Fit, and on a Mission
Can the human body survive a lengthy Martian sojourn?
By some estimates, astronauts could lose up to 20 percent of their bone mass on a trip to Mars and back. Thirty-year-olds could return as frail as people in their 80s. Heart and other muscles deteriorate in similar dramatic fashion, and even the immune system seems to stumble badly. NASA makes clear that medical studies of zero gravity take center stage. "We will have a baseline for a whole new biology up there," says the project's senior scientist, NASA physicist and two-time shuttle crew member Roger Crouch.
Gravity dreams. But there is growing debate, between top NASA managers like Crouch and the agency's own midlevel scientists, over whether to install a centrifuge on board big enough to whirl a person around and imitate the very thing the station gets away from: gravity. Long before the space age dawned, space dreamers were sketching ways to provide gravity in space. "It's not like on Star Trek, where you throw the artificial-gravity switch," said Charles Lloyd, manager of a NASA program to study "countermeasures" against the hazards of space, including low gravity. Back in the 1950s, rocket pioneer Wernher von Braun imagined a wheel-shape space station 125 feet across, turning fast enough to provide constant, simulated gravity along its rim. Nobody is thinking that big quite yet. "What we really want is a human-rated centrifuge," Lloyd says. It is possible, he contends, that just an hour or so a day exercising in simulated gravity would stem the body's decline--"but we will never know if we don't try it."
The present space station plan foresees--in 2006--a centrifuge only about 8 feet in diameter, enough for cell cultures or small rodents. "We are starting small and working our way up," says Crouch. Until more is known from simple living systems, he argues, there is no strong justification for one big enough for a person, one that might require about twice as much room.
Not everybody buys that argument. "There have been workshops, task force reports, and on and on, but we can't seem to get them [NASA officials] off the dime on this," said Kenneth Baldwin of the University of California-Irvine, leader of a NASA-funded research group studying muscle weakness from spaceflight. "It seems obvious. Let's put a centrifuge up there--and put people in it." He worries that if a Mars expedition is to get going within 20 years, work needs to start now to find how to keep the voyagers healthy.
Cycling epiphany. There is no shortage of ideas where to start. "This thing may do it all," said Arthur Kreitenberg, an orthopedic surgeon in Southern California who moonlights in a laboratory whose door reads "Space Cycle." Working with Baldwin and others at UC-Irvine and with a manufacturer of dirt bikes, he has invented and patented a "self-powered human centrifuge." The idea came to Kreitenberg in "an epiphany" in 1991, when as a would-be astronaut he toured a space station mock-up at Johnson Space Center. He rushed home and sketched out a bicycle seat mounted at the end of a rotating arm, with pedals and a chain drive so the rider sends the whole thing spinning. In Earthbound tests, riders have gotten spinning so fast their feet reached eight times the force of gravity (their heads, nearer the center, aren't weighed down nearly as much). Dizziness and nausea, remarkably, don't afflict riders if they don't speed up or slow down too fast and don't move their heads very much. The centrifuge would be about 15 feet across--and could be provided in an inflated space station module called TransHab that NASA has been considering as an eventual add-on.
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