In the summer of 1966, Greg Hill and four other American college students went to bed. They stayed there for three weeks.

Their protracted bedrest was part of a University of Texas Southwestern Medical School experiment to determine how astronauts might respond to extended spaceflight. "It was boring," says Hill. "We got one shower, but that was it. We could sit up and watch TV, but we had to use a bedpan."

Even that may have been too much activity to properly simulate weightlessness. Today's volunteers in similar experiments spend the whole time with their feet elevated, so their hearts never have to fight gravity to pump blood to the brain and other vital organs.

Still, the original study revealed an astounding fact: by the end of 20 days confined to bed, Hill and his friends' hearts had effectively aged by more than 30 years.

The change was only temporary, but it sounded an important warning for space agenices: if we're ever going to send people to Mars and expect them to be able to stand up when they get there, their spacecraft is going to need exercise facilities. However, a fully equipped gymnasium won't be necessary, according to the experts; a few high-tech versions of those workout gadgets peddled by washed-up movie stars and sports personalities on late-night TV should do the trick.

But experience suggests that exercise alone might not be enough to counter the negative effects of space travel. As Graeme Wren, an adjunct associate professor at Charles Sturt University in Wagga Wagga, NSW, points out, the International Space Station has exercise facilities, but 98 per cent of astronauts have nevertheless experienced physical problems.

Motion sickness is the most common complaint, but more than half the astronauts also reported headaches, respiratory problems, and a condition called 'facial fullness' in which blood pools uncomfortably in the face. "The bottom line is that no one who goes into space gets away scot-free," says Wren.

To settle queasy stomachs and other astronaut ailments, scientists are trying to find ways to simulate gravity in space. One approach is to create a spinning spacecraft, like an over-sized hamster wheel, using centrifugal forces to press astronauts to the outside wall. Another solution, says Californian science fiction writer Larry Niven, would be a two-part vessel whose sections rotate on a long tether, resembling a giant bolas.

Both of these ideas, however, pose huge engineering challenges. Researchers at NASA's Johnson Space Flight Centre in Houston, Texas, are testing an alternative strategy. They're studying the effects on astronauts of spending as little as an hour a day strapped to a spinning table designed to simulate two-and-a-half times normal gravity.

Eventually, Wren believes, the negative effects of weightlessness will be conquered by the right combination of medicine, exercise, and spin-created artificial gravity. But a bigger problem, he says, is radiation. In principle, the solution is simple: make sure the ship's walls are thick enough to block it. But shielding adds unwanted weight to a spacecraft.

Today's missions are carried out close enough to the Earth that shielding is only required during solar storms, which are brief enough to be weathered in cramped radiation shelters. But beyond the safety of the Earth's magnetic field, the entire ship is going to need protection from the background radiation of deep space, either via shielding or some kind of electrical or magnetic force field designed to do for the spacecraft what the Earth's magnetic field does for us.

Others wonder what might happen to people who live, die, and are born in space or on other worlds. In fact, at about the same time Hill was spending a summer as the ultimate couch potato, Niven was writing a series of now-classic novels (the Known Space series) in which he speculated that people born on high-gravity worlds would grow up short and powerful, while those raised in space would be thin and elongated. Forty years later, scientists still think that this might be a real consideration, though some say that Niven may have gotten it backwards.

Instead of weightlessness causing elongation, lack of blood pressure to the extremities might have the opposite effect. "If a foetus grew up in that environment, you could imagine something with a large head and chest and not much else," Wren says. Of course, he's quick to add, "It's conjecture. Speculation with a capital 'S'."

How to deal with medical emergencies on extended spaceflights is another concern. We've already learned, through trial and error, how to effectively manage a broad spectrum of medical crises on Earth. Platoons of soldiers operating in remote locations, for example, will routinely include a trained medic and carry a compact medical kit designed to handle anything from a heart attack to a broken bone. During military operations, "even amputations have been done," Wren says.

Alternatively, perhaps machines will replace the medic. In his fiction, Niven created a coffin-like 'autodoc' which would cure you of just about anything if you were healthy enough to be able to crawl inside. Wren suggests we could employ a robotic surgeon manipulated by remote control from Earth.

But the distance between Mars and Earth makes Wren's proposal difficult. Imagine a 40-minute delay between the time you tell the remote-controlled surgeon to take out an appendix, and the time you learn that it accidentally removed a gall bladder.

Still, the folks at NASA have become fairly accomplished at driving the Mars rovers, and perhaps the robotic surgeon will be semi-autonomous and capable of making many decisions of its own volition.

But even if emergency medical care in space isn't perfect, the show will certainly go on. After all, humanity has been exploring far from medical help for millennia. Compared to the manifold perils of delving into the thick of the Amazon basin or trekking to the South Pole, a few million kilometres, an absence of gravity and the perpetual barrage of radiation are hardly going to stop us.

---

Readers' comments