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Aviation History
1953
1953 - 1086.PDF
238 FLIGHT, 21 August 1953 Those familiar with the Sprite will observe the greatly increased length of the new motor. ENGINES IN THE NEWS D.H. SUPER SPRITE T HE existence of a new de Havilland assisted-take-off rocket motor—intended, in the first place at any rate, for military application—is revealed today. Known as the Super Sprite, die new unit follows a constructional layout generally similar to that of the well-known Sprite, but is considerably greater in overall length and shows a departure from me simple monopropellant system of die smaller motor. It gives more man double the total impulse of the Sprite— 12,000 lb sec as against 55,000 lb sec; maximum thrust is reduced from 5,000 to 4,000 lb, but duration has been increased from 12 sec to 40 sec. The existing Sprite is, of course, a so-called "cold" motor. A potassium permanganate solution serves as a catalytic agent for the purely chemical dissociation of the hydrogen peroxide propellant. The reaction produces superheated steam and oxygen, which are discharged as a high velocity jet to produce die propul sive thrust. There is no combustion in the accepted sense. In the new motor the same principle is employed to provide the major portion of the thrust, with the difference that a solid catalyst (the nature of which is not yet disclosed) is used instead of the fluid potassium permanganate. The presence of free oxygen in the effluent, however, makes possible the burning of liquid fuel, to add heat to the jet (and consequently to add to its velocity) in the manner of an after burner in a turbojet. An injection of gasoline or kerosine is employed for this purpose in the Super Sprite. The introduction of the solid catalyst eliminates the need for a separate permanganate tank and allows simplification of design and greater ease of handling. It also has the advantage of eliminating the "brown steam" exhaust of rockets using permanganate; the exhaust jet of the new unit is said to be com pletely smokeless. The kerosine or petrol used in the Super Sprite is drawn from the main tanks of the aircraft, and it is this factor which dictates the choice between the alternative fuels, both of which are equally suitable foi the rocket. Hydrogen peroxide, state de Havillands, has a marked advantage over many fluids commonly used in rocket propulsion, in that it is safe and relatively easy to handle and has good long-storage characteristics. TWO-ROW LEONIDES ~|W"EWS is received as we go to press of the successful first run -L^ of the Alvis Leonides Major, a new two-row 14-cylinder engine, developed primarily for the Westland-Sikorsky S.55— although many other applications both for helicopters and for fixed-wing aircraft are foreseen. The unit is designed to give 870 h.p., and an example of the installation in the S.55 will, it is hoped, be shown statically at Farnborough. NOMAD NNm.6 QUILL SHAFT (turbine power) AXIAL-FLOW COMPRESSOR (turbine driven) TURBINI AIR AT INTAKE PRESSURE • AIR AFTER AXIAL COMPRESSION AIR AFTER PISTON COMPRESSION I ENGINE EXHAUST GASES Air- and gas-flow diagram for the Nomad. The reciprocating unit is a twelve-cylinder opposed two-stroke C.I. engine. AN important Napier exhibit at the forthcoming S.B.A.C • Exhibition will be the latest Nomad NNm.6. Many features have still to be revealed by the makers but the above air- and gas-flow diagram, which applies to all recent marks of Nomad, will help those who have not studied this unique compounded engine to appreciate its working principle. Weight figure released for the Nomad is 3,550 lb, the power rating 3135 e.h.p. and the specific consumption about 0.33 lb/e.h.p./hr. AVON RA.7 WITH REHEAT A PHOTOGRAPH of the 9,500 lb Avon RA.14 together with brief data were recently released, and now it is possible to mention another mark of Avon—the RA.7R, which, with reheat, gives the same power as the 14, namely, 9,500 lb tiirust. The first photograph of this unit which passed its type test in January is reproduced here. The RA.7 from which the engine is derived is rated at 7,500 lb thrust and has a specific consumption of 0.92 lb/hr/lb. The length of this engine without reheat jet-pipe is 82.2in and the diameter 42.225m. The dry weight is 2,460 lb and the addition of reheat adds 500 lb to this figure. For comparison the RA.14, which, around the combustion area and compressor casing, is markedly different in appearance from the RA.7, weighs 2,860 lb, has a length of 77.45m and a diameter of 41.sin. It is understood that the earlier RA.3 of 6,500 lb thrust may soon be up-rated by 500 or 600 pounds without appreciable alteration to components as a result of the satisfactory and very considerable experience that manufacturers and the R.A.F havs had with this unit. Very similar Avons were used in the Comet 2. The Alvis Leonides Major on the test-bed for the first time. The first picture to be rehased by Rolls-Royce of a "reheat" RAJ.
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