Surviving the Extremes: A Doctor's Journey to the Limits of Human Endurance (39 page)

Under so-called normal conditions—that is, conditions that have existed for the past 2 million years—the eyes and vestibular system work extremely well together. The eyes are quick enough to keep an animal in focus as it passes across your field of view, while chasing it down means moving rapidly over uneven terrain as your eyes keep the animal in perfect focus so you can throw your spear accurately. Nevertheless, the system does not have the design specifications to deal
with G forces, acceleration, and zero gravity. The limits of the vestibular system are soon exceeded in an unearthly environment. Though capable of detecting the up-and-down motion of an elevator, it cannot make sense out of space travel. The brain cannot comprehend that gravity has changed that much; it was never programmed to process such unlikely data. Rather, it constructs other “more likely” scenarios to explain the confusing sensory input.

When the launch began, you felt sudden acceleration because your otoliths were pulled backward to the extreme. When you reached orbit, however, the main engine was cut since the pull of gravity was neutralized. Your otoliths, which had been pinned back by the constant acceleration, were suddenly released and thrust forward. To a brain that has grown up in a 1G world, this can mean only one thing: your head has suddenly gone from tilting way back to tilting way forward. No longer held down by gravity, the otolith has lost contact with its underlying hair cells. Your brain “knows” this can only happen when you stand on your head, so even as your spacecraft is slipping smoothly into orbit, the brain concludes that you have just tumbled forward and are now upside down.

For a pilot taking off from an aircraft carrier, the design of the otolith and the semicircular canals can prove fatal. As they are catapulted off the deck, pilots receive a nearly instantaneous impulse of 5Gs. The otolith shoots backward and their brains tell them they’re tilted up at least 45°. If no outside visibility counters the misinterpretation, a pilot may believe he is climbing too steeply and will “correct” his flight path by flying into the sea. Furthermore, the semicircular canals were built to let you know you have turned your head; they were not made to orient pilots making prolonged banked turns. At the start of the turn, the tube fluid is set in motion and the pilot knows he is turning. As the turn becomes steady, the fluid “catches up” and stops flowing. When the pilot finishes the turn, momentum drives the fluid the other way, and he may assume that he has over-corrected. Should he continue to correct this perceived overcorrection, he will progressively lose altitude and put the plane into a spiral dive. The pilot can make an appropriate adjustment when there is a visible horizon, but if there is nothing to be seen out the window,
the only recourse is instrument flying. A scenario such as this may well have caused John F. Kennedy Jr.’s tragic crash into the sea on a foggy night off Martha’s Vineyard.

A pilot can disregard what his inner ear tells him when and if he can see that it is not so. The brain will believe its eyes over its ears every time. Consider what happens when you watch a wide-screen movie of a roller-coaster ride. Though you know your chair is not moving, you become nauseated and may even throw up. When there is discordance between visual and vestibular input, the brain puts its trust in what it sees, setting in motion a well-coordinated bodily response to a problem that does not exist.

You cannot change the design of your otolith and semicircular canals, but you can learn to overcome the illusions they create through training sessions in a centrifuge. As part of your training you were strapped into a barbershop chair mounted on a turntable. When the chair was spun and tilted, you experienced all the effects of increased gravity, learning what signals to expect from the balance center in your cerebellum and how to disregard them by imposing logical thought from the frontal lobes. In other words, you learned to use your brain to override your brain. The treatment is effective but can be frightful. Cosmonaut Viktor Savinykh told me that one of his sessions was abruptly terminated—not by him, but by the scientist monitoring him. The scientist had said, “I can’t take it anymore.”

A centrifuge creates an outward pull (centrifugal force) by spinning around a fixed point to which it is tethered. You experience centrifugal force when you’re pushed against the door of a car making a high-speed turn. Contrary to what people assume, the weightlessness of a body in orbit around Earth does not stem from the absence of gravity; the distance isn’t even halfway far enough away to escape Earth’s pull.
Orbital altitude
means the distance required for gravity to be weakened enough so that it can be exactly offset by the centrifugal force created by orbital speed. The rocket and its contents are still tethered by gravity but precisely balanced by the outward pull of the centrifugal force created as it rotates around Earth. Were gravity to let go completely, the rocket would fly off into space, the same way you would if a car door suddenly swung open.

As you spin around Earth, your body, which only recently weighed 600 pounds, now discovers it weighs nothing at all. You release your harness and float upward, experiencing the delightful sensation of being as light as air. But inside your body, things are floating too. Your internal organs have become buoyant. You subconsciously keep tightening your abdomen to push them back down. Having just been jerked back and forth by excess Gs, the poor vestibular system in your ears now receives no input at all. The pressure receptors in your feet aren’t firing either. As a result of all this you feel as if you are upside down. Orienting yourself depends on visual cues, but they are often absent or misleading. Nothing in the capsule helps you distinguish top from bottom—up is wherever your head is. Turning a dial provides a sensation that the dial remains stationary and the control panel and entire spacecraft are rotating around it in the opposite direction. Nausea wells up inside you.

Space sickness affects about two-thirds of the astronauts and seems to have no correlation with a propensity for seasickness or even for airsickness. Lots of treatments have been tried, but none have worked too well. Despite not having gravity to work with, however, the vestibular system somehow adapts, and the condition usually clears up within a few days. Until it does, however, a space capsule cannot be a drug-free zone. Temporary relief is provided by medications such as Phenergan or scopolamine, mixed with a little Dexedrine to prevent drowsiness. Sick astronauts and cosmonauts take downers and uppers to keep flying.

You’re still in low Earth orbit so that you can temporarily dock at the ISS. Extra fuel tanks have been prepositioned there by earlier missions; these tanks will be hooked up to your rocket for the long voyage ahead. Out the window the space station comes into view. It is either above or below you—the terms are irrelevant—but you have to align and slow the spacecraft to achieve a gentle docking of two vehicles, both traveling at 18,000 miles per hour. The approach has to be head-on and the closing speed reduced to less than 2 miles per hour. Anything else would cause a collision—and provide a quick reminder of how thin are the walls separating you from the vacuum of space.

________

Cosmonauts Vasily Tsibliyev and Aleksandr Lazutkin and Astronaut Michael Foale got just such a reminder when their
Mir
space station was rammed by
Progress M34
, an unmanned supply ship. Tsibliyev was handling the docking of the ship by remote control—using two joysticks to align the ship and a lever to brake it while watching a blip on a radar screen. The last part of the docking had to be done visually, but when the ship approached, Tsibliyev, Lazutkin, and Foale could not see it out the window. Finally the ship came into view when it passed in front of an extended solar array that had been blocking their line of sight. It was both bigger and nearer than they had expected, and closing on them much too fast. Tsibliyev fired the ship’s retro-rockets too late to reverse its momentum. They watched helplessly as the 7-ton
Progress M34
, traveling at 1 meter per second, passed over the docking port and crashed into the belly of the space station.

There was a violent shaking. Foale felt his ears pop, as might occur from the decrease in air pressure when a plane takes off. That he was alive at all told him the impact was not—yet—catastrophic, but the pop meant the cabin was decompressing.
Mir
had sprung a leak. With atmospheric pressure rapidly decreasing, the spacemen’s bodies were undergoing the same kind of stress they would have endured in a balloon floating upward into ever thinner air. Diminishing outside counterpressure allows air within closed compartments to expand. The air-filled cavities within human bodies distend. If the pressure drops too rapidly or too far, they will burst like overinflated balloons.

While the body has outlet valves to equalize pressure in most of its air spaces, their functioning appears quaint compared to the exigencies for survival during rapid depressurization. A valve in the middle ear connects to the throat and can be opened to relieve pressure by swallowing hard—something passengers do instinctively when their flight takes off. Expanding gas in a stomach can be relieved by belching, and pressure in the intestines can be relieved by passing gas. Although there is plenty of air in the lungs, much of it in tiny air sacs far from the outlet valves of the mouth and nose, excess air will work its way out through normal respiration. All these natural escape valves
work well when internal gas buildup occurs slowly, such as while hiking up a mountain trail or after eating spoiled food. They were never meant to keep up with pressure changes in leaky spacecraft, however, and they quickly fall short.

Moreover, some body spaces that contain gas have no outlet. All our joints are bathed in synovial fluid to reduce contact friction between bones, much as lubricating oil helps gears mesh smoothly. The nitrogen dissolved in this fluid is held in solution by atmospheric pressure. When the pressure is suddenly reduced, the expanding gas has no natural escape route from the joint. It can only be removed slowly, through metabolism by body enzymes. The decompression of the astronauts on
Mir
was exactly analogous to what scuba divers experience. Survival on board
Mir
depended on slowing the leak so that it would be gradual enough for humans’ cumbersome adjustment mechanisms to work and buy enough reaction time for the brain to devise, and the body to carry out, a plan to prevent the pressure from dropping so low that no further adjustment would be possible.

The space station was a construct of interconnected modules. If the ruptured module were sealed off, the pressure in the rest of the station could be maintained. A series of cables and a ventilation tube passed through the module, all of which had to be cut to allow the connecting hatch to shut. Working furiously, Lazutkin and Foale managed to cut the cables and tube, but even with the hatchway cleared, they still couldn’t close the hatch. It was hinged on the inside, and they were unable to pull it shut against the stream of air being sucked out the hole. Tsibliyev opened an extra tank of air to slow the steady drop in pressure and prolonged their “time of useful consciousness”—the time in which they could act purposefully to correct the situation. Lazutkin got the idea of sealing the passage with a hatch cover originally used to cover the opening until the module had been fully assembled. Once the lid had been placed in front of the hatchway, the vacuum inside the module sucked it against the opening, forming an airtight seal. The pressure stabilized, and the men survived.

The pressure drop hadn’t been rapid enough for anyone to explode, but it could have been enough to cause the bends—yet, strangely, no one got bent. Many pressure drops have occurred in outer
space, albeit in less critical situations, but so far no astronaut has ever been afflicted with the disease. Weightlessness may prevent the bends in some way not yet fully understood.

The
Soyuz 11
mission was heralded as the beginning of a new era in space exploration. Its crew was the first to board a space station, the
Salyut 1
, where they studied the effects of weightlessness. After twenty-four days, they reboarded
Soyuz 11
for their return flight. At a height of 100 miles, where atmospheric pressure is still close to zero, they fired explosive bolts to separate their reentry capsule. The explosion knocked loose a pressure-equalization valve, and the capsule began depressurizing. The limit of human tolerance is about one-third atmospheric pressure, a level not reached until descent to an altitude of 5 miles above Earth (coincidentally, that is precisely the air pressure and height at the top of Mount Everest, putting the summit at the very borderline for human survival). The pressure-equalization valve is not supposed to open until
2½
miles up (the approximate height of the Everest base camp), where the outside pressure of one-half that at sea level is adequate to sustain life. Two of the cosmonauts tried to shut the valve manually but, weakened by prolonged weightlessness, they were unable to turn it fast enough to prevent total depressurization. With no surrounding atmosphere, air is sucked out of the lungs and blood boils at body temperature. After the capsule completed the automatic reentry-and-landing sequence, the recovery team arrived on the scene. They were surprised to find that the cosmonauts had not yet emerged. Opening the hatch, they found out why. The capsule had survived intact; the three crewmen, still strapped into their seats, had not.

Thoughts of what happened on
Mir
and
Salyut 1
fade away as your craft lines up with the space station and coasts smoothly into the docking port. You and the rest of the crew are focused on the tasks ahead; these involve attaching the auxiliary fuel tanks and verifying vehicle system readiness prior to leaving Earth’s orbit. This will require numerous space walks.

Space walks are high-risk exercises because they put astronauts at their lowest level of protection. Once you step outside, your margin of safety is as thin as your space suit—your personal spacecraft. To
keep you alive it must surround you with enough counterpressure to hold back the vacuum of space, insulate you from temperatures varying from 200°F below zero to 200°F above zero, provide you with an oxygen supply and handle carbon dioxide removal, and protect you from any haphazard micrometeor strikes. Your space suit has to do all that and still be flexible enough to allow you to mount solar panels, install cameras, and repair who knows what.