By 1952 Saunders-Roe produced the SR.53 design for a single-seat target defence interceptor combining a liquid-fuel rocket motor with an auxiliary turbojet. Submitted to the Ministry of Supply (MoS) the design based on the pairing of the de Havilland Engines DGJ.1OR Gyron junior turbojet and Spectre rocket motor, to meet the requirements of Specification F.124T. This was accepted with high regard, and Specification F.177D was written around it to meet Operational Requirement (OR) 337. Furthermore, naval requirement NR/AA7 was combined in the specification, the designation SR.177R being applied to the RAF aircraft and SR. 177N to those for the Fleet Air Arm (FAA). The SR.53 was recipient of a three-prototype contract in October 1952. Armament proposed was a Red Top missile on each wingtip.
On September 4, 1956, Saro received an initial order for nine aircraft, and West Germany expressed enough interest for the eventual figure of 600 production aircraft to be mooted. Production was to be shared among Saro and other companies, and German companies were to manufacture that nation's variant, so the whole programme would benefit a large European workforce.
With one 8,0001b-thrust de Havilland Spectre rocket engine and one 1,6401b-thrust Armstrong Siddeley Viper turbojet. Of clipped delta wing configuration with a specified armament of two wingtip-mounted Blue Jay (de Havilland Firestreak) AAMs, the SR.53 was powered by an 3629kg de Havilland Spectre HTP rocket and a 744kg Armstrong Siddeley Viper turbojet superimposed one above the other in the rear fuselage.
In the event, only two of the SR.53s were to be completed (XD145 and XD151), these making their initial flights on 16 May and 8 December 1957, prior to which, in April 1957, all rocket-powered fighter development in the UK had been cancelled.
Duncan Sandys' Defence the White Paper of 1957 resulted in the cancellation of the whole project. When a British request to the USA for funding under the Mutual Weapons Development Program (MWDP) was turned down, West Germany dropped out and turned to the Lockheed F-104 Starfighter.
Nonetheless, the two SR.53s performed 42 test flights before, on 15 June 1958, the second aircraft crashed, the surviving aircraft then being permanently grounded.
Max take-off weight: 8618 kg / 19000 lb
Empty weight: 3357 kg / 7401 lb
Wingspan: 7.65 m / 25 ft 1 in
Length: 13.72 m / 45 ft 0 in
Height: 3.29 m / 11 ft 10 in
Wing area: 25.45 sq.m / 273.94 sq ft
Max. speed: 2135 km/h / 1327 mph