Proton-K with LK-1

8K82K UR-500K

Mission Profile

Proton-K with LK-1 was a proposed configuration of the Soviet Proton heavy-lift rocket intended to support the crewed circumlunar program as part of the USSR's secret race to reach the Moon. Standing 55.4 meters tall with a liftoff mass of 705,000 kg and generating 9,870 kN of thrust across its four stages, the vehicle would have mated the Proton-K core with the LK-1 crewed spacecraft. The design was studied in the mid-1960s but never flew in this configuration, as the Soviet manned lunar program was reorganized and ultimately focused on the N1 rocket for the Moon landing mission. Nevertheless, the Proton-K in its uncrewed forms went on to become one of the most successful heavy-lift vehicles in history.