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Aviation History
1953
1953 - 1576.PDF
730 FLIGHT BEYOND MACH 1 The Remarkable Vehicles tof Airborne Supersonic Research A LTHOUGH World War II was fought entirely with /% subsonic aircraft of what was then a conventional lay- out, that conflict left an enormous legacy of research in the fields of high-speed aerodynamics and power units. So great was this legacy that it opened the way to aircraft with a standard of performance which could only be dreamed of at the time. In 1945 it was, therefore, perfecdy natural that any country with sufficient resources should pick up the threads of research, sort diem out and build experimental aircraft capable of evaluating all the projected novel wing plans and control systems and, into the bargain, piercing the mysterious "sonic barrier." It must be remembered that, although a great deal had been known about supersonic flight for many years, from the study of projectiles, mere still existed at mat time an almost complete transonic-region gap in all the plotted curves of Mach number against drag coeffi cient. This gap could not be filled by tunnel experiments owing to unavoidable choking as sonic speed was reached. It had always been clear that, for proper transonic data, full- scale free flight experiments were essential. Eight years ago this country could spare litde effort on such work. The Miles com pany, with their M.52, had made a characteristically bold attempt at building a supersonic research aircraft around a reheated Whittie W.2/700 turbojet. The design was started in die middle of the war, and the razor-edged wing of double-convex section had already been successfully flight-tested in the "Gillette" Falcon. In 1946 die Ministry of Supply cancelled die contract for die M.52 as it was felt that the project was too hazardous. This decision, for which we believe Sir Ben Lockspeiser was principally responsible, has since been die subject of considerable controversy. In place of the M.52 a contract was placed with Vickers- Armstrongs for a number of small unmanned vehicles powered by liquid-fuel rockets, which were launched over the sea from Mosquitoes. It appears to be generally agreed mat die data provided by these models was a poor substitute for that which would have been gained from tests with a manned aircraft. Across the Atlantic, it must be admitted, national temperament and resources combined to present a far more effective challenge to the problems involved. Several distinct programmes were under taken, correlated by die National Advisory Committee for Aero nautics, and using aircraft ordered under normal Air Force or Navy contracts. As in other aspects of American aeronautical progress, too, the keen rivalry between these two Services was a further spur. It should be stated at die outset mat, in the design of diese aircraft, very considerable use was made of German data. Initially, die Bell company were asked to build a rocket-propelled supersonic aircraft for die Air Force, while Douglas began the development of high-speed machines for the Navy. At the same time, Convair were given a contract for a delta-wing machine, Northrop for an aircraft to test the tailless configuration at sub sonic speeds, and Bell a furmer contract for a machine witii a variable-sweep wing. The last three designs materialized as the XF-92, X-4 and X-5, and, in uieir own fields, have provided immensely valuable data. The supersonic machines of Bell and Douglas are best treated quite separately. Bell were first, for die X-l (originally XS-1) flew in die early part of 1947. It was a straight-wing machine with quite conventional controls and powered by a four-barrelled bi-fuel rocket motor of 6,000 lb thrust. With mis aircraft, the technique of air-launching was pioneered, in order to permit full- load take-offs at wing loadings too great to permit operation from existing runways. On October 14th, 1947, the aircraft exceeded Mach 1, becoming the first manned vehicle to do so. The pilot was Major Charles E. ("Chuck") Yeager, U.S.A.F. The limits reached with die X-l were 967 m.p.h. (1948), 70,140ft (1949), and Mach 1.5 (1947). The chief disadvantage of the original Bell was its general inflexibility and short duration. A direct development was the X-l A, a larger aircraft differing principally in having greater tankage and a turbine-driven fuel pump (the X-l used compressed- gas bottles). Pilot-view was also improved by fitting a raised canopy joined to the fin by a dorsal spine. The X-l A flew in the spring of this year, piloted by Jean L. ("Skip") Ziegler, Bell's chief of flight research. It has since proved a useful vehicle widi a duration of 4$ minutes at full thrust, double mat of the X-l. A still later development is the X-1B, the existence of which was revealed last September. It is superficially similar to the X-1A. The fastest Bell of all is die X-2, powered by a Curtiss XLR-25 rocket motor, the thrust of which is controllable by a throttle. Of stainless-steel construction, the X-2 has highly swept wing and tail surfaces, and is designed for Mach numbers in excess of 2. The first machine was finished in the spring of this year, and was tiien taken aloft in a B-50 for trial launching. Unfortunately, there was inadvertent mixing of die alcohol and liquid-oxygen propellants as die tanks were being topped up immediately prior to release; in the resulting explosion, die X-2 was blown clear and completely destroyed, and two Bell employees, one of them Ziegler, were killed. A second X-2 has now been finished, but details of this aircraft or of its progress are not available. The joint Douglas/Navy work began with the turbojet D.558-1 Skystreak, a straight-winged aircraft which set up a world speed record of 650 m.p.h. in 1947. The level Mach limitation was 0.85, aldiough die airframe was strong enough to reach the speed of sound, which it almost achieved while diving. The D.558-2 Skyrocket is a quite different machine. It has a huge fuselage to house sufficient rocket fuel, and the wings and tail are swept, although the control system remains conventional. Each powered by a Westinghouse J34 turbojet in the belly, and a four-barrelled rocket in the tail, tiiree Skyrockets were built, and they were initially flown from Edwards A.F.B., California. One aircraft was later air-launched from over 30,000ft and, in 1951, had its turbojet removed to make way for additional rocket-fuel tankage. Since that time, many notable Skyrocket flights have been achieved, all of mem on aircraft powered solely by the tail rocket. Back in 1951, the Douglas engineering test pilot. Bill Bridgeman, reached speeds and heights exceeding 1,200 m.p.h. and 75,000ft, after launching at heights around 33,000ft. During the current year, an equally noteworthy series of trials has established figures such as the following: altitude 83,235ft (Lt. Col. Marion Carl, U.S.M.C., August 21st); 1,143 m.pJi., Mach 1.7 at 68,000ft (same The Douglas Skyrocket in its purely rocket-propelled form. Originally it was powered both by a rocket motor and a Westinghouse J34 turbojet, the flush intakes for which were situated one on each side of the nosewheel, while the efflux emerged beneath the tail, at a position under the U.S.N, insignia.
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