WASHINGTON -- Consider it a stretch of the imagination or the ultimate high-wire act. All aboard the space elevator, to be whisked above Earth in an electromagnetic-powered cable car.
Taking an elevator to space has largely been in the realm of science fiction -- more engineering fancy than fact.
But recent studies suggest that a melding of space tether, magnetic levitation and
carbon nanotube technologies could transform this "Jack and the Beanstalk" idea into a mass transit system for the 21st century space traveler.
Uptown traffic
Keep your mind open and think big.
The space elevator concept is based on a structure stretching from the Earth's surface, up through the atmosphere, all the way to geostationary Earth orbit -- 22,300 miles (36,000 kilometers) high above the equator.
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Work underway on magnetic levitation launch technology may give the space elevator idea a boost
At the space end of the structure,
an asteroid or some large mass serves as a counterweight. That puts the center of mass of the elevator right at geostationary Earth orbit. The entire structure would slip through space in sync with our planet's rotation. Therefore, the elevator hardware maintains a stationary position at an equatorial locale on Earth.
The length of the elevator would be busy as electromagnetic passenger pods scoot up and down tracks, traveling at high speeds between Earth and a geostationary transfer station.
Still thinking big?
Each equatorial base site that anchors space elevator operations would feature a huge tower that is a true skyscraper at 31 miles (50 kilometers) tall.
Key research areas
A workshop on space elevators was held last year at NASA's Marshall Space Flight Center in Huntsville, Alabama.
The outcome of the gathering was uplifting, in more ways that one, said David Smitherman of Marshall's advanced projects office. "The idea is still futuristic...50 years away probably. But it does look like new high-strength materials may make possible the building of a space elevator," he told SPACE.com.
Smitherman said the space elevator concept is doable, but research in several key areas is needed, such as:
- Fully developing carbon nanotube material that exhibits strengths 100 times stronger than steel.
- Continue evolving space-tether technologies to gain experience in deploying and controlling long structures in space.
- Further work on high-speed electromagnetic propulsion for accelerating vehicles along a track.
- Growth of government and industrial infrastructure in space from low Earth orbit to geostationary orbit that would benefit from utilization of the space elevator.
Although the space elevator is not a NASA program or project, it is a prospect that deserves keeping an eye on, Smitherman said. "The space elevator is not something insurmountable. It is something that could be done, but it will need to be planned for," he said.
Tether try out
At the Marshall Space Flight Center, several projects are now underway that, while not tied to the space elevator notion, could help foster its creation.
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Engineers are developing magnetic levitation -- also labeled "maglev" -- technologies that could give a space launch vehicle a running start to break free from Earth's gravity. One rocket on the drawing board is tagged the Spaceliner 100. It uses magnetic fields to levitate and move along a track at high speeds.
Yet another project is the Propulsive Small Expendable Deployer System (ProSEDS). This unique space-tether experiment is being readied for flight next June, said Les Johnson, NASA's principal investigator at Marshall for this project.
[inset]
The experiment will test deploying in space a tether that's 9.3 miles (15 kilometers) long. Three miles (5 kilometers) of the tether is made to generate electrical current by cutting through Earth's magnetic field.
This
electrodynamic tether test should show that propellant-free spacecraft maneuvers can be made, either speeding up or slowing down by varying the tether's orientation within the magnetic field, Johnson said.
It's an experiment in the true sense of the word," Johnson said. While not being flown to further space elevator work, ProSEDS is "inextricably linked" to the idea, he said.
"I don't know how we ever go about building a space elevator without going through the evolution of space tethers to get there," Johnson said.
Cable operator
Bradley Edwards, a physicist at Los Alamos National Laboratories in New Mexico, is a keen supporter of fabricating an elevator to space. He recently completed research on lengthy space elevators thanks to a NASA Institute for Advanced Concepts grant.
"The space elevator appears much closer to reality than has been suspected in terms of available technology, cost and schedule," Edwards said. "The major hurdle is the required carbon nanotubes, but that's getting closer each day," he said.
Edwards has scripted a plan that suggests an operational cable to space can be installed within 10 to 20 years.
"There doesn't seem to be a whole lot of hurdles," Edwards said. "It looks like there are viable solutions to every aspect," he said.
Across the great divide
Edwards plans to use an old technique for
building bridges that span gulfs of space here on Earth.
First thing to do: throw or shoot a small string across a canyon. Then a larger string is attached to this first small string and pulled across. This process is repeated until many ropes and eventually structures are placed across the canyon.
The great gulf between our planet and outer space can be bridged by first having a satellite deploy a small cable back down to Earth. Then a robotic "climber" ascends the string while attaching a second string alongside the first to make it stronger. This process is repeated until a thick, usable, high-capacity cable is fashioned.
Edwards said he hopes to do follow-on work, refining his space elevator thinking. He wants to acquire nanotube materials for making short lengths of cable. Those specimens could then be subjected to extensive tests that
mimic the space environment.
"With the construction of multiple space elevators, there can be the start of new commercial markets, new resources and possibly a true spacefaring society. Just as the transistor was the first small step in the current computer age, the space elevator may be the step that takes our children to the stars," Edwards said.
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