By the close of World War 2 (1939-1945), it became a certainty to the victorious powers that the jet age had arrived. All sides undertook various experiments and developments related to military aircraft - especially Britain, the United States and the Soviet Union. The prospect of a jet-powered bomber was first realized with the German Luftwaffe Arado Ar 234 "Blitz" (detailed elsewhere on this site) which graced the skies in limited numbers towards the end of the war - while it did not impact the war as a whole, it provided glimpse into a future battlefield.
Sensing this "change in the wind", the Soviets pushed onward in getting jet-powered types into the skies as quickly as possible and the jet age arms race with the West was officially on. The classic Tupolev Tu-2 ("Bat") twin-engined, piston-powered medium bomber was selected for modification into a jet-powered form that would help up-and-coming pilots and associated bomber crews learn the nuances of jet-powered flight concerning larger-than-fighter, multi-engined platforms. This aircraft would more or less become a "trainer" and feed pilots into the new Soviet Air Force bomber system that was soon to involve several competing jet-powered bomber designs (the Ilyushin Il-28 "Beagle" being one product of the period).
The British Rolls-Royce "Nene" turbojet engine of World War 2 fame found its way into Soviet hands by import and this engine was used to hasten development of many Soviet aircraft projects. Andrei Tupelov, having survived Stalin's "Great Purge" of World War 2, headed the program as he did many of Tupolev's classic period designs. A Tu-2S production model was the specimen in focus and Zavod Factory No.23 was where the work took place beginning in May of 1947.
In the revised bomber form (designated developmentally as "Tu-77"), the air-cooled radial engines were, of course, replaced by 2 x Rolls-Royce Nene I series turbojet engines of 5,000lb thrust each (this same engine was re-engineered by the Soviets to produce the unlicensed Klimov RD-45 series powerplant in time). The structure, particularly the wing surfaces, were all strengthened to better counteract the violent forces at play in high-speed flight. Instead of the "tail-dragger" undercarriage used in the traditional Tu-2 arrangement, a more modern tricycle system was installed. The fuselage was reworked dimensionally with some 16 inches added to the length.
Instead of the two fixed, forward-firing 20mm ShVAK autocannons found in the wing roots of the Tu-2, the new aircraft carried a single, starboard side-mounted 23mm Nudelman-Suranov NS-23 autocannon and standard armament. This was supplemented by 2 x 12.7mm Berezin UBT machine guns and a bomb load of up to 6,615lb.
Work continued into the summer of 1947 when a first-flight was recorded on July 27th. The following month, two additional airframes were revealed at Aviation Day (Tishino) and state trials were had from October into the early part of 1948. This period ultimately showcased some inherent deficiencies when attempting to convert an established piston-powered aircraft to a jet-powered one: the original electrical system was not up to the task and the powerful 23mm autocannon, when fired, caused damage to more sensitive components of the aircraft. Fuel burn for the thirsty jets was also a noted concern but, for all this, the Tu-12 gained in performance over its original from - increased to speed, rate-of-climb and service ceiling were well noted and the aircraft proved useful in establishing all-new defensive armament doctrine for future Soviet bombers.
As completed, the Tu-12 featured an operating crew of five. Structurally it was given an overall length of 54 feet with a wingspan of 62 feet and carried an empty weight reached 20,000lb against a gross weight of 35,000lb. Performance-wise, the Tu-12 clocked a maximum speed of nearly 490 miles-per-hour and could range out to 1,370 miles with a service ceiling reaching 37,305 feet.
Including the prototype, six total aircraft were used to complete the Tu-12 jet bomber project. These examples were used in crew training as designed but were also influential in other testing work done. Beyond this, the short-lived series was ultimately abandoned in pursuit of more advanced programs that would additionally help to establish the Soviet bomber force as one to be reckoned with heading into the 1950s, 1960s, and 1970s.