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During the closing weeks of World War II, the German work at Peenemünde was investigated by Soviet intelligence, amongst whom was rocket motor constructor Alexey Isayev, who found a copy of Sänger and Bredt's report. A translation was soon circulating among Soviet rocket designers, and a condensed version made its way to Stalin himself.
In November 1946 the NII-1 NKAP research institute was formed with mathematician Mstislav Vsevolodovich Keldysh as its head to investigate and develop the German Sänger-Bredt design. In 1947, studies indicated that the high fuel consumption of Sänger's rocket-based design rendered the concept impracticable in the short term. Using engines which were considered to be available in a reasonable timespan, 95% of the vehicle's initial mass would have to be propellant. However, use of ramjets during the acceleration phase would give the craft a more reasonable 22% dead weight and still achieve the 5 km/s velocity required for a 12,000 km intercontinental range.
It was estimated that it would take until the mid-1950s before a draft project of a feasible design could be prepared, and by that time the design had been made obsolete by more advanced designs. However, the work carried out would lead to the EKR, MKR, Buran, and Burya ramjet cruise missiles.
Proposed mission profile
- The 100 tonne craft would be accelerated to 500 m/s using a sled running along a 3 km track and powered by five or six RKDS-100 rocket engines of 600 tonnes total thrust. Separation velocity would be reached 11 seconds after ignition.
- After separation from the sled, the craft would climb using its main RKDS-100 rocket engine and two wingtip-mounted ramjets which would accelerate it to an altitude of 20 km and a speed of over Mach 3.
- The rocket would continue working after the ramjets had flamed out at high altitude; it had a specific impulse of 285 seconds, a thrust of 100 tonnes, and used Liquid oxygen/Kerosene propellants.
- Function: Sub-orbital bomber
- Launch mass: 100,000 kg
- Total length: 28 m
- Launch platform: Rocket sled
- Status: Canceled
Launch sled (stage 0)
- Engine: 5/6 × RKDS-100 rocket engines
- Length: 14 m (45 ft)
- Diameter: 3.6 m (11.8 ft)
- Thrust: 5,880 kN (1,321,870 lbf)
- Oxidizer: LOx
- Combustible: Kerosene
Keldysh bomber (stage 1)
- Engine: 1 × RKDS-100 rocket, 2 x ramjets
- Speed : Mach 3
- Range: 12,000 km
- Flight altitude:
- Length: 28.0 m
- Diameter: 3.6 m
- Wing span: 15 m
- Wing area: 126 m²