Groettrup G-2

The G-2 design objective was to create the first IRBM - to deliver a 1000 kg payload over a 2500 km range. The missile would use three V-2 derived engines with a total thrust of 100 tonnes. A variety of alternate configurations (R-12A through R-12K) were considered by the German team in Russia. These included parallel and consecutive staging, gimballed motors, and other innovations. The R-12K was particularly interesting because it represented a concept later used on the US Atlas missile - jettisoning of the two outboard engines at altitude to significantly improve range. The G-2 was given the secret designation R-6 and overt designation R-12 by the Russians.

More than ten G-2/R-12 variants were studied in detail to determine the optimum technical solution. All used a common bulkhead between the aft fuel and forward liquid oxygen tank. Two major aerodynamic forms were considered - conical, which was aerodynamic stable regardless of the stage velocity and vehicle centre of gravity, and cylindrical stages with fins. The variants studied were as follows:

• G-1 cluster - two G-1's as the first stage flanking a single G-1 as the second stage. Lift-off mass 50 tonnes, lift-off thrust 100 tonnes, total span 6 m, length 15 m.
• R-12A dual sequential stage. Conical form, with 3 G-1 engines in the first stage and a single G-1 engine in the second stage. Length 25.3 m, diameter at the base 4.0 m.
• R-12B short-range V-2 replacement based on second stage of R-12A. 2.4 m base diameter, 16.0 m long.
• R-12C dual stage. A variation of the R-12A with a larger-diameter upper stage. 19.2 m long.
• R-12E dual stage. Cylindrical first stage with aerodynamic stabilising fins
• R-12G single stage design with conical form
• R-12H single stage with cylindrical form and aerodynamic stabilising fins
• R-12K with jettisonable booster engines.

The optimum technical solution seemed to be the R-12G single-stage conical design. In comparing the G-2 with Korolev's R-2, the state commission favored the Groettrup design. But the Russian designers convinced the government that the G-2 required innovations beyond the immediate capability of Soviet technology. Koroelv's R-2, a modest upgrade of the V-2, was selected for production instead.

Manufacturer: Groettrup. to a: 2500 km trajectory. Liftoff Thrust: 1,000.000 kN (224,800 lbf). Total Mass: 50,000 kg (110,000 lb). Core Diameter: 3.70 m (12.10 ft). Total Length: 24.50 m (80.30 ft). Standard warhead mass: 1,000 kg (2,200 lb). Maximum range: 2,500 km (1,500 mi).

1946 September - Launch Vehicle: G-2.

• Groettrup team designs 2 stage IRBM. Nation: USSR. Groettrup sketches design for a 2500 km range missile. References: 86.

• Groettrup team transported to Soviet Union. Nation: USSR. In overnight roundup, 20,000 Germans transported to USSR to transfer technology on aerospace and other technical fields. References: 86.

• Groettrup team completes G-2 design. Nation: USSR. Groettrup completes design work on G-2, 1,000 kg warhead, 2500 km range. References: 86.

• Ordway, Frank, and Sharpe, Mitchell, The Rocket Team, Collector's Guide Publishing, Ontario, Canada, 2000. ISBN: 1894959000. Original published by Thomas Y Crowell, New York, 1979. Updated edition published in 2000. More at amazon.com...

• Michels, Juergen and Przybilski, Olaf, Peenemuende und seine Erben in Ost und West, Bernard & Graefe, Bonn, 1997. ISBN: 3763759603. Marvelous German language book traces the 'technology transfer' from the Peenemuende refugees to the rocketry programs of America, Russia, Germany, and other countries. More at amazon.com...

• Karpenko, A V, Utkin, A F and Popov,A D, Otechestvenniye strategischeskiye raketnoye kompleks, Sankt-Peterburg: Nevskii bastion; Gangut 1999.. Well-illustrated encyclopedia of the missiles of the Russian strategic missile forces.