Vostok programme

At 26 years old he started his cosmonaut training at Zhukovsky Military Engineering academy. His first assignment was as the backup pilot of Vostok 3.

Bykovsky launched on the Vostok 5 mission on 14 June 1963. During the flight he conducted experiments, such as photographing the Earth's horizon and documenting the growth of peas. Two days into his flight, Valentina Tereshkova flew the Vostok 6 spacecraft within five kilometers of his spacecraft. He set a space endurance record when he spent five days in orbit aboard Vostok 5 in 1963 where his call-sign was "Hawk" (Russian: Ястреб). Although this flight duration has since been surpassed by crews of more than one person, it remains the endurance record for a solo spaceflight as of 2019. During his orbit aboard Vostok 5, Bykovsky was also made a member of the communist party. He was promoted to colonel on 30 April 1966.

Soyuz programme

Bykovsky was assigned to be the commander of the original Soyuz 2 mission, which was planned to be launched soon after Soyuz 1. Two of the three crewmen from Soyuz 2 were to conduct an extravehicular activity (EVA) and enter Soyuz 1. During the Soyuz 1 flight, many concurrent problems forced mission control to command an early reentry of the spacecraft. This also caused them to cancel the Soyuz 2 flight as no rendezvous could occur. On Soyuz 1, tube holding the main parachute was too rough, which created enough friction that the drogue parachute was unable to pull it out. The spacecraft struck the ground at approximately 93 miles per hour, killing Vladimir Komarov. As the Soyuz 2 capsule was made with the same specifications as Soyuz 1, if the mission had flown Bykovsky and his crew would have been killed.

He flew the Soyuz 22 mission with Vladimir Aksyonov. The mission launched on 15 September 1976. The capsule was originally a backup for the Apollo–Soyuz Test Project (ASTP). The main purpose of the mission was studying and practising Earth observation techniques.

He flew the Soyuz 31 mission to the Salyut 6 space station with the East German Sigmund Jähn. It was launched on 26 August 1978. They joined two other cosmonauts on the space station that had arrived on Soyuz 29. The four conducted biological experiments on themselves during their stay. Bykovsky and Jähn undocked from the station in the Soyuz 29 capsule on 3 September and landed back on Earth later that day.