Series of two Soviet manned spacecraft, capable of carrying up to three cosmonauts, which followed the VOSTOK series. It incorporated an AIRLOCK and had a mass of about 5.3 tonnes. On the Vostok 2 mission, launched on 18 March 1965, Alexai Leonov made an EVA (or "spacewalk") for 12 1/2 minutes' this was the first time such a manoeuvre had been attempted.
