The collective experience has taught us about the body’s response to reduced gravity. Currently, the I.S.S. is shielded by the magnetosphere, and only 24 astronauts who took part in the Apollo program have ventured beyond it. These astronauts spent just a week at a time without the protection of the magnetosphere and they experienced a rate of cardiovascular disease four to five times higher than their counterparts who stayed in low Earth orbit or never entered orbit. This suggests that cosmic radiation may have damaged their cardiovascular system.
Until it can be reasonably guaranteed that people can survive and live on Mars or the moon, space-based medical science is hindered by small sample sizes that don’t represent the general population. Space tourism offers opportunities to study the effects of radiation and low gravity on a broader demographic. “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, director of the Translational Research Institute for Space Health (TRISH) at the Baylor College of Medicine.
Epidemiologists face the same challenge on Earth. They must wait for harm to come to enough people before they can expose the causes. Aerospace medicine is one of three specialties certified by the American Board of Preventive Medicine. Surgeons for a given flight must optimize the health of their patients and ward off potential disasters before departure. But the specific disasters cannot be known until they occur.
Scientists once predicted that we couldn’t live without Earth’s gravity. However, Yuri Gagarin’s 1961 orbit around the Earth proved that our internal musculature could maintain our vital functions in conditions of weightlessness. Space travelers initially experience space-adaptation syndrome (S.A.S.), causing symptoms such as nausea, headache, and vomiting. Astronauts only reported these symptoms in the 1970s, as they are usually stoic and unforthcoming about any symptom that might ground them.