Joint flight with Vostok 4. The first such flight, where Vostok capsules were launched one day apart, coming within a few kilometers of each other at the orbital insertion of the second spacecraft. The flight was supposed to occur in March, but following various delays, one of the two Vostok pads was damaged in the explosion of the booster of the third Zenit-2 reconnsat in May. Repairs were not completed until August. Vostok 3 studied man's ability to function under conditions of weightlessness; conducted scientific observations; furthered improvement of space ship systems, communications, guidance and landing. Immediately at orbital insertion of Vostok 4, the spacecraft were less than 5 km apart. Popovich made radio contact with Cosmonaut Nikolayev. Nikolayev reported shortly thereafter that he had sighted Vostok 4. Since the Vostok had no maneuvering capability, they could not rendezvous or dock, and quickly drifted apart. The launches did allow Korolev to offer something new and different, and gave the launch and ground control crews practice in launching and handling more than one manned spacecraft at a time. The cosmonaut took colour motion pictures of the earth and the cabin interior.

Korolev is still in action the next morning. There are thousands of tiny details he personally monitors. He has good technical deputies, but in Kamanin's opinion, not a single good organiser to take care of the necessary details. The State Commission meets at the pad at 07:30 and confirms the launch order. The weather is good (high pressure, clear, 6 to 7 m/s wind). At 08:50 Nikolayev and Bykovsky drive in a Volga to the MIK assembly building. Medical checkout is routine, and they suit up. At 11:30 they leave the bus and take the lift to the spacecraft. At the command bunker, only 10 m from the rocket, are Korolev, Gagarin, Smirnov, Barmin, Kirillov, and Kamanin. The launch proceeds perfectly on schedule, third stage shutdown coming exactly on time at T+687 seconds. Nikolayev sends peaceful greetings to the people of earth and announcing this great new victory of the Soviet people in the mastery of space. Two hours later, after confirmation of orbit, Khrushchev, Kozlov and Ustinov are informed of the successful launch.