History of Research in Space Biology and Biodynamics
Deceleration and Windblast Experiments on the Holloman Track
[46] The Holloman track had previously been used for captive testing of missiles and their components, but until Colonel Stapp's arrival had never been used in biophysical research. To be sure, Colonel Stapp did not take a high-speed ride on the track himself until he had been at Holloman almost a year. First he had to wait for the sled, known as Sonic Wind Number 1, which was specially constructed for his test program by Northrop Aircraft, Incorporated; then the sled and track equipment had to be put through a series of practice runs starting 23 November 1953. The first ran with a living subject--a chimpanzee-took place on 28 January 1954.9
On 17 March, finally, Headquarters, Air Research and Development Command gave its authorization to conduct human runs;10 and on 19 March, Colonel Stapp was strapped in for his first Holloman sled ride. Apart from testing the feasibility of the equipment for human experiments, the objective of Colonel Stapp's first ride was to "evaluate human reaction to exposure to about 15 g of linear deceleration for about 0.6 seconds duration, approximately double the duration possible for the same magnitude of force on the crash decelerator previously used at Edwards...."11 The run was essentially successful, reaching peak velocity of 615 feet per second and up to twenty-two g's deceleration, with only momentary ill effects.12
A second human experiment took place on 20 August, with Colonel Stapp again serving as subject. This test was primarily to explore the effects of abrupt windblast, which had not been a factor in the previous test because of a solid panel windshield installed on the sled. A special helmet was devised, completely covering the head, by Dr. Charles F. Lombard of Protection, Incorporated, a division of the Mine Safety Appliances Company. At the same time, to provide the abrupt exposure required, the sled was equipped with
.... a rectangular frame holding two doors hinged to the sides which opened inward by outside....

[47] ....wind pressure when a cam mounted at the selected point on the track tripped a mechanism releasing the catches. Abrupt impingement of windblast against the subject through the 34.5 by 62.50 inch opening thus provided would simulate the effect of jettisoning an aircraft canopy.13

This mechanism had first been tested with a chimpanzee run on 9 April, when only one door opened, but it had undergone additional tests since then, and on the 20 August run it functioned as scheduled. Colonel Stapp was exposed to an estimated maximum of 5.4 pounds per square inch of wind pressure, with maximum velocity of 736 feet per second and peak deceleration of only 12 g's. He suffered no apparent ill effects save temporary and quite minor injury from flapping clothes and windblown grains of sand. It was, he said, the "easiest" of all the runs he had made so far.14

During September 1954, the principal sled experiment was one that made use of a tumbling seat attached to the rocket sled in order to evaluate the effect of tumbling in combination with deceleration and windblast. The tumbling seat had been tried out before in static tests, and in one preliminary test on a moving sled, but the first full-scale experiment was held on 14 September. A chimpanzee was spun at the rate of 105 revolutions per minute at the same time as it was being exposed to sudden windblast (through the same opening windshield used on Colonel Stapp's previous run) and to braking deceleration that reached a peak of forty-five g's; yet the subject came through very nicely.15 This type of experimentation supplemented research done elsewhere on the effects of pure tumbling, for instance on a spinning turntable, but with its fixed axis of rotation the tumbling seat did not wholly simulate free-fall tumbling as encountered during escape from aircraft. Moreover, known instances of tumbling in the thin air at high altitudes all suggest that rapid tumbling must be eliminated if at all possible. And it largely can be, by means of stabilizing devices. For all these reasons the Aeromedical Field Laboratory has not continued its tumbling seat experiments, but instead continued work on deceleration and windblast both separately and in combination with each other.16
The month of September also saw the first testing, with a chimpanzee subject, of a new device for producing abrupt windblast-a windshield that could be jettisoned explosively at a given point during the run. Unfortunately, the jettisonable windshield inflicted quite a bit of damage on chimpanzees, causing the death of more than one, before this method finally proved its value.17 During October, Colonel Stapp went to California, where he performed an autopsy on a Northrop test pilot believed to be the first person who had actually ejected from an aircraft at supersonic speed. For his own research on human tolerances, Colonel Stapp was interested to learn whether the pilot had suffered any major harm from windblast, tumbling, and deceleration. He could find none, concluding that the fatal injuries were due to being struck by the tail surface of the plane.18
Much of the activity of the Aeromedical Field Laboratory in the autmun of 1954 consisted of preparations-including chimpanzee control runs at 600 miles an hour and faster 19 - for the most memorable of all Colonel Stapp's rocket sled rides, the one of 10 December 1954. This test was designed to explore both deceleration and windblast, but there was no attempt to simulate abrupt onset of wind pressure. The jettisonable windshield was still unreliable, and the swinging-door system used in August weighed too much for the sled to attain desired velocity. Hence no windshield at all was used. Colonel Stapp merely wore the helmet he had used in August, completely covering his head, and saw to it, as before, that his arms and legs were well secured against flailing, which was one effect of windblast already known to induce injuries in actual escape from aircraft.
The run itself reached a maximum speed of 937 feet per second, or mach .9. This was fast enough for the sled to overtake and pass a T-33 aircraft that was flying overhead. Windblast was as high as 7.7 pounds per square inch, or better than 1,100 pounds per square foot, and water brakes brought the sled to a stop in just 1.4 seconds from maximum velocity. Rate of onset of deceleration was 600 g's per second, reaching a plateau of twenty-five g's and over for more than a second, with peaks of thirty-five and forty g's. The jolt Colonel Stapp received has been compared with that "an auto driver would experience were he to crash into a solid brick wall at 120 miles per hour."20
As was to be expected, this time Colonel Stapp showed much more obvious effects of his ride. There were some strap bruises and the usual blood blisters from grains of sand, but in addition he suffered extremely painful effects on the eyes. In...

Colonel Stapp Preparing for 10 December 1954 Sled Run
[49] Colonel Stapp's own words, on entry into the water brakes his vision became a "shimmering salmon," followed by "a sensation in the eyes ... somewhat like the extraction of a molar without an anesthetic."21 This one aspect of the experiment, which was due purely to deceleration and not to windblast, overshadowed all other minor injuries and physical sensations during and after the run. Yet not even the eyes suffered any long-range or irreversible damage. Colonel Stapp's experience left him with two black eyes, which lasted the usual length of time, but vision returned in about eight and a half minutes. To use his own words once again,
There was no fuzziness of vision or sensations of retinal spasms as had been experienced in 1951 following a run [at Edwards] in which a retinal hemorrhage occurred. Aside from congestion of the nasal passages and blocking of paranasal sinuses, hoarseness and occasional coughing from congestion of the larynx, and the usual burning sensation from strap abrasions, there was only a feeling of relief and elation in completing the run and in knowing that vision was unimpaired.22
As soon as possible after his admission to the base hospital, where he went for further examination, Colonel Stapp "ate heartily and spent two hours accommodating demands of motion picture photographers making documentary coverage of the run."23
What the run proved, essentially, was that windblast on a properly secured and protected body at over 600 miles per hour and at 4100 feet above sea level-equivalent to mach 1.6 at 40,000 feet-24 was "negligible and unnoticeable in comparison with deceleration effects of g-plateaus of more than 25 g's for 1.1 seconds."25 This duration was the longest yet attained for such high g-forces, but the deceleration, too, was shown to be humanly tolerable. Moreover, it "exceeded any predicted g time pattern for high speed aircraft ejection."26 Although acceleration effects were not a primary object of study, the run also demonstrated that acceleration exceeding six g's for more than three seconds, as attained in the first phase of the run, could produce brief visual blackout but again no serious injury-in fact nothing that would hamper a pilot exposed to similar thrust in high-speed catapult or jet-assisted takeoff from "taking over control of the aircraft within several seconds after launching."27
One other result of the 10 December experiment-and to a lesser extent of Colonel Stapp's two previous rides on the Holloman high-speed track-was to give the Air Force doctor a measure of popular renown as "the fastest man on earth" that was comparable to the esteem he already enjoyed among aeromedical scientists. His sudden emergence as a national hero led to a spate of television appearances, including one with Ralph Edwards' "This is Your Life," which required him to be mysteriously called away to Los Angeles from a conference he was attending on the east coast.28 His portrait appeared on the cover of Time, and for obvious reasons it was news throughout the nation when the "fastest man" was cited by the Alamogordo, New Mexico, police for speeding at forty miles an hour (unspecified rate of onset) in a twenty-five-mile zone. However, the Justice of the Peace before whom he appeared managed to divert part of the publicity to himself by dismissing the charge against Stapp, issuing a new citation against a fictitious "Capt. Ray Darr," and paying the fine from his own pocket.29
Then, too, Colonel Stapp's famous ride was reproduced, in a fictional and somewhat romanticized version, as part of the Twentieth Century Fox motion picture "Threshold of Space." This picture was partially filmed at Holloman, where a number of special sled runs were staged in the fall of 1955 in cooperation with the film company. Likewise, an advance showing of the picture itself was held at the Holloman base theater, on 2 March 1956, with a collection of Hollywood stars imported for the occasion.30
On a more serious level, Colonel Stapp received many additions to his already substantial collection of honors and awards. Among these were the Air Force's own Cheney Award, granted yearly "for an act of valor, extreme fortitude, or self-sacrifice in an humanitarian interest performed in the preceding year. . .," which was personally given to him in August 1955 by General Nathan F. Twining, Chief of Staff. He also received an Oak Leaf Cluster to the Legion of Merit award he held before. An honorary Doctor of Science degree from Baylor University, his alma mater, was granted in May 1956 during the same ceremony in which an honorary degree was given to President Dwight D. Eisenhower. In November 1957, Colonel Stapp obtained the $1,000 Service Award offered by the Omaha Mutual Benefit Insurance Company, of which he was the third recipient. There were many other awards and citations, too, and of course [50] they were not based solely on the rocket sled experiments performed at Holloman in 1954. Colonel Stapp's achievements before coming to Holloman were naturally taken into account when he received professional or scientific recognition, and so was all his other work in directing the Aeromedical Field Laboratory since 1953.31
In some respects, national prestige was almost a disadvantage. Brigadier General Marvin C. Demler, Deputy Commander for Research and Development, Air Research and Development Command, at one point raised a "military objection" to Colonel Stapp's participation in a professional gathering on the ground that public appearances (both professional and otherwise) were causing "dissipation of his time into non-research and development efforts. . ." The message signed by General Demler counted sixty-two "known" appearances in roughly the first eight months of 1956.32 Close contact with researchers elsewhere was, of course, extremely valuable for the Aeromedical Field Laboratory's program; yet Colonel Stapp himself calculated that in the second half of 1956 trips and appearances kept him away from the Laboratory for more time than he was actually present.33
Fortunately, Colonel Stapp managed somehow to proceed with his research despite such distractions. In fact he had scarcely recovered from his ride of 10 December 1954 before he was speaking of his desire to make another human experiment in the future at supersonic speed. What he had in mind was a sled ride at about 1,000 miles an hour, designed primarily to explore tolerance to windblast as such, rather than windblast combined with deceleration. Colonel Stapp suggested that a longer track would be needed both to develop such speed and to have enough room to come to a stop without the decelerative forces completely overshadowing those of windblast; and a likely candidate was the 4.1-mile "SNORT" or Supersonic Naval Ordnance Research Track at China Lake Naval Ordnance Test Station, Inyokern, California.34
However, Colonel Stapp has not yet taken his supersonic sled ride. He was even startled in June 1956 to read in the newspapers that he had been "grounded" from any future high-speed runs on the basis that he was too valuable for the Air Force to risk. The grounding statement was attributed to the same General Demler who shortly afterward "grounded" Colonel Stapp from attending a professional meeting. But in actual fact General Demler's remarks were somewhat over-played in the press. Admittedly, command headquarters did not look with much favor on the possibility of another sled ride by Colonel Stapp, but he did not receive official notification of being "grounded,"35 and he merely proceeded-as before-on the assumption that no further high-speed experiment with himself or any other human subject would be made without first carefully weighing all the advantages to be gained by it and receiving specific command approval. Until more preliminary tests were conducted, without human subjects, no concrete plans for another such human experiment could even be discussed.36
Chimpanzee tests, at any rate, have been continuing at regular intervals since December 1954. Within a week after Colonel Stapp's famous ride, a chimpanzee went down the Holloman high-speed track for another test of the jettisonable windshield, which this time failed to jettison at all. Early in the following year, a series of sled runs was held to explore the effect on chimpanzees of abrupt windblast in combination with forty-g deceleration for various durations. The stated objective was "to evaluate the exact transition point from purely impact effects to circulatory effects typical of centrifuge." Speeds were comparable to that attained by Colonel Stapp, and windblast effects were again negligible. The results also indicated that a chimpanzee could take forty g's for fourtenths second without critical injury, although they were inconclusive concerning longer exposure.37
Since the spring of 1955, both deceleration and windblast studies on the Holloman high-speed track have attained progressively higher values, but they have also followed increasingly separate lines of development. In the case of deceleration experiments, a number of sled runs were held from April through June 1955 with a drop seat mounted on the sled to explore the combination of vertical with horizontal deceleration. Windblast was not a serious factor in these tests, which were actually concerned with aircraft crash forces rather than high-speed escape. This type of experimentation will therefore be considered in a separate monograph related to other accomplishments in biodynamics at the Air Force Missile Development Center.38
Tests designed specifically for horizontal (transverse) deceleration were resumed on 31 August 1955 with another forty-g experiment. Later tests in November [51] 1955 and March 1956 subjected chimpanzees to eighty g's of programmed deceleration, with rates of onset exceeding 4000 g's per second. Tests were then interrupted for about a half year, while the sled itself was reconstructed following an accident in which it became airborne, and also while the track was lengthened to 5000 feet. This extension was justified primarily for aeromedical research, was funded through an emergency allocation to the Aeromedical Field Laboratory and permitted the attainment of significantly higher speeds with even the relatively heavy sled Sonic Wind Number 1. Deceleration runs began again, on the 5000-foot track, in October 1956, and fifteen were conducted from then through the following March. Subjects were exposed to peak decelerations above 200 g's, with rates of onset ranging as high as 16,800 g's per second.39
These figures, obviously, far surpassed the limits of voluntary tolerance, and far surpassed any conceivable g-forces that might be encountered in high-speed escape from aircraft. Indeed, deceleration tests on the high-speed track since the summer of 1955 have been more concerned with pure research on deceleration forces than with any single applied research problem. Hence these experiments, too, will require further discussion in a later monograph.