Spaceflight's Toll on the Body: Boiling Saliva, Bone Loss and Molting Feet

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In 1966 NASA engineer Jim LeBlanc was testing a prototype spacesuit in a vacuum chamber when his pressurization hose came loose. Within 10 seconds his suit pressure fell to near zero, and he stayed conscious for 14 seconds, long enough to feel the saliva on his tongue begin to boil. A colleague got oxygen to him within about 25 seconds, and he walked away with an earache. This episode works through what leaving Earth does to a body built for one g, a thick atmosphere and a magnetic shield: launch forces of four to six g that drain blood from the brain, the Armstrong limit at about 19 kilometers where water boils at body temperature, and the 1971 Soyuz 11 depressurization that killed all three crew members.

The slower dangers fall under NASA's RIDGE hazards. Cosmic rays shatter DNA and damage lymphocytes, letting latent viruses such as Epstein-Barr reawaken. In microgravity astronauts can lose up to 20 percent of their muscle mass in five to 11 days and 1 to 1.5 percent of their bone density each month, fluids shift toward the head and can flatten the eyeball, and blood volume can drop by up to 22 percent. A 2006 experiment found salmonella grew more virulent in orbit. The episode closes on a Mars round trip of roughly 18 months in transit and how little is known about older travelers, children and reproduction in space.

• Why a body in a vacuum swells but does not explode, and the 90 second survival window
• Space adaptation syndrome, which hits roughly 45 percent of space travelers
• Spaceflight-associated neuro-ocular syndrome and astronauts returning with permanently blurred vision
• Hot sauce cravings, a gag reflex triggered by cream sherry, and tears that pool over the eye
• Molting foot soles, cooling fans that stop exhaled carbon dioxide from pooling, and Valery Ryumin quoting O. Henry on confinement