The USSR continued to use its Vostok capsule to send cosmonauts into orbit for increasingly long periods of time.
Early in the 1960s, no one knew for sure whether people could survive space travel without serious side effects.
Testing the limits of human endurance in space was an important process.
Launched on August 6, 1961, Vostok 2 carried cosmonaut Gherman Titov in orbit for more than one day, or 25 hours and 18 minutes.
Vostok 3 was launched on August 11, 1962.
To the world’s surprise, Vostok 4 took off one day later. The two capsules intentionally came within 4 miles (7 km) of each other and communicated by radio. They stayed in orbit for 4 and 3 days, respectively.
In June 1963, Vostok 5 and Vostok 6 were launched. Their plan was also to meet and establish radio contact in space.
What most people didn’t know at the time was that Vostok 6 had a female cosmonaut, Valentina Tereshkova, at the controls.
The first American female astronaut in space was Sally Ride, aboard the space shuttle, the Challenger some 20 years later.
The flights of Vostok 5 and Vostok 6 went smoothly, with Vostok 5 setting a record for how long a person stayed in space: 5 days.