On March 18, 1965, about a week before the first American piloted Project Gemini space flight, the USSR accelerated the competition, by launching the two-cosmonaut Voskhod 2 mission with Pavel Belyayev and Alexey Leonov. Voskhod 2's design modifications included the addition of an inflatable airlock to allow for extravehicular activity (EVA), also known as a spacewalk, while keeping the cabin pressurized so that the capsule's electronics wouldn't overheat. Leonov performed the first-ever EVA as part of the mission. A fatality was narrowly avoided when Leonov's spacesuit expanded in the vacuum of space, preventing him from re-entering the airlock. In order to overcome this, he had to partially depressurize his spacesuit to a potentially dangerous level. He succeeded in safely re-entering the ship, but he and Belyayev faced further challenges when the spacecraft's atmospheric controls flooded the cabin with 45% pure oxygen, which had to be lowered to acceptable levels before re-entry. The reentry involved two more challenges: an improperly timed retrorocket firing caused the Voskhod 2 to land 386 kilometers (240 mi) off its designated target area, the town of Perm; and the instrument compartment's failure to detach from the descent apparatus caused the spacecraft to become unstable during reentry.