Soviet authorities 'worried' about female cosmonauts
When the space race began, it was the Soviet Union which led the way. Not only did they put the first man, Yuri Gagarin, in space, but also the first woman.
Valentina Tereshkova, now 78, has been reunited with Vostok 6, the spacecraft in which she made her historic flight.
Speaking at the launch of a Science Museum exhibition, Ms Tereshkova revealed that the Soviet authorities thought it was "too dangerous" to send more female cosmonauts into orbit.
The BBC's science correspondent, Pallab Ghosh, went to meet her.