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Aviation History
1961
1961 - 1337.PDF
FLIGHT, 14 September 1961 441 One of the first photographs to be released of the Gamma 301 rocket engine, three of which are here seen being assembled by Bristol Siddeley's Rocket Division at Ansty. In the background is a Stentor, the small thrust chamber of which is employed in the new Gamma 301 ground-running. Special protection treatments are utilized onmagnesium-alloy components, particularly fluoride anodizing, epoxy-resin impregnation and final coating with epoxy-based paintsand clear epoxy resin. Today the British firm making the broadest effort in the field ofliquid-propellant rocket propulsion is Bristol Siddeley Engines. For ] 5 years this company and its predecessor Armstrong SiddeleyMotors have supported major programmes of research, develop- ment and production into all kinds of units burning a variety ofpropellant combinations, and having fixed or gimballed chambers and fixed or variable thrust. In recent years the work has beenconcentrated upon HTP/kerosine engines fed by turbopump, and these have found very important research and military productionapplications. Most advanced of the company's engines is the Stentor power-plant for the Avro Blue Steel Mk 1 stand-off bomb for RAF Bomber Command. This aerodynamic-cruise vehicle can bereleased "within a circle several hundred miles in diameter, the centre of which is the target" and it thereafter flies "at altitudes andvelocities which defy interception" (these statements have only just been cleared for publication). For many months Stentor has beenin quantity production at the company's Rocket Division at Ansty, near Coventry, and it recently completed the MoA TypeApproval Test (a confirmatory test for similar tests completed "over the previous few years"). The large and small thrust chambers are both pump-fed withHTP and kerosine, which although having only modest specific impulse is considered an ideal combination for such a weapon (asdiscussed in Flight for June 1). After leaving the factory the engine is not fired again until the missile is on its way to the target. Thisdemands extreme reliability, and flight experience to date indicates that such reliability has been achieved. Moreover, each Blue Steelis held at instant readiness with its tanks filled with propellants. which are drained and refilled once per month during stand-by. Bristol Siddeley are permitted to emphasize the precision withwhich the thrust and mixture-ratio of Stentor may be controlled. In order to reap the maximum reward from this outstandingpowerplant. many of its components—obviously including the smaller of the two thrust chambers—have been used as a I asis foran improved version of the Gamma engine which powers the Black Knight ballistic research vehicle. It will be recalled that the earlierGamma 201 achieved an enviable record of reliability, all ten launchings of the Black Knight to date having been successful.The new engine, designated Gamma 301, employs four chambers each pivoted about a radial gimbal-axis; and, from its appearance,it seems to be the powerplant of the hypothetical second-stage satellite launcher which the RAE suggested could be mounted atopBlue Streak rather more than a year ago. Now, however. Gamma 301 is matched to an "improved Black Knight," and is accordinglyin receipt of an MoA development contract. The engine is not only more precise in operation than Gamma 201 but also has alonger rated life, is simpler to prepare before firing and utilizes its propellants more efficiently. One of the smallest liquid-propellant rocket engines in the worldis the PR.37, of which a Flight artist has prepared a skeich. Although its design has been carried out with a variety of applica-tions in mind, it has been sponsored by the MoA as a booster unit to enable the latest mark of Jindivik target to reach an altitude of65,000ft. In view of its application the PR.37 is at present tuned for operation at such altitudes, where it gives a thrusl variablebetween 501b and 1701b. Propellants are HTP and kerosine, which are stored in identical pods attached close together beneath thewing. The fluids are expelled by spheres of gaseous nitrogen at high pressure, and the sketch shows the basic operation of the thrustchamber. The complete Jindivik installation weighs about 1201b, not including 3251b of propellants. Since Jindivik is a pilotlesstarget, means have had lo be found for replacing components damaged during missions without extensive check firings; andanother feature is the satisfactory cooling of the chamber al very low thrust levels. Although the engines themselves are well enough knov n. it isappropriate to comment upon the three light and executr e power- plants of Continental design exhibited by Rolls-Royce Ltd. Thisis the first time Rolls-Royce Continental units have been displayed in Britain, and each was, of course, manufactured in Muskegonby the US firm. The first model to go into production at the Light Aircraft Engine Department at Crewe is the O200A flat-four, ratedat 100 h.p. and used in a wide range of British and (particularly) European light aircraft. Tooling up is proceeding rapidly, andproduction examples should appear in something less than a year. From the viewpoint of size, the second engine to be displayed atFarnborough was the 145 h.p. O300C flat-six, with a swept volume of 4.9 litres and weight of 2771b. This engine is also fast approach-ing production, and the geared GO300C, rated at 175 h.p., is flying in a Beagle Airedale. Most powerful of the engines so far designatedfor production at Crewe is another flat-six, the direct-injection GIO470A. Rated at 310 h.p., this beautiful piece of machineryweighs only 4551b and will be matched with a 7ft 6in McCauley propeller (to be made under licence by Dowty-Rotol) as the power-plant of the production Beagle B.206. The prototype of this aircraft is at present flying with US-built 260 h.p. IO470D engines,with direct drive to 7ft propellers. Largest of the range likely to be built in Britain is the GTSIO520, rated at 390 h.p., chosen byShort Bros for the Skyvan I. The three basic Bristol Siddeley rocket thrust chamber, which can be grouped as shown on the opposite page to meet thrust requirements from 50 to 100,0001b. The two largest chambers are used in the Stentor; the smaller of these is also employed in the Gamma 301, and the two miniature units are part of the PR.37
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