Sukhoi S-6

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The Sukhoi S-6 (Russian Сухой С-6) was a design for a two-seated tactical bomber (front bomber), which was developed in the Soviet Union. As a starting point, the construction of the Su-15U served. Further development of the project leads from the S-6 to the T-6-1 and via the T-6-2 to the Su-24.

History
In the mid-1960s, the Soviet aviation forces sought a successor to the now obsolete Yak-28 and Il-28. The experimental design office Suchoi was also aware that a new aircraft was needed for this task. The political leadership of the Soviet Union was at this time, however, the view that there is only a need for intercontinental ballistic missiles, anti-aircraft missiles and interceptors. Projects for bombers, ground attack aircraft or fighter-bombers were not considered necessary. Therefore, on the S-6, chief engineer Yevgeny Felsner and Oleg S. Samoilovich worked mainly in their spare time, and the necessary resources were also obtained by submitting the S-6 project to the authorities as a modernization of the T-58 (Su -15 program designation by Suchoi).

Parameter
The S-6 was to be equipped with the Puma Weapon Computer System, which will provide Orion Pulse Doppler Radar and the Relief Monopulse Soil Radar, which later became part of the Su-24. The engines were two R-21F-300 with 46.1 kN (70.6 kN with afterburner) thrust provided. These engines were modified Tumanski R-11F-300. The S-6 should reach a maximum speed of 1400 km / h at sea level and 2500 km / h in transit flight.

The starting point for the aircraft was the Su-15U Su-15 coach version. In the rear cockpit of the S-6, the space of the weapons system officer was provided. For the planned supersonic low-level flight, it was apparent that despite the high level of automation, flying and operating the weapon system was too much work for the pilot. Therefore, the S-6 was designed from the beginning as a two-seater. In contrast to the Su-15, the rear hull is slightly more angular, the radius of the upper transition from the trunk flanks to the fuselage is smaller than in the Su-15. The air brakes are now on the rump back next to the vertical stabilizer and above the afterburner section of the engines. Behind the cockpit runs a fuselage bulge, which goes all the way back on the fuselage back and opens at the end of the vertical stabilizer in Bremsschirmbehälter. The S-6 is a low wing with delta treads and swept elevator. When the S-6 project and the fixed-wing T-6 project ended, both had delta wings. Based on the development of the Su-15 fighter planes, as with the Su-15, the change to a double delta wing would probably have been made as well.

The S-6 had a two-wheel nose landing gear, which feeds into the front fuselage. One single-wheeled main landing gear, which feeds into the hull. The radome is not round, but appears slightly flattened with an edge on the side and at the top of a larger radius due to the larger radar antenna of the gun radar, which is mounted above the terrain follower radar. A striking feature of the S-6 is its shovel-shaped combined laser / infrared sensor, which also includes the data transmission for the anti-radar weapons Ch-24. This is attached to the bow base immediately after the radome on a swept forward carrier. The most striking visual feature of the S-6 is its air intakes. First studies were based on rectangular air intakes, which were pulled forward at the top than at the inlet lips, about the shape of the air inlets corresponded to those of the MiG -25, later, the unique design was chosen, where the inlet lips were placed ahead of the upper inlet edge. Roughly speaking, it looked as if the air intakes à la MiG-25 were mounted on the head.

Project progress to Su-24
Project progression of the S-6 continued until a full-scale model and development of subsystems (notably the Puma-S weapon system) and the model was inspected by the relevant military authorities. The initial requirements in terms of range, weapon loading and field aerodrome capability could still meet the S-6 with the booster rockets; she outshone Mikoyan's heavier competition project based on the MiG-25.

However, the military then demanded in addition a larger weapon load. As a result, Sukhoi brought in the less advanced T-58M project. In contrast to the S-6 with only one weapon station on the fuselage, the T-58M had four weapon stations on the fuselage. Due to the greater weight, the main landing gear of the T-58M was equipped with two wheels to operate on unpaved runways. In principle, the T-58-M design was identical to the Su-15, but differentiated by a longer hull. The extension was about the length of the second cockpit. The main landing gear with two wheels, the same radar system as the S-6, a continuous bead from the cockpit to the brake screen container on the fuselage back and half-round air inlets with adjustable diffuser cones. Visually, the design T-58-M resembled the La-250.

However, this design also failed to meet military demands for maximum speed and weight on the one hand and STOL capability for operation on makeshift runs. Also, the required performance of the radar system could not be met with limited by the fuselage cross-section antenna size. At that time, the use of vertical jet engines in East and West seemed a promising solution to shorten take-off and landing distances. Suchoi itself gained experience with the technology carrier T-58WD (a Su-15 prototype equipped with three lifting units Kolessow RD-36-35). Therefore, projects S-6 and T-58-M have been radically revised. The fuselage was widened to accommodate the lift engines, allowing a larger radome to accommodate the larger radar antennas. The sensor attached to the carrier under the radome on the S-6 could now be installed in the bow. This widening of the fuselage gave the opportunity to place pilot and weapons officer side by side in the same cockpit. This increased the work efficiency of the crew.

This resulted in the project T-58-M, which had in contrast to the design T-58-M semi-circular air inlets, but no diffuser cone. Finally, test aircraft T-6-1 were built. These had rectangular air inlets, as they were used in the Su-24. At the same time, Sukhoi had good experiences with the development of the Su-7-Arrows with the introduction of swing-wings, which led to the production of the Su-17. Based on these experiences, prototypes without lifting engines, but with swing wings were built, these were given the designation T-6-2. Both swing leaf mechanisms and lifting engines increase the weight. Hubtriebwerke consume but on the one hand more internal space (thus less space for fuel) and consume at takeoff and landing more fuel than comparable rolling distances with the swing wings with maximum span adjustment. For these reasons, the T-6-2 prototypes prevail over the T-6-1 and went into mass production as Su-24.

The existence of the S-6 project, the T-58-M project and also the T-6-1 prototypes were unknown to the West at the time. Sometimes these are associated with the name Sukhoi Su-19. The "Sukhoi Su-19" but was the Pentagon suspected designation for the production version of the Su-24, as their existence in the West was known, but whose official name was not public.

Arment
The S-6 had a cannon GSh-6-23, two weapon stations on each wing, under the fuselage one weapon stations, behind the fuselage two more mounts. The outer wing stations and under the fuselage could be used to accommodate additional tanks. The rear fuselage stations were only usable for booster rockets or unguided free-fall bombs. Foreseen as weapons were conventional free-fall bombs, heavy unguided air-to-surface missiles, multiple launchers with unguided air-to-surface missiles, Ch-24 antiradalist weapons, and tactical nuclear weapons. The total weapon load was 3000 kg.