Vostok 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. 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.