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G-4

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Groettrup G-4

AKA: R-10;R-14. Status: Study 1949. Payload: 3,400 kg (7,400 lb). Thrust: 990.00 kN (222,560 lbf). Gross mass: 66,600 kg (146,800 lb). Height: 28.00 m (91.00 ft). Diameter: 3.73 m (12.23 ft).

The G-4 was designed by the Groettrup German team in the Soviet Union in competition with Korolev's R-3. Rocket chief Ustinov informed Groettrup of the new requirement on 9 April 1949. The specification was to deliver the first Soviet atomic bomb - total mass 3000 kg - to a 3000 km range - anywhere in Western Europe. This requirement meant a massive improvement over existing V-2 technology. A wide range of technical solutions were considered. These included use of 3 G-1's in a parallel-staging 'bundle' (or 'packet' as the Russians would later term it); winged missiles along the lines of the wartime A9/A10 or Saenger Antipodal Bomber (the G-3); or sequential stages, as used on the earlier G-1 and G-2 designs. Consideration was even given of using balloon tanks of high quality steel (as would be adopted in the USA for the Atlas ICBM). But the Russians did not have such alloys available, and the Germans kept the idea to themselves, 'in reserve'.

Groettrup's team finished the 20 volume design study in June 1949, three months after go-ahead. The selected configuration was a cylindrical single-stage design, which was aerodynamically stable in all flight regimes. As in previous designs, the liquid oxygen tank was switched to the forward position in comparison with the V-2, eliminating instrument and engine pre-cooling problems. The warhead was contained in a 1.40 m diameter cylinder, and the re-entry vehicle used the sharp-nosed 'fast point' preferred by the Soviet engineers. The Germans preferred the 'slow point' design - a blunt nose and conical sides - but the Russians feared a slow-falling warhead could be intercepted and felt the thermal problems of the sharp point could be solved.

The R-14 would use a new design high pressure cylindrical combustion chamber. This would feed a spherical mixing chamber. The German engineers worked with Glushko to build a subscale 7 metric ton thrust, 60 atmosphere chamber pressure test model. Given the Russian designation ED-140, this was run 100 times between the summer of 1949 and April of 1950. 19 of these chambers would feed the chamber of the Glushko RD-110 engine slated for use in Korolev's competing R-3 rocket.

Unknown to the German team, their approach was evaluated against Korolev's R-3 on 7 December 1949 - and their design was found to be superior. Neither ended up in production, but the design concepts of the G-4 led directly to Korolev's R-7 ICBM (essentially a cluster of G-4's or R-3A's) and the N1 superbooster. Notable unique features of these rockets borrowed from the G-4 work included conical rocket body forms, 'sharp point' warheads or payload shrouds, forward positioning of the oxygen tanks, and elimination of aerodynamic surfaces.

The G-4 was the last design project worked on by the team. The G-4 was designated as the R-10 in the original secret Russian numbering scheme; and known to the Russians as the R-14 (the same designation given to the 3000 km range single stage IRBM finally delivered by Yangel to the Soviet armed forces in 1962).

Maximum range: 3,000 km (1,800 mi).

Stage Data - G-4

• Stage 1. 1 x G-4. Gross Mass: 66,600 kg (146,800 lb). Empty Mass: 2,760 kg (6,080 lb). Thrust (vac): 1,059.000 kN (238,072 lbf). Isp: 249 sec. Burn time: 145 sec. Isp(sl): 233 sec. Diameter: 3.73 m (12.23 ft). Span: 3.73 m (12.23 ft). Length: 23.50 m (77.00 ft). Propellants: Lox/Alcohol. No Engines: 1. Status: Study 1949. Comments: Residuals 940 kg. Burnout mass with 3400 kg warhead 7100 kg. Cutoff velocity 4500 m/s, maximum altitude 120 km over 3000 km range. With 10 G limiter thrust would be throttled back and burn time would be 156 seconds.

• Ustinov instructs German rocket engineers to design '3000/3000' missile. - . Nation: Russia. Related Persons: Ustinov. Ustinov's requirement was to deliver a 3000 kg nuclear warhead over a 3000 km range (eg to reach the United Kingdom)..

• Russo-German advanced rocket engine tests. - . Nation: Russia. Related Persons: Glushko.

  The planned IRBM's (R-3 or G-4) would use a new design high pressure cylindrical combustion chamber. This would feed a spherical mixing chamber. The German engineers worked with Glushko to build a subscale 7 tonne thrust, 60 atmosphere chamber pressure test model. Given the Russian designation ED-140, this was run 100 times between the summer of 1949 and April of 1950. 19 of these chambers would feed the chamber of the Glushko RD-110 engine slated for use in Korolev's competing R-3 rocket.

• Groettrup G-4 IRBM design complete - . Nation: Russia. Related Persons: Groettrup. Groettrup's team finished the 20 volume design study three months after go-ahead. The selected configuration was a conical single-stage design, which was aerodynamically stable in all flight regimes..

• Groettrup team briefs G-4 - . Nation: Russia. Related Persons: Groettrup.

  The Scientific-Technical Soviet of NII-88 receives a briefing on Groettrup's G-4 IRBM design: 23.7 m long, 2.74 m diameter, 70.800 kg takeoff mass, 7000 kg empty, 3,000 kg warhead, turbine exhaust for roll control (as in Jupiter), plywood RV, lox/alcohol propellants.

• German assistance to Soviet rocketry to be ended. - . Nation: Russia. Decree 3456-1446 'On termination or the work of German scientists in the Soviet missile program.' was issued..

• First Germans returned to Germany. - . Nation: Russia. First Germans sent back to Germany. Were not used to generate new designs after the G-4.

• Groettrup and last Germans return to Germany. - . Nation: Russia.