Soviet space dogs
During the 1950s and 1960s the USSR used a number of dogs for sub-orbital and orbital space flights to determine whether human spaceflight was feasible. In the 1950s and 60s, the Soviet Union launched missions with passenger slots for at least 57 dogs. The actual number of dogs in space is smaller, as some dogs flew more than once. Most survived; the few that died were lost mostly through technical failures.

# Training
Dogs were the preferred animal for the experiments because scientists felt that dogs were better suited to endure long periods of inactivity. As part of their training, they were confined in small boxes for 15-20 days at a time. Stray dogs, rather than animals accustomed to living in a house, were chosen because the scientists felt they would be able to tolerate the riguours and extreme stresses of space flight better than other dogs.  Female dogs were used because of their temperament and because the suit for the dogs in order to collect urine and faeces was equipped with a special device, designed to work only with females.
Their training included standing still for long periods of time, wearing space suits, being placed in simulators that acted like a rocket during launch, riding in centrifuges that simulated the high acceleration of a rocket launch and being kept in progressively smaller cages to prepare them for the confines of the space capsules.  Dogs that flew in orbit were fed a nutritious jelly-like protein. This was highly fibrous, and assisted the dogs to excrete during large amounts of vegetating time. More than 60% of dogs to enter space were reportedly suffering from constipation and gall bladder stones on arrival back to base.

# Sub-orbital flights
Several dogs made high-altitude flights on R-1 series geophysical rockets between 1951 and 1952.

## Dezik, Tsygan and Lisa
Dezik () and Tsygan (, "Gypsy") were the first dogs to make a sub-orbital flight on July 22, 1951.  Both dogs were recovered unharmed after travelling to a maximum altitude of 100 km.  After the flight, Tsygan was adopted as a pet by Soviet physicist Anatoli Blagonravov .  Dezik made another sub-orbital flight in September 1951 with a dog named Lisa, although neither survived.

## Lisa and Ryzhik
Lisa (, "Fox" or "Vixen") and Ryzhik (, "Ginger" (red-haired)) flew to an altitude of 100 km on June 2, 1954.

## Smelaya and Malyshka
Smelaya (, "Bold" or "Courageous") was due to make a flight in September but ran away the day before the launch.  Russian officials feared she had been eaten by wolves, but she was found the next day and went on to make a successful flight with a dog named Malyshka (, "Little One").

## Bolik and ZIB
Bolik () ran away just days before her flight in September 1951.  A replacement named ZIB (allegedly a Russian acronym for "Substitute for Missing Bolik", "  "), who was an untrained street dog found running around barracks was quickly located and made a successful flight.

## Otvazhnaya and Snezhinka
Otvazhnaya (, "Brave One") made a flight on July 2, 1959 along with a rabbit named Marfusha (, "Martha") and another dog named Snezhinka (, "Snowflake").  She went on to make 5 other flights between 1959 and 1960.

## Albina and Tsyganka
Albina (, a real female name) and Tsyganka (, "Gypsy girl") were both ejected out of their capsule at an altitude of 85 km and landed safely.  Albina was one of the dogs shortlisted for Sputnik 2, but never flew in orbit.

## Damka and Krasavka
Damka (, "Little Lady") and Krasavka (, "Little Beauty") were both planned to make an orbital flight on December 22, 1960; however, after the upper stage rocket failed, the flight was aborted.  Both were recovered successfully after an unplanned sub-orbital flight.  Damka was also known as Shutka (, "Joke") and Zhemchuzhnaya (, "Pearly") and Krasavka was also known as Kometka (, "Little Comet") and Zhulka (, "Cheater").
Other dogs that flew on sub-orbital flights include Dymka (, "Smoky"), Modnitsa (, "Fashionable") and Kozyavka (, "Little Gnat").
At least four other dogs flew in September 1951, and two or more were lost.

# Orbital Flights

## Laika
Laika (, "Barker"), originally named Kudryavka (, "Little Curly"), became the first living Earth-born creature (other than microbes) in orbit aboard Sputnik II on November 3, 1957.  Some call her the first living passenger to go into space, but others claim sub-orbital flights passed the edge of space first.  She was also known as Zhuchka (, "Little Beetle") and Limonchik (, "Lemon").  The American media dubbed her "Muttnik".  She died between five and seven hours into the flight from stress and overheating.  Her true cause of death was not made public until October 2002; officials previously gave conflicting reports that she was either euthanized by poisoned food or died when the oxygen supply ran out. The Russian scientist responsible for the project has since expressed regret for allowing Laika to die.

## Bars and Lisichka
Bars (, "Panther" or "Lynx") and Lisichka (, "Little Fox") died after their rocket exploded 28.5 seconds into the launch on July 28, 1960.  Bars was also known as Chayka ("Gull").

## Belka and Strelka
Belka (, literally, "Squirrel", but as a dog's name most likely means "Whitey", from Russian: "" (for "white")) and Strelka (, "Little Arrow") spent a day in space aboard Korabl-Sputnik-2 (Sputnik 5) on August 19, 1960 before safely returning to Earth.
They were accompanied by a grey rabbit, 42 mice, 2 rats, flies and a number of plants and fungi. All passengers survived. They were the first Earth-born creatures to go into orbit and return alive.
Strelka went on to have six puppies with a male dog named Pushok who participated in many ground based space experiments, but never made it into space. One of of the pups was named Pushinka (, "Fluffy") and was presented to President John F. Kennedy's daughter Caroline by Nikita Khrushchev in 1961. Pushinka was required to pass a security inspection to rule out the possibility that she was a spy dog. A Cold War romance bloomed between Pushinka and a Kennedy dog named Charlie resulting in the birth of 4 pups that JFK referred to jokingly as pupniks.  Two of their pups, Butterfly and Streaker were given away to children in the Midwest. The other two puppies, White Tips and Blackie, stayed at the Kennedy home on Squaw Island but were eventually given away to family friends.. Pushinka's descendants are still living today. A photo of descendants of some of the Space Dogs is on display at the Zvezda Museum outside Moscow.

## Pchelka and Mushka
Pchelka (, "Little Bee") and Mushka (, "Little Fly") spent a day in orbit on December 1, 1960 on board Korabl-Sputnik-3 (Sputnik 6) with "other animals", plants and insects.  Due to a navigation error, their spacecraft disintegrated during re-entry on December 2 and all were killed.  Mushka was one of the three dogs trained for Sputnik 2 and was used during ground tests.  She did not fly on Sputnik 2 because she refused to eat properly.

## Chernushka
Chernushka (, "Blackie") made one orbit on board Korabl-Sputnik-4 (Sputnik 9) on March 9, 1961 with a cosmonaut dummy (whom Russian officials nicknamed "Ivan Ivanovich"), mice and a guinea pig.  The dummy was ejected out of the capsule during re-entry and made a soft landing using a parachute.  Chernushka was recovered unharmed inside the capsule.

## Zvezdochka
Zvezdochka (, "Little Star"), who was named by Yuri Gagarin, made one orbit on board Sputnik 10 on March 25, 1961 with a wooden cosmonaut dummy in the final practice flight before Gagarin's historic flight on April 12.  Again, the dummy was ejected out of the capsule while Zvezdochka remained inside.  Both were recovered successfully.

## Veterok and Ugolyok
Veterok (, "Little Wind/Breeze") and Ugolyok (, "Little Piece of Coal") were launched on February 22, 1966 on board Cosmos 110, and spent 22 days in orbit before landing on March 16.  This spaceflight of record-breaking duration was not surpassed by humans until Skylab 2 in June 1973 and still stands as the longest space flight by dogs.