Mary Roach - Packing for Mars

Nothing works as it’s supposed to in zero gravity, or zero G, as it’s also known. “Even something as simple as a fuse,” astronaut Chris Hadfield told me, mistaking me for someone who knows how a fuse works. Now I know: Fuses have a metal strip that melts in response to a surplus of current. The molten bit drips away, leaving a gap that interrupts the power flow. Without gravity, the droplet doesn’t drip, so the power continues to flow until the metal boils, by which time the equipment has fried. Zero gravity is part of the reason NASA price tags seem so extravagant. For every new piece of equipment that goes up on a mission—every pump, fan, throttle, widget—a prototype must be flown on the C-9 to be sure it works in weightlessness.

Overheating equipment is a common theme in zero G. Anything that generates heat tends to overheat, because there are no convection currents in the air. Normally, hot air rises—because it’s thinner and lighter; the livelier molecules are all bouncing off each other and spreading out more than they do in cooler air. When hot air rises, cooler air flows in to fill the vacuum left behind. Without gravity, nothing is any lighter than anything else. It’s all weightless. The heated air just sits where it is, getting hotter and hotter and eventually causing damage to the equipment.

Human machinery tends to overheat for the same reason. Without fans, all the heat that exercising astronauts generate would hang around their body in a tropical miasma. As would exhaled breath. Crew members who hang their sleeping sacks in poorly ventilated spots get carbon dioxide headaches.

In the case of the Space Weld Team, it is the human machinery that’s most notably out of commission. It’s not something you can fix with a fan.

On the ceiling of the C-9 is a red numerical display of the type you see at deli counters, telling patrons which number is being served. This one is counting parabolas, twenty-seven so far. Three more and it’s over. We were told not to “go Supermanning around the cabin,” but I have to break the rules. As gravity fades out on the twenty-eighth parabola, I pull up my legs, crouch on the windowpane, and then gently uncoil, launching myself across the cabin of the plane. It’s like pushing off from the wall of a swimming pool, but the pool is empty and it’s air you’re gliding through. It’s probably the coolest moment of my entire life. But not of Pat Zerkel’s life. The Missouri space welder has been belted down in the front row of seats. Though weightless, he appears heavily burdened. A white bag hovers near his face. It is held open with both hands, like a hat carried through a crowd for tips.

“ OOOooulllrr-aaghchkkk, khkkk. ” Pat has been ill since the fourth parabola. At parabola number 7, the flight surgeon came over to hold him steady during the weightlessness, hoping it would help. (And to keep him, as he told me later, from “floating away helpless and vomiting everywhere.”) At parabola number 12, men in blue flight suits gave Pat a shot and helped him to the back of the plane, where he would remain for the rest of the flight.

The special evil of motion sickness, the genius of its cruelty, is that, generally speaking, it hits you when you’re up. A sunset sail on the San Francisco Bay, a child’s first roller-coaster ride, a rookie astronaut’s first trip to space. [21] A journalist’s ride in Tom Cruise’s two-seat biplane. Cruise piloted us through a run of aerobatic stunts, the last of which, a “hammerhead,” did me in. The plane had an open cockpit, and I was in the front seat, meaning that anything that might escape the “Sic Sac” that flapped in the breeze at my elbow would blow back onto Mr. Cruise’s tanned and flawless face. Cruise is a cleanly man. Disaster loomed. I managed to keep my tacos down, though barely. There is no faster route from joy to misery, from yee-ha to oooulllrr-aaghchkkk.

In space, motion sickness is more than an unpleasant embarrassment. An incapacitated crew member makes for the most costly sick day in the world. An entire Soviet mission, Soyuz 10, was aborted due to motion sickness. You’d think science would have it licked by now. It’s not for want of trying.

TO FIGURE OUT how best to prevent motion sickness, you first need to figure out how best to bring it on. Aerospace research has excelled at the latter, if not the former, and perhaps nowhere more triumphantly than at the U.S. Naval Aerospace Medical Institute in Pensacola, Florida: the birthplace of the human disorientation device. In a 1962 NASA-funded study, twenty cadets agreed to be harnessed to a chair mounted on its side on a horizontal pole. Thus affixed, the men were rotated, rotisserie style, at up to thirty revolutions per minute. As a reference point, a chicken on a motorized spit typically turns at five revolutions per minute. Only eight of the twenty made it to the end of the experiment.

The motion sickness inducer of choice these days is the rotating chair. [22] Aerospace medicine cannot take credit for this one. Nineteenth-century insane asylums often prescribed a whirl in the Cox’s chair for their more turbulent patients. Wrote one physician in an 1834 report on novel psychiatric techniques: “After having committed some irrational and spiteful act, the patient is forthwith placed on the rotating chair and revolved…until he becomes quiet, apologizes, and promises improvement, or until he starts to vomit.” These were trying times for the mad. Alternate “treatments” included “surprise plunges into icy water.” Here the rider sits upright upon the seat, as if preparing to take dictation. A small motor causes the chair to spin on its base, conferring, at first glance, a joyful air to the proceedings, as though the subject had set herself awhirl—the tipsy stenographer at the office Christmas party. At the experimenter’s command, the subjects, eyes closed, tilt their heads left and then right while spinning. I took a brief turn in the rotating chair that resides in the lab of space motion sickness researcher Pat Cowings, at NASA Ames. At the first head tilt, something lurched inside. “I can make a rock sick,” said Cowings, and I believe her.

What has aeromedical science learned from the combined tortures of motion sickness research? For starters, we now know what causes it: sensory conflict. Your eyes and your vestibular system can’t get their stories straight. Say you are a passenger belowdecks on a heaving ship. Since you are moving along with the walls and floor, your eyes report to your brain that you are sitting still in the room. But your inner ear tells a conflicting story. As the ship moves you up and down and around, your otoliths—tiny calcium pebbles that rest atop hairs that line the vestibule of the inner ear—register these movements. If the ship dips down into a trough, for instance, the otoliths rise; when the ship crests, they press down. Because the room is moving with you, your eyes detect neither. The brain gets confused and, for reasons not well understood, responds by nauseating you. Soon you are heaving too. (This is why it helps to stay up on deck, where your eyes can register the boat’s motion relative to the horizon.)

Zero gravity presents a uniquely perplexing sensory conflict. On Earth, when you’re upright, gravity brings your otoliths to rest on the hair cells along the bottom of the inner ear. When you lie down on your side, they come to rest on the hairs on that side. During weightlessness, the otoliths, in both situations, just float around in the middle. Now if you suddenly turn your head, they are free to ricochet back and forth off the walls. “So your inner ear says you just laid down and stood up and laid down and stood up,” says Cowings. Until your brain learns to reinterpret the signals, the contradiction can be sick-making.