Binoche plays a scientist carrying out an experiment to see if humans can reproduce in space in the movie High Life. Picture: YouTube.com

London - Jane Fonda performed one of cinema’s most memorable stripteases as she floated around in zero gravity and slipped out of her spacesuit in Barbarella.

Roger Moore had no trouble with weightlessness as he made love to Bond  girl Holly Goodhead on a space shuttle in Moonraker. "Take me round the world one more time, James," she purred.

Now there are two more members of the 100 000-Mile High Club in a new movie starring Juliette Binoche and Robert Pattinson. In High Life, they are travelling in a spaceship towards a black hole.

Binoche plays a scientist carrying out an experiment to see if humans can reproduce in space. When Pattinson’s character - like his crewmates, a condemned criminal used as a guinea pig  - refuses to donate sperm, she resorts to more conventional methods.

Sex in space may seem a daft fixation of movie producers, but it is a serious subject for scientists.

Nasa and its Russian equivalent insist that they have no knowledge of anyone having had sex in space. However, space scientists say they wouldn’t be surprised if some had tried.

The first mission to include both sexes went up in 1982 to the Soviets’ Salyut 7 space station, but the female cosmonaut, Svetlana Savitskaya, was married.

Nasa doesn’t send couples into space together for fear of damaging the team dynamic. But it was forced to make an exception when training-camp sweethearts Jan Davis and Mark Lee married just before they went into space on the Space Shuttle Endeavour in 1992.

They have always refused to discuss whether they had conjugal relations on the mission.

Rumours circulated in the  Nineties that Russian cosmonauts Valery Polyakov and Yelena Kondakova had become more than friends on the Mir space station.

The story was given a little credence by footage showing Polyakov flirtatiously splashing Kondakova with water.

Inevitably, there have been false alarms and hoaxes in the quest to boldly go where no lovers have gone before. French astronomer and writer Pierre Kohler wrote a book about Mir, claiming that astronauts had enjoyed "cosmic couplings" for tests designed to see how husband-and-wife teams could have "normal marital relations" on long missions.

Kohler cited a purported Nasa document on research into approved sexual positions.

Astronauts discovered that four positions were possible without "mechanical assistance", while six others involved the couple attaching themselves with an elastic belt or an inflatable tube that pressed them together. The document turned out to be a fake.

The truth is that having sex in zero gravity takes a lot of work. "The No 1 enemy of sex in space is Sir Isaac Newton’s laws of motion," says physicist Michio Kaku. "It’s the third law - for every action there’s an equal and opposite reaction. If you push against something, it pushes back against you."

Kira Bacal, a Nasa clinical consultant who has researched sex in space, says: "If you’re trying something that involves force against the other person, it takes a lot of strength to hold you together."

So the slightest nudge from a partner can send the other person reeling across the cabin. Experts believe at least one partner would need to be anchored.

Some have even suggested that a third person could help hold a pair together. Harry Stine, a former Nasa technician, claimed that the agency had simulated sex in space and concluded that the assistance of a third person would indeed be the best technique.

In practice, though, even staying together long enough to exchange a kiss is difficult in zero gravity.

Daily Mail