Tumansky R-15

The Soyuz/Tumansky R-15BD-300 is an axial flow, single shaft turbojet with afterburning capabilities.

Design and development

The Tumansky R-15BD-300 was designed by Sergei Tumansky in the late 1950s. The engine was originally designed to be used in high altitude high speed drones, however the scheme was scrapped some years later. Due to lacking Soviet resources and funding the engine casing was mainly steel, and in areas exposed to high levels of heat, 30 micrometre silver-plated steel. At the time, the USSR did not have the resources to exploit metals such as titanium, or other composite alloys, which could have greatly reduced the engine's weight. The original engine was used in Tupolev Tu-123 reconnaissance drone.

Performance

The engine provides massive thrust and high performance at altitude, but at a cost. At dry thrust the engine could produce 7,500 kilograms force (73.5 kN, 16,500 lbf); with afterburners the output is 11,200 kilograms force (110 kN, 24,700 lbf). This allowed speeds of up to mach 3.2 in the Mikoyan-Gurevich MiG-25 (which used two engines). However, at speeds above mach 3, the force of the engine sucking fuel through the pumps overwhelmed the pumps' ability to limit the flow. At this point, the engines effectively became ramjets, as air began to bypass the low pressure compressors, accelerating out of control until the pilot could regain throttle control through using firewalls or compressor stall, or the tanks ran dry. However, a more probable series of events would be the eventual destruction of the engine as the suction force of the compressors began to pull various engine parts through the ignition chamber and turbines. The engine also suffered from huge fuel consumption issues, especially at low altitudes (which is consistent with most jet engines). This was also a limiting factor in the engine's role in aircraft, as the Mig 25 had a maximum combat radius of 744 miles (without using afterburners and operating at optimum altitude and in optimum atmospheric conditions). The engines did give excellent performance at high altitude though, with good fuel consumption and speeds at 80,000 ft, which was considerably better than any Western aircraft at the time (early 1960s). The MiG-25 was able to supercruise. The R-15BD-300, in short, was known for ease of maintenance, performance, and good monitoring systems for both pilots and engineers.

Variants

• R-15-300 : Original version. Used in Tupolev Tu-123 Yasterb drone.
• R-15-300M :
• R-15B-300 : Electronic engine controls(the first for the Soviet engine). and modifications to increase life span. Original engine for the MiG-25.
• R-15BD-300 :
• R-15BF2-300 : Uprated version. Used in Ye-266M high-performance MiG-25 prototype. Not put into production.

Applications

The only aircraft that uses or will use the R-15BD-300 is the MiG-25. These engines made this the fastest (clocked at mach 3.2) fighter aircraft ever put into production. Prototypes were also used for Ye-150A MiG interceptor prototype.

External links

• Tumansky R-15 (in Czech)