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Aviation History
1961
1961 - 1119.PDF
FLIGHT, 17 August 1961 221 at the time, an agreement with the San Diego firm was concluded in 1957, when the design was well advanced. The flow of information between the two countries has not been all one-way. The Blue Streak team gradually became self-supporting, and able to hand out a great deal of information themselves. Their work is still proving of value to US programmes; for example, as this journal reported on June 29, Blue Streak research on firing from the bottom of silos has been of direct benefit to Titan 2. As might be expected, the development of Blue Streak as an LRBM was very much a full-time job; sometimes a day and night job. But many engaged in the work were interested in space research, and in their spare time studied the British vehicle as a satellite launcher. Once Sputnik 1 had been launched in October 1957 this work became open and official, and during 1959 a com- bination of Blue Streak with Black Knight as a second stage was investigated in detail. Much work was also carried out with specially designed second and third stages, as reported in Flight for February 17 last. In April 1960 the Minister of Defence announced that a deterrent based on fixed sites was no longer good value for money, and that Blue Streak as a weapon was being terminated. At one stroke this made the satellite studies dominant. It is fortunate that, had Blue Streak been specifically designed for the sole purpose of placing payloads in orbit, it would differ hardly at all from the LRBM cancelled 16 months ago. The greatest problems were not technical but financial and political. The Minister of Aviation very soon satisfied himself and the British Government that Blue Streak as a satellite launcher was a good idea; and he assumed the difficult role of travelling salesman for the entire project throughout Europe and the Commonwealth. The big questions were whether Britain could go it alone; whether we should work with Europe, or with the Commonwealth or both; to what extent assistance should be sought from the United States; and whether either Blue Streak or the whole idea of spaceflight should be abandoned. Door-to-door hawking across the face of the Earth, and at ministerial level, takes time; but it was soon evident that, apart from Australia, the Commonwealth countries were not prepared—or could not afford—to come in. But in Europe Mr Thomeycroft's words did not fall on deaf ears. Last winter a preliminary agreement was reached with France, covering the first two vehicle stages and outlining a possible pro- gramme which could be completed by the addition of a suitable third stage. These proposals were put forward jointly by the two nations at Strasbourg during the week January 30 to February 3 last. The audience was made up of technical and diplomatic representa- tives from West Germany, Italy, Spain, Sweden, Belgium, The Netherlands, Switzerland, Denmark, Austria and Norway. According to the British and French hosts, the overall cost of the proposed initial programme to develop a three-stage launcher would be of the order of £70m, spread over five years. Finance would be provided by all the members of the suggested European Launcher Development Organization, on a basis having regard to each state's national income; and contracts would be placed to ensure a "rational distribution of work" among members. Yet to be resolved are the detailed engineering and mating of the second stage to the first, the design of the third stage, the payloads to be carried, and the overall objects of the exercise, i.e., the order in which the many possible scientific and commercial programmes shall be attempted. There is already a nearly operational launch facility at the Weapons Research Establishment in Australia; but the members of the European Launcher Development Organization will have to decide whether it shall be used, and if so on what basis. Meanwhile, the huge industrial team that brought the first stage close to the start of flight trials in April 1960 has not been allowed to break up. Some major contractors—Sperry in particular—have had to leave the programme, owing to the fact that their contribu- bution was necessary for a weapon but not for a satellite launcher; but D.H. and Rolls-Royce have preserved a substantial Blue Streak staff. During the past 12 months all work has been financed directly by the MoA, whose own experts at the RAE have played a leading part, and much has been accomplished since April 1960. The original prime contractor ceased to exist last September, as a result of merging with de Havilland Aircraft; and since January 1960 the whole de Havilland enterprise has been part of Hawker Siddeley Aviation. Having thus filled in the background, attention can be turned to Blue Streak itself. BLUE STREAK IN DETAIL From the bottom, Blue Streak's airframe consists of a propulsion bay, a short stress-diffusion section, the kerosine (K) tank, the liquid-oxygen (Lox) tank and the new transition section, or separa- tion bay, mating with the French second stage. This bay is not yet finalized, since certain inter-stage design features have yet to be agreed. In general, the construction of the propulsion bay follows con- ventional light-alloy aircraft practice. The skin is supported on a riveted structure of internal frames and stringers, and longitudinal channel and Z sections riveted along the exterior. The two engines are hung on a pair of large I-beams. The ruling material in the propulsion-bay structure is L.72, but the booms of the two motor beams are high-strength DTD.363. A transverse truss bridge fabricated in light-alloy tube bears the loads from the thrust- chamber pitch actuators, and an additional suspension, consisting of a tie-girder pin-jointed to a tubular member, hangs from the motor beams and carries the pair of engine turbopumps. On either side of the bay large pannier fairings form hinged doors over the gaseous- nitrogen (GN) bottles, autopilot and telemetry equipment, and provide aerodynamic fairings ahead of the motor effluxes. At each end of both motor beams is an upper and lower anchor- age fitting. The four lower fittings support the weight of the vehicle on the launcher, and withstand the thrust of the mainstage during the period of hold-down between engine-start and release of the launcher clamps. The four upper fittings are the only structural connection between the propulsion bay and the tank section and upper stages above. From the four precision-ground bolts the loads are diffused around the circumference in a section of aircraft-type construction. There is a 6in peripheral step between the 9ft-diameter propulsion bay into the 10ft-diameter tank. The complete tank is fabricated from Firth-Vickers FSM.l stainless-steel sheet, with thicknesses varying from 0.019in to O.O35in. The two tanks form a monocoque cylinder 10ft in diameter and 46ft in length, designed largely by the lateral loads. The latter arise from motor vibration and thrust-axis variation, wind gust loads before and after launch, and, to a small degree, aeroelastic flexure. To position the e.g. of the fully loaded vehicle as far for- ward as possible, it was decided to place the Lox tank above the K tank, the respective specific gravities being about 1.1 and 0.78. Material for the tanks is received as close-tolerance sheet about 36in wide, lengths of which are cut off with diagonal ends, wrapped round and joined by Argonarc butt-welding backed by a spot- welded strap to form a complete tank section. Adjacent sections are then seam- and spot-welded along a lap joint to form the com- plete tank, extreme accuracy being ensured by extensive jigging. A 0.025in-thick dome diaphragm separates the two tanks; anti-slosh baffles run longitudinally down part of the inner walls of the Lox tank, and three baffle rings, one with an anti-quake truss, are attached inside the K tank. The latter is further stiffened by spot- welding longitudinal top-hat stringers around its outer circum- ference. This makes it sufficiently rigid to support the weight of the filled Lox tank and upper stages in the event of failure of K-tank pressurization. At all times the K-tank pressure is lower than that in the Lox tank, to ensure that the inter-tank diaphragm is never made to "oil-can" upwards (which would be disastrous). Any ballistic vehicle, especially a very large one with a light air- frame and enormous propellant loads, has to be most carefully analysed from the viewpoint of vibration. These dynamic difficulties are intensified by any increase in vehicle length, and Blue Streak has recently been extensively examined to ascertain that it will behave satisfactorily when the second and hypothetical third stages are added. Primarily the problem is not one of strength, but of having to allow for the effect of all structural deflections upon the control system. Dominant factors in the dynamics of the control system are determined by the system itself, so its behaviour can be investiga- ted on the ground. The complete vehicle is hung from a rigid tower in a soft suspension of steel hawsers, and, with the loop of the control system closed, vibrations are induced by passing electrical impulses to the engine gimballing actuators. The offset inertia of the engines causes vibrations to ripple up and down the entire structure at the natural frequency of about 0.5c/s, and their character must be investigated for all conditions of tank loading. Computers are necessary to determine the theory of the motion, digital language being used for the bending mode and analogue and digital for final incorporation into a complete system solution. Eventually it is possible to position all instrumentation—such as rate-gyros—in such a manner that it picks up a minimum of extraneous movement, and nothing that is not allowed for. Wind gust loads and propellant sloshing are all taken into account. As already noted, one tangible result of these investigations is the anti-quake truss forming a slightly asymmetrical "Star of David" across the centre of the K tank. This maintains a basically circular cross-section even under heavy bending loads. When the tank is complete it is transferred to a handling frame, in which it stays until the complete vehicle is standing vertically on its launcher. The frame, visible in the heading picture opposite, has a gaseous-nitrogen (GN) system which pressurizes the Lox tank at 3.51b/sq in, while a mechanical system imposes a tensile load of 16,0001b. [Continued on page 223]
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