Though we live in the universe, there's still a heck of a lot we don't know about it. Even with that limited information, there are dozens of scientific theories about space and time to explain away the greatest mysteries of our intergalactic neighborhood. Not all of them are pleasant, though.
Some of them are downright terrifying, and even more highlight just how alone we are out in this void we call space.
We know what you're thinking: they're just theories, why should I be creeped out? Well, these scientific theories about the universe have been devised by some of the greatest minds in the fields of cosmology and physics. These guys have a pretty good idea what they're talking about... and what they're talking about isn’t pretty. So sit back and prepare to stare into the void.
While Astronauts Are Up, Their Junk Stays Down
Before we get into all the dirty details about what would make sex super hard in space, let's acknowledge the fact that it probably wouldn't get hard at all. Low gravity messes with blood flow regulation, meaning it doesn't move through the body the way it does down on Earth.
Getting down requires increased blood flow to the male ~organ~, so without it (or with less of it), you're in for a more disappointing time than you're used to on Earth.
Sex in Space Is Likely Nauseating
Space Adaptation Sickness is the cosmic equivalent to car sickness and affects about half of space travelers. It basically makes you super nauseous while your body adjusts to the lack of gravity and, although astronauts eventually acclimate, twisting all over the place during sex would probably have an adverse effect on your SAS. It's probably best to stick to the basics. Save the sexy space swirls for your second mission.
Ladies Stay Dry in the Sky
It's not just men who struggle with the funky blood flow situation of zero gravity; on and off switches in women operate in the same way. Because the blood can't rush below the space belt as easily as it does on Earth, it would be really difficult for women to prepare for takeoff. That's just basic aerospace biology.
Any Fluids Would Pool on Your Body
As a result of micro gravity, any fluids - bodily or otherwise - would simply pool at the area of secretion, because natural convection isn't possible in outer space. So, when astronauts perform their daily exercises, they still need to excrete toxins and cool off via sweat, but must constantly wipe the building layers of salty liquid from their bodies. While this wouldn't necessarily have an effect on sexual stimulation, it could get pretty gross.
Ejaculation Probably Couldn't Happen
Just as blood flow is challenged in micro-gravity, other bodily fluids also struggle to perform the way they otherwise would. Although no scientific reports on this subject are published, it's safe to imagine other fluids would struggle in a similar way. In other words, ejaculation is probably difficult, but the only real effect that would have on space sex is on the possibility of conception.
Things Are a Bit Tight
The living areas on a standard shuttle are tiny (and this goes for any spacecraft, really, including the ISS). There are only two main areas and then a small bathroom, so the crew is essentially together all of the time. This makes personal time a little tricky - even if a quickie were possible, which, given the evidence, isn't likely. While the three person crew of a space station mission has a little more room to groove, there's still very little opportunity for exploration. Of any kind.
Space Travel Causes 'Low'bido
Testosterone has the steering wheel on sex drive, but a study showed that those levels drop in space. Science isn't entirely conclusive on why that is, but it's definitely a factor worth looking into if inhabiting other planets in the future is a real possibility.
Before all of you aspiring astronauts panic, however, it's important to note that those levels returned to normal once feet were back on Earth and you can do whatever the way you want once you are on Earth.
Sex in Space Is Exhausting
After a very short amount of time in zero gravity the body begins deteriorating any unnecessary muscle mass, and because such little strength is required to perform daily tasks, that's quite a bit. In an attempt to combat this, astronauts exercise for at least two hours a day. Sex with all earthly muscle mass can be exhausting. Imagine trying to keep it going with the strength of a scarecrow. Heart rates would increase, excessive sweat would starting pooling on the skin, and the participants would likely burn out quickly.
It Could Feel a Little Distant
Your astronaut lover floats across the cabin toward you. She bashfully lowers her eyes, giggling before reaching out her hand to touch you, and in that moment you remember: it takes next-to-no force to launch something across the cabin. It's too late. Her attempt at a loving caress has sent you soaring out of reach. This is one of the many grim realities of sex in zero gravity. In order to engage in any consistent physical contact, astronauts would require harnesses and straps, even if you aren't into that kind of thing.