History of Research in Space Biology and Biodynamics
[45] During recent years the Air Force Missile Development Center has made important contributions to the Air Force human factors program in two broad fields: space biology and biodynamics. Under the heading of space biology, it has been engaged in research on biological effects of cosmic radiation, on sealed cabin environment, and on subgravity, all of which have been discussed in previous historical monographs.1 Under the heading of biodynamics-which can be defined as the study of the effects of mechanical forces on living tissues-its research efforts cover a variety of problems ranging from the merits of automotive seat belts to patterns of deceleration in space flight. At first glance, some of these problems of biodynamics have little in common. In each case, however, the research program is centered around a unique Holloman complex of test facilities, of which the 35,000-foot high-speed test track is only the best known example. Moreover, each of the various research tasks in biodynamics is in some measure an outgrowth of the deceleration and windblast studies which began at Holloman Air Force Base in 1953 under the direction of Doctor (Lieutenant Colonel and later Colonel) John Paul Stapp, and which were related primarily (though not exclusively) to the problem of escape from high-performance aircraft.
The research project that Colonel Stapp personally brought to Holloman when he came to assume command of the Center's Aeromedical Field Laboratory in April 1953-Biophysics of Abrupt Deceleration-was specifically oriented toward the study of high-speed escape from aircraft. The escape problem remained one of the most important research topics of Project 7850, Biodynamics of Human Factors in Aviation, that was drawn up in 1954 to supplement and in large measure to supersede the former project. Research on this same theme has been reoriented but by no means eliminated since March 1958, when Project 7850 was rewritten as Biodynamics of Space Flight. And it was a series of experiments directly related to escape physiology, Colonel Stapp's own rocket-sled rides on the Holloman track, that first brought nationwide attention to the Holloman aeromedical organization.
The high-speed escape problem was one of imposing magnitude. A pilot bailing out at transonic or supersonic speed had to face first the ejection force required to get him out of his plane, then the sudden onslaught of windblast and wind-drag deceleration, likely to be followed by dangerous tumbling and spinning. Any one of these forces taken separately was a potential cause of injury or death, not to mention the anxiety on the part of aircraft pilots who did not know if they would survive or not in case of ejection. For, at the time research on this problem at Holloman began, the escape systems available were either admittedly inadequate or of unproven worth for aircraft having performance capabilities above mach one in speed and 45,000 feet in altitude.2 Since aircraft with this range of performance were already in existence, and were destined to assume ever greater importance in the Air Force inventory, there was a glaring need for reliable data on human tolerance to all the forces that could be encountered in escape at the indicated speeds and elevations. The fact that such information was not already available was another case of the lag, often deplored by aeromedical scientists, between aircraft design and human factors research.3
Test Directive 5200-H1 for Biophysics of Abrupt Deceleration, dated 15 April 1953, proposed to remedy this situation at least in part, setting forth as its objective:
A program of experiments with the High Performance Linear Decelerator to study tolerance and survival limits for (1) Linear Deceleration, (2) Windblast in a Linear Deceleration Field, (3) Tumbling in a Linear Deceleration Field, and (4) Linear Deceleration with Tumbling and Windblast, as factors of the problem of escape from high speed, high altitude aircraft . . . . Recommended limiting values established by these experiments will determine the design of escape devices and the choice of ejection seats or of ejection capsules for a particular aircraft.
This test directive, with later amendments, was the official basis for Colonel Stapp's research at Holloman until Project 7850 became fully operative early in 1955. It stated further that the "current military need" was to study tolerance to deceleration up to fifty-five g's, but this [46] figure was subsequently revised,4 and all such figures were naturally for rough guidance only. In any case, the maximum number of g's was only one of the factors involved in this study. Not only were tumbling and windblast to be explored, as stated in the directive, but also the rate of onset and duration of g-forces would be considered as affecting the total deceleration that a human body can withstand. The research assignment was thus arduous and complex, but, as Colonel Stapp once stated in a slightly different connection,
. . . . one factor is encouraging. There are only two models [male and female] of the human body currently available, with no immediate prospects of a new design; any findings in this research should provide permanent standards.5
In his own previous experiments on the 2,000- foot deceleration track at Edwards Air Force Base, California, Colonel Stapp had already experienced forces up to roughly 46 g's at 500 g's per second rate of onset. Both this experiment and one in which a co-worker withstood over 38 g's at 1370 g's per second produced definite signs of shock but no permanent ill effects. Colonel Stapp also directed chimpanzee tests while at Edwards, exposing the animal subjects to plateaus of 65 g's, rates of onset of approximately 3400 g's per second, and peaks of about 150 g's, without finding the lethal point or even the point of irreversible injury. However, the duration of decelerative forces was always very short. Durations ranged from .15 to .42 second in the human experiments, which attained a top speed of only 226 feet per second; and there were no experiments on deceleration combined with windblast and tumbling.6
Thus the Edwards tests did not adequately answer the questions posed in the project Biophysics of Abrupt Deceleration. They clearly suggested that the human body, if properly positioned and secured, could endure any aircraft crash forces in which the aircraft itself survived,7 but they did not duplicate the conditions of highspeed escape. For the latter purpose, the Holloman high-speed track, originally built in 1949 as a rail launcher for the Snark missile was especially well suited. It was 3550 feet long (before the first of a series of track extensions) and was fully instrumented. It also had a water braking system as compared with the mechanical friction brakes used on the 2000-foot Edwards deceleration track. The water brakes permitted both high deceleration forces and a wide range of duration and rate of onset.8