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 metric tons. A variety of alternate configurations (R-12A through R-12K) were considered by the German team in Russia. These included parallel and consecutive staging, gimbaled 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 center 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 metric tons, lift-off thrust 100 metric tons, 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 stabilizing fins
• R-12G single stage design with conical form
• R-12H single stage with cylindrical form and aerodynamic stabilizing 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. Korolev's R-2, a modest upgrade of the V-2, was selected for production instead.

Maximum range: 2,500 km (1,500 mi).