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First mammals in space

The US and the USSR sent animals into space to determine the safety of the environment before sending the first humans. The USSR used dogs for this purpose, and the US used monkeys and apes. The first mammal in space was Albert II, a rhesus monkey launched by the US on a sub-orbital flight on June 14, 1949, who died on landing due to a parachute malfunction.

The USSR sent the dog Laika into orbit on Sputnik 2 on November 3, 1957, for an intended ten-day flight. They did not yet have the technology to return Laika safely to Earth, and the government reported Laika died when the oxygen ran out, but in October 2002 her true cause of death was reported as stress and overheating on the fourth orbit due to failure of the air conditioning system. At a Moscow press conference in 1998 Oleg Gazenko, a senior Soviet scientist involved in the project, stated "The more time passes, the more I'm sorry about it. We did not learn enough from the mission to justify the death of the dog...".

On August 19, 1960, the dogs Belka and Strelka were sent into orbit aboard Sputnik 5 and safely returned.

The Americans sent the chimpanzee Ham on a suborbital flight of the Mercury capsule on Mercury-Redstone 2 and recovered him safely on January 31, 1961.

The chimpanzee Enos was launched on Mercury-Atlas 5 on November 29, 1961, into what was supposed to be a three-orbit flight. However, the mission was aborted after two orbits due to capsule overheating, and a malfunctioning "avoidance conditioning" test subjecting him to 76 electrical shocks.