In the mid-Fifties the analysts and planners believed that from 1960 the UK would be under threat of attack by medium range missiles. These were the missiles that would trigger the Cuban Missile Crisis, such as the 750 mile (1200Km) range R-5 (NATO designation: SS-3 Shyster) launched from Eastern Europe or 1100 mile (1700Km) range R-12 (NATO designation: SS-4 Sandal) launched from the Soviet Union.

The UK had weathered attack by ballistic missiles in the late war years when the Wermacht had launched its A4 rockets at London, so the memory of the lack of defensive capability was still fresh in the planners' minds. Given the situation, a research programme was set up to counter such threats. The Ministry of Supply (charged with weapons development and procurement) had placed study contracts with English Electric Co and Marconi to develop a defence against ballistic missiles in 1954. By February 1955 Air Staff Target AST 1135 for defence against ballistic missiles was drawn up. As the programme grew, the other main players in the SAM business, Bristol Aircraft Ltd and Ferranti Ltd became involved. The entire programme was given the colour code name "Violet Friend".

The vulgar fractions solution

To expedite the interim system's entry into service, existing hardware or hardware in the later stages of development was to be used as far as possible. This would also allow the programme to be cancelled at minimal cost if a more complex threat evolved before the system was deployed. The system was required to handle up to six ballistic missiles engagements at a time, each missile requiring dedicated tracking radars.

The Blue Yeoman early warning radar would be located in East Anglia, possibly at RAF Watton. The warhead tracking AN/FPS-16 radars would be sited in Holland, in the south near Terneuzen and in the north on the island of Terschelling. The rationale behind this was that the conical shaped re-entry vehicle had a very small frontal radar cross-section, so it was thought that a radar transmitting from the side had a better chance of tracking the re-entry vehicle. These locations also allowed improved missile tracking and targeting information for the interception system. Further AN/FPS-16 radar sets would be sited in the interception area in Eastern England to track the boosters. These would be co-located with the missiles at sites such as Coltishall, Felixstowe and Strubby.

"Blue Yeoman" would detect the MRBM as it rose above the radar horizon. The booster tracking AN/FPS-16 would be directed onto the booster and track it until RV separation.

The warhead tracking AN/FPS-16 would use the boost tracker information to acquire the warhead.

The warhead would be tracked until it came within the engagement envelope of the Bloodhound.

RV trajectory and speed data would be fed to the missile guidance computer and the Bloodhound would be launched. The "Yellow River" Target Illumination Radar would guide the Bloodhound to its target. The Bloodhound would intercept the RV at an altitude between 30000 - 40000ft (9144 - 12192m), hopefully before the warhead was armed.

The Violet Friend project was terminated in 1962. In a summary report on ABM systems in general, Theodore Von Karman, the aerodynamicist and highly respected analyst, summed it all up in a single sentence: "Whoever solves the ABM puzzle first will have a considerable advantage".

Perhaps forty years on Von Karman's successors might see this puzzle solved. Not many people are holding their breath.

For more information see "Violet Friend" Air Pictorial, Nov 2001