ORANGE, Calif. (AP) -- Astronauts may soon be able to participate in a Tour de Space of sorts.
Researchers at the University of California, Irvine, have developed an exercise bicycle to be used in the zero-gravity environment of space.
They say the bike, dubbed Space Cycle, would combat the loss of bone and muscle density, along with cardiovascular fitness, that astronauts suffer during long stints in space.
"A bicycle in space. It sounds like a simple idea, right?" researcher Vince Caiozzo said during a recent interview. "But it's a lot more complicated than that when you realize it has to function without gravity...and still have some impact on the astronauts."
A bicycle built for two
More sci-fi amusement ride than traditional bicycle, the Space Cycle operates as a human centrifuge. Similar in appearance to a spinning wheel, the astronauts sit opposite one another -- head-to-head -- in chairs. As they pedal, they move in a circular motion around a bar. The motion forces them against the seat, mimicking the effect of gravity on Earth.
into space to be used on the International Space Station. But NASA spokesman John Ira Petty said researchers continue to look at other possibilities.
Secret origins of exercise machines
The Space Cycle was developed by Dr. Art Kreitenberg, an orthopedic surgeon who first came up with the idea as a finalist in NASA's astronaut program in 1991.
During a tour, he saw a wooden mock-up of the stationary bicycle later placed on the space station.
"The first thing I thought was, 'why not have this bicycle whip around inside the can and create your own gravity?'" he said. "I talked to a former astronaut about it and he said, 'It would probably make you sick to your stomach."'
Undaunted, Kreitenberg drew up plans and approached Cook Bros., a high-end mountain bicycle manufacturer, for help building the first prototype. They dubbed it the Millennium Falcon, after the ship Harrison Ford's character piloted in Star Wars, because "it didn't look like much, but it got the job done."
Kreitenberg and his team used the model to obtain a $70,000 grant from NASA in 1995.
To deal with existing gravity, the latest prototype resembles a carnival swing ride, where riders begin in a horizontal position and, as they build speed, rise into a vertical position.
"It's a little different than riding a regular bicycle. The positioning is totally different...and stopping is much harder. You can't just hit the brakes," said Julia Dierks, 27, of Placentia, who was enlisted along with other members of her Southern California bicycle club to test Space Cycle. "You have to look straight ahead or the spinning makes you dizzy."
The future of biking?
The research team says it has spent $200,000 to date developing the bike. They estimate it will cost about $500,000 to complete the project, which will include several more prototypes.
The researchers also are designing a virtual reality system to combat the dizziness and make the ride more enjoyable. Possible designs include allowing riders to participate in a virtual Tour de France or a ride along the beach, Kreitenberg said.
In addition, the bike's design takes into account the physics principle that every action has a reaction.
When astronauts were aboard the U.S. Skylab in the 1970s, they exercised by jogging. But their workouts caused the space station to move, and the station's thrusters had to be fired to keep it in position.
But the Space Cycle, the researchers believe, can be operated with its own vibration-free system -- a collection of wires, cords and dampening mechanisms that would halt the transfer of any vibrations to the station's structure.
Kreitenberg, who has patented the human centrifuge cycle, believes, along with the research team, there may be commercial and medical applications for the bicycle on Earth.
