later revealed that all Vostok cosmonauts ejected and landed separately from the capsule. The capsule was serviced by an aft-facing conical equipment module long by , weighing containing nitrogen and oxygen breathing gasses, batteries, fuel, attitude control thrusters, and the retrorocket. It could support flights as long as ten days. Six Vostok launches were successfully conducted, the last two pairs in concurrent flights. The longest flight was just short of five days, on Vostok 5 on June 14–19, 1963. Since the attitude control thrusters were located in the instrument module which was discarded immediately prior to reentry, the reentry module's path and orientation could not be actively controlled. This meant that the capsule had to be protected from reentry heat on all sides, determining the spherical design (as opposed to Project Mercury's conical design, which allowed for maximum volume while minimizing the heat shield diameter). Some control of the capsule's reentry orientation was possible by offsetting its center of gravity. Proper orientation with the cosmonaut's back to the direction of flight was necessary in order to best sustain the which also maximized the 8 to 9 g-force. Voskhod The Vostok design was modified to permit carrying multi-cosmonaut crews, and flown as two flights of the Voskhod programme. The cylindrical interior cabin was replaced with a wider, rectangular cabin which could hold either three cosmonauts seated abreast (Voskhod 1), or two cosmonauts with an inflatable airlock in between them, to permit extravehicular activity (Voskhod 2). A backup solid-fuel retro rocket was added to the top of the descent module. Vostok's ejection seat was removed to save space (thus there was no provision for crew escape in the event of a launch or landing emergency). The complete Voskhod spacecraft weighed . Lack of space meant that the crew members of Voskhod 1 did not wear space suits. Both Voskhod 2 crew members wore spacesuits, as it involved an EVA by cosmonaut Alexei Leonov. An airlock was needed because the vehicle's electrical and environmental systems were air-cooled, and complete capsule depressurization would lead to overheating. The airlock weighed , was in diameter, high when collapsed for launch. When extended in orbit, it was long, had an internal diameter of and an external diameter of . The second crew member wore a spacesuit as a precaution against accidental descent module depressurization. The airlock was jettisoned after use. The lack of ejection seats meant that