Man has been in outer space for 40 years. The first American woman went up 18 years ago. So far, NASA insists, there has been no carnal docking aboard any of its missions.
Sure, there were rumors when a married couple flew aboard a space shuttle mission in 1992, but the National Aeronautics and Space Administration says two tiny fish are the only couple to experience the joys of sex in true weightlessness.
That could soon change.
Space tourism, now a reality after American businessman Dennis Tito spent $20 million for a trip aboard a Russian spacecraft to the orbiting International Space Station, has caused the question of sex in space to be viewed with a bit more gravity.
"This [Tito's trip] was kind of a wake-up call, and I think this would bring about some significant new attitudes about private trips to space," said Clinton Wallington, a professor who teaches a course in space tourism at the Rochester Institute of Technology.
Wallington said sex undoubtedly will be part of the draw: "We're talking about a commercial venture here, and sex sells. ... If you can sell a honeymoon vacation in the Poconos, why not one in space?"
Such vacations are being considered. Entrepreneurs hope to one day offer excursions to extraterrestrial sex palaces for couples hoping to join the 200-mile-high club.
Gene Meyers, founder and president of Space Island Group, said he hopes to have orbiting hotels with hundreds of guests at a time by 2008.
He envisions a fleet of space shuttles, configured like passenger airplanes, to transport guests to his hotels, which would be built from discarded aluminum space-shuttle fuel tanks.
Meyers, who said his start-up has $2 billion in investment capital, believes zero-gravity honeymoon suites would not lack for atmosphere.
"In weightlessness, if neither partner is wearing any clothing, the only physical contact is the touch of a partner, a kiss, a caress," Meyers said. "The physical experience and sensations of contact would be much more intense than anything you could get on Earth."
Of course, Meyers noted, couples might need certain aids -- bungee cords or harnesses, for example -- to keep themselves united as they float about a padded zero-G chamber.
Though NASA has generally steered shy of the space-sex issue, one of its Web pages does note that at least some human senses are dulled in a zero-G environment. Taste and smell are limited when astronauts' sinuses fill with fluid as their bodies adjust to weightlessness.
Other simple pleasures, such as sleeping even without a partner, also are complicated by the lack of gravity.
"When you try to sleep, you need to get used to the lack of touch on your back or side, because you are really floating. ... Some astronauts cannot really get used to this ... and wind up taking sleeping pills," NASA said.
Kirsten Larson, a NASA spokeswoman, said the agency will soon issue a new set of physical and psychological criteria for people who fly to the space station, including any future space tourists. For now, however, civilian passengers remain banned from space missions.
Not everyone is buying the idea that NASA flights have been chaste. "I have to assume that it [sex on NASA flights] has happened, just based on the nature of human beings," said Ray Noonan, a professor of human sexuality at the State University of New York and a leading expert on the topic of sex in space.
"NASA is trying to send the best, healthiest and brightest people into space as astronauts. We are being asked to assume that they are healthy in every respect except sexually."
What information NASA has made publicly available tends to deal with the reproductive, rather than recreational, aspects of sex.
A Web site from NASA's Space Biomedical Research Institute said that scientists foresee significant problems in space reproduction, including the physiological development of humans conceived and born in space.
"Ethical, social and political factors also affect developmental biology, especially in humans. While it might be possible to conceive, give birth to, and rear a human child on a space station, doing so without considerable prior animal experiments would be unacceptable," the Web page said.
Which brings us to the only NASA-sanctioned outer-space sexual encounter, a 1994 union of a pair of tiny Japanese Medaka fish. Not only did the Medakas have no problems with the sex act itself, eight healthy offspring were soon born in space.
Truth or fantasy?
Over the years, NASA has been called on repeatedly to deny claims of orbital sexual liaisons. In 1996, for example, French astronomer Pierre Kohler published a book called "The Final Mission" that detailed space sex experiments.
Kohler based his claims on a supposed NASA document that detailed experimental zero-G encounters -- including analysis of various sexual positions and the necessary physical aids. The document turned out to be an Internet parody.