The Boulton Paul P.123 was a design for a radio guided surface-to-surface missile, produced to fill a gap between the entry into service of the post-war 'V' bombers.
The idea of an unmanned missile had emerged during the Second World War with the German V-1 flying bomb. This concept had undergone further development in the United States, where in 1949 work began on the Martin Matador, which used a turbojet engine and could be radio controlled to increase its accuracy.
In Britain the idea of a simple surface-to-surface missile had great appeal. By the start of the 1950s the RAF had a mix of Avro Lincolns and American B-29 Superfortresses. The next generation of British bombers were under development, but these V-Bombers weren't expected to enter service until the mid 1950s (this turned out to be a good estimate - the Vickers Valient entered service in 1955, the Avro Vulcan in 1956 and the Handley Page Victor in 1958, although all three made their maiden flights in 1951-52).
In order to fill this gap on 9 February 1951 the Air Ministry issued specification UB.109T. This called for a short-range expendable bomber, with a radius of operation of 400 miles, a payload of 5,000lb, and a cruising speed of 450kt at 45,000ft. Any successful design was expected to be ordered in very large numbers, perhaps as many as 20,000. Boulton Paul, Bristol and Vickers all produced designs in response to UB.109T.
The Boulton Paul P.123 was a fairly basic looking design. The fuselage had a circular cross section, was straight sided for most of its length, curving to a pointed nose and tail, and rather resembled a wartime drop tank. It had mid-mounted swept back wings, and a 'V' tail, with two surfaces at 45 degrees on each side, with the control surfaces at the end. There were no control surfaces on the wings. It was powered by two Rolls Royce RB.93 expendable turbojets, each providing 1,750lb static thrust.
The fuselage was a modular system, made up of three sections. The fuel tanks were in the central section, and the payload in the front and rear sections. There were two different payload systems. The Blast version carried two 2,000lb charges, one in each weapon section. This was expected to be used as a conventional missile, diving onto its target. The Multi-bomb version carried eight 500lb bombs (four at each end), and operated like a manned bomber. As a result there were seven different modules, which could be combined at the launch side as required. The wings and tail surfaces were to be made of glass-fibre, a novel idea in the early 1950s, but acceptable in such a disposable weapon.
Two launch systems were investigated. Boulton Paul's first design was for a railway launching system, which required a 580yard long run of straight track for the take off, and a return track to bring the trolley back to the loading area. This system would have been fairly expensive, and made the system vulnerable to attack. The second system was developed after the Martin Matador was launched on the back of a booster rocket from a short ramp. This system was then adopted for the P.123.
A piloted test version was also designed. This would have had a cockpit in the nose section, retractable tricycle landing gear, and ailerons in the wings. The pilot would have been able to fly the aircraft manually, test out the various automatic systems separately, or run a full automatic flight.
The P.123 didn't progress beyond the design stage. Work did begin on prototypes of the Bristol Type 182R Blue Reaper and the Vickers Red Reaper, but neither had been completed when the project was cancelled in 1953. By then it was clear that the first of the V bombers would probably be ready before any of the missile designs could enter service, negating the entire point of the project.
Engine: Two Rolls Royce RB.93 expendable turbojets
Power: 1,750lb static thrust each
Length: 30.33ft (fuselage)
Loaded weight: 9,297lb
Minimum flying speed: 200kt
Bomb load: 4,000lb (2 x 2,000lb or 8 x 500lb)