| Blue Envoy | |
|---|---|
| Type | Surface-to-air missile |
| Place of origin | United Kingdom |
| Service history | |
| In service | Never entered service |
| Production history | |
| Designed | 1950s |
| Manufacturer | Bristol Aeroplane Co. |
| Specifications | |
| Warhead | Continuous-rod warhead Possible small nuclear |
Detonation mechanism | Proximity fuse |
| Engine | 2× Bristol BRJ.811 ramjets, 4× Borzoi solid fuel boosters |
Operational range | 150 miles (240 km)[1] |
| Maximum speed | Mach 3[2] |
Guidance system | Semi-active radar homing |
Launch platform | Fixed installation |
Blue Envoy (a Rainbow Code name) was a British project to develop a ramjet-powered surface-to-air missile. It was tasked with countering supersonic bomber aircraft launching stand-off missiles, and thus had to have very long range and high-speed capabilities. The final design was expected to fly at Mach 3 (3,700 km/h; 2,300 mph) with a maximum range of over 200 miles (320 km).
Development started as Green Sparkler sometime in the early 1950s.[a] Green Sparkler featured active radar homing, but it was quickly decided this was beyond the state of the art. Replacing the active homing with semi-active radar homing produced Blue Envoy. The designs were otherwise similar, and similar to the US CIM-10 Bomarc as well.
Test launches of sub-scale models were carried out successfully, and development of the new ramjet engines and seeker electronics was well advanced when the project was cancelled in April 1957 as part of the 1957 Defence White Paper. Its cancellation made Blue Envoy "possibly the most enigmatic project in the field of 1950s United Kingdom weapons development."[3]
An impromptu meeting between the contractors led to a proposal to use the guidance system and ramjets to upgrade the Bloodhound Mk. I missile design. This private proposal was accepted and became Bloodhound Mk. II, which increased range from 35 miles (56 km) to 75 miles (121 km) and offered much greater performance against low-level targets and radar jamming efforts. The Bloodhound Mk. II would ultimately serve as Britain's primary air defence missile into the 1990s.
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