Might solar energy provide the power needed to send cars up a space elevator? Could you build one fat elevator and split it into two? Can as many as six cars travel up and down a space elevator?
Those are just some of the questions that attendees at the annual Space Elevator Conference on Friday in Seattle wondered about.
"These are ideas we want to hear and we want people to follow up on," said Bryan Laubscher, one of the leading space elevator enthusiasts and principle at Odysseus Technologies, a company working on high-strength materials.
Similar to past years at the conference, Laubscher's introductory talk spilled into a general brainstorming session where attendees discussed possible solutions to problems that dog the development of a space elevator.
The general idea of a space elevator, imagined first by scientists but popularized in science fiction, involves stretching a ribbon, probably made out of carbon nanotubes, from Earth into space. Elevator cars would travel up and down the ribbon. While it would cost perhaps US$18 billion to build a space elevator, carrying items into space would be far cheaper via an elevator than it is using current rocket technology, Laubscher said.
Still, there are many issues that still need to be studied. One attendee asked about the operational costs once a space elevator is built. "It's been nine years we've been looking for someone" to study that, Laubscher said.
There would be costs associated with running the lasers that power the cars up the ribbon, as well as simpler costs associated with transferring goods to the platform at the bottom of the ribbon, which will be located in the ocean.
Another person at the conference asked about why the current model has just three cars that could climb up and down at once -- why not six? It's possible, Laubscher said, but someone would have to work out how they'd pass each other on the ribbon and the elevator would require six laser beaming stations if they all were to climb at the same time. That would require more study.
Some enthusiasts are investigating ways to use solar panels on the ribbon in order to provide power, rather than using lasers beamed up from Earth. Peter Swan, a scientist who has worked for the U.S. Air Force and worked on the Iridium satellite system for Motorola, is collaborating with 27 other authors on a book on the feasibility of the space elevator, and they have begun looking into the possibility of using solar panels along the ribbon.
But why not put the solar panels on the cars, one attendee wondered. It's possible, Laubscher said, but the idea would need to be investigated in terms of the mass the panels would add to the cars.
Another person wondered if an efficient way to build multiple elevators could be to construct the first one twice as wide as necessary so that it could be then split in half. "No one's really looked into it," Laubscher said.
Even though there are lots of areas that need further study, there are other areas of research into technology required for the space elevator under way.
For instance, the ribbon must be made out of carbon nanotubes, because that is the only known way to create a strong enough fiber. "We could use steel, but the mass of the elevator would exceed the mass of the universe," Laubscher said.
Vasilii Artyukhov, a researcher from Rice University, presented some of his study into how and under what conditions nanocarbon breaks, an important issue for the space elevator.
In addition, on Friday at the conference NASA will oversee a strong-tether competition that is part of its Centennial Challenges program. This will be the fifth strong-tether competition as part of the challenge and no one has come close yet to meeting the strength requirement set out in the challenge, said Larry Cooper, program executive of the Centennial Challenge for NASA.
If someone wins that challenge it would be a step in the right direction, but a tether strong enough to build a space elevator would have to be six times stronger than the goal of the challenge, he said.
NASA has other challenges aimed at encouraging people to develop the kinds of technologies required to build a space elevator. For instance, the power-beaming Centennial Challenge is focused on the kind of technology required to power the cars up and down the elevator.
While NASA doesn't have an office dedicated to working toward building a space elevator, it has identified a space elevator as one potential avenue for exploring space beyond Low Earth Orbit, said Sam Ortega, a program manager with the Centennial Challenges group at NASA.
He was reluctant to guess when a space elevator could actually begin to be built. "We try not to be narrow-minded and say it won't happen for 150 years. Breakthroughs in technology innovation occur on a daily basis," he said.