Other rocket scientists, meanwhile, are investigating a form of space sailing that wouldn't rely on energy from the sun. Robert Winglee of the University of Washington in Seattle says his concept could get people to Mars and back in an astounding 90 days (current technology would require about two-and-a-half years of travel to make the trip).
The new concept would deploy an intermediate space station that would beam a stream of plasma, or magnetized particles. The space station would use solar energy to generate the beam of magnetized particles from a nozzle about 100 feet wide. By capturing these particles in its sail, the spacecraft would be propelled as the particles bounce from its surface. Winglee estimates the system could propel a craft to spectacular speeds of about seven miles per second.
Winglee and his students are refining models for the idea with funding from NASA's Institute for Advanced Concepts.
"Standard chemical propulsion systems would require long missions to Mars," said Winglee. "What we're saying is you can put the power on a space station, lighten up the spacecraft and increase speed. This will give you major savings in cost."
Even though it might be the fastest idea out there, it's unlikely to play an immediate role in President Bush's mandate, announced last January, to launch manned missions to the moon and on to Mars. Despite the advantage in speed, the science, says Friedman, is still far out.
One of the main challenges now, is making sure the sails unfurl without a hitch in space and can then be adequately manipulated by remote control. In a test three years ago, Friedman's group launched a suborbital version of Cosmos 1 that never managed to open its two-bladed sail. This time around, Friedman says he's more hopeful the test will work. But, he adds, there's still a lot of work ahead.
"It will take time," he said. "But in the long run I think sailing of some form will be what space exploration will look like. This is just the beginning."