The Vulcans were intended to be equipped with the Skybolt missile to replace the Blue Steel, with Vulcan B.2s carrying two Skybolts under the wings. The last 28 B.2s were modified on the production line to fit pylons to carry the Skybolt.Laming 2002, p. 88.Darling 2007, p. 116. A B.3 variant with increased wingspan to carry up to six Skybolts was proposed in 1960.Laming 2002, p. 89. When the Skybolt missile system was cancelled by U.S. President John F. Kennedy on the recommendation of his Secretary of Defense, Robert McNamara in 1962, precipitating the Skybolt Crisis, Blue Steel was retained. To supplement it until the Royal Navy took on the deterrent role with Polaris SLBM-equipped submarines, the Vulcan bombers adopted a new mission profile of flying high during clear transit, dropping down low to avoid enemy defences on approach, and deploying a parachute-retarded bomb, the WE.177B. However, since the aircraft had been designed for high-altitude flight, at low altitudes it could not exceed 350 knots. RAF Air Vice Marshal Ron Dick, a former Vulcan pilot, said "it is [thus] questionable whether it could have been effective flying at low level in a war against ... the Soviet Union."
