Among the most basic needs - not to mention, desires - that human beings must contend with is the very complicated task of reproduction. The complexities and pleasures of this instinctual act are as beautiful as they are important. It, like most "normal" tasks, becomes much more difficult once you fly beyond the thin band that separates Earth from the heavens. So, what's the big deal, you may ask?
Sex in Space:
First, both NASA and the Russian Federal Space Agency officially claim that the act of sexual penetration has never occurred in space, but (as always) there are rumors and innuendos that indicate otherwise. Conspiracy or not, there is little doubt that, in space, sex will be different and more difficult than on Earth. But different how? What complications and problems would arise if humans had to attempt a multi-generational space flight using current technology? Or to put it less subtly, what makes sex and the birth process problematic in space?
With nothing to keep you in place - every touch, turn and movement would equate to effort. Newton's third law of motion, in layman terms, says that for every action, there is an equal and opposite reaction. Pushing against something else results in it pushing back against you. Simply staying close to your companion would be a task in and of itself. Furthermore, the effects of zero gravity (and prolonged exposure to weightlessness) on the human body are far reaching, with wide implications (implications that we are still in the process of discovering).
Effects of Space on the Body:
Some of those implications prove problematic with important things such as the heart, red blood cells and the skeletal muscle. During intercourse heart rate and blood flow increases significantly. Blood flow in weightlessness differs from that on Earth and may impact erection in the male.
Sweat plays an important role in this because humans perspire more in micro gravity. The droplets that fall from the body on earth will form little pools of floating sweat spheres in a weightless environment. This applies to semen as well. Not a very romantic clean up process, to say the least. The gradual decline of bone and muscle needs to be counteracted with serious amounts of daily exercise, but mental health is just as important as physical health. Relationships gone awry could seriously affect everyone else on board, perhaps putting the lives of fellow comrades in danger at times. We also can't negate the possibility of personal and interpersonal tensions jeopardizing the integrity of our experiments. And when tension builds you cannot just "go home and forget about it".
Then, there is the problem of solar and cosmic radiation. Earth's magnetic field protects us from the bulk of high-energy radiation, but in space, the radiation could have a serious effect on sperm count, which lowers the chances of conception. The radiation can also damage sperm and egg cells leading to malformations in the fetus. This radiation directly impacts any possibility of a child, as it will most likely cause real havoc for any cells attempting to multiply and develop. In addition, it would be stressful for astronauts in our current age, considering that times are logged, spaces are small and privacy is rare.
Animal studies have shown that it is possible for mice to mate and give birth in space, but the offspring of these cute little critters could not have a litter of their own. Another problem the space mice faced was turning from their backs to their bellies, a task that's not required in space. How strenuous and difficult it would be returning to earth after a life of weightlessness. It seems likely that a child born in space would have to stay in space unless an exoskeleton is used as assistance.
But there are signs that seem more promising. Human beings have always been very capable of finding solutions to problems. Perhaps Velcro and duct tape? Invented by Vanna Bonta, the 2Suit allows for two people to attach themselves comfortably to each other through the magic of Velcro. Couples can attach and detach themselves when required, allowing for one of nature's great pleasures to occur. These suits are soft, comfortable and provide relative freedom and practicality.
With our closest spiral galaxy neighbor located about 2.5 million light years away, with the closest star (Alpha Centauri) and exoplanet are around 4.5 light years from Earth, reproduction is space may forever remain a requirement and a hurdle if we are to explore the vast, vaguely known universe. The reason for the word "may" is that perhaps some new technology, invention (or something) may allow us to avoid all the risks above. There is much to be considered and many problems that may arise. "More research is required." - a phrase that most certainly applies.
The first baby born in a celestial environment will be a huge achievement and perhaps everyone can agree that the names "Adam" and "Eve" may be too much of a cliché.