Violet Friend
Violet Friend was the Ministry of Supply rainbow codename for an anti-ballistic missile system developed in the United Kingdom. The project began in 1954 with study contracts for a suitable early warning radar system, which was followed by the February 1955 release of Air Staff Target 1135 calling for a complete system to counter intermediate range ballistic missiles being fired at the UK from eastern Europe. AST.1135 required the system to be able to attack six targets at once and be ready for initial deployment in 1963.
After many changes, due both to technical progress and changes in the strategic mission, in 1958 an interim design emerged that used existing missiles and radars to lower development costs. The concept used AMES Type 85 radars in East Anglia for long-range early detection as soon as the missiles rose above the radar horizon. Initial tracking of the warheads would then be handed off to AN/FPS-16 radars in the UK and the Netherlands. As they approached the UK, track information from the FPS-16 would direct an AMES Type 86 fire control radar to begin illuminating each selected target.
The enemy warheads would be attacked by a nuclear-armed Bloodhound Mk. 3, with interceptions taking place between. Due to the short flight times of the ballistic missiles and relatively slow speeds of the Bloodhound, the Bloodhound had to be launched within 30 seconds of the initial early warning. The Bloodhound would at first fly under direct radio control from the ground while the warhead was still too far to be illuminated, and would then do a "jerk" manoeuvre onto the target trajectory once the Type 86 picked it up.
The project took place during an extended debate about the nature of the defence, ongoing since 1947. By the late 1950s, the plan was to move the deterrent from the V bomber fleet to the silo-based Blue Streak IRBM. It was believed the Soviets would be able to directly attack these by about 1970, and an ABM would be needed to retain the deterrent. Protecting the silos required a new ABM with improved performance, but the cancellation of the Blue Streak in 1960 ended much of the system's raison d'être. Ongoing concerns about the size of the Soviet missile fleet and the use of radar decoys led to serious questions about any system's effectiveness. Development largely wound down in 1960, and was formally abandoned in 1965.
History
Early studies
The UK became the first nation to be subject to attack by ballistic missiles when V-2 missiles began falling on London in 1944. At the time, some consideration was given to attacking them with huge barrages of anti-aircraft artillery fire, but some calculations suggested that dud rounds falling back to the ground presented a greater threat than the missile warheads.In the immediate post-war era, Henry Tizard was once again called upon to consider the topic of air defence. Promoted to lead the new Defence Research Policy Committee, in 1947 he noted: "there is no more likelihood of active defence against rockets of the V.2 type than there is of defence against a long-range shell." He went to an outside source for a second opinion, which was produced by the Atomic Energy Study Group at Chatham House. They reached similar conclusions, suggesting guns and counter-rockets might "do something... But the proportion brought down could scarcely be considerable." They suggested the only solution was some sort of radio-based weapon. Tizard concluded that "there is none, and no sign of any, practicable defence being developed as yet." and ultimately suggested spending no effort on the issue.
The Air Ministry continued to consider the issue and published something of a counter-note to Tizard's report. They noted that the existing Chain Home radars, then undergoing refits as part of the ROTOR system, could provide two to three minutes warning of an attack from a short-range weapon like the V-2. They also re-considered the topic of AA-guns against missiles, suggesting that modern radars might reduce the number of rounds required to kill a warhead from as much as 1.5 million to as "few" as 18,000. This was not unlike the number needed to bring down a bomber at the start of World War II. Nevertheless, they concluded the only way to ensure a hit on an enemy missile was to use a guided missile of their own, and with those still years off, the only practical solution was to keep the ballistic missiles out of range, deep in Europe.
Continuing study
In May 1952, as part of a wide review by the Chief of the Air Staff and their counterparts in the British Army, it was agreed that the RAF would be responsible for providing early warning of ballistic missiles. A short time later, the DRPC's Guided Weapons Sub-committee was asked to consider "a GW for defence against V.2 type of attack." This was followed by the Ministry of Supply's Guided Weapons Advisory Board forming a subcommittee to more seriously consider the issue in early 1953.The committee concluded that early warning could be improved to four to five minutes and that this would reduce the casualties in an attack on London from 118,000 to 30,000. Considering the incoming warheads, they concluded that they could be successfully attacked with conventional high explosive weapons. But they lacked any significant information on the radar signatures for tracking and guidance, passing that topic back to the DRPC. Studies of an actual interceptor rocket were put off until this could be better understood.
As part of the "Ally" conference from 18 to 20 February 1953, the UK and US both presented papers on the topic of missile defence. The US concluded that attacking an ICBM was beyond current capabilities, and came to the same conclusion as the UK in terms of radar signatures. The UK paper considered only the V-2 type missiles, and concluded that the only solution to tracking the missile with the required accuracy was to use semi-active radar homing and that interceptions beyond about were unlikely.
They also concluded that the warhead could be easily modified to strengthen it against attack, noting:
Increasing concern
Despite this continual, and international, stream of negative reviews of the potential effectiveness of ABMs, in March 1954 another review by the DRPC noted that the issue was becoming more urgent. They stated that while the actual interception remained an area of great uncertainty, there were areas, especially radar, where useful work could begin immediately. By this time, the newly renamed Royal Radar Establishment had begun work on radar and infrared detectors that suggested the warning time might be increased to as much as 15 minutes against an attack from a missile with range.A major report by the Air Defence Committee in January 1955 stated that short-range missiles were already available to the Soviets and that the UK would come within range of longer-ranged weapons by about 1960. These were apparently references to the range R-5 Pobeda which was based in East Germany starting in 1956 and was known by British intelligence to be equipped with chemical weapons and aimed at London. They were additionally aware of the ongoing development of the medium-range R-12 Dvina which could reach the UK from western Soviet areas.
The ADC stated that "Although the nuclear deterrent is the prime means of defence, a direct defence should be developed to a significantly high level." The next month, this was formalized as Air Staff Target OR.1135. In response, the Ministry of Supply placed contracts with English Electric and Marconi Electronic Systems to begin studies on an overall defensive system. This marks the official beginning of Violet Friend.
OR.1135 was concerned only with countering weapons with a range over, as it was assumed they could be kept that far from UK shores. This eliminated the need to deal with shorter-ranged weapons like Scud, which had very short flight times. It also ignored conventionally armed weapons, as they believed these did not present a credible threat. Further, the need was to protect only the UK, not overseas locations or the Army in the field. An advanced draft of the OR was sent to Canada, who issued the Canadian General Air Staff Target written along the same lines but aimed only at ICBMs. The Canadians expressed their concerns about a suitable radar being available by 1960/61.
A review of the work by English Electric and Marconi was carried out in December 1955 by the Deputy Director Operational Requirements. The basic outline was a system using a Mach 2 interceptor missile based about from the defended area, and covering a radius of about. An attack by a total of 150 enemy missiles was assumed. A basic system would require eight bases, but had no redundancy and would provide no coverage over Belfast or Plymouth. A larger system with some redundancy and coverage of those cities and all bomber airfields required fourteen bases. Each site expected to have to attack ten missiles at once.
Considering the smaller deployment, the system required six operations rooms, six early warning radars, 150 tracking radars, 15 launch control sites, 600 launchers and 1,000 missiles. Such a system was estimated to cost £70 million, which was rounded up to £100 million. This was about the same price as the "Stage 1" anti-aircraft system, which was already approved for deployment.
A serious concern was raised at this point; if one assumed that a ballistic missile with a range of would cost about £200,000, and based on the assumption that a salvo of four missiles would be fired at each warhead, this meant the defensive volley cost twice as much as its target. They concluded that "the position of the defence tends to be economically unfavourable even in the best case." This basic idea would become a serious concern in the future, when it would be formalized as the cost-exchange ratio, and was ultimately one of the major arguments against a national-scale ABM system being deployed in the US.