The collective experience has taught us how the body responds when gravity’s pull is substantially reduced. The I.S.S. is still shielded by the magnetosphere, and only the 24 astronauts who flew in the Apollo program have gone beyond it. They spent little more than a week at a time without its protection and have died of cardiovascular disease at a rate four to five times as high as their counterparts who stayed in low Earth orbit or never entered orbit at all, suggesting that exposure to cosmic radiation might have damaged their arteries, veins, and capillaries.
Space tourism promises to offer opportunities to study the effects of radiation and low gravity on a much broader demographic than historically qualified astronauts. The space-based medical science needed to make living on Mars or the moon possible has been hindered by small sample sizes that aren’t representative of the general population. “Old, young, pre-existing health conditions — we are starting to gather a knowledge base that in the future will be essential even for NASA,” said Dorit Donoviel, the director of the Translational Research Institute for Space Health at the Baylor College of Medicine.
Epidemiologists face the same predicament on Earth: Before they can figure out how to protect the population, they must wait for harm to come to enough people to expose the causes. When less-rigorous medical screening allows more tourists to reach space, the chances increase significantly that someone will get hurt or have a health emergency there.
The problem is, surgeons for a given flight tend to be stuck on the ground and have to optimize the health of their patients and ward off potential disasters before departure. As with every expedition into the unknown, at some point some intrepid or desperate souls are just going to have to blast off and see what happens.
Scientists once predicted that we couldn’t live without Earth’s gravity. But when Yuri Gagarin returned from his single, 108-minute orbit around our world in 1961, he proved that our internal musculature could maintain our vital functions in conditions of weightlessness. Initially, many space travelers experience space-adaptation syndrome (S.A.S.), with symptoms like nausea, headache, and vomiting. Just like in childhood, sitting in the back of a car with your head down, a mismatch of what the eyes are seeing and what the inner ear is telling you causes this sensation. It’s a result of the organs and hairs of the vestibular system floating free without their usual gravitational signals.