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Aviation History
1955
1955 - 1072.PDF
184 FLIGHT SUPER SPRITE.. These drawings are the first to be published of the production type of A.T.O. pack. The basic motor is shown above the nacelle into which it fits. DE HAV1LLAND SUPER SPRITE Basic motor: overall dimensions, length, 117±in, diameter, 20£in. Empty weight, 620 Ib ±2i per cent; fuelled weight, 1,460 Ib ±2£ per cent. Standard maximum rated thrust, 4,200 Ib for 40 seconds total duration (see thrust curve); total impulse, 120.0CO Ib-sec. Propel- lants: 57 gal hydrogen peroxide at 80 to 85 per cent concentration and 5 gal kerosine or wide-cut gasoline. Feed by 3,690 cu in nitrogen initially at 2,900 to 3,100 Ib/sq in. Nacelle: approximate overall dimensions, length, 150in, height, 32in and width 28iri. Total weight nacelle and fuelled motor, about 1,900 Ib; fall weight of expended nacelle, about 1,100 Ib. PEROXIDE TANK NITROGEN INLET \ FRONT MOTOR STEADY PEROXIDE FILLING POINT NITROGEN FEED PIPE TO PEROXIDE TANK. PEROXIDE / COLLECTOR I'll THRUST SPIGOT BOMB SUP LUG RESTRAINER TAPE BRIDLE FABRIC TEAR-OFF COVER FRONT CRUTCH FRONT SUSPENSION LUG . MAIN PARACHUTE RAY FRONT STABILIZER FRONT MOTOR STEADY PEROXIDE FILLING POINT but the catalyst was completely wasted; further, the valvingsequence had to ensure that the catalyst was injected into the chamber in advance of the peroxide, to prevent a build-up of thelatter before the start of the reaction. Again, the free catalyst added weight to the products of reaction without adding thrust,and so reduced the specific impulse (thrust divided by rate of propellant consumption). In any case, it was necessary only to bring the catalyst intocontact with the H.T.P. in order to cause decomposition, and this could clearly be achieved without mixing both as fluids. Con-centrated peroxides are decomposed by contact with a number of metals, and it seemed quite feasible to promote the reactionsimply by causing the H.T.P. to flow across some form of metal surface fixed inside the motor upstream of the reaction chamber.After exploring various alternatives, it was decided that the best solution would be to inject the peroxide through an appropriatelyengineered assembly of a suitable metal (precise details are with- held). This would bring the entire flow into intimate contactwith the metal without causing an undue drop in pressure. Three Sprites were converted to use such a metal catalyst,with the M.o.S. designation DSpr.2. Ground and flight trials culminated in daily demonstrations at the 1951 S.B.A.C. show, inwhich G-ALVG gave the public their first view of the "smoke- DOORBUNGEfc VENTING INTAKE PEROXIDE 1 PANEL PEROXIDE CHECK VALVE DRAIN POINT less" rocket in action. The revised motor performed excellently.The necessity of injecting the catalyst in advance of the H.T.P. no longer applied, as the catalyst was always present; further-more, the elimination of the second fluid made possible further simplification. In the mono-propellant Sprite, the decomposing H.T.P. formeda jet of superheated steam and free oxygen. The specific impulse of such a motor is low, at a value of about 100 (lb-thrust dividedby lb/sec). The presence of free oxygen in the jet was an invitation to the de Havilland designers to inject a hydrocarbonfuel into the peroxide dissociation products, thereby greatly raising the temperature and velocity of the jet and increasingthe specific impulse by 50 per cent or more. Such injection, with consequent chemical combustion—as distinct from mere decom-
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