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Aviation History
1959
1959 - 2746.PDF
FLIGHT, 2b October 1959 431 IN the sub-title below, the initial letters SAGW signify "surface-to-air guided weapon." At the outset it must be made clearthat the complete SAGW system includes special radars, fire- control equipment, ground-handling gear, workshops, storage, launchers, control posts and, by no means least, a highly trained team of operators—and a missile. It is now proposed to outline the history of the Bloodhound system and, within the limits imposed by security, to describe its function as a vital defender of the United Kingdom against attack by manned aircraft. An authoritative history of the entire project was read by David Farrar (chief designer, guided weapons, Bristol Aircraft) before the Guided Flight Section of the Royal Aeronautical Society a year ago; his paper, entitled The Bloodhound, appeared in the Society's Journal for January last. It is worth emphasizing that, when the programme started, other companies were already well advanced with the development of similar weapon systems for the Navy and Army. The latter were the Seaslug and Red Shoes (Thunderbird); the new missile system BLOODHOUND The SAGW System of the Royal Air Force for the R.A.F. was given the code name Red Duster, and its development was entrusted to the Bristol Aeroplane Company and Ferranti Ltd. From the beginning Bristol and Ferranti worked as equal partners, and both have borne witness to the success of this arrangement. Initial stages of the project can best be related by Mr. Farrar himself. He said: — "The general considerations taken into account were the need for highfire-power and the use of tracking radars which did not impose major radar development problems. For reasons of ability to achieve long rangethe guidance system had to permit much of the missile flight to be at high altitudes, and for accuracy of intercepti"- .-it long range the use ofhoming was essential. All these requirements were met by the use of semi-active homing from launch. In this system, the target is illuminatedby a ground radar while a receiver in the missile is locked on to the reflected signal from the target. The missile is not then constrained tofollow a line-of-sight trajectory, and the fire-power is not limited by the number of radars available. "The use of rocket, ramjet or turbojet was considered. The ramjetwas competitive with the rocket at short ranges and gave great range development potential because of its lower piopellant consumption.The expendable turbojet engine was not competitive at any range. The choice of ramjet propulsion was therefore made on grounds of perform-ance, although not without some misgivings from the point of view of development time since supersonic ramjet propulsion had not then beenachieved in this country. "No attempt was made to design a weapon system at once, andattention was concentrated on building up the engineering team and establishing the techniques of guidance and propulsion. Two testvehicles, initiated by the Royal Aircraft Establishment and subsequently developed by the firms, enabled this to be done. Firings of both typesof test vehicle began less than six months after the decision on choice of guidance and propulsion had been made." As is invariably the case with a major G.W. development programme,specialized test vehicles were evolved in order to prove individual func- tions. To assist in the development of the control system, Ferrantiemployed the CTV-4, whidi was flown in guidance, control and parachute-recovery experiments. Displayed anonymously at the S.B.A.C.show in 1956, CTV-4 was a simple unpowered Dart with cruciforms of wings and aft control surfaces, indexed in line. It could carry ahoming receiver and, after acceleration to supersonic speed by a tandem boost, its trajectory could be controlled via an actuator block and thecrudform tail fins. Much difficulty was experienced in achieving Fig. I. Boost separation of the production weapon satisfactory reliability with these vehicles; at the time of their design nosuper-miniature valves were available, and the complexity of the circuits and the difficulty of fault-finding caused appreciable delays. Neverthelessit is fair to state that, by learning the hard way with CTV-4, Ferranti were able to evolve techniques which are today largely responsible forthe reliability of the airborne guidance system of Bloodhound as a whole. While these studies were going on, Bristol Aero-Engines (now BristolSiddeley Engines) started their investigation into the propulsion system. At the outset the Engine Company had collaborated with the BoeingAirplane Company in the field of ramjet propulsion, and by about 1950 were undoubtedly in possession of more design information on super-sonic ramjets than any other firm in Europe. Their first task was to decide how many engines to employ and how they should be installed. To begin with, Bristol Aero-Engines studied a simple 6in-diameterunit (doubtless the largest size which could readily be handled at that time) and, after basic rig-testing, began to fly a pair of these engines onthe JTV-1 test vehicle (Fig, 2). After severe initial structural problems with the airframe—Mr. Farrar recalled that the JTV-1 was once knownas "the only fully separating test vehicle"—several families of JTV were made to work, and it finally became the first British flying machine to besustained at supersonic speed by ramjets. After thus initially proving the system of propulsion, an overall look was taken at three basic con-figurations (Fig. 3). The integral ramjet with a nose intake left little space for tankage and guidance, and also seemed likely to engendersevere vibration, while the design with side intakes would then have involved too many unknowns for it to be attractive. Accordingly, develop-ment proceeded on a twin-engined weapon, roughly according to configuration X. By this time it had also been decided that, in view ofthe fact that a long range was demanded, ram-air turbines should be used to drive the fuel pump, hydraulic pump and alternator. Having elected to use more than one engine, the question next aroseof how many wings to employ and what form these should take. At this time all other British missiles had fixed wings, moving rear controlsurfaces and cruciform surfaces (i.e., four wings and four fins each indexed at 90 deg to its neighbours). Notwithstanding this, calculationsshowed that the best overall results could be obtained by employing a monoplane moving wing; not only was this the neatest arrangementin view of the twin ramjets, but also it gave much shorter response times without suffering from the radome aberration effects suffered by thefixed-wing vehicles. Choice of a monoplane configuration at once imposed the twist-and-steer form of manoeuvring. Mr. Farrar hasdescribed the reasons for such a choice in the following terms : — "A Cartesian missile manoeuvres so as to achieve a collision course (Continued on p. 434, after double-page drawing of Bloodhound) Fig. 2. A JTV-1 on its launcher Fig. 3. The three basic configurations
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