The first living creatures to travel in space were the dogs of the Soviet Unions space program.Beginning in 1951 dogs flew aboard sub－orbital flights to the height of 63 miles and higher.They helped to test the equipment that would later be used by humans.The first pair of dogs to fly，on July 22，1951，were named Tsygan and Dezik.

     Space dogs would make history on November 3，1957.On this date，just one month after the historic launch of the world's first artificial satellite，Sputnik，the Soviet Union shocked the world again by launching Sputnik 2.This satellite contained the first living creature to travel in space，a dog named Laika.Laika was to have orbited for a week or more until her food and oxygen ran out.In fact，Laika lasted only hours in orbit before over heating in her capsule(太空舱) took her life.

     That next step，occurred in August 1960，when the dogs Belka and Strelka made 18 orbits of earth and returned alive.Like Laika before them，they became distinguished ， featured in newspapers and magazines around the world.

     Six more orbital dog flights over the next eight months further tested the equipment necessary for humans to follow in the dogs' footsteps.That historic event happened on April 12，1961，when Yuri Gagarin became the first human to travel in space.

     The role of the space dogs had proven important in advancing the exploration of space.But，they would make one final flight.In 1966，traveling aboard the Cosmos 110 satellite，the dogs Ugolek and Veterok spent 22 days in orbit.Once again dogs led the way.Humans would not achieve a space flight that long for eight more years，in Skylab 2.