Blue Streak - Technical Description
Operational Requirement OR 1139 was issued in mid 1955, calling for a missile with a 2000 mile range which could carry a thermonuclear warhead. However, the Atomic Weapons Research Establishment (AWRE) at Aldermaston had not tested a thermonuclear device (and would not until 1957), and even then, the design would probably have been too heavy. In order to reach its target range, the warhead would have to weigh less than 2,000 pounds. Penny, Director at AWRE, suggested a large fission device instead. This design, Orange Herald, was fired at the Grapple tests at Christmas Island in 1957, with a yield of 720kT.
De Havilland Propellers began design and construction in 1957, having licensed the Atlas tank construction technique from Convair. Rolls Royce licensed the S3 motor from NAA, and built a copy designated the RZ1. This was redesigned to save weight, and the new design was designated the RZ 2.
From the bottom, Blue Streak's airframe consisted of a propulsion bay, a short stress-diffusion section, the kerosine tank, the liquid-oxygen (Lox) tank and the inter-stage. In general, the construction of the propulsion bay followed conventional light-alloy aircraft practice. The skin was supported on a riveted structure of internal frames and stringers, and longitudinal channel and Z sections riveted along the exterior. The two engines were hung on a pair of large I-beams. The ruling material in the propulsion-bay structure was L.72, but the booms of the two motor beams were high-strength DTD.363.
A transverse truss bridge fabricated in light-alloy tube bears the loads from the thrustchamber 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 anchorage 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 were the only structural connection between the propulsion bay and the tank section and upper stages above. From the four precision-ground bolts the loads were 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 was fabricated from Firth-Vickers FSM.l stainless-steel sheet, with thicknesses varying from 0.019in to 0.035in. The two tanks formed a monocoque cylinder 10ft in diameter and 46ft in length, designed largely by the lateral loads. The latter arose from motor vibration and thrust-axis variation, wind gust loads before and after launch, and, to a small degree, aeroelastic flexure. To position the c.g. of the fully loaded vehicle as far forward as possible, it was decided to place the Lox tank above the Kerosine tank, the respective specific gravities being about 1.1 and 0.78.
Material for the tanks was received as close-tolerance sheet about 36in wide, lengths of which were cut off with diagonal ends, wrapped round and joined by Argon arc butt-welding backed by a spotwelded strap to form a complete tank section. Adjacent sections were then seam- and spot-welded along a lap joint to form the complete tank, extreme accuracy being ensured by extensive jigging. A 0.025in-thick dome diaphragm separated the two tanks; anti-slosh baffles ran longitudinally down part of the inner walls of the Lox tank, and three baffle rings, one with an anti-quake truss, were attached inside the K tank. The latter was further stiffened by spotwelding longitudinal top-hat stringers around its outer circumference.
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).
Blue Streak was powered by two Rolls-Royce RZ.2 rocket engines, the complete installation being designated RZ.12. Each engine was completely self-contained, with its own gas-generator and turbopump. Engine operation is controlled electro-pneumatically, GN being used to actuate all valves as described in the "Systems" section which follows. Engine-starting takes place according to an automatic ladder-type sequence, the successful completion of each step allowing the next step to take place.
Propellants were liquid oxygen and kerosine to DEngRD.2495, a domestic fuel of high calorific value. Lox and K for starting were supplied from ground tanks, which, together with the lube-oil tank for the gsarboxes, were pressurized at the beginning of the START sequence. Firing of the pyrotechnic igniters in the two thrust chambers is then initiated, and the burning-through of an electrical link in each igniter allows the main Lox and K-igniter valves to be opened.
Thrust-chamber construction followed traditional Rocketdyne brazed-tube principles, the divergent nozzle being a simple cone, rather than the fractionally more efficient bell form. Regenerative cooling was provided by the full flow of fuel. Before starting, the chamber tubes were filled with water, which precedes the K. into the chamber in order to reduce the thrust build-up rate. When the wire mentioned above burns through, K under starting-tank pressure and Lox under tank head were allowed to flow gently into the chambers and be ignited. The resulting flame is Lox-rich, and it at once burns through a wire stretched across the chamber nozzle.
This signals MAINSTAGE, by firing the gas-generator igniters. Each gas-generator burns a very K-rich mixture giving a uniform flow of gas at about 640 C. About 8 per cent of the K input enters through the end injection tube to provide additional cooling, and the inner chamber assists mixing. Fine control is exercised on the Lox input. Fuel and Lox enter the gas-generator after ignition of the igniters has been proved by burning through a link which signals the main K valves to open. This in turn triggers the gas-generator blade valve, allowing propellant to flow to the gas generator from the start tanks. The gas then drives the turbopump.
It was not a failure, technically, but highly succesful; not too expensive, as other systems were costed at equivalent sums; but possibly gave the impression of obsolescence. Its major problem was the use of liquid oxygen: de Havilland reckoned it could be topped in seconds rather than minutes, but it could not be left fueled for any length of time. And defuelling would take the missile out of service for some hours.
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