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Aviation History
1962
1962 - 0142.PDF
142 FLIGHT International, 25 January 1962 Missiles and Spaceflight SEASLUG DEVELOPMENT A common key applies to these four cutaway drawings portraying the evolution of Seaslug Mk I through a series of test vehicles. A, telemetry; 6, rear boost sockets: C, wing strong ring; D, nitrogen control system; E, ballast; F, instrumentation; G, nitrogen bottles; H, flares; J, GFC Seaslug Story ON January 18 a paper entitled The Development of Seaslug was read before the Astronautics and Guided Flight section of the Royal Aeronautical Society by C. Bayly, MnuechE, FRAes, and A. Lightbody, DCAe, BSC, MiMechE, FRAes, respectively general manager and techni cal executive (armaments) of Whitworth Gloster Aircraft Ltd. This was the first time that the principal industrial contractor for the Royal Navy's medium ship-to-air guided weapon has described its evolution publicly; this journal printed a preliminary account on November 21, 1958. Seaslug (said the lecturers) descended from LOP/GAP (liquid- oxygen/petrol, guided air projectile) initiated for the Royal Navy in 1944. After feasibility studies at Westcott in 1946-47 the project was transferred to industry in 1948, thereby becoming the first Service guided weapon to have been worked on in either Government establishments or industry. Sir W. G. Armstrong Whitworth Aircraft (now Whitworth Gloster Aircraft) were appointed design co-ordinators of a team consisting of GEC and Sperry Gyroscope, respectively responsible for the guidance and the control system. By January 1951 the basis of the design had been agreed, with a body 16in diameter and 19ft 6in long, and the first test vehicle had been successfully flown. The following key decisions were taken: to use a nitric acid and kerosine sustainer motor, and four solid- propellant boost motors wrapped round the forebody to obviate the need for boost stabilizer fins; and to employ beam-riding guidance (using the Type 901 radar designed for LOP/GAP), with fixed wings and in-line rear controls in cartesian configuration. Preceding the operational weapon came a series of test vehicles. The first of these was the STV, boosted by four pairs of Demon motors, with which the boost separation techique was proved during tests at Aberporth and Woomera. It was followed by the MTV/C [first drawing above], without a sustainer but including the complete control system, guidance receiver and extensive telemetry. Then came the MTV/H, incorporating an acid/methanol sustainer and requiring four triple Demon boosts. This had one of the first nitric-acid systems with a shelf life of two years. In 1952 it was decided to procure from ICI a solid sustainer motor, and development of the prototype solid, or P(S), missile parallelled that of the liquid P(L). In the latter the tanks and plumbing were drastically simplified, and a shelf life greater than three years was obtained, but in 1955 the decision was taken to dis card the liquid sustainer and concentrate on the P(S). Subsequently the improved P(G) series was very successfully fired from HMS Girdle Ness, leading up to the SC, or Seaslug Mk 1, which has now completed its acceptance trials and is in production. Construction The last of the cutaway drawings illustrates the Mk 1 Seaslug, showing the division into interchangeable sections. The fuze compartment is replacable as a unit on the boosted weapon, and it is followed by the safety and arming unit and warhead, which for trials purposes may be replaced by the telemetry illustrated. Each of the four wings and four control fins are interchangeable, and the three large packages housing guidance, controls and power supplies occupy the section between them. All major handling and launching loads act through the rear boost attachments on to the wing strong ring, thus minimizing the weight penalty for non-flight loadings (particularly important in view of the Admiralty need to withstand the shock of nearby explosions). The wing is a light-alloy structure which concentrates loads to a single high-tensile steel spigot, while the control fins are machined fight-alloy forgings. The main part of the body is the shell of the sustainer motor. Guidance After the missile has been gathered in a wide-angle beam, a rearward-looking aerial in the boat-tail of the missile receives the pencil beam of the 901 radar, which presents the control system with two voltages corresponding to up/down and left/right demands to keep the missile in the centre of the beam. When firing at low angles of elevation the scan pattern of the gathering beam is offset upwards to prevent missiles from being lost in the sea. a form of modulation being used to bring the missile down to the guiding beam. Airborne equipment comprises the aerial in the rear face of the boat-tail and the guidance receiver. The latter has evolved through a number of prototype stages to a printed-circuit and potted package measuring 27in X 11 in x 5 Jin and containing approximately 100 valves and 500 resistors and capacitors.
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