Researchers gathered at the Space Elevator Conference on Thursday said that an elevator could make transportation to space so much more inexpensive than it is now, that companies could build large solar-power farms in space to provide energy for people on Earth. That could eliminate the need to burn fossil fuels and thus reduce global warming.
Gathered on Microsoft's campus in Redmond, Washington, presenters at the conference said they've worked out some problems but continue to face challenges to building a space elevator.
A space elevator would essentially be a long rope made of nanomaterials, stretching from Earth to a counterweight at geosynchronous altitude, about 22,000 miles (35,406 kilometers) above Earth's surface. Special craft, like elevator cars, would travel along the ribbon, carrying people and goods into space in a matter of days.
The idea was first popularized in science-fiction novels, but with the discovery of carbon nanotubes in 1991, the outlandish concept became a real possibility, the researchers say. That's because now scientists can imagine building a strong enough and long enough tether to build a space elevator.
They say the elevator would make space travel far cheaper than it is now. The cost to send the space shuttle into low Earth orbit is about US$64,000 per kilogram, said Bryan Laubscher, president of Odysseus Technologies. "The cost of chemical rockets will keep us from exploring more of the solar system," he said. Chemical rockets, like those used on the space shuttle, use a chemical fuel for power.
He estimated it would cost more like $3,000 per kilogram to send items into the higher geosynchronous orbit on a space elevator.
Several of the experts agreed that one reason to build a low-cost transportation method is to build satellites for generating solar energy. "Solar-power satellites is really the biggest need to haul heavy stuff to geosynchronous altitude," said Keith Henson, founder of L5 Society.
Laubscher agreed, saying that space solar power will be the second big money-maker in space, after the existing communications market.
But it's clear that the researchers continue to wrangle with difficult challenges to building an elevator.
One issue discussed at last year's get-together was that of space junk. Every satellite or piece of debris at the same altitude as the elevator would eventually crash into it and destroy it, Ivan Bekey, a former NASA scientist currently with Bekey Designs, said last year.
One speaker this year said parts of that problem can be overcome. The tether would connect on Earth to a ship that could be moved to drag the tether out of the way of major objects such as satellites, said Ben Shelef, founder of the Spaceward Foundation. Also, the tether should be flat and very thin, like a piece of Saran wrap, rather than round like a rope. Smaller objects would simply puncture the tether rather than break it, he said.
Still, his solution does not answer the question Bekey raised last year about the effect of oscillations that might result along the length of the tether when the ship on Earth moved. "We hadn't thought of that," Laubscher said Thursday. At this year's conference, he put out a call for people who might be interested in joining a team of people to study and solve the issue.
Other people are proposing variations on the architecture. Henson said using large pulleys to move the cables would make for an efficient and less expensive architecture. However, Shelef said that the problem with moving cables is that the moment they stop, they will get tangled together. "If you build a system that relies on constant motion to keep it alive, if it ever stops, the ribbons will touch, and then you're done," he said. He doesn't think it's realistic to imagine there would be no problems that would require operators to stop the cables.
Researchers are also learning that some of their expectations haven't proved true. For example, carbon nanotubes aren't as strong as originally though, Shelef said. Power systems for sending cars along an elevator are also trickier to design then initially thought, he said. But none of these issues is a "showstopper," he said. They just mean that once the system is built, a trip up the elevator might take a few days instead of one, he said.
The researchers will be discussing the elevator through the end of this week. On Friday, they'll hear an update on a competition spearheaded by NASA for people interested in building strong tethers that could be used in a space elevator.