The Bristol Bloodhound is a British ramjet powered surface-to-air missile developed during the 1950s. It served as the UK's main air defence weapon into the 1990s and was in large-scale service with the Royal Air Force (RAF) and the forces of four other countries.
Part of sweeping changes to the UK's defence posture, the Bloodhound was intended to protect the RAF's V bomber bases to preserve the deterrent force from attacking bombers that made it past the Lightning interceptor force. Bloodhound Mk. I entered service in December 1958, the first British guided weapon to enter full operational service. This was part of Stage 1 upgrades to the defensive systems, in the later Stage 2, both Bloodhound and the fighters would be replaced by a longer-range missile code named Blue Envoy. When this was cancelled in 1957, parts of its design were worked into Bloodhound Mk. II, roughly doubling the range of the missile. The Mk. I began to be replaced by the Mk. II starting in 1964. Mk. II performance was such that it was also selected as the interceptor missile in the Violet Friend ABM system, although this was ultimately cancelled.
The Bloodhound Mk. II was a relatively advanced missile for its era, roughly comparable to the US's Nike Hercules in terms of range and performance, but using an advanced continuous-wave semi-active radar homing system, offering excellent performance against electronic countermeasures and low-altitude targets. It also featured a digital computer for fire control that was also used for readiness checks and various calculations. It was a relatively large missile, which limited it to stationary defensive roles similar to the Hercules or the Soviets' S-25 Berkut, although Sweden operated its Bloodhounds in a semi-mobile form.
Bloodhound shares much in common with the English Electric Thunderbird, including some of the radar systems and guidance features. Thunderbird was smaller and much more mobile, seeing service with the British Army and several other forces. The two missiles served in tandem for some time, until the shorter-range role of the Thunderbird was replaced by the much smaller and fast-acting BAC Rapier starting in 1971. Bloodhound's longer range kept it in service until the threat of bomber attack by the Soviet Union was deemed to have disappeared with the dissolution of the union in 1991. The last Mk. II missile squadron stood down in July 1991, although Swiss examples remained operational until 1999.
History Early SAM development During the late stages of World War II, the British armed forces began the development of surface-to-air missiles (SAMs), or as they became known in the UK, surface-to-air guided weapons (SAGW). The Royal Navy was primarily interested in weapons to counteract Luftwaffe bombers dropping glide bombs, which had been used with great effectiveness during the invasion of Italy, and looking toward countering the kamikaze threat in the Pacific. The British Army was interested in a longer-ranged system to supplant or even replace their anti-aircraft artillery. The Royal Air Force was largely uninterested at this point, and put their effort into air-to-air missiles.
From these different needs, two experimental SAGW systems emerged, the Navy's Fairey Stooge and Army's Brakemine. Stooge was a low-performance system, more of a drone aircraft than a missile, which had to be manually guided in front of approaching aircraft using radio control and then detonated by the operator. This limited it to daytime visual range and good weather, neither of which was satisfying. In contrast to Stooge, Brakemine was a more modern concept. While it offered only marginally better range than Stooge, its beam riding guidance was highly automated and allowed the missile to fly directly at its targets at high speed in any conditions, day or night.
Looking to the future, the Navy saw a need to counter jet-powered aircraft, demanding a much higher-performance system. In 1944, the Navy formed the "Guided Anti-Aircraft Projectile Committee", or GAP Committee, to consider such a design. The GAP team suggested combining the Navy's new Type 909 radar with a new missile to produce a Brakemine-like system but with considerably higher accuracy and much longer range. This was initially known as LOPGAP, for Liquid-Oxygen and Petrol, the proposed fuel.
In January 1947, the new Navy design was given the name Seaslug. Around the same time, an effort was underway to centralise all guided missile development at the Royal Aircraft Establishment's (RAE) new Guided Weapons Department. They took over LOPGAP development from the Navy, as well as using up most existing Stooge and Brakemine systems to gain familiarity with the needs of missile testing. They also issued a requirement for the Army and Air Force for a very long-range weapon to protect important installations like airfields and cities. This became the "Red Heathen" concept, with a desired range on the order of 91 km (56.81 mi, 49.37 nmi).
Seaslug and Red Heathen During a review of the RAE's work by the Defence Research Policy Committee (DRPC) in March 1948, a lack of manpower at the RAE was a serious issue and Seaslug was downgraded in importance in favour of Red Heathen. Around the same time, the Army began to express doubts about the Red Heathen as it became clear that the beam riding guidance systems of the early experimental missiles did not work at long range. They suggested Seaslug might be a good interim development.
After considerable debate, in September 1948 Seaslug was restarted as "insurance" against problems in Red Heathen, and in 1949, moved to "top priority". A development contract was signed with Armstrong Whitworth lead development, and the Project 502 industry group was organized in 1949 to produce it. The DRPC suggested downgrading Red Heathen to use a missile with performance roughly equal to Seaslug, but replacing its guidance with a semi-active radar homing system which was more suitable for development of a long-range system in the future. English Electric continued development of this "new" Red Heathen. Later, looking for a second approach to the requirement, using a ramjet instead of a rocket motor, the RAE approached de Havilland, but they declined due to workload. The RAE then turned to the Bristol Aeroplane Company, signing an agreement late in 1949 for "Red Duster", which Bristol referred to as "Project 1220". Armstrong, Bristol and EE were now all working on different approaches to the same basic requirement. Ferranti was brought on to begin development of the new radars and guidance systems.
Before long, the two Red Heathen entries began to diverge, and the two designs were given their own rainbow codes; EE's design became "Red Shoes", and Bristol's became "Red Duster". Bristol's efforts were fairly similar to EE's in most ways, although it was somewhat less mobile while offering somewhat better range.
The Stage Plan After the end of the Second World War, UK air defences were run down, on the assumption that it would be at least a decade before another war started. However, the Soviet atomic bomb test of 1949 forced a re-evaluation of that policy, and UK defence planners started studying the problems of building a more integrated air defence network than the patchwork of WWII expediencies.
The Cherry Report called for a reorganisation of existing radars under the ROTOR project along with new control centres to better coordinate fighters and anti-aircraft guns. This was strictly a stop-gap measure however; over the longer term there would be a requirement for deployment of new long-range radars in place of the Chain Home systems from the war, construction of command and control sites able to survive a nuclear attack, interceptors of ever-increasing performance, and anti-aircraft missiles and guns to provide a last-ditch defence.
The missile portion was the newest and least understood technology. In order to deploy quickly and gain experience with these systems, the "Stage Plan" was developed. "Stage 1" called for missiles based on a LOPGAP/Seaslug-type missile with a range of only 20 miles with capabilities against subsonic or low-supersonic attacking aircraft, which were assumed to be at medium or high altitudes. The original long-range Red Heathen concept then became Stage 2, aiming to replace the Stage 1 design in the 1960s The Stage 1 missile would be based on LOPGAP.
Development The RAE had suggested the use of a ramjet for power as it offered better fuel economy, and thus allowed for longer range. Bristol had only passing experience with this engine design, so they began a long series of tests to develop it. As the ramjet only operates effectively at high speeds over Mach 1, Bristol built a series of testbed airframes to flight-test the engines. The first, JTV-1, resembled a flying torpedo with the ramjets fitted to the end of the cruciform rear fins. Early problems were ironed out and the JTV series was the first British ramjet powered aircraft to operate continually at supersonic speeds.King 1959, p. 431.
Once the JTV testing started to proceed, Bristol studied a series of airframe designs. The first was a long tube with an intake at the front, and four delta-shaped fins arranged near the front of the fuselage. The intake and wings give it some resemblance to the English Electric Lightning, albeit with a long tube sticking out of the aft end. This arrangement left little internal room for fuel or guidance, as the tube ran down the centre of the entire fuselage. A second design was similar, but used mid-mounted fins of reverse-delta shape (flat at the front) with small intakes at their roots. The performance of these intakes was not well understood, and considered risky. The final design was essentially a small aircraft, with mid-set trapezoidal wings and four small swept wing fins at the extreme rear. In this version, two engines were mounted on the wing tips, similar to the mounting used on the JTV series and thus better understood.
One unique feature of the new design was the aerodynamic control system known as "twist and steer". Typical large missile designs use control surfaces at the tail mounted in-line with symmetric wings mounted near the fuselage midpoint. The control surfaces tilt the missile relative to its direction of travel, causing the wings to become non-symmetrical relative the airflow, generating lift that turns the missile. Bristol was concerned that the angles needed to generate the required lift using this method would be too great for the engines intakes to deal with, so it adopted the twist and steer system, first experimented with on the war-era Brakemine project.
In this system the four cropped-delta surfaces at the tail were fixed and used only for stability, not control. Directional control was provided though two large mid-mounted wings which could be rotated independently to large angles. The guidance system rotated the wings in opposite directions to roll the missile until the wings were perpendicular to the target, and then rotated them in the same direction to provide lift in the required direction. This meant that the wings could be rotated to the angles required to generate large amounts of lift, without rotating the missile body itself. This kept airflow in the direction of the missile body, and thus the engine intakes, as well as greatly reducing the drag caused by the tilting of the fuselage across the relative wind. The long, thin fuselage offered very low rotational inertia, conferring excellent homing performance in the last few seconds. The engines were mounted above and below these wings on short extensions.King 1959, p. 434.
In the initial designs, a single very large solid fuel booster launched the missile off its launcher and powered it to speeds where the ramjets could take over.
Flight testing