Wouldn’t it be lovely if life imitated art – if the zero-gravity love-in depicted in the sci-fi flick Supernova happened every day men and women ventured into the stratosphere? But it doesn’t. Sex in space has happened only once, officially, and it involved two small freshwater fish. From Japan. Spacemen and spacewomen have been entering and re-entering the Earth’s atmosphere for the past 25 years, but there’s been no reported extraterrestrial sexual activity. That, however, is all about to change. Space hotels are taking bookings, and, according to Gene Meyers, president of the Space Island Group, “the main reason people want to spend a week in space is the fabulous sex”. For around £500,000, Meyers’s group hopes to offer, by 2015, a honeymoon suite. And there’s no shortage of takers.

On the original space shuttles, there was just no room for sex. The other astronauts wouldn’t have known where to put themselves. According to Nasa, the astronauts just got on with analysing soil samples. But the public weren’t convinced. They pointed to The Final Mission, a book by the French astronomer Pierre Kohler. It dealt with “Document 12-571-3570”, a supposedly secret Nasa report about sex experiments in space. Of 10 different male-female positions tested, only four were possible without harnesses. Nasa denounced it all as a hoax, but people started to wonder, asking why sex hadn’t happened. After all, Spacelab modules were more roomy, with private bunks and sliding doors. Whatever Nasa said, it’s possible a spaceman and woman, at some point, had decided to forget the soil samples for a night.

When the International Space Station introduced pregnancy tests into medical packs in 2001, the public concluded that sex in space had become a reality. And if, owing to overcrowding, we end up colonising the universe, sex in space will be a necessity, and we need to understand its workings. Gravity affects everything, including the movement of sperm. Even if a sperm reaches an egg, it will have to endure radiation and incredible acceleration on re-entering Earth’s orbit. There are statistics concerning pregnant lab rats (in zero gravity, the foetal skeletons were 13% to 17% smaller), but nothing about humans. Truth is, we need more sex.

When the human body is “weightless” in space, nothing sags. You will be taller, as the spine unbends, and you’ll be lighter from all the liquid that your body loses. But you will adopt what space scientists call “a neutral body posture”, so you’ll be crouched like a monkey. And you won’t have the strength to do anything about it.

“The first thing you notice when you go into space,” says the astronaut William Pogue, who was on the support crews for Apollos 7, 11 and 14 and a Skylab pilot, “is an absence of pressure on your body. You may feel light-headed or giddy.” So, if you cry off with a headache, you’ve got a Skylab astronaut to back you up. It’s a thought: booking the £500,000 honeymoon suite, and ending up with room service in bed. I say “bed”. There will be no bed as we know it, because the slightest downward movement against a solid surface produces an upward impetus. So how can coitus be achieved when you’re flying around the room?

Nasa solved the problem for its spacecraft by fitting them with “male” and “female” parts that fit together when they’re “mated”. In Nasa-speak it’s called a “rendezvous” or a “docking”. It can be done by remote control from the ground. But humans want to do their own docking. And that means choreographing your moves in advance. Your partner will need to be anchored to the wall and/or to you, which is why designers are working on special garments, like the 2Suit. Sad, really. All that moonlight, but not much romance – not in a pair of four-legged underpants.

In space, men have to address an additional complication: their blood pressure will drop, which means a decrease in penis size. Well, if space tourists are planning a dirty weekend with lots of astronautiness, they ought to know the facts. It will be hotter and wetter than on Earth as there’s no natural convection to carry away body heat, and humans perspire more in space. The moisture associated with sexual congress (and we’re not just talking perspiration here) will gather in pools, and fly off goodness knows where. It was never like that in Supernova.