Soviet Composite Bomber Projects: The Early Tsybin Concepts

The idea of combining “two-aircraft”, a mother-ship and a deployable extended plane; has been around since the late 1920s. In fact, it was the Russian whom developed the world’s first true operational composite project, the Vakhmistrov Zveno bomber. As promising as strange, the Zveno concept did performed several successful detachments proving the concept’s capability. But promising as the Vakhmistrov aircraft was, the Russian halted further in-depth researcher into the concept by the end of WW II until the early years of the 1950s when the advent of the powerful United States’ Air Force B-58 Hustler Bomber gave rise to the Soviet Union’s first true modern composite programs. The idea behind the new Soviet concept was simple enough. A heavy lifting strike airplane would carry a fully loaded bomber to a point within its operational range. The bomber will then be deployed and proceed to its assigned target area by its own power. By the early part of the 1950s, all of the Soviet Union’s Experimental Design Bureaux (OKB) were well entrenched among the USSR’s state-run aircraft industry. They were extremely well funded, by Soviet standards, and well connected politically. This was probably one of the better examples of the USSR’s industrial monopoly. The OKB’s divided the design and development aspects among each other, thus preventing a new member to move in on what they believed was their territory.

Two OKBs were able to break the Experimentals’ hold on design and development. One was the famous Myasishchev Bureau. The other, more obscure one, was the OKB headed by Pavel Tsybin. Tsybin was a major glider designer as well as designer and pilot of several rocket-propelled research aircrafts. Since the early 1950s, Tsybin had worked on nuclear weapons delivery platforms which were to be deployed from a larger, “mother-ship”-type of aircraft. Later his research of this unusual field earned him the establishment of his own Bureau, OKB Number 256. No small feat on such tense times. But his OKB’s independence was short lived and in October 1959, the Myasishchev Bureau absorbed Tsybin’s small venture. Before Tsybin’s beloved 256 was register, let alone acquired by the powerful Myasishchev OKB, he was in charge of the development of a supersonic heavy bomber capable of deploying the new thermonuclear weapons just arriving to operational status. On March 4th 1954, Pavel sent his design for such a platform to top aerospace officials inside the Kremlin. His design for called for a Reaktivnyi Samolyot or RS platform. One that could be capable of achieving speeds up to 1865 mph with an operational range of 8701 nautical miles. Top ceiling was assessed at 98425′. It would had an operational maximum takeoff weight of 36376 pound. In order to achieve this impressive profile, the RS design called for extremely thin wing structures fitted with two powerful engines on each wing tip. To reach the necessary thrust-to-weight ratio for the called profile, Tsybin’s design team streamlined the fuselage. They also added two forward canard foreplane. The new aircraft design would be able to deploy the new Soviet winged bomb based on the 244-N thermonuclear weapon. The top brass at the Kremlin took Tsybin’s proposal very seriously despite warnings from various quarters, mainly others OKBs, that the available technology to develop such an aircraft was not yet sufficiently tested. Nevertheless, work proceeded on the RS design and on May 5th 1955, Tsybin’s team presented the concept to leaders of the Communist Party. Tsybin’s presentation was a resounding success and on May 23rd, a Soviet Ministry (SovMin) resolution allowed the overachiever Tsybin to establish his own Bureau. The resolution also asked for a flying prototype to be delivered no later than February 1st 1957 followed by another unit by April 15th.

The establishment of an independently-run Bureau was a complex task. Hiring of a highly trained staff was a top priority, but with fierce competition among the other Bureaus, the new OKB 256 were unable to grab the “lion share” of the managers, designers, engineers, mechanics and other skilled workers needed for such a radical project. Beside those immense problems, Tsybin was also pinned against a powerful dateline. Notwithstanding, he and his small team pushed ahead and by the winter of 1955, the OKB’s design team modified the original RS’s profile. Operational range was now established at 4661 miles. Also, work on a newly designed RD-013 ram jet engine had commenced in earnest. With the change of range profile came the idea of joining or “pegging” the new platform to a Tupolev’s Tu-95. It was determinate that a Tu-95 could “carry” the RS up to 2485 miles before deploying the platform for its own flight engagement. By January 1956, the RS program had develop its first mock-up, vaguely similar to the British Avro 730 supersonic bomber. The new RS incarnation had a long and narrow airframe with a small trapezoidal wing structure supporting one engine on each wing tip. The team reformed the two canards foreplanes, now each would measure 10′-2″ instead of the original 12′-0″. Plans called for the RS to be loaded into the belly of a Tu-95-N (N) for the carrier version of the aircraft. Once the Tu-95 reached the pre-arrange altitude of 29530′, it would deploy the RS which would then proceed to its assigned target at speeds of up to 1865 mph. On its first solo stage, the RS would be powered by two assisting rocket engines which would be jettison soon after they spent themselves. Then, the two wing tipped ram engines would ignite powering the craft to its destination. The engines, capable of powering the RS at speeds near Mach 2.8, were configured on a fixed geometry, multi shock inlets with convergent divergent nozzles. The RS’ fuel tanks were able to carry 23083 lb of aviation fuel. The bomber’s nuclear weapon, weight in at 2425 lb, would had been carried on a tailless delta platform fitted on the rear end of the fuselage.

As promising as the RS project seemed to be shaping, it was destined to fail. At the same time Tsybin and his team was developing the outlines and designs of the RS, the Korolyov OKB was hard at work on an Intercontinental Ballistic Missile (ICBM) system code-named R7. In early 1957, the new ICBM made its maiden flight and later that year, it achieve production status. The development of the R7 was a sever blow to the RS concept. Immediately after the successful test flight of the R7, all worked related to the RS was terminated. Although work on the RS was canceled, Tsybin still manage to work of an offspring project called 2RS Reconnaissance Aircraft. The 2RS concept was first conceived in January 1956 and was also designed to use the Tu-95N as its springboard plane. But, unlike the RS, the 2RS was not designed as a nuclear delivery bomber, thus the designers replaced the canard foreplanes with a slab tailplane configuration. The fuselage specifications, beside the replacement of the canards structures, were the same of the original concept. The only difference was a reduction in frame length to 89′-11″. Maximum takeoff weight (loaded with camera systems) was now 46186 lb. The 2RS would had been able, accordingly to its specs, to reach a top speed of Mach 2.54. Ceiling was estimated at 88583′ with an operational range of 4351 miles. But by the time the 2RS was ready for mock-up design, passion for this particular reconnaissance platform has dramatically receded among Kremlin leaders. From August 1956 onward, OKB 256 shifted its design effort from the 2RS to the newly constituted RSR aircraft. The RSR project, which called for an all jet, instead of ram engine configuration, was born on August 31st 1956. Most of the preliminary work on the concept was completed by June of the following year. The new platform was designed to takeoff and land on its own power. To accomplish this new task, the RSR was fitted with a reenforced bicycle undercarriage with a double wheeled main and nose gears. Powering the RSR were two Solovyov Low Ratio D-21 Turbofan engines. The new concept airframe, instead of being develop out of titanium and steel alloys, was made out of lighter materials. This is due to the expected less stress being applied to the fuselage by the turbofan engines. The aircraft’s profile called for outside temperatures of around 200 degrees C.

The new project was one of the first Soviet aircrafts fitted with a rudimentary feature of stealth. The advent of ever more powerful Surface-to-Air Missiles (SAM) forced this seldom mentioned development. The RSR’s lower fuselage section and wing structure were coated with a porous material designed to absorb the electronic energy emanating from an enemy’s radar arrays. Beside the coating, the plane’ fuselage was re-stressed to allow the pilot to make a barrel role to an altitude of 137795′ or to perform a climb and turn at the same time with a rapid chance in altitude. Both maneuvers were designed to exceed the estimated 2.5G force needed to escape an incoming Western-built SAM. Two massive storage tanks were able to carried up to 26455 lb of fuel. Two additional external fuel tanks, housed underneath the wing structure, were capable of supplying another 4850 lb of fuel thus extending the aircraft’s range. The RSR proposed range was now a more realistic 2339 miles radius. Accordingly to the SovMin resolution of 1957, the first RSR prototype would be rolled out of the production line no later than the spring of 1958. As the same time Tsybin’s team was working on the RSR project, another concept, the 3RS began to take shape. The 3RS was intended to be a dual use platform. It would be able to takeoff on its own or it can be deployed the same way the RS and 2RS were designed to do. The whole idea behind the 3RS was range. Soviet military leaders were still searching for the ultimate bomber. One capable of reaching America from Soviet-held land bases. Another step towards the realization of Tsybin’s dream became true when on March 20th 1958, the SovMin authorized full development of the Tu-95N platform. The Tupolev Bureau was not please with the resolution. Andrei Tupolev himself though of the whole concept as a complete waste of, not only valuable technical resources, but more importantly; time. Utilizing his enormous influence, Tupolev was able to shift the development of the ‘mother-ship” or main aircraft to the Myasishchev Bureau freeing himself to develop more heavy bomber concepts.

Meanwhile, Tsybin team was laying the ground work for the creation of a scale model known as NM-1 (Naturnaya Model). On November 1956, the Kremlin made available the necessary funds for the whole program. Another major accomplishment for such small enterprise as the 256 was. The experimental NM-1 was fitted with two Mikulin AM5 engines mounted on simple nacelles, which meant that the aircraft could only achieve subsonic speeds due to the nacelles’ low power rating. A retractable skid arrangement was placed under the engines’ nacelles. For takeoff operations, a two-wheeled trolley was installed under the skids. This mechanism would be jettison once the aircraft was aloft. A small tail wheel was also installed for taxing control. Beside a shorter nose cone section, the NM-1 fuselage and materials were almost identical to that of the original RSR concept. On April 7th 1959, after several aborted attempts, the NM-1 took to the air for the first time. Overall, 32 test flights took place between the spring of 1959 and autumn 1960. Results from the tests were timid at best. Data collected demonstrated that the aircraft was not able to maintain a regular flight pattern. Plus, its takeoff profiles made it easy to roll over. Those deficiencies meant that the developmental phase of the concept needed to be pushed farther than the OKB wanted. Not the news Tsybin was looking for. He understood that delaying the rollout of the first true prototype could very well lead to the termination of its beloved OKB. He was determinate not to had his OKB terminated. Tsybin feverously lobbied the Soviet Politburo and the VVS Command for extensions. Both institutions saw the creation of such a radical platform as a necessity paving the way for Tsybin was gain its extension on the aircraft’s delivery date. The new dateline was now pushed to December 1960.

With his extension on hand, Tsybin re-doubled his effort on the RSR concept. He redesigned some of the aircraft’s features and tested its profiles on several mock-ups. Everything seemed to be ready for development, everything except the D-21 engines. The Tupolev Bureau pressured the Factory 19, the main manufacture center for aircraft engines in the USSR, to built more of the D-20 engines for its popular Tu-124 airliner jet, thus placing strains in the Factory’s ability to delivery new and revolutionizer engines systems on time. When all was set and done, Tsybin did not received a single D-21 from the Factory. He replaced the highly anticipated D-21 with two Tumansky R-11F jet engine with reheat capability. Unfortunately for Tsybin, the new engine required further fuselage modifications. To accommodated the new engines, he and his team slimmer and enlarger the engines’ nacelles. They also installed a central shock cone on each intake similar to that used on the vaunted Mig-21F. The new engines also gave the plane a change of code names to RSR R-020. Engineers began to strip down the new RSR version in an effort to reduce its weight. The volume of internal ribbing in the wing structure was increased. Thinner areas were applied throughout and welding replaced many of the fuselage’s riveted joints. The titanium and steels alloys were replaced by Dural as the airframe primary structural material. All those modifications had the effect of reducing significantly the fuselage’s fatigue life to just about 200 flying hours or three to six flights. The resulting airframe was one extremely light compare to other similar structures. New external self-sealing fuel tanks, capable of storing 2866 lb of fuel, were added to the plane. Total fuel load capacity was now 10700 lb. The wings were also re-fitted. More taper was applied to their trailing edges and tailplane sections. Also the fin area was reduced. The RSR-020 sported a new undercarriage arrangement. Gone was the two large wheels, replaced by four smaller sets. The modified version would had a serviceable ceiling of 73819′ with an operational range of 2486 miles.

Five RSR R-020 units were ordered in early 1959, but again, the development of the ICBM as a formidable weapon platform trumped Tsybin’s dream aircraft and on October 1st, Soviet Premier Nikita Khrushchev ordered the termination of OKB 256. The cancelation of Tsybin’s OKB contract did not meant that the RSR program was death. Design and development of the RSR aircraft passed on to the Myasishchev OKB. At the time of the transfer, Myasishchev was immerse on its own bomber concept which gave Tsybin almost a free hand in developing the RSR concept. Development of the RSR was relocated to the Myasishchev OKB’s Zhukovsky facility on September 29th 1960. Work was again halted the next month. On October 1960, Vladimir Myasishchev was appointed head of the Tsentrahl’nyy Aero-I Ghdrodinameecheskiy Institoot (TsAGI) or Central State Aerodynamic and Hydrodynamic Institute. For a brief time, the Chelomey OKB took control of the project, but it was short lived. By now, most of the Soviet’s OKBs were either performing work on ballistic missile systems or on the country’s nascent space program. As the new head of the powerful TsAGI, Myasishchev officially ended all work related to the RSR platform. He transferred Tsybin and most of his original engineering team to his OKB’s space division which at the time was developing the Soyuz space capsule. With his transfer and the cancelation of all RS-programs, all of the RS-related data was sealed or destroyed.

Today what remains of the original RSR concept are but a few documents and drawings which clearly indicated that the aircraft was in its initial construction stage when the program was axed. Some documents suggested that up to three units were completed but there’s no evidence to support this claim. What is well documented was that soon after the RSR program was canceled, Myasishchev wrote a letter to Tsybin that contained a TsAGI drawing for a supersonic reconnaissance platform very similar, if not almost identically, to the RSR. A fact that did not sat well with Pavel Tsybin or his team. For years, Tsybin suspected that Myasishchev had a hand in the cancelation of, not only his RS platform, but his beloved OKB. With the termination of the RSR and the British Avro 730 programs, only the United States developed a RSR-type platform that actually flew. It was the spectacular Lockheed SR-71 Blackbird.

– Raul Colon

More information:
Soviet X-Planes, Yefim Gordon and Bill Gunston, Midland Publishing 2000
Aircraft of the OKB Tupolev, Vladimir Rigmant, Moscow Russavia 2001
Russian X-Planes, Alan Dawes, Key Publishing 2001
Concept Aircraft: Prototypes, X-Planes and Experimental Aircrafts, Editor Jim Winchester, Thunder Bay Press 2005

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