Could the ambitious project of developing a laser-powered space elevator turn science fiction into reality?
Scientists say such an elevator could enable inexpensive and complete expansion of society into space. They have been seriously considering space elevators as a far-out space transportation system for the next century, which could make travel to geostationary earth orbit a daily event. Beyond earth, space elevators on the moon and Mars open new economic opportunities and expand humanity's reach ever so slightly into the solar system.
At present, rockets are used to ship anything into space, costing several thousands of dollars per kilogram. The cargo will be subjected to severe 'shake, rattle and roll' and g-stress forces. Rockets also generate a tremendous amount of pollution.
To change the equation, instead of using rockets, build a transportation infrastructure, a ‘railway line’ into space. A space elevator is the way to provide scalable, inexpensive and reliable access to space, scientists say.
The space elevator uses a carbon nanotube ribbon that stretches from the surface of the earth to a counterweight in space. A thin vertical cable (tether) stretches from the earth to orbit, about 100,000 km into space. Elevator cars (climbers) ascend the ribbon carrying cargo and eventually humans to and from space as well as launching spacecraft to distant planets. A combination of sunlight and laser light projected from the ground powers the climbers.
However, various engineering challenges lay between present technologies and what is required for a space elevator. According to the International Space Elevator Consortium (ISEC), the main hurdles from a technical point of view are tether strength and power systems with space debris and tether dynamics also posing a significant challenge. Some of these challenges are rapidly being met and others are not.
Tether strength and power systems are linked because a strength in one can make up for a lack in the other. If the tether is not as strong as hoped, a more robust power system would be able to push climbers up the tether faster and thus still allow for a large amount of cargo to be moved, ISEC says.
Nanotechnology could provide the very high-strength, low-weight fibers that would be needed to build the cable of a space elevator. Till now, only carbon nanotubes (CNTs) promise adequate strength. NASA scientists say nanotubes have 100 times the tensile strength of steel, are 40 times stronger than graphite fibers, conduct electricity better than copper and can be either conductors or semiconductors.
Made from CNTs, the tether will be stronger than any construction material today. As of today, such materials are still in early stages of development. Entrepreneurs such as the LiftPort group are researching to develop such materials.
Seattle-based LaserMotive is developing laser power beaming systems to power the climbers. The truly 21st-century power beaming technology involves the wireless transfer of energy over distances using laser light - that has the potential to provide a virtually endless supply of power to a variety of applications.
The Strong Tether Challenge is a NASA-sponsored contest to create tethers with the highest strength-to-weight ratio and demonstrate a material that is at least 50 percent stronger than the strongest commercially available. NASA's another challenge - the Power Beaming Challenge - supports the development of far-term space infrastructure concepts such as space elevators and solar power satellites.
The concept of such an elevator was being spread to a larger audience by Arthur Clark in his novel The Fountains of Paradise in 1979.
During a speech he once gave, someone in the audience asked Clarke when the space elevator would become a reality.
Clarke answered, 'Probably about 50 years after everybody quits laughing,' related Pearson in a NASA report. He's got a point. Once you stop dismissing something as unattainable, then you start working on its development. This is exciting!