After almost a year in the area around Peenemünde, Soviet officials moved most of the captured German rocket specialists to Gorodomlya Island on Lake Seliger, about 240 kilometers (150 mi) northwest of Moscow. They were not allowed to participate in Soviet missile design, but were used as problem-solving consultants to the Soviet engineers. They helped in the following areas: the creation of a Soviet version of the A-4; work on "organizational schemes"; research in improving the A-4 main engine; development of a 100-ton engine; assistance in the "layout" of plant production rooms; and preparation of rocket assembly using German components. With their help, particularly Helmut Groettrup's group, Korolev reverse-engineered the A-4 and built his own version of the rocket, the R-1, in 1948. Later, he developed his own distinct designs, though many of these designs were influenced by the Groettrup Group's G4-R10 design from 1949. The Germans were eventually repatriated in 1951–53.