Tuesday, November 9, 2010

Gas-Propelled Astronauts?

Mary Roach, Packing for Mars (New York: W.W. Norton, 2010), 305-6.

The zero-gravity fart has been a popular orbital pursuit, particularly on all-male flights. One hears tell of astronauts using intestinal gas like rocket propellant to "launch themselves across the middeck," as astronaut Roger Crouch puts it. He had heard the claims and was dubious. "The mass and velocity of the expelled gas," he told me in an email that has forever endeared him to me, "is very small compared to the mass of the human body." Thus it was unlikely that it could accelerate a 180-pound astronaut. Crouch pointed out that an exhaled breath doesn't propel an astronaut in any direction, and the lungs hold about six liters of air -- versus the fart, which, as we learned from Dr. Murphy, holds at most three soda cans' worth.

Or the average person's, anyway. "My genes have blessed me with an extraordinary ability to expel some of the byproducts of digestion," wrote Crouch. "So given that, I thought that it should be tested. In what I thought was a real voluminous and rapidly expelled purge, I failed to move noticeably." Crouch surmised that his experiment may have been compromised by the "action/reaction of the gas passing through the pants." Disappointingly, both his flights were mixed-gender, so Crouch was disinclined to "strip down naked" and try it again.