In space, no one can hear you bark.

Two mongrels named Belka and Strelka made history in 1960 when they went into orbit in a Soviet space ship and then returned to Earth -- the first animals ever to survive the trip.

Half a century on, the two dogs are the stars of a full-length Russian cartoon feature, "Belka and Strelka: Star Dogs," which tells the true story of their iconic space mission in 3-D.

The dogs are shown being caught on a Moscow street and taken to a research centre where they are trained for space flight with a series of gruelling tests and sessions in a spinning centrifuge.

Then it's time for them to blast off into space, along with a fast-talking rat called Venya -- in real life, the dogs travelled with mice, plants and insects.

The film, to be released around Russia this week, takes some other liberties with history.

Belka and Strelka do not just spend a day in orbit, but go on a space walk and even change the batteries in a Soviet Sputnik.

Made in Moscow on a four million-euro (5.4 million dollars) budget, the film is "a fairytale based on real events," its co-director, Svyatoslav Ushakov, said in an interview.

Ushakov learned his animation skills at the respected Pilot studio in Moscow, but moved to work in Los Angeles in the 1990s, including at Klasky Csupo, the company behind shows such as "Rugrats".

At 42, he's too young to remember Belka and Strelka's space flight, but old enough to have been a member of the Young Pioneers, a Soviet-era youth group.

The film is packed with loving detail of Soviet everyday life -- from Pobeda cars to automatic lemonade dispensers and copies of the Soviet daily Pravda -- but Ushakov says this is about entertaining, not indoctrination.

"Naturally we didn't want any politics or revival of the Soviet Union," he said. "When children see a bust of Lenin in the metro, it doesn't provoke any emotions in them. It's like any art object.

The film has an uplifting message, all the same, he said. "This is a wonderful story about friendship and overcoming troubles, I think it's what children need."

-- Belka and Strelka were instant celebrities --

The story of Belka and Strelka -- whose names mean Squirrel and Arrow -- came as a welcome relief to the Soviet people after the tragedy of Laika, the first dog in orbit.

She died in 1957 from overheating a few hours after take-off in her tiny craft, but in any case, her ticket to space was strictly one-way.

Belka and Strelka, both females, became instant celebrities when they landed on August 20. The film ends with archive footage of the dogs being dangled in front of reporters and being chauffeured in the back of a limousine.

Their winsome faces were used to decorate household wares such as matchboxes.

The first man in space, Yury Gagarin, later reportedly quipped: "I'm not sure whether I'm the first man or the last dog."

Gagarin himself is absent from the film. Originally, makers planned to show him interacting with the dogs, including a scene inspired by often-shown archive footage where he walks along with his shoelaces apparently undone.

But the cosmonaut's heirs vetoed the idea. "We received a letter saying 'It's a pity that you see Gagarin, the hero of the Soviet Union and the first cosmonaut, as an officer with his laces undone'," Ushakov said.

Gagarin's daughters have previously taken a tough line on screen depictions of their father. In 2007, they forced the makers of a Russian comedy film about a young black boy who fantasizes that he is Gagarin's grandson to remove all references to the cosmonaut.

Ushakov said he is pleased that the makers worked round the problem by shooting the film entirely from a dog's-eye-view.

The human supervisors of the space experiment are shown only as slightly sinister figures in overcoats with their faces out of view.

But there is a reference to a real historical figure. After landing from space, Strelka gave birth to puppies and in a brilliant Soviet PR move, one was subsequently sent as a gift to then US president John F. Kennedy.

This story is used as a framing device in the film, which is narrated by the puppy in a White House office, while Kennedy is shown phoning Soviet leader Nikita Khrushchev to thank him.

What happened next to the dogs is glossed over in the film. In reality, the dogs were guinea pigs for research, referred to as "cosmic biology".

In a recent documentary on Russia's Channel One, scientists said that they put the animals to sleep after the space flights so they could examine the physical changes in their bodies.

It's unclear how long the dogs lived after their return to earth. But today, their small, stuffed bodies are on display in the Moscow Cosmonautics Museum, their muzzles turned up to the stars.

"I think animation is for children and we don't reveal some things such as them being turned into stuffed animals," Ushakov said.

In the film, events take a happier turn. Belka finds love with a hunky Alsatian and Strelka is reunited with her long-lost mother.