Science fiction? Not according to NASA. The US space agency predicts that in 2066, with a lot of research and a little luck, the first space lift will be ready to whisk passengers and cargo from Earth to an orbiting space station. And it is not only the boffins at NASA who are having trouble keeping their feet on the ground. Lift manufacturer Otis has said the company already has the technology in place for many of the components required.
The "space elevator" was the subject of a paper published last August based on a workshop held at NASA's Marshall Space Centre in Huntsville, Alabama, in 1999. The paper proposed a space elevator that would "make a physical connection from Earth to space in the same way a bridge connects two cities across a body of water".
NASA has developed this idea into the concept of a series of lifts shuttling back and forth into space along an ultra-thin, immensely strong cable. This cable would stretch from the top of a cloud-penetrating 50 km high tower to a space station held in geosynchronous orbit. Because objects in a geosynchronous orbit travel at a speed that matches the spin of the earth, this means that the space station would hover over one spot on the planet's surface.
The tower would hold the cable clear of the earth's soupy atmosphere that would otherwise tug and drag at it. To align with the space station's geostationary orbit, this tower would have to be constructed somewhere on the equator; this would also ensure that it is away from the main hurricane and tornado areas.
The world's tallest freestanding tower, the CN Tower in Toronto, stands at just over 600 m, but by developing ultra-strong and light materials, NASA hopes to make the construction of a 50 km high tower possible.
A 10-hour elevator ride may sound far-fetched, but the boffins at NASA have come up with an even crazier idea to keep the lift in orbit. Its far end would be tied to a captured asteroid, which would act as a counterweight for the structure and keep the space station in geostationary orbit.
The lift cars shuttling back and forth along the cable would be driven by electromagnetic propulsion. Electromagnetic drives work by using the repulsion force of a magnet and have already been developed to run airport shuttle trains. This type of drive is ideal for the space lift because even at high speed, no part of the mechanism will touch the cable so it will not be subject to friction or wear and tear.
It will be 50 years before work starts on the construction of the first lift. In the mean time, NASA will be working on the technology to make the structure possible. One of the first problems the agency faces is finding a suitable material for the cable. This will have to be both light and strong and at the same time capable of resisting impact from passing space debris. NASA has already developed a thin fibre with the strength of a diamond using carbon nanotube technology – in which carbon atoms are manipulated into elongated configurations to form a material more than 200 times stronger than steel. These cables could be bundled together to form an even stronger cable along which the lift could run.
The next problem will be how to install the cable. One proposal is to launch a small satellite to drop a very thin string down to earth. A robotic climber would then ascend the string to attach a second string alongside the first, increasing the cable's strength. This process could be repeated until a cable strong enough to be used by a space lift is created.
Then, NASA will have to tackle a safety problem: how to avoid dropping thousands of kilometres of cable on the earth if the cable breaks. Active materials would need to be developed to monitor and repair flaws in the cable and to detect the potential of a major failure.
If all this seems a little far-fetched, Jack Leingang, chief executive of lift manufacturer Otis, claims that the company already has lift systems for a five-mile high tower, so a space lift could become fact rather than fantasy. "At the rate of our development efforts, we could apply technology we are working on for today's market to the NASA concept within the next 10 years," he says.
Developments for earthbound markets that could be adapted for space lifts include self-propelled and lightweight vehicles and stackable or multi-deck cars that could be used for food preparation areas, sleeping quarters, toilet areas and cargo storage for the 10-hour journey. Intelligent door systems that maintain the same open and close profiles under standard pressure or zero gravity are also under development.
Because repairs to such a system would be expensive, Leingang says the system would require on-board diagnostics that could not only warn maintenance personnel on Earth of potential problems, but also enable repairs to be carried out from a very remote location.
Sceptics argue that such a scheme would be extremely expensive. However, when compared with the cost of using a spaceship to put materials into space, NASA says the project starts to make sense. Of course, this comparison only becomes valid when there are companies willing to pay for the service. This same note of caution is echoed by Mike Jordan-Reilly, communications manager at Otis Engineering: "We don't have the dollars to invest in products that aren't driven by the market," he says. But 50 years from now, who knows what will drive the market?
