History of Research in Space Biology and Biodynamics
 
 
- PART IV -
 
Specialized Windblast Studies, 1955-1958
 
 
 
[51] Even by the end of 1954, a significant amount of data had been accumulated on tolerance to the forces of wind-drag deceleration encountered in high-speed escape from aircraft. With the use of adequate restraint, these forces appeared humanly tolerable, to judge from Colonel Stapp's experiments, and escape system designers could plan accordingly. But it was not clear that the effects of windblast as such in high-speed escape would be similarly tolerable. Windblast encountered on Colonel Stapp's memorable ride did not even approach the maximum that might be expected in actual escape situations.40
 
The later deceleration runs from August 1955 through March 1957 did not use any sort of windshield, and therefore they also exposed test subjects to relatively high windblast. Once the track was lengthened, the deceleration sled reached velocities roughly as high as 775 miles an hour, or slightly over mach one.41 Yet not even this increase in speed was enough to duplicate the maximum windblast possible in escape from high-performance aircraft. Certainly the windblast produced on these runs did not cause major ill effects, especially as the test subjects were well secured and used a type of face mask; in any case, windblast effects were bound to be over-shadowed by the extreme g-forces experience on the very same runs. Accordingly, as early as May 1955, the Aeromedical Field Laboratory began a series of tests carefully planned so that supersonic windblast as such, not deceleration, would be the primary interest. Unlike the later deceleration tests, these very clearly fell within the scope of research of high-speed escape from aircraft.
 
Specialized study of windblast effects was in accord with the April 1953 test directive for Biophysics of Abrupt Deceleration, which called for data on windblast alone as well as windblast in combination with deceleration. It was also foreshadowed by the theoretical organization of Project 7850, Biodynamics of Human Factors in Aviation, since a separate Task 78505, Tolerance to Abrupt Windblast, was included in the original project development plan. Major Joseph V. Michalski, who was also Chief of the Aeromedical Field Laboratory's Biodynamics Branch in 1954-1955, was listed as the original task scientist. Moreover, in the spring of 1955 the Laboratory received a new high-speed sled, Sonic Wind Number 2, which was specifically designed for windblast studies. It was lighter than Sonic Wind Number 1, and therefore capable of exploring windblast at supersonic speeds even within the original 3550-foot track length. Weight was saved by designing the sled for performance only at "25 g with a safety factor of 1.5."42
 
Fifteen runs were made at Holloman on the 3550-foot track with Sonic Wind Number 2 from 17 May 1955 through 2 March 1956. In three cases, anthropomophic dummies rode the rails, but otherwise chimpanzee subjects were used. Tests were planned with ejectable windshield, with no windshield, and also (for certain sled-performance and control tests) with a fixed windshield. The top speed attained on a single run was 1445 feet per second, which was about mach 1.3 or just short of 1000 miles an hour. This happened to be a control run with fixed windshield, but on other runs, with animal subjects exposed to windblast, the sled reached velocities up to ....
 
(MISSING PHOTO)
CAPTAIN JOHN D. MOSELY
 
[52] ....roughly 1350 feet per second and encountered wind pressure well above 2000 pounds per square foot. This compared with 1107 per square foot sustained by Colonel Stapp in December 1954. It was also more than the estimated 1280 pounds per square foot encountered in February 1955 by test pilot George Smith, at mach 1.05 and 6500 feet, in the first definitely recorded instance of survival in supersonic escape. G-forces were comparable to or slightly greater than on Colonel Stapp's last ride, but the fixed-windshield control runs helped isolate any effects due solely to acceleration or deceleration forces.43
 
None of these experiments found what could be called a tolerance limit for windblast, much less the lethal point. Different chimpanzees suffered varying degrees of injury, mostly minor, depending on the type of harness and protective covering worn, but there was no indication that even the highest level of windblast experienced so far was necessarily injurious to a properly secured and protected subject. The next step was to develop still greater sled velocities, and the extension of the Holloman track to 5000 feet should have helped somewhat. However, the extension was not yet finished when still another construction project was started, this time designed to lengthen the facility to 35,000 feet, which would make it the longest in the world, and also to replace existing rails with continuous-weld track. The 35,000-foot track would not be ready for many months, and though the construction work did not at once put an end to test activities, it did seriously interfere with them. In these circumstances, Colonel Stapp and his associates simply transferred the windblast test operations (and the sled Sonic Wind Number 2) to the Supersonic Naval Ordnance Research Track at China Lake.44
 
Colonel Stapp's principal collaborator for the forthcoming China Lake tests was Doctor (Captain) John D. Mosely, who arrived at Holloman in the latter part of 1956 and was made Chief of the Biodynamics Branch as well as task scientist for Task 78505, Tolerance to Windblast. Captain Mosely's first windblast test, on 18 February 1957, was the first at China Lake and also the first high-speed track experiment since 2 March 1956 that was primarily designed for windblast. It was a checkout run, reaching a velocity of 1,333 feet per second. The first full-scale experiment came on 13 April, with very moderate acceleration and deceleration but a peak velocity of 1,945 feet per second (about mach 1.7). The chimpanzee subject wore a special flying suit devised by the Aeromedical Field Laboratory and a helmet developed by Protection, Incorporated. Unfortunately, the headrest failed even before the sled reached supersonic speed, the helmet failed in turn, and the head was yanked so violently as to break the subject's neck. There was some burned tissue due to windblast, but chiefly the run underscored the danger that exists from flailing if the subject is not adequately secured.45
 
The next run at China Lake was held on 27 June, and reached 1,905 feet per second, with a duration of two seconds at roughly mach 1.7. Maximum windblast was about 3,500 pounds per square foot. The test again resulted in the subject's death, but this time it occurred twenty-four hours after the run, and the cause was different. The chimpanzee was adequately secured against flailing, but helmet and clothing proved unsatisfactory; the flying suit tore and exposed the subject to serious burning from windblast. Roughly forty per cent of the body was covered with second and third degree burns. The chimpanzee at least fared better than certain guinea pigs attached to the same test sled by the Bio-Acoustics Branch of Wright Air Development Center's Aero Medical Laboratory. Two guinea pigs were attached merely with nylon netting, and the third was placed in a metal container whose largest opening measured one inch by two inches. The can itself stood up through the test, but all three guinea pigs vanished into thin air.46
 
Colonel Stapp and Captain Mosely were confident that just as the flailing that had lethal effect in April was prevented in June, the burning encountered in the June test could likewise be avoided. Dacron sail cloth used for strap material did not fail in the June run, suggesting that an entire suit made from the same cloth might provide the necessary protection. When the next test in the series took place on 12 March 1958--with speed and windblast about the same as before-a suit of the new material did prove satisfactory. Once again the subject was lost, because of a harness failure that in turn caused the helmet to come off, but it is hoped that this, too, will be prevented on the two remaining tests that are planned in the present windblast series.
 
On the last three tests, wind pressure still did not reach the highest levels [53] conceivable in an operational escape situation. Even so, the levels attained are impressive, especially when it is kept in mind that for flight at higher altitudes than China Lake (elevation 2,218 feet) the air density and thus potential wind pressure for any given speed will naturally be less. It was even possible, in a sense, to take encouragement from the fact that damage from windblast was no worse. Then, too, some real progress has been made in devising means of protection, which further underscored the possibilities for adapting an open escape system, such as the ejection seat, for use with advanced supersonic aircraft. As Colonel Stapp has pointed out, the greatest advantage of a completely enclosed system-that is, of an escape capsule-is simply the elimination of windblast, since the problems of tumbling and deceleration must be met in either case.47
 
To be sure, not everyone agrees with this line of reasoning, and more will be said on the arguments for and against different escape systems toward the end of this study. However, it was not the role of the Aeromedical Field Laboratory to dictate the design of escape systems. Its role was to provide experimental data on which final decisions could be based, and from this standpoint the windblast experiments will have fulfilled their objective no matter what the final test results may be.
 
It is worth noting that the Holloman laboratory received excellent cooperation from the Navy for its series of China Lake sled runs. When unexpected delays arose during preparations for the June 1957 run, certain tests relating to high-priority missile development were temporarily "bounced" in order to hold the track for the Aeromedical Field Laboratory. On the other hand, operations at China Lake could be a rather expensive proposition. Quite apart from the cost of moving people, equipment, and chimpanzees to California, Colonel Stapp had been quoted an estimate of $75,000 for use of the Navy track on five test runs; but the first run alone took more than a third of this amount. Because of bookkeeping technicalities, the second run, on 13 April 1957, was much cheaper even though it happened to fall on a Saturday. Weekend testing required payment of overtime to employees but did not saddle the Air Force with a large share of base overhead.48
 
For various reasons, the March 1958 run was cheaper still-but it will be the last at China Lake. The remaining tests in the current series will be conducted on the newly-completed 35,000-foot track at Holloman. They will also be conducted by Captain Mosely without the assistance of Colonel Stapp, unless he returns for the occasion from Wright Air Development Center, where he went to assume direction of the much larger Aero Medical Laboratory in April 1958.
 
After that, the task program will continue to use the local test facilities, but it will undergo a definite reorientation. The windblast task of Project 7850 (Task 78505) has been renamed Tolerance to Ram Pressure and Thermal Effects in line with the general revision of Project 7850, which is now entitled Biodynamics of Space Flight. Thus in future the problem of escape from aircraft-meaning principally escape from high-performance aircraft at low or medium altitude-will no longer be the primary concern of Task 78505. The latter will have more to do with problems of flight through the upper atmosphere (120,000 feet or higher) and in space, including emergency escape from a manned vehicle re-entering the atmosphere.49
 
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