Vostok 2 (Russian: Восток-2, Orient 2 or East 2) was a Soviet space mission which carried cosmonaut Gherman Titov into orbit for a full day on August 6, 1961 to study the effects of a more prolonged period of weightlessness on the human body. Titov orbited the Earth over 17 times, exceeding the single orbit of Yuri Gagarin on Vostok 1 − as well as the suborbital spaceflights of American astronauts Alan Shepard and Gus Grissom aboard their respective Mercury-Redstone 3 and 4 missions. Indeed, Titov's number of orbits and flight time would not be surpassed by an American astronaut until Gordon Cooper's Mercury-Atlas 9 spaceflight in May 1963.
After the flight of Vostok 1, Sergei Korolev took a short vacation in Crimea where he began working out the flight plan for the next mission. There were considerable arguments over the duration of the mission as flight doctors argued for no more than three orbits. The flight of Korabl-Sputnik 2 nine months earlier had carried two dogs on a six orbit mission, during which the animals had experienced convulsions and thus all subsequent Vostok missions were limited to three orbits maximum. Although dogs and humans were very different physiologically, the doctors were worried about the risks posed on a longer flight. There was also the purely practical aspect of spacecraft recovery. If Vostok 2 flew three orbits, reentry and landing would take place in the wide open steppes of southern Russia, the landing site moving steadily further west with each orbit. Orbits 8-13 would drop the capsule into the Pacific Ocean, after which landing would again occur in Soviet territory, but in the remote, frozen wastes of Siberia. Thus, it was necessary to spend a full 24 hours in space before it would be once again possible to land in the prime recovery area in southern Russia. The three orbit limit thus would not only make landing easy, but minimize risks to the cosmonaut posed by prolonged weightlessness.
Korolev argued that since it would still take an entire day for landing in southern Russia to be possible again, there was no reason not to go for it. Besides, he argued, missions of the future would inevitably require lengthy stays in space. The flight was targeted for somewhere between July 25 and August 5. To ensure safe radiation levels, balloons equipped with Geiger counters were flown aloft, in addition similar equipment would be carried on Vostok 2. Several enhancements were made to Vostok 2, including an improved TV transmission system and better climate control systems.
Liftoff took place August 6 at 8:57 AM Moscow time and booster performance was almost flawless, placing the spacecraft into a 184x244 km orbit.
The flight was an almost complete success, marred only by a heater that had inadvertently been turned off prior to liftoff and that allowed the inside temperature to drop to 50 °F (10 °C),:113 a bout of space sickness, and a troublesome re-entry when the reentry module failed to separate cleanly from its service module.
Unlike Yuri Gagarin on Vostok 1, Titov took manual control of the spacecraft for a short while. Another change came when the Soviets admitted that Titov did not land with his spacecraft. Titov would claim in an interview that he ejected from his capsule as a test of an alternative landing system; it is now known that all Vostok program landings were performed this way.