Meanwhile, Chelomei's OKB-52 proposed an alternate mission with much lower risk. Instead of a crewed landing, Chelomei proposed a series of circumlunar missions to beat the US to the vicinity of the Moon. He also proposed a new booster for the mission, clustering three of his existing UR-200s (known as the SS-10 in the west) to produce a single larger booster, the UR-500. These plans were dropped when Glushko offered Chelomei the RD-270, which allowed the construction of the UR-500 in a much simpler "monoblock" design. He also proposed adapting an existing spacecraft design for the circumlunar mission, the single-cosmonaut LK-1. Chelomei felt that improvements in early UR-500/LK-1 missions would allow the spacecraft to be adapted for two cosmonauts.