Republic XR-12 Rainbow
The Republic XR-12 Rainbow is in many peoples opinion one of the most graceful aircraft of all time, as well as being probably the most streamlined piston-engined aircraft every built. The Rainbow was built to an exacting 1943 USAAF requirement for a purpose-built reconnaissance aircraft. The requirement specification was drawn up by the photographic Section of the Air Technical Service from recommendations made by Colonel Elliot Roosevelt and called for a very long range, high speed aircraft specifically tailored for photographic reconnaissance. Republic's chief designer, Alexander Kartveli, felt that to achieve the required altitude and speed, over 40,000ft and 400mph, four large pistion engines would be required and selected the Pratt & Whitney R-4360 Wasp Major radial of 3,500hp. The aircraft eventually proved capable of maintaining Mach.8 at 40,000ft.
With a beautifully streamlined body and an elegant 129ft wing, the aircraft was designed from the outset to carry, not just any combination of cameras in three special camera compartments, but also a complete dark room for developing the photographs in flight. The first prototype flew on 4 Feb 46 and, although the aircraft was extensively tested, the end of the Second World War meant that the urgency was lost from the programme and the second aircraft did not fly until 12 Aug 47. Unfortunately the second aircraft was badly damaged when its number two engine exploded on a test flight. In addition, a 'Peace Dividend' was needed to appease the usual 'bean-counters' and despite the Cold War beginning to settle in, the short-sighted individuals in charge of the USAF could see no need for a specialised reconnaissance aircraft and the requirement was withdrawn.
Flight testing of the Rainbows continued for some time to assess the aircraft's suitability as a high-speed transatlantic airliner for Pan-Am. However, after the USAF cancelled the military requirement for 20 aircraft, Republic could not afford to produce an affordable airliner and the these two superb aircraft were eventually broken up for scrap. As the Cold War built up and a variety of converted bombers were hastely pressed into reconnaissance duties, I can only surmise that many USAF Generals must have bitterly regretted the decision to scrap the Rainbow. Neither the RB-17 or the RB-29 used on early overflights of Russia possessed anything like the performance of the Rainbow and if the aircraft had been developed it could have roamed freely over vast tracts of Eastern Europe and Russia for many years with virtual impunity.
The use by the USA of converted bomber aircraft with comparitively modest performance, to perform reconnaissance duties in the early cold war years ended up costing the lives of many brave men.