Valentin Bondarenko was a young cosmonaut who, on March 23 of 1961, had been doing routine medical tests in a pressure chamber as part of an isolation exercise. A fire was accidentally started in the chamber, and, because the chamber's atmosphere was pure oxygen, the fire spread quickly. Bondarenko was removed from the chamber alive, but he died soon after of shock.
This tragedy was not the result of the rushing of a mission to gain an advantage in the space race. However, for propaganda purposes, the Soviet Union concealed Valentin Bondarenko's death from the rest of the world until 1986. If it were not for the competition between the USA and the USSR, the United States would have found out about this tragedy, and NASA might have taken precautions that could have prevented the deaths of the crewmembers of Apollo 1.