Childhood dreams of being an astronaut are easy. Actually blasting off is a little harder.
But now people who have longed to go into space can buy a ticket, if they've got the cash. Are they healthy enough to make the voyage, though?
That's becoming a pressing question as the options for leaving Earth multiply.
A company called Space Adventures has been sending tourists to the International Space Station since 2001. Virgin Galactic has already signed up more than 500 people to take trips to the edge of space. They'll start blasting off next year. And startup Golden Spike said earlier this month it plans to start sending people to the moon, perhaps as soon as 2020.
"If space tourism starts, everyone who can afford to will be able to fly," says S. Marlene Grenon, a vascular surgeon at the University of California, San Francisco. "That raises the question of how we can make it possible for anyone to fly into space if that's their dream."
With costs ranging from $200,000 to $750 million per flyer, space isn't likely to rival Disneyland for tourists anytime soon. But thousands of people could soon be headed up into space.
NASA's corps of astronauts are pretty fit to begin with. They're put through rigorous medical testing and can be disqualified for conditions ranging from kidney stones to cardiovascular problems. Space tourists and workers could be a less healthy lot.
"All that's required by the FAA is informed consent," Grenon says. "It's up to the operators to decide" who's fit to fly.
Depending on the rules that those operators institute, physicians could be faced with clearing their patients for flight. So Grenon gathered a group of aerospace medical professionals, including astronaut Millie Hughes-Fulford, to provide some advice. Their paper appears in the British Medical Journal.
Space travel, Grenon notes, is very different from life on earth. "Your body doesn't feel gravity," she says, and "the blood volume goes more towards the chest and the face. That's why astronauts have bird legs and puffy faces." Within a few days, space travelers could be experiencing motion sickness, nausea, sinus congestion or dizziness.
Those risks are all known from extensive studies of the 500 or so people who have gone into space since Russian Yuri Gagarin orbited the planet in 1961. But people with all sorts of pre-existing conditions could soon be following Gagarin's path.
That doesn't mean, however, that any old medical condition should bar someone from space, Grenon and her colleagues say. Instead, a physician might help a patient with coronary artery disease to stabilize his blood pressure and heart rhythm . A pregnant woman would be advised to postpone her trip until after she gives birth.
Grenon recommends that doctors "optimize their medical treatment and make sure the risks are discussed and document those discussions."