Surviving the Extremes: A Doctor's Journey to the Limits of Human Endurance (38 page)

Clay’s laceration, only about an inch long, ran obliquely across the last joint of the thumb on the outside. There was no nerve, tendon, or major blood vessel damage. Although it would require stitches, the repair would be easy. I cleaned the wound and placed a sterile drape around the hand, then injected lidocaine at the base of the thumb to block the nerves. I inspected the wound from the inside, and once I was sure there was no other damage, I sewed it closed with three nylon sutures and covered it with a compressive dressing. It was a routine repair, but the first operation I had ever done wearing only a towel.

Jay and I escorted Clay back to his bunk, passing through another
portal into the main chamber that contained the living quarters. There I met the other two astronauts, Garrett Reisman and Peggy Whitson, the mission leader, who had already logged over six months on the ISS. They had just finished their videocast. While Clay rested, we relaxed for a few minutes, sitting at the dining table, conversing over cups of hot cocoa and looking at the ever-changing parade of sea creatures that passed by the large porthole. Less than an hour before, I had been one of those creatures looking in.

There was a knock on the entry port—Otto was giving us our ten-minute warning. My patient was doing well enough now to escort me to the wet-porch and tell me to “Stop by anytime you’re in the neighborhood.” I submerged through the moon pool, leaving behind a tiny island in a vast ocean, but taking with me the haunting sense of what life is like for astronauts inside a cramped metal canister surrounded by an immense and hostile wilderness. I had been inside for fifty-three minutes. You, on the other hand, on your journey to Mars, will be inside for three years.

Can a group of six humans survive so far away from Earth for so long? In space our enemies would be some of the same environmental hazards we encounter on Earth—radiation, cold, low air pressure. However, there they exist at such extremes that our body’s slowly evolved adaptations and carefully learned defenses are instantly and piteously rendered irrelevant. Skin pigmentation, sunscreen, tightly woven fabrics, and even umbrellas may protect us from solar radiation at the beach or in the desert, but we have never been exposed to the most powerful radioactive particles: the cosmic and solar rays that are blocked by Earth’s atmosphere and magnetic field. Once we travel outside those shields, we become fair game for a whole army of high-energy atomic particles that travel at nearly the speed of light and create tiny nuclear reactions each time they pass through our bodies.

We may be able to maintain our internal temperature by shivering and adding layers of clothes in Arctic conditions that would otherwise be cold enough to halt the chemical reactions that keep us alive. But what chance do we have when exposed to temperatures approaching absolute zero, minus 463°F, the temperature at which all atomic motion stops?

The lower the air pressure, the lower the temperature at which a liquid boils. People who live in the mountainous regions of Colorado have to use pressure cookers to maintain enough air pressure so their soup won’t boil before it’s cooked. At the highest camp on Mount Everest, 5 miles up, water boils at such a low temperature that it can be drunk right away. In space, 130 miles above the earth, the boiling point drops below 98°F, meaning that our blood would boil away just from body heat alone.

There is one more environmental enemy in space, and it’s not like anything we might experience naturally. Though less deadly than the others it remains all the more diabolical because it subverts an immutable fact of life on Earth: constant gravity. Because gravity doesn’t change, no living organism has adapted with any special designs to deal with variations in its intensity. Once we leave the earth, gravity problems begin immediately—first there’s too much gravity and then too little.

Knowing all this, you have nonetheless volunteered for this pioneering expedition. You’ve gone through all the years of training, and your rocket to Mars has finally lifted off. Accelerating toward a speed of 10 miles per second, your body weight is effectively increasing 100 pounds per second. Your stomach has gotten so heavy that it’s falling through your abdomen, though it’s still tethered to your throat by a hyperextended esophagus. The delicate air sacs at the bottom of your lungs are breaking from the pressure and air is leaking out. Your blood now weighs nine times more than it did several heartbeats ago and your heart is no longer strong enough to pump any of it up to your brain. The launch may be proceeding smoothly, but your body is frantically trying to handle the chaos created by the rapidly increasing gravitational force.

Gravity pulls everything to Earth. When a rocket pulls you the other way, you’re swimming upstream. The more it accelerates, the greater the drag on your body and the heavier your body becomes. An acceleration of 3Gs (three times the force of gravity) is necessary to pull away from Earth. Fighter pilots routinely make turns in the
7G to 9G range. Doubling the G force has doubled your weight. At 2Gs your face droops and your internal organs begin to shift. As the third G is added, the liquids in your body (which is 60 percent water) become hard to lift. They pool in your legs, and your heart has a tough time pumping them up to your head. One more G and your vision dims—you’re experiencing a “grayout” because the blood flow to your eyes has diminished to a trickle. You’re at your limit. If no countermeasures are taken and the Gs continue to mount, flow to your eyes will stop completely and your vision will black out, though you will still be able to hear and think. Adding another few Gs will stop blood flow to your brain, rendering you unconscious.

Just as it does in high altitudes, the lack of oxygen affects your whole brain, not just your higher senses of consciousness. Your lower “body maintenance” areas begin to misfire, sending uncoordinated signals. This results in seizures when your large muscle groups are affected, or convulsions when your internal organs are involved. Mistimed signals to your heart will cause inefficient pumping or even stop it entirely. What blood your heart does manage to distribute around your body will not contain its normal amount of oxygen, for your lungs are also suffering from the increased G force. Your trachea, or windpipe, has been flattened. The alveoli in the lower part of your lungs have broken under the pressure, allowing air to escape before it can be transferred to your blood. Though your upper alveoli are still intact, the increased weight of your blood prevents it from reaching them.

Your body is breaking down everywhere. Your kidneys can’t filter enough blood to make urine. The compressive pressure on your spine is so severe that the fluid-filled discs separating and cushioning the vertebrae are in danger of exploding.

Your response to this overwhelming onslaught will be valiant but feeble. Pressure receptors in your aorta and carotid arteries, sensing a decrease in blood flow (just as they would at high altitude), send signals that increase heart rate while at the same time constricting blood vessels. This forces more blood through a narrower space, increasing the pressure head in an attempt to force blood into the tissues. Evolved over thousands of years, the system makes the internal pressure adjustments
necessary on Earth, but it was never designed to fend off the six-second, ninefold increase in gravity that fighter pilots experience, or even the threefold increase you are experiencing now.

To survive liftoff, you will need help—anything that works. No treatment is either too complex or too simple. Lying on your back will greatly increase your tolerance of G force. With Gs pushing on you from chest to back rather than from head to foot, the direction of acceleration becomes “eyeballs in” rather than “eyeballs down.” Body weight is spread over a larger surface, organs are compressed front to back (the shortest internal distance), and to distribute blood throughout the body the heart only has to pump it sideways. Combating gravity in the horizontal position is familiar to all of us; we apply it regularly when we go to sleep.

Lying down on the job still won’t be enough. You should be grunting. Pilots are trained to perform the “hook maneuver”: bending forward, taking a deep breath, and then grunting the word
hook
. This closes the throat and increases the blood pressure in a way very similar to bearing down to move your bowels.

You’re under attack by increased gravity, a powerful and strange enemy, and your defensive response is to lie down and grunt? That’s just not going to be enough. Venturing into space requires a completely different form of treatment—applied technology.

As G forces mount, your blood and other body fluids become increasingly reluctant to leave your legs and lower body. Encouragement will be provided by your anti-G suit—a series of bladders inside your space suit that are wrapped around your legs and abdomen. The bladders inflate instantly in response to the increased G force, much as a car air bag inflates in response to contact. The resulting squeeze injects fluid back into your upper body, and periodic pressure pulses continue to milk blood from your legs. Your blood pressure rises to its normal level, and your beleaguered heart can maintain blood flow. I have applied the same suit many times in hospital trauma units, where it is called “antishock trousers.” It saves lives by preventing shock from blood loss.

Your respiration is also under attack. G stress will flatten your windpipe and break your air sacs, leaving your lungs incapable of
providing adequate oxygen to your blood. The treatment is a positive-pressure breathing device, an air pump that forces high concentrations of oxygen deep into your lung tissues. That reduces the amount of work you need to do to breathe, and each breath brings you more oxygen. Similar units, commonly known as respirators, are used on patients in ICUs to ease the burden on their failing lungs.

The ultimate treatment for too much gravity is not a medical treatment at all but a device called an auto-recovery system. Once you lose consciousness, recovery is not instantaneous even when the G forces are off-loaded. It will take twelve to fifteen seconds for consciousness to return, and then another fifteen or so seconds until you become reoriented and coordinated enough to resume control of a rocket or an aircraft. Rockets can be guided from the ground, but with the high speed and ground-hugging capabilities of high-performance jet aircraft, thirty seconds is more than enough time to crash. Body sensors on an unconscious pilot will activate an auto-recovery system that decelerates the plane and flies it until the pilot recovers. Theoretically, the system can prevent crashes. It has been resisted by airplane pilots, however, who are uneasy about letting machines do their flying.

That uneasiness has been justified on at least two occasions, when Soviet crews headed for the
Salyut 4
space station involuntarily tested how much sustained G force a human body can withstand. Less than a minute before takeoff, cosmonauts Vladimir Titov and Gennadi Strekalov, aboard the
Soyuz 10a
, spotted smoke and flames after spilled fuel ignited around the base of their booster rocket. The automatic launch abort system failed to activate; its control wires had already burned. Fire quickly engulfed the rocket and Titov felt the booster below him sway. The escape system was not crew controlled. The only way to activate it was for two ground controllers, sitting in separate buildings, each to turn a key on their control panel simultaneously. Twelve long seconds later the cosmonauts felt two explosive bolts firing—the capsule had disengaged from the booster. The emergency engine was ignited by radio signal, and Titov and Strekalov were instantaneously subjected to a violent acceleration as their capsule
pulled away from the burning rocket. Six seconds later the booster exploded. Their flight lasted less than six minutes, landing them within sight of the burning launch pad. They had experienced 17Gs, but only for five seconds. Neither sustained any serious injuries. They had passed their medical examinations and were drinking vodka long before the fire at the launch pad was out.

The record for enduring the longest sustained high G force is one that cosmonauts Vasily Lazarev and Oleg Makarov would rather not have been a part of. The empty first-stage booster of their
Soyuz 18-1
spacecraft was supposed to jettison at an altitude of 72 miles, with propulsion shifting to the second stage. The parts failed to separate, but the second stage ignited anyway. Powered from the middle, the rocket began twirling end over end like a baton. Ground telemetry was unable to detect any abnormality in the flight path, so it took some time, and some increasingly loud shouting, for the cosmonauts to convince mission controllers to fire the escape rocket. The capsule fell from a height of 120 miles after a wild twenty-one-minute suborbital ride, and landed in the Altai Mountains, 1,000 miles from the launch site. It tumbled down a slope and was about to go over a cliff when its parachute lines got tangled in some trees. Miraculously, Lazarev and Makarov survived with relatively minor injuries, though the acceleration gauge in the capsule had broken after it reached 20.6Gs.

That’s not something you want to imagine as you watch the acceleration gauge in your capsule holding reassuringly steady at 3Gs. The combination of recumbent position, anti-G suit, positive pressure breathing, and occasional grunting is enough to counteract the gravity overdose you experience as your rocket heads for temporary Earth orbit. Technology has cured your first space disease, proving that humans can be kept alive under high G loads. With the engine roaring behind you, you’re pressed back in your seat but still feeling reasonably comfortable as the spacecraft reaches its orbital speed of 18,000 miles per hour. The main engine cuts off. Suddenly you feel yourself being flipped upside down. But there’s no problem with the spacecraft—and
you aren’t really being flipped at all. The problem is in your ears. Having just dealt with too much gravity, you now have to deal with too little. As you enter orbit, welcome to your next space disease, weightlessness.

Gravity has been a part of life ever since there has been life—a downward pull that has been incorporated into our bodies throughout their development, most especially in the design of our body stabilizers, the vestibular organs of the inner ear. There are two kinds: the semicircular canals and the otolith. To do their jobs right, they both need gravity to be unchanging and reliable, but now suddenly inside your ears the gravity is gone. The semicircular canals consist of three tubes perpendicular to each other that detect turning motion. The tubes are filled with fluid, which flows when the head rotates. Hairs connected to nerves stick up into the tube and sway with the current. When the head turns right, the fluid sloshes left; when the head turns up, the fluid sloshes down. The hairs stimulate the nerves, and the signals tell the brain which way you are headed. The otolith is a platform suspended in a gel just above another set of hairs projecting up from a nerve. It floats backward when you move ahead and pushes down when you rise, so it detects forward-backward and up-down motion. You can see for yourself how fine-tuned the vestibular system is. If you pass your finger back and forth in front of your eyes, the image will very quickly become blurred, as your eyes can’t keep up. Then hold your finger steady and move your head back and forth at the same speed. The image stays in sharp focus. The vestibular reflexes can react much faster than the muscles that control eye motion to stabilize an image.