Yuri Alekseyevich Gagarin was a Soviet pilot and cosmonaut. He was the first human to journey into outer space, when his Vostok spacecraft completed an orbit of the Earth on 12 April 1961.
The first successful orbital launch was of the Soviet unmanned Sputnik 1 (“Satellite 1”) mission on 4 October 1957. The satellite weighed about 83 kg (183 lb), and is believed to have orbited Earth at a height of about 250 km (160 mi). It had two radio transmitters (20 and 40 MHz), which emitted “beeps” that could be heard by radios around the globe. Analysis of the radio signals was used to gather information about the electron density of the ionosphere, while temperature and pressure data was encoded in the duration of radio beeps. The results indicated that the satellite was not punctured by a meteoroid. Sputnik 1 was launched by an R-7 rocket. It burned up upon re-entry on 3 January 1958.
The second one was Sputnik 2. Launched by the USSR on November 3, 1957, it carried the dog Laika, who became the first animal in orbit.
This success led to an escalation of the American space program, which unsuccessfully attempted to launch a Vanguard satellite into orbit two months later. On 31 January 1958, the U.S. successfully orbited Explorer 1 on a Juno rocket.After this US worked on Project Mercury to launch men singly into orbit, while the USSR secretly pursued the Vostok program to accomplish the same thing.
In 1960, after much searching and a selection process, Yuri Gagarin was chosen with 19 other pilots for the Soviet space program. Gagarin was further selected for an elite training group known as the Sochi Six, from which the first cosmonauts of the Vostok programme would be chosen. Gagarin and other prospective candidates were subjected to experiments designed to test physical and psychological endurance; he also underwent training for the upcoming flight. Out of the twenty selected, the eventual choices for the first launch were Gagarin and Gherman Titov due to their performance during training sessions as well as their physical characteristics — space was limited in the small Vostok cockpit, and both men were rather short. Gagarin was 1.57 metres (5 ft 2 in) tall. The first human spaceflight was launched by the Soviet Union as a part of the Vostok program, with cosmonaut Yuri Gagarin aboard. Humans have been continuously present in space for 16 years and 288 days on the International Space Station .