Medicine: Aviation Medicine Takes Up the Challenge of Space

The Vertical Frontier

NATURE designed man’s body for a groundling’s life, never more than treetop height above the earth’s surface. In the upper reaches of the atmosphere or in the airless space beyond, man is as much out of his element as a mackerel marching across the Sahara. But unlike the mackerel, man is determined to transcend his environment. He reaches for the stars. A short half-century after the Wright brothers skittered over the sand dunes of Kitty Hawk aircraft now on the designers’ boardswill fly at heights of 100,000 to 125,000 ft. Man (Major Arthur Murray) has already flown up to 90,000 ft. and at 2½ times the speed of sound. Rockets have gone up 250 miles at speeds up to 3,600 m.p.h., and two rhesus monkeys (named Pat and Mike) have survived the ordeal of being rocketed up to 190,080 ft., are thus the current holders of the world’s altitude record.

Man’s body puts sharp limitations on how high he can go and how fast he can be accelerated to supersonic speeds. He has reached what Space Physiologist Hubertus Strughold aptly calls “the vertical frontier.” To help conquer the frontier is the task of a young and bustling specialty: aviation medicine.

Most active in the field is the U.S. Air Force, which made great strides under its longtime surgeon general, Major General Harry George Armstrong (since July, surgeon of U.S. Air Forces in Europe). Just as busy on a smaller scale is the Navy, with most of its air-medical research directed the by top U.S. Captain Ashton Graybiel, one of the topU.S. heart experts. Scores of university laboratories are helping the armed forces. Eager researchers are using themselves as guinea pigs for experiments in low-pressure chambers, on high-speed centrifuges and rocket-powered sleds. They are toiling up the Andes to find out how Peruvian Indians stand the strain of high altitude, breathing radioactive gases, and sweating in 122° chambers on low oxygen.

The Dangers of Altitude

The researchers’ first problem was to find out in detail what happens to the human body during an ascent, and why Aviation medicinemen now give this picture of men at steadily increasing altitudes:

Sea Level to 8,000 Ft. In a moderate-paced climb, the human machine does all right if no great demands are made on it. At this level, most flyers feel nothing more than a ping in the ears.

10,000 to 18,000 Ft. The field of vision narrow’s, so the armed forces require all flyers to breathe extra oxygen above 10,000 ft. in daylight (above 5,000 in darkness). Up to 15,000 ft., most flyers remain conscious without oxygen, but their working efficiency is reduced. After 15 minutes to an hour at approximately 18,000 ft., nearly all (unless acclimatized like Alpinists) lose consciousness. But before a man does so, he may have strange delusions. Classic example: a reconnaissance pilot in the western Pacific in World War II refused to bother with oxygen and thought he was taking magnificently daring pictures of enemy positions. It turned out that instead he had urinated into his camera. Says General Armstrong, soberly: “A man is not himself when he is suffering from oxygen lack, even when he believes he is.”

18,000 to 30,000 Ft. An unacclimatized man must have oxygen or lose consciousness in a maximum of 45 minutes, perhaps as little as 1½minutes. Around 25,000, many a man has trouble with the expansion of gases trapped in his intestines, especially if he has drunk beer or pop or eaten beans, corn or fried foods.

30,000 to 43,000 Ft. A flyer must wear a tight-fitting mask over nose and mouth, breathe oxygen under pressure. In effect, this turns his windpipe and lungs into an internal pressurized cabin. The natural breathing process is reversed: the gadget forces the oxygen into the flyer, and he must make a positive effort to exhale. One major effect is to make communication more difficult. A pilot cannot utter a whole sentence, can gasp only a few words, perhaps mere syllables at a time. Even with oxygen, pilots may get the bends or the chokes.*Also: a man cannot whistle, and he is likely to suffer from formication —the feeling that ants are marching over his body.

43,000 Ft. Pressure breathing becomes impractical for long periods because of the strain on the chest. But up to 50,000 ft. an experienced pilot might remain conscious for one to ten minutes. Without oxygen he would pass out cold in 15 seconds.

50,000 Ft. The heart could no longer tolerate, even for a minute, the strain of an internally pressurized chest. So the whole body must be kept under pressure, in either a suit or a cabin. Most likely the pilot is now deep in the stratosphere (reached at a mere 24,000 ft. over the poles, at 60,000 ft. over the equator). With the clouds and the earth far below him, he has no points of reference for depth perception (judgment of distances) or focusing. He tends to keep his eyes in focus a short distance from the plane, will not see a distant enemy. This is the “pseudo-myopia” of altitude. At supersonic speeds, if he sees another plane approaching half a mile away, it will have passed him before the message from the retina registers on the perception center in his brain. This is “distance scotoma.” The quality of light itself is changed: there are not enough dust particles to diffuse it. Even with sunshine all around, the pilot cannot see instruments in the shadows unless they are lighted.

63,000 Ft. “The Armstrong line,” named for General Armstrong, who forecast it on a theoretical basis, later proved it with animals. Here, without protection, the blood boils, because the air pressure (57 mm. of mercury) equals the vapor pressure of water at body temperature.

80,000 Ft. Oxygen in the outside air now becomes poisonous because ionizing rays turn some of it into ozone, with three atoms to the molecule instead of two. Ozone rots rubber, corrodes metal and ruins a man’s lungs. From here on up, only a sealed cabin with a built-in climate including its own air supply can sustain life.

120,000 Ft. Cosmic rays may be hazardous, with heavy nuclei in the raw. One can bore through a man, killing a “column” of tissue of 1,500 to 3,000 cells. An unlucky hit on the macula, the point of clearest vision at the center of the retina, could cause partial blindness. Even the rarefied air at this level will create enough friction, at speeds already foreseeable, to raise cockpit temperatures to 400° or 500° F. Air conditioning is a must, but to cool the air to a comfortable 80° would require forbiddingly heavy gear, so some designers have hit upon 120° as an attainable mark (if man can be equipped to withstand this sweltering heat).

The Dangers of Gravity

Next to the dangers caused by low atmospheric pressure at high altitude, the biggest perils on the vertical frontier are gravity forces. Every time a human body is subjected to acceleration (a word that scientists use broadly to include slowdowns and changes in direction as well as speed-ups), it feels the pull or push of gravity, or “G” forces. Common example: the passenger in the hot-rod who is thrown against the seat-back when the driver makes a jackrabbit start. In an airplane the crew is subject to sharp acceleration forces in any quick burst of speed, e.g., a jet-assisted takeoff, or in an abrupt change in direction of flight. At high speeds even gentle turns can set up heavy acceleration forces. Thus when a fighter pilot makes a turn, his blood and guts are pulled by acceleration to the outside of the turn: blood flows from head to feet, and organs in the abdomen are pushed down to the pelvis. If the turn is sharp enough or fast enough to develop forces of two Gs (double the ordinary force of gravity) or more, the drainage of blood from the head and heart may make him black out.

One G is a force equal to that of gravity, which makes a body in free fall (without air drag) pick up speed at the rate of 32 ft. per second for every second of fall. The human body’s ability to withstand G forces without injury varies enormously, from about two Gs to 15 or more, depending on the position and protection afforded. Damage is smallest if the shock is taken through the body’s smallest dimension, from nose to nape and from the navel to the small of the back. Damage is greater if the shock is taken so that blood rushes from head to feet (positive Gs), and worst of all from feet to head (negative Gs). Dr. Armstrong calculates that when a man jumps from a table 30 in. high and lands flat-footed on a hard floor, he subjects himself to the frightening force of 16 Gs, but is not harmed because the shock is taken head to feet. The daring experiments of Lieut. Colonel John Paul Stapp on a rocket sled show that the human frame can withstand great stresses (up to 45 Gs) if it is properly supported and can take them in the right direction.

In early experiments with a primitive centrifuge, Dr. Armstrong subjected a human volunteer —himself—to forces as high as 14 positive Gs and 4½ negative Gs. He reported: “The [facial] skin is markedly red and congested . . . There are small hemorrhages beneath the skin. The skull seems as if about to burst. The eyes feel as though burned from their sockets, and there is a dry, gritty feeling to the eyelids . . . General reactions are similar to those of one who has suffered a concussion of the brain, and there may be neuromuscular incoordination, and the gait is slightly staggering . . . Mental confusion may persist for several hours.”

To man’s five senses, the Navy’s Dr. Graybiel adds two others, both of which are thrown out of kilter by G forces: 1) the sense of balance and posture * controlled by the inner ear’s semicircular canals * which is lost when a pilot stands on his ear in a turn; as a consequence he cannot tell whether a distant line is tilted or horizontal ; and 2 ) the sense of relation to gravity forces, which has its seat in a pea-sized gadget in the head called the otolith organ; when this is disturbed by fast spinning of the body, a pilot might see the Leaning Tower of Pisa straighten up and then lean over backward —a phenomenon that might make even a veteran flyer crash.

But if gravity forces are dangerous, so may be the lack of them in outer space. Says Dr. Graybiel: “I don’t see how our heart-and-artery system can function in a weightless environment.” He suggests a partial solution: the spaceship pilot should create his own gravity forces by flying a slightly curved or zigzag course. Better still, say others, rotate the ship.

The Only Cure

Medical men have no hope that they will ever concoct a pill to counteract gravity, or an injection to let man get along without breathing oxygen. The only solution in sight for the dangers of both altitude and gravity is to equip man with an artificial skin and artificial organs.

First is the problem of oxygen. Today’s pressure masks are thoroughly effective, though cumbersome and a bit uncomfortable. Soon they may even include an automatic indicator, which the Navy is perfecting, to tell a flyer when he is not getting as much oxygen as he needs long before he would realize it himself.

At the same 30,000-ft. level where he needs pressure oxygen, a flyer needs a pressure suit. If he is in a pressurized cabin or cockpit, the suit is only insurance—in case the cabin pressure fails accidentally or is shot out.

The Air Force Medical Services worked first on the “partial-pressure suit,” which covers the trunk, arms and legs but leaves the hands and head free. The Navy took the job of trying to devise a full (i.e., overall) pressure suit without the disadvantages of “frozen” joints and clubfingers. Now the Air Force is trying to improve on the Navy’s work, and under military security both services are testing suits that they believe are markedly superior to any models the public has been told about. In everyday use, the “partial” suit is worn with a pressurized crash helmet, and the two are hooked together to give an almost full pressure suit, still leaving the hands free. But this rig will not give as much protection against the bends or the boiling of blood as an overall pressure suit.

Another type of suit is needed to counteract the effect of gravity forces. “G suits” do that job in the crudest way possible—by restricting the flow of blood. The G suit looks like a pair of close-fitting overalls, with five rubber bladders set in: one over the belly, two over the thighs, and a pair around the calves. Automatically inflated, these check the footward blood flow, and they can be deflated for straightaway flight.

Theoretically, the G suit makes it possible for a pilot to tolerate as much as two Gs more than human nature in the raw. In practice, however, any flyer tenses his belly muscles when he is going into a tight turn, and this tends to dam the blood stream. Some authorities question whether it really gives any more protection than good muscle tone, properly used. The Navy’s Captain Charles F. Gell believes that the answer to G forces is not a suit but a reclining seat. At the Johnsville (Pa.) Air Development Center, he has experimented with tilt-back models which would enable a pilot to take the stresses fore and aft instead of up and down. But this makes for difficulties in seeing out and handling the controls.

On top of a G suit and a pressure suit, plus helmet and gloves, the pilot must wear protection against cold and immersion (he might have to bail out over the ocean). This means a quilted “liner,” much like the Chinese army’s winter gear (gadgeteers are trying to save weight and bulk by getting rid of the quilting), with a waterproof suit worn over everything.

By this time the pilot is wearing so many protective layers that he is in danger of stewing in his own juices, so researchers of the U.S.A.F. Air Research and Development Command at Wright Air Force Base have developed a cooling suit to be worn under everything but the underwear. This consists of two layers of rubberized nylon, quilted together, with two sets of air holes. A hose from a valve near the pilot’s navel hooks the suit into the plane’s air-conditioning system, and cooled air pours through small holes around his body. Warmed and spent, it escapes through larger holes and a set of dump valves.

His six suits may be cut down to five now that G bladders can be built into the pressure suit. But over the five, the human Christmas tree must drape more decorations: a parachute pack, a shoulder harness and lap belt, and underarm life preservers (replacing the gaudy old Mae West). For bail-out at high altitude, he dangles an oxygen cylinder. With an assortment of minor hardware such as a knife, flashlight and aluminum pistol, he is equipped for virtually any hazard, but miserably handicapped in flying a plane.

Thus attired, the fighter pilot cannot possibly empty his bowels in flight, and the only arrangements so far devised to let him urinate are minor variants of the old “motorman’s pal.” It is almost impossible for pilots to eat in flight, though altitude (for reasons not yet known) increases appetite, and a man begins to feel uncomfortably hungry after three to six hours. The Air Force is using gadgets that fit into cans of soup, fruit juice or milk and allow the pilot to suck the contents through a plastic tube let into a side port in his helmet visor.

The Future

Scientists do not hope ever basically to change man’s earthbound nature. Butthey know that in the machine age, man has managed to adapt himself to conditions that seemed “inhuman” and “impossible” only 50 years ago. To ease hisadaptation to space and speed, scientists are continuously studying examples ofsuch adaptations in nature.

When man has equipped his body and built his spaceships to break through thevertical frontier, he will have new emotional problems to contend with. WritesDr. Armstrong: “One peculiar and very interesting psychological reaction to high-altitude flight is the tendency to conceive the airplane as being a totally independent habitation or planet, free of all earthly connection or relationship … At extreme heights, where the earth is almost invisible through its ever-present enveloping haze, this conception in some instances becomes absolute. The result is astate of mental depression and apprehension, as though one were irrevocably separated from the earth and all its inhabitants.”

But the monkeys were shot up to 190,080 ft. in an Aerobee rocket showedno signs of neurosis. Says General Armstrong: “If monkeys can do it, we canlearn to do it, too.”

* Bends: when pressure is released, the blood and other body fluids will hold less nitrogen and other gases in solution; these begin to bubble out, especially in the knees and wrists, causing great pain. Chokes: gas bubbles form in tissues inside the chest, cause pain probably through pressure on nerve endings. Breathing becomes impossible, and the whole circulatory system is in danger of collapse.