Give a stream of consciousness and then the final answer. The Space Race refers to the 20th-century competition between two Cold War rivals, the Soviet Union (USSR) and the United States (US), for dominance in spaceflight capability. It had its origins in the missile-based nuclear arms race between the two nations that occurred following World War II, aided by captured German missile technology and personnel from the Aggregat program. The technological superiority required for such dominance was seen as necessary for national security, and symbolic of ideological superiority. The Space Race spawned pioneering efforts to launch artificial satellites, uncrewed space probes of the Moon, Venus, and Mars, and human spaceflight in low Earth orbit and to the Moon.

Based on this passage, who were the two superpowers during the cold war space race?
The relevant information to answer the above question is: The Space Race refers to the 20th-century competition between two Cold War rivals, the Soviet Union (USSR) and the United States (US), for dominance in spaceflight capability.
So, the final answer is the Soviet Union ( USSR ).