Myasishchev M-50

To quote Bill Gunston in one of his many books on Soviet aircraft, this huge aeroplane was ‘one of the most breathtaking aircraft of its day’. The seeds for the M-50’s relatively brief moment of glory were first planted in 1954. Soon after Myasishchev’s M-32 was dropped in 1953, the Soviet Union received its first news of the forthcoming American Convair B-58 Hustler bomber, which essentially comprised a relatively small aircraft with all of the disposable load, fuel and bombs, housed in an external pod underneath the fuselage; this was key because the pod helped to keep down the bomber’s overall size. In response, the Myasishchev OKB, backed up by a new SovMin resolution dated 30th July 1954, began work on a ‘composite long-range bomber’, of its own (composed of a strike aircraft and a launch aircraft) which it designated the M-50.

The aircraft, powered by four Dobrynin or Mikulin jet engines, was to be capable of 1,119mph (1,800km/h) and achieve a range approaching 8,080 miles (13,000km) when carrying a 11,023 lb (5,000kg) load. Early studies included a twin-boom carrier aircraft that looked more like a contemporary airliner with the supersonic bomber attached underneath, or the attachment of a large float to allow the bomber to take-off from water. Another design had a droop nose (somewhat similar to the Concorde supersonic airliner) and another used ten engines – four in pairs in two underwing nacelles, four stacked in pairs in two wingtip nacelles plus one either side of the fin root. Other preliminary projects looked at using between two and ten engines with the NK-6, VD-9 and AL-9 as the possible alternative engines.

However, some of the basic problems to appear during the first quarter of 1955 included a lack of sufficient knowledge for the stability and controllability afforded by the canard over such a wide speed range, that it was impossible to obtain a higher relative weight/load for the attack component of the composite bomber, the difficulties in flight testing this type of combined aeroplane (especially after separation since the attack element would not be recovered) and the difficulties of creating a launch system that could reach a speed of 404mph (650km/h) for a launch weight of at least 551,146 lb (250,000kg). TsAGI wind tunnel test also showed that the aerodynamic efficiency of a combined aeroplane was inferior to a conventional aircraft. In March 1955 the M-50 ‘composite bomber’ was halted and replaced by a more conventional aeroplane.

The first ‘single aircraft’ designs were actually completed in February 1955 and on 19th July a new SovMin resolution upgraded the M-50 to a conventional long-range type with a powerplant of four VD-9 turbojets or NK-6 bypass turbofans, giving a maximum speed of 1,243mph (2,000km/h) and a service ceiling approaching 52,493ft (16,000m). I P Tolstykh was nominated as the chief designer and on 28th March 1956 another resolution was passed authorising the installation of 46,295 lb (205.8kN) Zubets RD16-17 engines or VD-9As. The RD16-17 could sustain supersonic flight without afterburning and it also offered a fuel consumption that did not exceed the requirements. Designed by OKB-16 led by P F Zubets, the engine offered 40,785 lb (181.3kN) of dry thrust and 46,295 lb (205.8kN) in reheat. The M-50 was to begin its state acceptance trials in the first three months of 1958.

Despite Myasishchev’s heavy commitments on the M-4/3M series of bombers, the huge programme that this new aircraft represented meant there was no possibility of a competition between prototypes from different OKBs. One of the key factors in achieving the required performance was a big reduction in the weight of equipment carried, plus a crew of only two. Myasishchev and TsAGI conducted a joint research programme which analyzed no less than 39 possible configurations, each tunnel tested in model form, and these embraced tailless and canard formats and tandem wing designs, but the final choice centred on a more conventional delta plus swept tail layout.

The design and development of the M-50, both through its advanced shape and capability but also its sheer size, presented many new problems for which no existing data was available to help in solving them. For example, new calculations and formulae had to be devised by the Myasishchev design bureau to determine the resistance to deformation exhibited by this type of wing. In fact this was the first time that such logarithmic structural stress calculations were used in the USSR to determine the properties of a new aircraft’s wing, but the task was still so complex that it took four years to complete, from 1955 to 1959. Other features that needed to be designed from scratch included the nacelles and their intakes and the need to ensure optimum stability and controllability at all speeds, for which the all-flying tailplane and tailfin were essential. Several fatal crashes of early supersonic aircraft types had occurred because the centre of lift forces moved rearwards when an aircraft passed from subsonic into supersonic flight; for the M-50 longitudinal stability and controllability were vital.

New methods of construction were also required including the employment of large stringers and milled skin panels, the structural materials used in the greatest quantities being V-95 light alloy and 30KhGSNA steel. Another substantial task was to match these features with the huge amount of fuel needed to achieve a satisfactory range because current jet engines were still heavy consumers of fuel. Since there were only two crew members, to keep down the workload many of the flight systems had to be made to operate automatically which meant much better and lighter electronics had to be created to prevent this new equipment from being too heavy, thus cancelling out the progress in weight reduction already achieved. Nevertheless, despite these measures, the final structure weight was 39,683 lb (18,000kg) higher than required; the empty weight was estimated to be 131,393 lb (59,600kg). Thanks to the extreme performance demands coupled with the size of the aircraft, the M-50 did have a new control system that was capable of transmitting signals electronically to the control surfaces. In addition an automatic system was used to adjust the balance of the CofG by transferring fuel between the various internal tanks. The airborne requirements included the ability to fly at between 168mph and 1,243mph (270km/h and 2,000km/h) while the unrefuelled range had to be 7,458 miles (12,000km) maximum. Normal cruise speed would fall within the range 1,056mph to 1,119mph (1,700km/h to l, 800km/h) but the M-50 had to be capable of a dash at 1,180mph to 1,243mph (1,900km/h to 2,000km/h) over the target. A long-range mission would require at least two in-flight refuelling operations (the first after 1,243 miles [2,000km]) but the aircraft itself could carry 385,8021b (175,000kg) of fuel at take-off (in an all-up-weight of 557,760 lb [253,000kg]), although it would need RATOG to help get it off the ground.

Although first designed as a bomber, there were soon plans to adapt the type as a cruise missile carrier as well, with Myasishchev’s own ’45B’ missile the favoured choice. The M-50’s preliminary project was concluded in December 1955 and work began on a mockup early in the new year; when complete an official inspection by a Commission led by Marshal of Aviation V A Sudets was held in July 1956. It appeared that the aircraft should meet most of its requirements except for its unrefuelled range (which was eventually reduced to 6,215 miles [10,000km]) and a take-off run which was too long if RATOG was not used. The lower range meant IFR was essential which, because it was carried out at subsonic speed, also made the M-50 more vulnerable to enemy defences. Due to these weaknesses the Commission was unable to approve the M-50 mock-up but its findings were a surprise to the designers.

The M-50A made its maiden flight on 27th October 1959 and performed well. Initial flights were made without afterburning on any of the engines, but this facility was added when the inner VD-7s were replaced by VD-7MAs, giving 35,2751b (156.8kN) of thrust with reheat, in April 1961. It was hoped that these would deliver a top speed of Mach 1.35 but, in the event, reheat was only ever used on take-off. In 1958 the Myasishchev OKB was released from its obligation to present the M-50 for state testing because a decision had now been taken to use the two M-50s as part of the development programme for a derived follow-on design called the M-52. The limited power of the substitute flight test engines meant that the M-50 was never flown at weights above 253,527 lb (115,000kg); reports also suggest that flying the beast made massive demands on the crew.

A total of eleven sorties had been completed when the decision was taken in 1960 to abandon both the M-50 and M-52. A number of factors influenced this move but the shortfall in performance, despite the achievement of completing such a massive aeroplane to such a tight schedule, was especially important. However, there was also plenty of politics behind the issue because, by this time, the VVS was now considered to be less important for the Soviet Union’s planning for future warfare than in the past, strategic missiles were the way forward.

In late May 1961, after the Myasishchev OKB had been closed, it was decided that the M-50 should be displayed at that year’s Tushino Show. The aircraft had been lying idle for about a year and quite a bit of preparation was needed to make it airworthy again. Seven practice flights were completed before the M-50 made its final trip over Tushino on 9th July 1961, although Western observers did not know this and the aircraft received considerable attention from the world’s newspapers (and was eventually codenamed Bounder). The M-50 performed a roll over Tushino’s spectators, leaving behind its escorting MiG-21 fighters, but it was never to be seen in the air again. Despite making such a big technical advance and introducing many new features, the M-50 actually proved to be relatively free of major problems. Its weakness were the engines which could not combine the large thrust the aircraft needed together with an acceptably low fuel consumption.