Big Bang: The science of sex in space

With long-term space travel moving ever closer to reality, would-be spacefarers may be wondering if they'll be able to join the 10,000 Mile High Club.

Michelle Starr Science editor
Michelle Starr is CNET's science editor, and she hopes to get you as enthralled with the wonders of the universe as she is. When she's not daydreaming about flying through space, she's daydreaming about bats.
Michelle Starr
7 min read

This article is part of Turned On, our special report on the future of sex. It contains language and descriptions that may not be suited for younger readers.

In the first episode of the space drama "The Expanse," two characters are getting busy when the artificial gravity malfunctions. Elegantly, the pair floats up into the air, their cosmic coitus uninterrupted by the glitch, until the gravity slams back on and they collapse onto the bed below.

Enlarge Image

TV show "The Expanse" makes space sex look a lot easier than it actually is. 


As it turns out, sex in microgravity is a bit more complicated than that and other onscreen depictions might have you believe.

With NASA, the European Space Agency and other outfits declining to address the subject of hanky-panky in space, the official position seems to be that there has never, ever been any. (If there has, nobody's talking, not even the only married astronaut couple to have been in space together, NASA's Mark Lee and Jan Davis). It's also possible, though, that nobody has had space sex -- and for good reason.

It would be fiddly, tricky and messy. But it wouldn't be completely impossible. 

Astronauts who've spent six months on the space station may or may not already know that. But what about the rest of us? Will we be able to enjoy vacation sex on those upcoming space tourism journeys? More importantly, can we propagate the species once we've started colonizing the universe? 

Two to tango

First things first: You have to be able to contain your motion sickness. NASA's Boeing KC-135 Stratotanker, used for parabolic flight for microgravity training, isn't called the Vomit Comet for nothing. But it is possible to become acclimated to microgravity, as the pilots who fly the Vomit Comet have proven. By the time astronauts are sent to the International Space Station, they've gotten used to weightlessness too.

OK, good. They're probably not going to ralph on their partner should they engage in some microgravity nookie. Tick that one off the list.

But can lovers hovering above Earth really go at it as gracefully as they do in this NSFW GIF from "The Expanse"? Not exactly. You're floating weightless in zero G. And on the ISS, a constant small breeze that keeps the station ventilated presents an additional challenge. Not only would you have to hold on to your partner to avoid being pushed apart with each thrust, you'd have to fight the breeze pushing against you.

"If you're trying to do something that involves a certain amount of pushing or force against the other person, it takes a lot of strength to hold you together," says Kira Bacal, a physician and scientist who worked as a clinical consultant for NASA and penned an in-depth article on frisky business in zero G

Even something as simple as a kiss can be a challenge, as discovered by inventor and author Vanna Bonta, who took a parabolic flight with her husband and struggled to connect for a smooch. Her solution? The 2suit, a pair of space suits that can be Velcroed together so couples can be intimate. Sadly, Bonta passed away in 2014, and the 2suit never made it past the prototype stage. 

Get a room

Aboard the ISS, two people looking to avoid pushing themselves apart could sequester themselves in one of the small sleeping quarters. The tight fit could prove beneficial, bracing the participants against walls so they don't bounce apart. It would even provide a measure of privacy, since the quarters have doors that close.

But would the ventilation be adequate for two people breathing heavily?


Vanna Bonta hovers with her husband in zero gravity aboard the G-Force One during filming of a documentary on the 2suit. 

Wikimedia/CC BY 3.0

"If you're in a small space, you don't have a lot of ventilation there," Bacal says. "So, carbon dioxide levels are building up. 'I have a headache' takes on new meaning because well, yeah, you do."

Carbon dioxide isn't the only thing that builds up. Your body's going to heat up, and your sweat won't roll away, since there's no gravity working on it. And the ISS doesn't have a shower. NASA's Skylab had one, and it was pretty inefficient --  a single shower took two and a half hours. On the ISS, astronauts take something more akin to a cat bath, using a damp washcloth. It's possible to clean up, because astronauts need to exercise on the ISS, but it's going to be arduous.

Those are just the physical complications. When it comes to space missions, sex could mess with team dynamics. Add to that the relative lack of female astronauts -- some 10 or 12 percent of the more than 500 astronauts from around the world to have been to space have been female. Presumably, some of those 500-plus astronauts have been gay, but so far the only publicly known one is Sally Ride. 

"If you're the only woman on a three-person crew, and you're boinking one guy," Bacal says, "what's that gonna do to relations amongst the three of you? Or, what if the two guys are going at it, and you're the odd woman out?"

Astronauts have "had to give up enormous, enormous things to be an astronaut and have a mission given to them," Bacal adds. "There is a real sense that anything that you're gonna do that's gonna f**k up the mission, no pun intended, is a career-ending move. So put that alongside the potential public affairs disaster, and I think anybody who does it is going to be quite cautious."

People have claimed to have had microgravity sex, but their stories don't hold up to closer inspection. A series of 1999 pornographic films called "The Uranus Experiment" famously includes microgravity sex scenes, allegedly filmed aboard the Vomit Comet.

Alas, the scenes are clever fakes. In one, actor Silvia Saint's ponytail neatly hangs down her back instead of floating around her head as it would in microgravity. In another, the footage has merely been flipped upside down after filming, according to Mary Roach, author of "Packing for Mars," a book that examines humanity's incompatibility with space.

In 1989, a document allegedly detailing NASA's experiments with microgravity sex between heterosexual couples was posted to the alt.sex Usenet group. It, too, turned out to be a fake. The STS-75 shuttle mission on which these experiments supposedly took place had an all male crew -- and didn't fly until 1996.

A little self-care

What's almost certainly happening, though? Masturbation. You may have read that it's difficult for a male astronaut to get an erection in space because of the way blood moves through the body in microgravity, but this isn't necessarily true. For starters, we already know female astronauts menstruate normally, which seems to indicate fluid flow within the body can still function just fine. 


Click for more Turned On. 

As retired NASA astronaut Mike Mullane put it in a 2014 interview with Men's Health, "A couple of times, I would wake up from sleep periods and I had a boner that I could have drilled through kryptonite."  

So gravity, or lack thereof, shouldn't be a significant barrier to arousal for men or women.

It would arguably be within the astronauts' best interests to masturbate. Studies have shown that a healthy masturbation schedule correlates with a decreased risk of cervical infections and a stronger pelvic floor for women, and a decreased risk of prostate cancer for men. 

Getting official confirmation that astronauts masturbate proved tricky. Neither NASA nor the ESA responded to requests for comment, and former ISS Commander Chris Hadfield politely declined to talk.

Roach had more success getting answers from retired Soviet cosmonaut Aleksandr Laveykin, who spent 174 days in space in 1987 as part of the Mir-EO2 expedition. In "Packing for Mars," she shares Laveykin's response when friends ask him how he had sex in space. 

"I say, 'By hand!'' As for the logistics: 'There are possibilities,'" he told Roach. "And sometimes it happens automatically while you sleep. It's natural.'"

NASA astronaut Ron Garan said in a 2015 Reddit Ask Me Anything, "I know of nothing that happens to the human body on Earth that can't happen in space."

Survival of the species

NASA is planning a manned return trip to Mars in the 2030s. Mars One, as well as SpaceX CEO and Mars-obsessed magnate Elon Musk, are both looking toward creating a permanent colony on the Red Planet. We may not be getting an off-world colony anytime soon, but it's a real enough possibility that it's worth asking: Will we be able to make new humans?

We know from a mouse study that fertilization is as possible in microgravity as it is in 1G (gravity on the Earth's surface), at least in one mammalian species in a lab setting. But bringing the fetus to term and birthing it in microgravity may not be as smooth. 

One study involving rats found that microgravity hinders the development of balance. Another found a higher death rate for rat fetuses exposed to microgravity.

Space takes a toll on the adult body, with problems including muscle and bone density loss and hormone changes. We don't know how these affect a developing fetus, but a team of Serbian researchers led by Slobodan Sekulic hypothesized that microgravity in the third trimester could inhibit a fetus's musculoskeletal development.

And that's all without taking into account one of the most fundamental health concerns associated with space habitation.

"It's a radiation environment," Bacal says. "Astronauts are considered radiation workers, and nobody is going to allow a pregnant woman to work at Three Mile Island."

It takes at least six months to get to Mars. Once there, sex is a bit more plausible than sex in microgravity, since the Red Planet has some gravity, though it's only around 38 percent of what's found on Earth.

It takes at least six months to get to Mars. Once there, sex is a bit more plausible than sex in microgravity, since the Red Planet has some gravity, though it's only around 38 percent of what's found on Earth.

Mars One