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Aviation History
1957
1957 - 1780.PDF
870 FLIGHT Missiles 1957 . . . Interception of a Firefly target by a Seaslug surface-to-air weapon. Armstrong Whitworth Seaslug Surface-to-air. Four wrap-round boostmotors, internal sustainer motor. Overall length, about 20ft; body diameter, about 16in; wing span, about 63in; control-surface span, about 63in. Weights andperformance data restricted. ARMSTRONG WHITWORTH As oneof the principal members of the Hawker Sid- deley Group, Armstrong Whitworth have formany years been the Group's principal arma- ment company and they became involved inthe development of guided weapons shortly after World War 2. The company's first task wasthe production of liquid-propellant rocket motors for a large number of experimentalvehicles. In 1948 the company formed an Armaments Division, and when the RoyalNavy decided to place a development contract for an anti-aircraft guided-weapon systemearlier association with the company led them to turn to A.W.A. The resulting weapon,named Seaslug, is a large missile which, in view of its naval application, has required anexceptional amount of effort by a number of companies in order to bring it to its presentnear-operational state. There have been many stages in its develop-ment, and a typical early test vehicle was exhibited at the recent S.B.A.C. Show. Thisvehicle was illustrated on page 330 of our August 30 issue and the internal dispositionof its principal components was revealed in a sectioned drawing on page 444 of our issue ofSeptember 13. Although of typical British configuration inhaving a cruciform of wings, and a second cruciform of control surfaces at the rear, Sea-slug is normally indexed with all aerodynamic surfaces at the 45 deg position and the draw-ing shows the weapon from this angle. Both wings and controls in the test vehicle were ofrectangular form, both being built up from spars and chordwise members pressed fromsheet and transmitting aerodynamic loads to the main anchorages at the roots. The cylin-drical body was manufactured from light alloy and the bulk of its length was carefully profiledto form integral tanks for the liquid propellants (nitric acid and methanol), which were fed byfree pistons initially located near the e.g. and pumped outwards by gas pressure suppliedfrom a generator in the nose. All propulsion system piping was contained within the body.The cantilevered rocket chamber was regenera- tively cooled and provided with automatic con-trol through a sequence of valves and solenoids. These liquid-propellant development rounds were launched by four wrap-round boost units,each consisting of two or three motors strapped together and faired at their forward ends bypointed nose-wedges providing aerodynamic lift to swing the boosts clear at burn-out. Asthe contemporary GPV, Thunderbird and similar missiles employed but eight boosts, onecould assume that the twelve required by the A.W.A. round conferred higher accelerationfor naval purposes; alternatively the weapon itself may be heavier than its land-basedcounterparts. The overall boost system is exceptionally neat; unlike other Britishweapons, the boosts are mounted on the fore- body, thus obviating the need for boost finsand presenting a particularly compact overall envelope. In company with other weapons, Seaslug hasnow reverted to an I.C.I, solid sustainer motor, presumably employing a cast charge of thetype previously exhibited. This change, particu- larly beneficial to ship-board weapons, doesnot seem to have resulted in appreciable shortening of the rear body, so the motor tubemust be fairly long. Another major change is a switch to the employment of boost units eachconsisting of a single motor of very high thrust. The four barrels appear to be connected byforgings, and their blunt noses are approxi- mately in line with the tip of the nose of themissile body. Full details may not be published concern-ing the guidance of Seaslug, but it is known to be a beam-rider. Chief guidance and con-trol sub-contractors are G.E.C. and Sperry, and both these companies have borne a con-siderable part of the overall effort. Other com- panies which have been named include JohnThompson Conveyor Co.; Sir Geo. Godfrey and Partners; Vickers-Armstrongs, Ltd.;Metropolitan Vickers, Ltd.; McMichael Radio, Ltd.; E.M.I. Engineering Development, Ltd.;and Imperial Chemical Industries. An official statement reads as follows: "Sea-slug is the medium weapon which is designed to engage any enemy bomber which evadesthe fighter defences of the Fleet. It will do so at any height which modern aircraft are capableof flying. The weapon has been developed by the Ministry of Supply and has been tested atAberporth in Wales and Woomera in Australia. At Aberporth trial firings were made for theClausen Rolling Platform, which is a mock-up of part of a ship's structure and capable ofsimulating all the conditions of roll and pitch likely to be encountered at sea. "Seaslugs are fired from a triple ramplauncher which is automatically fed from a magazine below decks. The vast majority offirings which have been carried out at sea from H.M.S. Girdle Ness, the Navy's guidedweapons trials ship, have been successful. Tar- gets are detected at long distances by radarand plotted accurately for range, height and bearing. This information enables any particu-lar aircraft to be selected as the target for the missile. USing this information the missileguidance and control system positions the weapon launcher, and the operator determineswhen to fire the missile, without even seeing the target. The Admiralty directed the develop-ment of all seaborne equipment, apart from the missile itself. This includes the launcher,magazine handling gear, radar and associated weapon direction and control equipment." During recent months firing trials have beenvery satisfactory, and live targets have been successfully engaged. Quantity procurement isto be made and the first operational installa- tions will be on the four guided weapondestroyers which are now under construction. These ships will be essentially enlargeddevelopments of the Daring class. Meanwhile, the A.W.A. factory at Whitley has been com-pletely reconstructed, and is now one of the finest guided-weapon facilities in the country. AVRO This company, like ArmstrongWhitworth a member of the Hawker Siddeley Group, is the prime contractor for the stand-off bomb which will become operational with R.A.F. Bomber Command as a major part ofthe V-bomber weapon systems (certainly for the Vulcan and Victor). The task of develop-ing such a weapon is very great, but at present no details of the chosen configuration may berevealed nor of the present status of develop- ment. It is pertinent in this context to referreaders to the article beginning on page 891. The company's Weapon Research Divisionwere permitted to exhibit several items of "hardware" at the recent S.B.A.C. Show, andthese give an indication of the breadth of the company's programmes in basic research. BRISTOL Shortly after World War 2,the Bristol Aeroplane Company started investigations into the guided-weapon field,and this private work soon changed to officially sponsored development for the Ministry ofSupply. The M.o.S. suggested an alliance with Ferranti, Ltd., and for many years the twocompanies have been equal partners in the development of the Red Duster* (Bloodhound)weapon system. This exceedingly advanced ground-to-airsystem is very highly developed, and to it are committed four Bristol and two Ferranti fac-tories which together employ "the largest work- force in Europe devoted to such a purpose."As we described in detail in our August 30 issue, the Bloodhound weapon itself is reallya small aeroplane of extremely high perform- ance, fired from a zero-length launcher byfour solid boost motors, cruise propulsion be- ing provided by a pair of 16in Thor ramjets byBristol Aero-Engines, Ltd. The airframe, which is manufactured by Bristol Aircraft inCardiff, is of very advanced form and has an outstanding two-axis control system effected bya pair of pivoting wings which can move either together or in opposition. The only otheraerodynamic surface is a horizontal tailplane, the incidence of which is fixed. As the draw-ing shows, the cruise motors are mounted above and below the body, and each is fed withkerosine supplied by turbopumps fed with ram-air from an intake adjacent to that ofeach main engine. Ferranti have handled the major part of theelectronic and guidance effort. The Blood- hound has semi-active homing with a receiverdish in the nose of the missile picking up reflected radiation from the target while thelatter is illuminated by a powerful ground radar. Irrespective of target evasion, theBloodhound computer automatically follows the optimum trajectory for a collision course. T"?entire weapon system has been fully develop™ for operational service and should prove mo'-treliable and trouble-free. Several hundr:i * Aviation Week, September 30.
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