Two dogs sent into outer space by the Soviet Union after their safe return to earth. They spent 22 days in orbit. (Photo by Central Press/Getty Images). 22nd March 1966

Sam, a cheeky 7lb rhesus monkey, prepares for his flight into space. Sam rode a Project Mercury type capsule and travelled 55 miles high and 200 miles out into the Atlantic. (Photo by Keystone/Getty Images). 1959

Three monkeys strapped into chairs as they undergo tests in a space laboratory in Paris in preparation for a trip on the French rocket 'Vesta' to be launched from Hammaguir Base. (Photo by Keystone/Getty Images). 1967

Sam, a 7-lb rhesus monkey is prepared for his flight into space by being secured in a 100-lb biopack drum. Sam then rode a Project Mercury-type capsule to a height of 55 miles and landed 200 miles out in the Atlantic. The “Little Joe” experiment to test the capsule's escape rocket system was a success. (Photo by Keystone/Getty Images). 4th December 1959

A close-up of Laika, the dog used to relay biomedical information in the Soviet 'Sputnik II' outer-space investigation programme. (Photo by Keystone/Getty Images). 1957

A life-size replica of the original Sputnik satellite which carried two dogs into orbit, on display at a Moscow exhibition of space travel. (Photo by Keystone/Getty Images). 18th February 1959

A captain at the School of Aviation Medicine, Texas demonstrating how space monkey “Sam Soacem” is strapped into special padding and seat when sent up in rockets. Sam's name was formed from the school's acronym. (Photo by Keystone/Getty Images). 6th February 1959

Laika, the Soviet Satellite dog in the specially designed space equipment in Sputnik II. The capsule will probably burn up on re-entry. (Photo by Keystone/Getty Images). 5th November 1957

Two monkeys, Baker and Able, aboard USS Kiowa after their recovery from the cone of the Jupiter missile in which they travelled into space. (Photo by Keystone/Getty Images). 28th May 1959

A rabbit and “Daring”, one of the two dogs which completed a rocket flight as part of a Soviet experiment. (Photo by Keystone/Getty Images). 8th July 1959

Space monkeys Able and Baker at a Washington press conference to mark their return from an exploration to Jupiter. (Photo by Keystone/Getty Images). 1st June 1959

A packet of Russian cigarettes depicting the Sputnik space satellites and the first dog in space, Laika. (Photo by Fox Photos/Getty Images). 18th September 1958