Blue Steel.

Blue Steel was designed as a stand off missile for the V bombers:

from a Ministry of Supply note of, appropriately enough, 5th November 1954:

      "1.2. Present estimates are that medium range GW defences will make it excessively dangerous for the V bombers to fly over, or within about 50 miles of the target in 1960. ... The requirement is therefore for a flying bomb which will have its maximum use between 1960 and 1965. ....
      "1.3. It is expected that a fusion warhead will be available by 1960 and it seems generally agreed that the bomb should be designed to carry this warhead."

GW = Guided Weapon; i.e., surface to air mssiles.

      And again on 16th November 1954:

      "3. This bomb is indubitably much simpler than a fighter aircraft in the range of equipment that has to be provided. On the other hand it is a big step to go from the present speed range to Mach Nos. of 2 and above, and again in comparison with the development of a manned fighter, it is to be expected that the production of the many vehicles required for firing trials will lengthen the development time."

To look at the comparison with a fighter aircraft, here is a comparison with the contemporary SR 53 interceptor:

Blue Steel: 35 foot overall, SR53 45 foot overall.
Blue Steel: weight approx 16,000lb, SR53 take off weight 18,000lb.

to same scale

But there was more to Blue Steel: not only had it fly like a supersonic aircraft, but because it was designed to fly up to Mach 3, the airframe was to be of stainless steel rather than aluminium, and this gave AVRO considerable problems.

In addition, a fighter aircraft has a pilot: Blue Steel, being unmanned, needed an autipilot. Also, a pilot can fly an aircraft to its target: Blue Steel needed an electronic navigator, and was fitted with an inertial guidance system. In pre transistor days, this was a considerable challenge. Further, suitable gyros for such a system were hard to come by in 1954.

So in addition to AVRO, Elliots were given responsibility for the guidance, together with the RAE. Suitable gyros were eventually purchased in the US from Kearfoot then manufactured in the UK; all other Blue Steel technology was indigenous.

The power supply problems for the missile were also considerable: the electronics would have been valve driven, with all that means for power demand and heat dissipation, and the nuclear warhead in particular had to be maintained at a constant temperature, yet while at the altitude which the V bombers were capable the ambient temperature was -70oC, and after launch the skin temperature could rise very rapidly due to aerodynamic heating. An Auxiliary Power Unit was provided by de Havilland, although reading the progress reports the impression is gained that this unit was not always as reliable as it might be.

A further problem was that the weight of the warhead was unknown (the UK was not to produce a feasible warhead until 1957 or 58, by which time adaptations of American designs were being used).

In addition to all the individual problems, there was the further issue of integrating the new technology together. This also was to prove a challenge for AVRO, and the lack of progress from '59 to '62 produced considerable frustration in the Ministry of Aviation. Although many variants and improvements were suggested for the missile, in the end they were all dropped so as not to impede the in service date of Mark 1.

Blue Steel began to enter service with the V bombers in 1962, and 36 operational aircraft were fitted with Blue Steel. The V bombers maintained the British deterrent until Polaris became available, and the last flight with Blue Steel was on 21st December 1969.

Blue Steel stand off missile

A perspective view of Blue Steel.

The Stentor rocket motor.

Stentor rocket motor for Blue Steel

The motor was provided by Armstrong Siddeley and consisted of 2 chambers: both being used for the boost phase to altitude, and then the missile would cruise on the small chamber only.

General Specification - Stentor Mark 101 Rocket engine. 21 November 1960.

"3.2 Thrust. The large combustion chamber is to produce a fixed thrust of 25,200lb (+/-5%) at 45,000ft.
"The small combustion chamber is to be capable of producing a smoothly variable thrust from a minimum of 1000lb to a maximum of 6,200lb at 45,000ft. It should be possible to hold a constant thrust level within +-2.5% at any value between the maximum and the minimum."

The motor burned HTP and kerosene: more may be found out about the Stentor on the HTP page. The small chamber came to be used in later versions of Black Knight and in Black Arrow. Proposals for a satellite launcher based on the large Stentor chamber were also put forward.

There is also an excellent page on the trials unit in Woomera with pictures of Blue Steel and the V bombers.

19 July 1999

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