part4-5

History of Research in Space Biology and Biodynamics


- PART IV -

Seats and Capsules: Conflicting Views of Escape



[59] Colonel Stapp warmly welcomed all recent successes in the testing and development of open (seat-type) escape systems not only because of the intrinsic importance of these events but also because they appeared to support his own views on the relative merits of different escape devices. For Colonel Stapp has been outspoken in the belief that open systems, with technical improvements in the current models of seats and personal equipment, can continue for some time to meet most requirements for escape from high-performance aircraft. In his opinion, both his own research findings as to windblast and deceleration and the latest developments in seat design tend to confirm the usefulness of the ejection seat for supersonic escape. Referring to certain tests of the new Convair seat, he remarked with a measure of rhetorical exaggeration that they were "causing acres of grey hairs among the precocious proponent of the capsule."⁶⁰

Not all those proponents have yet come around to Colonel Stapp's viewpoint (which is generally shared by Captain Mosely also) . In fact a large body of thought both inside and outside the Air Force has held for some years that the ejection seat is obsolete for late-model aircraft and that an enclosed capsule system must take its place as quickly as possible. Such a system, it is argued, can offer full protection from windblast; lessen the rate of deceleration through streamlining, though increasing the duration of decelerative forces at the same time; enhance flying comfort by eliminating requirements for elaborate protective clothing (the "T-shirt concept of flying"); and serve as boat or igloo for any pilot forced to eject over water or on Arctic wastes. Those who take this view, while emphasizing the basic research value of data developed by the Aeromedical Field Laboratory on windblast and deceleration, profess some doubts as to whether the forces tolerated by Colonel Stapp and assorted chimpanzees in high-speed track experiments would necessarily be tolerable to pilots in operational escape situations. T-shirt enthusiasts, in particular, feel that the required amount of protective harnessing would not always be practical. Finally, supporters of the capsule system recognize that the experimental Convair seat incorporates some of the advantages that a capsule offers, but they are not yet wholly convinced it will work, and they insist that while it might somewhat extend the operational capability of the ejection seat, it cannot take the place of a true capsule.⁶¹

The idea of the capsule system can be traced back roughly as far as the ejection seat itself, to German developments during World War II. The German DFS-228 aircraft had a detachable nose that essentially served as a capsule to bring the pilot down to lower speed and altitude, where he could make his definitive escape by parachute. In the United States, both the Navy and Air Force began active study of capsule systems after the war, and the Bell X-2 rocket plane was equipped with a capsule escape system that was basically designed as far back as 1946. From 1947 to 1952 the Air Force, to avoid duplication of effort, left the major part of United States capsule research to the Navy, while concentrating on seat-ejection improvements, but in 1952 Air Research and Development Command put the Air Force back into full-scale study of capsule escape.⁶²

This renewed Air Force interest in capsules bore fruit in July 1956, when the Directorate of Engineering Standards at Wright Air Development Center revised the Handbook of Instructions for Aircraft Designers in such a way that manufacturers were frankly urged to provide capsules rather than ejection seats for aircraft "capable of speeds in excess of 600 KTs. EAS or altitudes in excess of 50,000 feet." The capsule was not made absolutely mandatory, but the wording of the revised Handbook showed a strong preference, which was also the preference of Lieutenant General Thomas S. Power, Commander of Air Research and Development Command, and of certain other high officers both of the Command and of Wright Air Development Center. Moreover, circular letters were dispatched to aircraft companies at the same time, calling their attention to the new [60] Handbook and in particular to the indicated preference for capsule escape.⁶³
These developments distressed Colonel Stapp. He felt, first of all, that no firm decisions on escape systems should be made until all relevant data had been gathered; and his own studies of supersonic windblast, in particular, were still incomplete. Nor was he overly impressed with the stated advantages of the escape capsule. In answer to the much-discussed comfort factor, he stated that "you can't build a weapon around a rocking chair just because a rocking chair is comfortable,"⁶⁴ and he has pointed out that the capsule also has its own disadvantages. These include the larger target area offered by a capsule when used in combat; the difference in cost, with capsules likely to be at least five times more expensive than improved supersonic ejection seats; and a great many technical complications, especially for low-altitude escape, which match or exceed the complications involved in firing the experimental Convair seat.
There are things that can go wrong with the capsule itself after separation from the aircraft, so that it would still be wise to have a pressure suit handy, and ideally (in Colonel Stapp's words) to build in "an escape system for an escape system."⁶⁵ In this connection, he has observed that the one recorded case in the United States Air Force of attempted capsular escape, in the X-2, was unsuccessful: the pilot managed to detach the capsule from the aircraft but the main capsule parachute failed to open, and the pilot was for some reason unable to abandon the capsule itself before impact.⁶⁶ By contrast, supersonic survival with an open escape system has actually taken place. The first man definitely known to have accomplished this feat, test pilot George Smith, suffered severe injuries, but these were due apparently to "high decelerative and rotational forces," sustained in unfavorable body position and with inadequate harnessing. There is no indication that they were due to windblast as such, the one mechanical force against which a capsule, unlike an open seat, can offer complete protection.⁶⁷
The official preference for capsules, as expressed in the Handbook of Instructions for Aircraft Designers, still stand. In practice, however, capsule development is not yet far enough advanced for much to be done about implementing that preference. Thus, for the present, supersonic aircraft-even the X-15-will continue to be produced with open escape systems. Indeed the Handbook revision was no sooner made than the Air Force itself set in motion the program of industry-wide cooperation whereby Lockheed and Convair received primary responsibility for devising improvements in downward and upward ejection seats respectively.⁶⁸ Even with these improvements, the performance of the capability of the open escape system is obviously limited-but so is that of an escape capsule. The difference is one of degree and the point at issue has been essentialy a matter of timing, concerning just how much useful life there still is in open escape systems before they are written off as obsolete.
As a matter of fact, neither the Convair "B" seat nor any escape capsule so far envisaged would be of much use for bailing out of a spaceship midway between Earth and Mars. Nevertheless, much of the research so far accomplished on escape physiology at Holloman and elsewhere has a direct significance for manned space flight. The most obvious example is the applicability of data on g-tolerances acquired from Colonel Stapp's Holloman sled rides to the coming problems of rocket acceleration and deceleration. Those same sled rides, along with other rocket-track experiments on windblast and deceleration, formed the point of departure for the development at Holloman of research efforts on a broad range of biodynamics problems to be treated in a subsequent monograph. And, needless to say, they will long be remembered among the dramatic high lights in the history of the entire Air For Missile Development Center.