During their stints on the International Space Station (ISS) – lasting for months at a time – astronauts spend their spare time doing many of the same things people do on Earth.
This raises the question: do astronauts masturbate or have sex in zero-gravity?
NASA has not issued any strict guidelines around ‘alone time’, although commanders have stated that they do not allow sexual intercourse on the ISS.
Now, two scientists have revealed what would happen if an astronaut ejaculated in space.
Sex historian, Dr Esme Louise James, and AI expert, Dr Matt Agnew, turned to the concept of conservation of momentum to understand what would happen if a ‘man’s rocket blasted off in space’.
According to the pair’s calculations, ejaculation would propel the astronaut backwards at a speed of around two metres/hour.
This could throw a spanner in the works for astronauts hoping to get frisky on future missions to Mars.
Dr Adam Watkins, Associate Professor in reproductive and developmental physiology, at the University of Nottingham previously told MailOnline: ‘Sex in space is physically possible, but would not be as easy as it is here on Earth.’
Sex historian, Dr Esme Louise James, and AI expert, Dr Matt Agnew , turned to the concept of conservation of momentum to understand what would happen if a ‘man’s rocket blasted off in space’
Dr James and Dr Agnew posted a video on TikTok, exploring what would happen if a male astronaut ejaculated in space.
‘I’m here with Matt Agnew to finally answer the question we’re sure has also plagued your mind for many years,’ Dr James wrote in the video’s caption.
To work it out, the pair used a fundamental concept of physics known as the ‘conservation of momentum’.
Dr Agnew explained: ‘The conservation of momentum says that the total momentum of two or more bodies in a system will remain the same.
‘This means that the mass multiplied by the velocity of the ejaculate will equal the mass multiplied by the velocity of the man.’
The pair estimate that the average volume of ejaculate would be around one teaspoon, while its density would be around one gram per millilitre.
Meanwhile, the average speed of ejaculation is an impressive 45km/hr (27mph), according to the scientists.
‘We multiply the mass by velocity, and that gives us the momentum of the ejaculate,’ Dr Agnew said.
No human has ever officially had sex in space (that they’ve admitted to…), and the lack of gravity could make it difficult
To conserve momentum and obey the fundamental laws of physics, the man’s velocity multiplied by his mass must also equal this number.
‘Let’s say the average man weighs 70 kilos. This means the velocity must equal 0.000562 metres/second,’ Dr Agnew explained.
In simple terms, this means the ejaculation would cause the astronaut to travel backwards at a speed of about two metres per hour.
‘How fast is that? About the speed of an average garden snail,’ Dr Agnew joked.
‘So, if you ever find yourself in the vacuum of space, and you want to use ejaculate as propellant, you’re not gonna be moving very quickly.’
The video has delighted many users, who flocked to the comments over on TikTok.
‘These school math problems are getting insane,’ one user joked.
Another added: ‘Physics has never been put to better use than this,’ while one joked: ‘Why aren’t they teaching this in school?’
No human has ever officially had sex in space (that they’ve admitted to…), and the lack of gravity could make it difficult.
German astronaut Ulrich Walter once suggested in an interview that humans could look to the animal kingdom for inspiration.
Dolphins will sometimes enlist the help of a third to push the couple together and prevent them from drifting apart while mating.
Mr Walter suggested that open-minded astronauts might also enlist the help of a willing friend to push them together.
Alternatively, Paul Root Wolpe, a former NASA Bioethicist, has described how the humble Velcro strap could be the answer.
Mr Wolpe told DW: ‘Everything on the walls of the space station is covered in Velcro, so you could take advantage of that by velcroing one partner to the wall.
‘You have to get creative in this space.’
