Good morning! It is a pleasure to be here and to have the opportunity to address such a meeting of aerospace professionals. We are here today, in part, to celebrate an organization that has, for seventy years, pioneered in studying and applying aerospace medicine to the problems of flight. When, at 10 a.m., on the morning of October 7, 1929, Louis Bauer called the first annual meeting of the "Aero Medical Association" to order in the old Statler Hotel in this city, about 60 physicians were present. Look around: we see how successful this organization has been, how compelling his vision was, how demanding the need has been for the aerospace medicine professional, in those who are here today. That year was a remarkable one in aviation, for only a week before, test pilot Jimmy Doolittle had completed the first blind flight in aviation history, a triumph of technology and courage that incorporated more than a little aerospace medicine itself. Today, seventy years later, this organization has, appropriately enough, changed its name to reflect the aerospace revolution. We are an aerospace nation, we are, indeed, an aerospace world. There is very little in this world that is unaffected by the revolution in flight.

The airplane has flown for little less than a century, yet, in that time, it has radically reshaped the world in which we live. Several weeks ago, at a fete offered by Time Magazine honoring their notable cover people, Bill Gates of Microsoft saluted the Wright brothers as the inventors of the first "World Wide Web." Now, at first thought, that may seem a little extreme. But if we really think of what has been accomplished in aerospace in this century, it makes a great deal of sense. For example, if any one of us wished to take a trip to Europe in the nineteenth century, such a venture required great wealth, a tremendous amount of time, a great deal of planning, and, frankly, not a little risk. Such voyages weren’t called "Grand Tours" for nothing. Yet today, you can’t find room to stow your briefcase on any transatlantic widebody for all the backpacks of vacationing students. That’s mass communication, and, as Gates so perceptively noted, it’s a direct outgrowth of the aerospace revolution. And it has been a factor in world affairs since 1958 when, for the first time, more people traveled across the North Atlantic by air than by sea.

Revolutions require revolutionaries—visionary figures that transform a field of endeavor or who otherwise take advantage of circumstances to change and alter previously accepted patterns of behavior and thought. The aerospace revolution is a classic example of this, and when it is examined in detail, we see that there was any number of individuals whose international efforts, combined together, worked to give to the world the ability to exploit the third dimension. While the popular mind naturally gravitates to the aeronauts, aviators, astronauts, and cosmonauts themselves, and the inventors, designers, engineers, and technicians who developed the remarkable flying machines that we have witnessed, there are many others who have contributed to the explosive growth of aviation in this century. In particular, the medical researcher and the medical practitioner stand tall in this pantheon, for medicine and medical concerns have been integral parts of the aerospace process since the very dawn of flight itself.

Take Icarus, who, together with his father Daedalus, fashioned crude wings to his arms using wax and feathers, and, flapping furiously, took off from Crete. Before take-off a flight surgeon had warned him not to fly too close to the sun, lest the wax melt and his feathers fall off. But like many pilots since that time, he ignored the advice, experienced structural failure from thermodynamic effects, and got waxed in the process. So there is a long tradition of mixing medicine and flight.

But seriously, it is worth noting a number of early aviation pioneers were also medical practitioners or interested in medicine: the Moorish physician Abbas b. Firnas, who completed a short glide in the tenth century; the Renaissance futurist Leonardo da Vinci who conceptualized ornithopters, helicopters, and parachutes; and Giovanni Borelli, a 17^th century mathematician who undertook pioneering studies of human musculature.

Clearly the history of aerospace medicine and the history of aerospace technology have advanced hand-in-hand. Put another way, the challenges and accomplishments that constitute the development of aerospace medicine have closely matched the challenging requirements of flight as it has evolved from within the atmosphere to within the harsh environment of near-Earth space. As you all recognize, aerospace medicine involves many discrete specialties and numerous major areas of practice and interest. In a broad sense, it ranges from the physician screening candidates for civil or military pilot training, to the aerospace health care professional supervising patient care during medical evacuations, to the laboratory researcher investigating g-induced loss of consciousness or the impact of long-duration space missions upon human physiology.

What I would like to concentrate upon in my remaining time is the relationship between aerospace medicine and the development of aerospace technology. This relationship has been characterized by:

--Forced adaptation to the opportunity afforded by rapid technological development in aeronautics and astronautics,

--Perceptive anticipation of future medical requirements for flight systems and human performance, and, finally,

--Rapid advancement of both fields: aerospace medicine as a discipline within the health sciences, and aerospace technology as a discipline within the matrix of engineering science and related fields.

Specifically I would like to examine the twin problems of aircrew safety and performance, particularly under high accelerations and at high-altitudes; and escape and survival in the advent of catastrophe. Several of the challenges within these two areas have struck me as of particular significance in revealing the critical role that aerospace medicine has played in aerospace development since Kitty Hawk and, indeed, since the development of the first crude balloons not quite 216 years ago. Listed in rough chronological order—for many represent continuing concerns through the years—we have the following challenges:

--Ensuring aircrew safety and performance during high-altitude flight.

--Studies of human susceptibility to disorientation during so-called "blind" flight.

--Interest in acceleration effects during abrupt maneuvering flight.

--Introduction of crude pressure suits and early pressure cabin technology.

--Introduction of the g-suit to enhance combat survivability and performance.

--Crew escape from high-altitude and at high-speeds.

--Development of practical partial and full-pressure pilot protection suits and helmets for flight above 50,000 ft.

--Resolving problems of long-duration missions in zero-g conditions and in conditions where spacecraft crews might be exposed to solar radiation.

Clearly, many of these challenges overlap and display a high degree of interrelatedness—as well as a high degree of persistence, in that they exhibit reoccurrence as the capabilities of aerospace systems evolve.

The first notable work in aerospace medicine accompanied the development of the balloon. While hot-air designs of the kind pioneered in 1783 by the brothers Joseph and Etienne Montgolfier cooled so quickly once aloft that they remained essentially "low altitude" systems, even the first crude cold-gas (hydrogen) balloons were capable from the outset of reaching remarkably high-altitudes for their time. Indeed, the very first balloonist to make an ascent in a hydrogen balloon, French physicist J. A. C. Charles, climbed to 10,000 feet on December 1, 1783, his second voyage aloft. On this thirty-minute journey, he grew so exceedingly cold that he could not hold a writing pen, and developed a "violent pain in my right ear and jaw" that forced him to valve off gas and descend. By the mid-1860’s, British balloonists had reached 25,000 feet, without using oxygen though they clearly recognized its desirability; one wrote that he had "experienced the limit of our power of breathing." This led the French physician Paul Bert to create the first pressure chamber capable of simulating ascents; this small test facility could produce an equivalent altitude of 28,000 feet. Bert subsequently undertook a variety of physiological experiments upon animal and human test subjects, evaluating the effects of various concentrations of oxygen, his efforts earning him recognition as the father of aerospace medicine. Sadly, two of his disciples, who ignored his advice to use oxygen throughout a high-altitude journey (and not just when they felt the need) perished from oxygen deprivation at 28,000 feet in the flight of the French balloon Zenith in 1875.

Using a more cautious approach, two German balloonists, students of the great Austrian physiologist Hermann von Schrotter, reached 34,500 feet in an open-gondola balloon in 1901, though even they nearly died in the attempt. (Afterwards, von Schrotter recommended all subsequent high-altitude balloons use a "hermetically sealed gondola"). But even over a quarter-century after this, in 1927, lack of adequate preparation and anticipation of flight conditions could lead to tragedy, as the death of U.S. Army balloonist Hawthorne Gray during an ascent to over 42,000 feet (using unpressurized oxygen delivery systems and an open gondola) dramatically illustrated. For aeronauts and aviators alike, the future of high-altitude flight belonged to the pressurized cabin or the pressure suit.

The invention and subsequent international development of the airplane occurred at a pace that is remarkable even today, in the era of the electronic revolution. To illustrate this, in 1903 the Wrights flew at Kitty Hawk, barely climbing higher than the height of a person, and covering only eight hundred feet on their best flight of the day, which lasted just short of a minute in duration. In 1908 they developed the first military airplane, demonstrating their aircraft to astonished Europeans the following year. An Italian military pilot flying a German-built airplane became the first airman to attack enemy ground forces using bombs dropped from an airplane, during the 1911 Italo-Turkish war over Tripoli. In 1914, eleven years after Kitty Hawk, the two great battles that shaped the future direction of the First World War, the battles of the Marne and Tannenberg, were decided on the basis of aerial reconnaissance. Aircraft served in a variety of roles during the First World War, and, in 1919, there were no less than three flights across the North Atlantic. In 1924, a small formation of U.S. Army biplanes circled the globe.

Given what we now know about the limitations of human performance at altitude, and what was even known at the time from balloon flights and the work of individuals such as Bert and von Schrotter, it is remarkable how cavalier the world’s airmen were about flying at high-altitudes in open-cockpit, unheated, and non-oxygen-equipped aircraft. By 1917, combat patrols and dogfights at altitudes between 16,000 and 18,000 feet were commonplace, some missions lasting upwards of 1-½ hours. Anoxia and hypothermia undoubtedly contributed to loss rates (as evidenced by the number of pilots who, in high-altitude combat, were taken by surprise, or showed little recognition of what was happening around them, or who simply fell out of control). The rigors of flying seem to have reduced pilot resistance to more common ailments as well. For example, when influenza swept with Western Front and British Isles in 1918, fighter squadrons seem to have been particularly hard hit.

Confronting the world’s first air war, medical researchers concentrated on attributes of aircrew performance that they considered significant, including vision, reaction time, heart rate and respiration, and vestibular response, the latter then based on the notion, later disproved, that the ear was more important than the eye in providing cues to the pilot as to aircraft orientation. Significantly, the United States introduced the innovation of having medical personnel familiar with aviation and possessing actual flying experience—the first genuine flight surgeons.

By 1918, largely on the recommendations of medical personnel coupled with the evidence of actual flying experience, oxygen-breathing systems were beginning to appear in combat aircraft, as were heated flying suits. Neither, however, was in widespread service.

 

Aerospace Medicine during Aviation’s Golden Age

The interwar years witnessed dramatic changes in aircraft capability and performance. Between the armistice in 1918 and the outbreak of the Second World War in 1939, aircraft flight speeds tripled, the airplane evolved from wood and fabric to rugged all-metal construction, and from an open-cockpit to an enclosed cabin design. By the end of the period, the turbojet engine promised an era of 500+ mph flight speeds at altitudes exceeding 40,000 feet, and a high-speed aerodynamic revolution offered the potentiality of exceeding the speed of sound.

Numerous challenges confronted aircraft designers, aircrew, aircraft operators, researchers, and medical personnel alike during this time period. Early in the 1920’s, the hazards of so-called "blind flying" led to international efforts to develop a better appreciation of pilot disorientation while operating in conditions where no clear horizon existed. Often, even the threat of zero visibility forced pilots to abandon their aircraft; as early British aviator John Grierson recollected, "when the weather became bad or the fuel ran out, the parachute was there to be used." As exemplified by tests using the Jones-Barany revolving chair, aeromedical researchers such as William Ocker and David Myers demonstrated that safe blind flying was not something dependent upon the individual’s own vestibular system or something that could be resolved physiologically by selecting a specially gifted individual or by special physical training. Rather, it required faith: it demanded a denial of the perceived motion generated by physical cues in favor of an acceptance of the revealed motion as indicated by onboard instrumentation.

This went very much against the pilot training culture of the time. Charles Lindbergh recalled that flight instructors warned students "A good pilot doesn’t depend on his instruments," and Harry Guggenheim, a World War I naval aviator whose postwar philanthropic foundation played the key role in resolving the challenge of blind flight, remembered his flight instructor stating "See those instruments? Pay no attention to them. I want you to get the feel of the ship regardless of instruments." It should not be surprising, then, how many pilots became disoriented and spun themselves into the ground.

Thanks to better appreciation of what a pilot needed, rapid instrumentation development efforts both followed this initial medical research and accompanied subsequent work: radio navigation systems for long-range precision flying and precision letdowns to landing, artificial horizons to compensate for the lack of a visible horizon reference line, and precision altimeters to give accurate vertical measurements. In September 1929, test pilot James H. Doolittle completed the first blind flight in aviation history, an epochal event ranking with the first supersonic flight in demonstrating the mastery of what had heretofore been considered not merely dangerous but perhaps impossible as well.

Related to this was the growing problem of accelerations in flight. Structural failures of new generations of military aircraft were commonplace; fortunately, the introduction of the personal parachute kept fatalities reasonably low. Nevertheless, researchers needed to understand the loads environment that these newer 200 mph+ encountered. In the course of this research, they discovered that it was equally important to understand what was happening to the crew. Early biplanes could exceed upwards of 7g in maneuvering flight, and when the all-metal revolution increased the strength of aircraft structures, the g limits rose appreciably. Thus, aeromedical researchers were particularly interested in 1927 when test pilot Luke Christopher of the National Advisory Committee for Aeronautics did an abrupt stick-snatch at 173 mph in a Navy Curtiss Hawk fighter, hitting 10.5g. Christopher suffered "generalized conjunctivitis of both eyes", and a "mild cerebral concussion with some generalized cerebral capillary hemorrhage," and required a month before fully recovering. Interestingly, some high-speed air racing accidents during tight pylon turns and crashes of dive-bombers (both in the U.S. and Germany) during dive pullouts strongly suggest, from today’s perspective, possible g-induced loss of consciousness (G-LOC).

Both in the United States and abroad, aeromedical researchers increasingly relied upon flight testing, using specially instrumented aircraft carrying test subjects to determine crew tolerance in maneuvering flight to a variety of g levels sustained over time. Very quickly they noted some of the characteristics we now associate with high-g flight such as graying of vision, and vision "tunneling." This generated growing interest in developing some sort of garment that might offset, in a manner analogous to the primitive pressure suits of the time, the limiting and, indeed, dangerous, effects of rapid g onset, as will be discussed shortly.

The defining drive in aeronautics in the interwar period was the goal of flying faster and further, which, of course, required flying higher—certainly above 30,000 feet. Even before the end of the First World War, the emergence of the gear-and-turbo-driven engine supercharger clearly established a technical ability for aircraft to reach higher altitudes. This, of course, drove a great deal of interest in protecting the pilot and passengers. Accordingly, significant high-altitude research, using both aircraft and balloons, occurred in virtually all advanced nations. Again, open-cockpit unpressurized flights were risky in the extreme, and numerous close calls characterized some of the flight tests. (In September 1934, for example, Italian test pilot Renato Donati reached an altitude of 47,358 feet in an open-cockpit biplane, but had to be carried from his plane after landing in a near-comatose condition, remaining so for nearly a day).

Pressure suit development intrigued a number of researchers, beginning with British physiologist J. B. S. Haldane, who had first proposed such an approach to high-altitude flight as early as 1920. In December 1934, wearing an experimental pressure suit with an internal absolute pressure of 7 pounds per square inch (psi) developed by B. F. Goodrich, Wiley Post reached an altitude of 48,000 feet, flying a supercharged Lockheed Vega monoplane, the famed Winnie Mae. The next year, Post flew from Burbank, California, to Cleveland, Ohio, cruising in the jet stream at an altitude in excess of 30,000 feet. Post’s suit is the direct ancestor of the modern full-pressure "space suit." By the end of the decade, other nations had flown generally similar suits, and, in 1938, Italian pilot Mario Pezzi reached an altitude of 56,046 feet, a record that still stands for a piston-engine airplane. But the suit, of course, was far from practicable for commercial applications, or even military ones.

Early pressure cabin research was hardly less risky than open cockpit high-altitude flying. In 1921, one U.S. Air Service test pilot discovered that his experimental pressurized aircraft worked too well: the pressurization system generated an equivalent altitude of –3,000 feet below sea level! Although experiencing a great deal of discomfort, the pilot was able to land safely, but the plane never flew again. Balloonists had greater early success. Using a sealed pressurized pure-oxygen gondola (in many ways, the predecessor of the modern space vehicle), the Swiss physicist August Piccard reached 51,775 feet in May 1931 in the research balloon FNRS, accompanied by Paul Kipfer. The similarly designed American Explorer II (which used a safer atmosphere of 46% oxygen and 54% nitrogen), crewed by Orvil Anderson and A. W. Stevens reached 72,395 feet in November 1935, a record, incidentally, that lasted nearly sixteen years, until exceeded by the Douglas D-558-2 rocket-propelled research airplane.

The first successful pressurized cabin airplane was the Junkers Ju 49, which flew to over 41,000 feet in May 1929, piloted by Willi Neuenhofen. The Ju 49, strictly experimental, had a small pressurized "capsule" with vision portholes for its pilot inserted into the structure of the aircraft. As for the United States, the death of balloonist Hawthorne Gray in 1927 had profoundly affected the engineering community at Wright Field, Ohio, and, under the leadership of Carl Greene, they devoted increasing attention to examining the potentiality for pressurized cabins. Greene and research associate John Younger designed a special pressurized cabin for use with a modified Lockheed Model 10 Electra twin-engine transport, using engine-driven air compressors. This testbed, the Lockheed XC-35, first flew in 1937, with a cabin that operated at a pressure of 9.5 psi, affording its passengers the ability to fly well above 30,000 feet in shirtsleeve comfort, without the need for oxygen breathing systems. The advent of the XC-35 marked the emergence of the practical pressurized cabin for high-altitude commercial and military aircraft, a milestone event in aerospace history suitably recognized by the award of the Collier Trophy to the XC-35 team in 1938. That same year, Boeing unveiled the world’s first production airliner designed for a pressurized fuselage, the Boeing 307 Stratoliner; the next year saw the first flight of a turbojet airplane. That combination--the turbojet and the pressurized cabin--would, in the 1950’s, revolutionize international air travel and, indeed, modern society.

The Second World War constituted a crucible in the rapid proliferation of aerospace medicine. It was the first conflict employing the mass application of aerospace medicine in every role from aircrew screening through medical research. Aerospace medical thrusts during the war concentrated on two primary areas: improving the ability of combat aircrew to fulfill military missions, and protection of aircrew from the hazards of combat, high-altitude flight, and emergency escape. The emergence of the pilot protection anti-g suit, the development of better oxygen delivery systems and masks, and the development of the first ejection seats all constitute notable examples of research in these areas, but particularly the g suit.

Ironically, few outside the medical community considered that g forces might prove a serious safety and operational limitation in fighter combat. During the late 1930’s, for example, a senior member of the Royal Air Force’s Air Staff informed the Flying Personnel Research Committee that modern fighter aircraft flew so fast (then about 300 mph) that dogfights would be essentially impossible. (Nor was the RAF alone in this; fighters in the 1930’s were seen primarily as bomber interceptors, not as aircraft that would clash in great numbers themselves. The FPRC persisted in g-suit research, largely because scientists were aware of a great deal of Nazi interest in acceleration effects due to the Luftwaffe’s investment in dive-bombers, and they concluded that such a course of action was only prudent). In America, the noted American aerospace practitioner and researcher, Harry G. Armstrong, had undertaken a number of g effects studies using an early centrifuge, as had the von Diringshofen brothers in Germany. The lack of suitable centrifuge test facilities caused British researchers to use both single and multiseat research airplanes instead. The combined results of both ground and flight-testing elaborated upon earlier work in the interwar years, and refined understanding of gray-out and black-out. Further, testing demonstrated the lasting effects accompanying over-g episodes, notably mental confusion, lethargy, and fatigue, all of which could become killers in the era of G-LOC. British researchers examined various options to prevent blood pooling in the lower extremities. These included fitting higher rudder pedals to operational fighter aircraft to raise the legs during combat (which increased g tolerance by more than 2g). Additionally, as early as 1940, they investigated angled seats--shades of the F-16 over three decades subsequently! --including one inclined at 45 degrees that enabled a pilot to sustained 6g for 9 seconds without vision impairment or blacking out.

Most serious medical researchers recognized that solving the g onset challenge required developing an anti-g suit of some sort that could prevent pooling of blood in the extremities. The pioneering nations in this work were, primarily, Canada, Australia, and the United States. The Canadian cancer researcher Wilbur Franks designed a full-coverall, water-filled anti-g suit in 1939. In 1942, Royal Navy fighter pilots employed a derivation of this suit during the invasion of North Africa with great success, though, interestingly, the RAF did not adopt it for fear pilots would overstress their aircraft. In contrast, the Australian exercise physiologist Frank Cotton derived a two-piece air-operated suit, which saw limited service with the Royal Australian Air Force. After assessing the merits of both the Franks and Cotton approach, American researchers emphasized using a simpler "exoskeleton" air bladder system, creating a lightweight and cool garment fed by air drawn from the aircraft’s engine intakes. The so-called G-2 and G-3A suits entered service with the U.S. Army Air Forces in 1944. Combat experience indicated that, under identical combat conditions over the same length of time, pilots wearing g-suits shot down twice as many enemy fighters compared to pilots without them. (Nazi Germany, despite all its interest and work on accelerations, did not employ a combat g-suit during the war). G-suit use likewise cut incidences of gray-out or black-out in half. One danger did exist: pilots could now withstand a higher g loading than their Mustangs, raising the specter of their inadvertently overstressing their airplanes.

By the end of the war, attention in aviation was turning to the problems of very high-speed flight, in excess of Mach 1, at altitudes higher than 50,000 feet. Here, the wartime investment in high-altitude and high acceleration protection paid off quickly, but new complications forced further work. For example, newer generations of jet aircraft operating to higher altitudes required stronger internal structures to permit a high level of pressure differential to avoid the problem of dysbarism. Even so, as altitudes exceeded 50,000 feet, crews had either to rely upon partial-or-full-pressure suits or, as with spacecraft, upon a completely sealed cabin, to avoid both the danger of anoxia and, at higher altitudes, vaporization of body fluids.

With this resurgent drive to altitude, a new problem grew in seriousness: explosive decompression. This had occurred occasionally during B-29 operations against Japan, typified by the blowing out of windows, bubbles, and hatches, sometimes with fatal results for a nearby crewman. But in the jet era, such decompression could be fatal to an entire airplane and its crew, as evidenced by the tragedy of the world’s first production jet airliner, the De Havilland Comet. A series of accidents claimed dozens of lives, and were eventually traced to structural failure leading to decompression and then the literally explosive disintegration of the fuselage. The subsequent Boeing 707 and Douglas DC-8 family of transports, which revolutionized intercontinental travel, was the direct beneficiaries of the long and detailed accident investigation undertaken after the Comet’s mysterious crashes.

In 1949, during a high-altitude flight attempt, explosive decompression nearly led to the loss of the first Bell X-1 aircraft; pilot Frank Everest’s life was saved by his partial pressure suit. On a later flight of the more advanced X-1A, Chuck Yeager’s life was arguably saved by his g suit, which enabled him to withstand punishing positive accelerations when the plane tumbled completely out of control at Mach 2.44. Other ideas for crew escape at high-altitude were less successful; for example, provision of an escape capsule failed to save the life of Milburn Apt when his X-2 research airplane likewise departed violently at Mach 3.2.

Much as a parachute had revolutionized aviation safety in the early 1920’s, the ejection seat--appearing in many nations, starting with Nazi Germany in the Second World War--did so again in the jet age. Initially fired using compressed air or a shell cartridge system, the seat eventually evolved into a complex aerospace system itself, with self-righting systems, rocket boost and attitude controls, built-in oxygen for its occupant, automatic seat disconnect systems and deployment systems for the crewman’s parachute, etc. The Korean War, the first jet air war, saw numerous ejections of both Western and Communist pilots from aircraft stricken by enemy fire or inflight failure. The value of automated seats was well illustrated in 1955 by test pilot George Smith, who survived an ejection in a near-vertical dive at Mach 1.05 and 6,000 feet from a North American F-100A Super Sabre. The ejection imposed 64g forces on the hapless pilot, with an onset rate of 700g per second. Rendered unconscious and seriously injured, the pilot survived because the seat automatically separated from him, and the ‘chute automatically deployed as well.

Acceleration research had continued after the Second World War and had led to some experimental work in Europe and America on prone-pilot tests to determine if such an awkward crew position may improve resistance to g-onset. But, as the Smith ejection showed, the most serious difficulty with acceleration in the early jet era was as a result of having to escape. Ejection at both low and high-speed, and at low and high-altitudes, presented numerous problems. Essentially, aeromedical researchers had to provide seat designers with information enabling them to design seats that could accelerate a pilot away from a crashing airplane in any sort of flight attitude The dynamic loadings experienced by the pilot were, of course, of critical interest, as was the behavior of his protection system--particularly his parachute and protective suit. In World War II, W. Randolph Lovelace had survived deliberately parachuting from a B-17 at over 40,000 feet to validate the use of a bail-out oxygen bottle during a high-altitude descent, experiencing an unexpectedly violent opening of his ‘chute that knocked him unconscious and stripped the gloves from his hands. Now, in the Lovelace tradition, aeromedical researchers offered themselves up as test subjects to resolve the problems of both low-and-high-altitude and low-and-high-speed escape. In Britain, some proved out the operation of the first low-altitude low-speed rocket ejection seats (which eventually led to the so-called "zero-zero" seats of the present day) capable of saving a pilot during ejections during takeoff or landing at very low altitudes. One Royal Navy aeromedical researcher, J. S. P. Rawlins, went a step further, and undertook extremely hazardous ejection trials underwater to validate the operation of ejection seats and oxygen systems as a means of escaping from sinking carrier-based aircraft, nearly drowning several times in the process—but always going back.

The most notable of these researchers was, of course, John Paul Stapp, who, at extreme personal risk, added greatly to understanding of drag deceleration during high-speed bailouts at high dynamic pressures ("q") by courageously subjecting himself to no less than 29 brutal rocket sled deceleration tests between 1947 and 1954. In the course of these tests, facing both forwards and to the rear, he suffered a variety of broken bones and sprains, retinal hemorrhage, and concussion, yet continued to offer himself up as a test subject. In December 1954, he experienced conditions only slightly less strenuous than those which seriously injured George Smith a little over two months later, during a test simulating pilot ejection at 1,000 mph at 40,000 feet. Stapp accelerated to 632 mph in five seconds, then stopped in 1.1 seconds, imposing a peak g loading of 40g’s, at a deceleration rate of 600g/sec. Stapp experienced a variety of daunting short-term physiological symptoms as a result, chief of which was acute eye pain that he equated to "extraction of a molar without an anaesthetic." (Later, in 1961, facing rearwards, Eli Breeding went even further, reaching a peak of 82.6g, which left him unconscious, with no measurable blood pressure for 30 seconds. Hospitalized for three days, Breeding made a full recovery).

Besides Stapp, there were a number of researchers in the United States and abroad who risked their own lives to further aerospace medicine. Using sealed gondolas, or open cabins and pressure suits, high-altitude balloonists such as M. Lee Lewis, Malcolm Ross, Charles Moore, David Simons, Clifton McClure, Joseph Kittinger, and Victor Prather took huge polyethylene balloons to altitudes as high as 113,700 feet in the years from 1947 to 1961. These flights always involved tremendous dangers, even near the surface, as the tragic deaths of Lewis and Victor Prather showed (the former perishing in a ground handling accident, and the latter falling and drowning during a landing at sea). Many of these long-duration flights were to validate the performance of aircrew in near-space environments, but Kittinger, in 1959-1960, made three notable free-fall parachute jumps, the last from 102,800 feet.

The courage and determination of these researcher-test subjects cannot be overemphasized, and, thanks to them, both the prospects of survival and the prospects of practical high-altitude, high-speed, and, even, practical near-earth space flight were considerably brightened. When Project Mercury took to space in 1962, it did so on the firm basis of aeromedical work accomplished in support of the earlier American rocket research aircraft program (typified by the supersonic X-1 and Douglas D-558-2, and the hypersonic X-15). Among many different areas of investigation, these aircraft had explored the problems of control at high-altitudes. They also furnished opportunities for evaluating crew performance during zero g flying conditions, under conditions of abrupt acceleration during rocket boost, and during high-workload powerless low-lift-to-drag-ratio landings. Such vehicles had required development of specialized aeromedical equipment (particularly pressure suits such as the David Clark X-15 suit of 1959, the first operational full-pressure suit, which anticipated later full-pressure suits for the manned space program). "X-series" research flights were themselves high risk missions, and not simply because of the aerodynamic and propulsion unknowns associated with the dawn of supersonic flight and early manned rocketry. For example, X-15 pilots tended to experience vertigo during acceleration and climb to altitude, and one of them, Michael Adams, was killed in an accident where this tendency almost certainly played a significant role.

The American manned spacecraft program went surprisingly smoothly, with the marked exception of the loss of the Apollo 1 test crew in 1967 during a pre-launch spacecraft fire (due in large measure to poor vehicle design that relied upon a pure oxygen environment), the near-loss of Apollo 13 (whose crew survived in part because of excellent aerospace medical technical support as well as training); and the Space Shuttle Challenger. As tragic as the latter was, the success of the space program to that time had been remarkable, without the loss of an astronaut in flight over the previous quarter-century. This success required challenging study, training, and evaluation procedures, and widespread and comprehensive laboratory and flight research.

Among the many unknowns and concerns affecting spaceflight at the dawn of the so-called "Space Age" were human performance and mobility in a weightless environment, nutritional and toxicological challenges and requirements, circadian cycle issues, prolonged isolation, protection from space radiation, and tolerance and performance during reentry. Short of actual in-space experience, all of these required creative means of research and assessment. For example, zero-g could be briefly simulated by flying so-called "Keplerian trajectories" in two-seat fighters such as the Lockheed F-94C Starfire and North American F-100F Super Sabre, and modified transports such as NASA’s infamous Boeing KC-135 "Vomit Comet." In other cases, to measure acceleration effects during launch, monkeys and other animals were launched aboard research rockets and then recovered for study. Test subjects, candidate astronauts, and X-15 pilots underwent centrifuge studies (in one case, in 1975, during tests of inclined seats, Navy volunteers withstood 14g for 45 seconds without loss of consciousness or vision disturbance). Special multiple-degree-of-freedom space motion simulators could disorient a test subject, who then had to use his controls to try to regain "control" of his "spacecraft." All of these proved useful, but no substitute for actual inflight space experience.

From the earliest days of NASA, the agency incorporated a biomedical study group as part of its manned spacecraft effort, complementing the well-established military aerospace research establishments then in existence, such as the Air Force’s Aerospace Medical Research Laboratory, or the Navy’s Aviation Medical Acceleration Laboratory. But exactly what conditions a spacefarer might have to encounter were so difficult to predict and assess, that, as an expedient, the physical standards for astronaut selection processes were almost arbitrarily high and demanding. In the most highly publicized result of these standards, Mercury astronaut Donald K. "Deke" Slayton was removed from flight status before he had his chance to fly in space, though he remained with the space program and eventually, in an era where better understanding of the physiological requirements of spaceflight existed, commanded the international Apollo-Soyuz Test Project (ASTP) in 1975, the famed "handshake in space" mission.

The nature of the space program gave a strong, structured focus to American aerospace medical research and support requirements. Mercury was essentially to orbit an astronaut and recover him successfully. Gemini would use a two-man spacecraft to assess team performance in space, and to accomplish early rendezvous and docking tasks. Apollo would take a team of astronauts, deploy two of them to land on the Moon, and then recover them and return to earth. After Apollo was a not-then-very-well-defined notion for some sort of space station with a logistical spacecraft (which became the Shuttle) to support it. The downturn in the national space program after Apollo suspended for well over a decade plans to build a genuine space station in orbit. Skylab (a short-term orbital research facility) and some of the longer Shuttle missions acquired some useful data on long-duration research. But the most dramatic and graphic data came from the extremely long duration Soviet missions, including some, after the end of the Cold War, which involved visits by American astronauts to the Soviet space station Mir.

Both American and Soviet shorter-duration missions indicated that problems people had presumed to be serious--for example accelerations and zero g, or blood pressure changes, or hallucinations and euphoria--were either nonexistent or of less consequence than thought. But longer duration missions by astronauts and cosmonauts alike witnessed more serious difficulties. These ranged from personal hygiene issues, to bickering, sulking, and other interpersonal conflict between crewmen, to isolation and boredom, and, more seriously still, unanticipated physiological problems typified by reduced exercise capacity, bone demineralization, muscle atrophy, and decreased red-cell mass. The image of returning cosmonauts lifted out of their Soyuz spacecraft in the steppes of Central Asia, placed in litters, and then whisked by helicopter to the nearest hospital as anxious medical personnel watch over them is not one to give much hope to enthusiasts wanting to fly to Mars.

Clearly in this century we have mastered manned flight within the atmosphere and, to a great degree, in the environment of low and medium earth orbit as well. The challenge over the next century will be to expand our ability to exploit both mediums but, increasingly, the space medium in particular. This is by no means easy. But then, neither was the invention and exploitation of the airplane or, perhaps more appropriately, the European colonization of the "New World."

If we, in closing, briefly cast back to that earlier era, we see some striking parallels to the century of flight that we have experienced, and the century that lies before us. The very late fifteenth and sixteenth centuries constituted an era of great exploration and increasing mastery of the intercontinental seas. The seventeenth century was the century of growing commercial and military exploitation, culminating in the explosive industrial revolution of the eighteenth and nineteenth century that set the stage for the technological revolution of this century as well.

Today, spaceflight is in the position that transoceanic voyages were after Columbus: humanity then could only grasp the potential, just as today spaceflight’s potential is still primarily in the future. As those early sea voyagers had to face considerable medical challenges, such as nutrition and disease, so, too, do we have to face considerable medical challenges as we contemplate extending our ability to operate beyond the Earth-Moon environment and on into interplanetary space. But if the history of flight in this century, and particularly the history of aerospace medicine in this century, has any lesson to teach us at all, it is that imagined barriers and actual barriers alike are all-too-often vanquished by resolute spirit, intelligence, and creativity. Those virtues have been innate in the aerospace medical profession in this century, and will, I am certain, carry us forward so that the first century of the next millennium is one of even more extraordinary accomplishment. Thank you all very much—and congratulations!