength [carbon nanotubes have the potential to be 100 times as strong as steel] is three times as great as what is needed for the space elevator. The most recent experiments have produced 4-centimeter-long pieces of carbon-nanotube materials that have 70 times the strength of steel.
Once we are able to scale up production of sufficiently strong carbon nanotubes, Edwards believes we can put up a space elevator in steps:
An initial "deployment spacecraft" and two smaller spools of ribbon massing 20 tons each would be launched separately into low-Earth orbit using expendable rockets. The deployment spacecraft and spools would be assembled together using techniques pioneered for the Mir space station and the International Space Station. The deployment spacecraft would then follow a spiral course out to geostationary orbit using a slow, but fuel-efficient, trajectory.
Upon arrival, the spacecraft would begin paying out the two spools side by side toward Earth. Meanwhile, the deployment spacecraft would fire its engine again, raising it above geostationary orbit. The spacecraft's motions would be synchronized with the unreeling cable so that the spacecraft would act as the counterweight to the rest of the cable: this would keep the center of gravity of the entire elevator structure in geostationary orbit [see illustration, "View From the Top"]. When the two halves of the ribbon reached Earth's surface, a special elevator car would be attached that would ascend the elevator, stitching the two side-by-side halves of the ribbon together. This initial system would have a 20-cm-wide ribbon and could support 1-ton climbers.
Other specialized climbers would then be sent up this initial ribbon, adding more small ribbons to the existing one. When one reached the far end of the elevator cable, the climber's mass would be added to the counterweight, keeping the elevator in balance so that its center of gravity would stay in geostationary orbit. After 280 such climbers, a meter-wide ribbon that could support 20-ton climbers would be complete.
The climbers, like most of the elevator system, would use off-the-shelf components wherever possible. One of the reasons the climbers would be so simple and have so much room for payload is that they would not carry power-generating equipment. Power would be delivered to climbers by lasers beaming 840-nm light from Earth onto an array of photovoltaic cells.
I think one last step would be in order. Once the first elevator ribbon is in place, another should be placed parallel to the first to allow climbers to ascend and descend simultaneously - a gondola to the stars.