primary. The Propellant and Explosives Research and Manufacturing Establishment (PERME) developed the solid rocket motor based on the successful Cuckoo originally developed for the Black Knight experimental rocket. The engines were built by Bristol Siddeley Engines Ltd. It gave a thrust of . Initial testing of the engine suggested it would be underpowered, and in 1959 the Ministry of Supply issued a contract to Bristol Aerojet for a new design. The first test vehicle flew in 1960 from Aberporth followed by full-range trials at Woomera. Cancellation Initial hopes for Blue Water had been optimistic, seeing it as a NATO-wide replacement for the clearly obsolete Corporal. The anticipated customer was the West German Bundeswehr, but there were serious expectations that this would become standard equipment across NATO. The US replacement for Corporal was the Sergeant. Sergeant was solid-fuelled and generally comparable to Blue Water, although it was more complex and slower to operate and, like Corporal, still required a train of semi-trailer vehicles. It was however promised for delivery in 1961. In 1960 West Germany agreed to buy Sergeant rather than to wait for Blue Water. As this represented the other major customer for Blue Water, and also the likelihood that other potential customers such as Turkey and Italy would then follow this American path, the sales prospects for Blue Water became bleak. The programme was cancelled on 10 August 1962, as the UK government, whilst still wishing to purchase the missile, was no longer willing to fund the entire development costs itself. The total costs were estimated at around £32.1 million. Additional funding already earmarked for Blue Water was instead directed to TSR-2. This, and other similar cancellations in this period, were a source of considerable criticism for years to come. At the time, it was suggested that the cancellation was also the outcome of a successful program to better integrate the RAF and Army. The program, started in 1960, aimed to improve air-ground coordination, allowing RAF aircraft to be used more effectively in the close-support role. Blue Water was, to a large degree, a replacement for long-range artillery, a role that was easily fulfilled by the RAF, as long as those aircraft were available to the Army on a timely basis. The need for missile artillery was replaced by the immediately availability of flying artillery. This suggestion is backed by public comments at the time of the cancellation; "there