Picking a single-sex crew doesn’t preclude intimate relations among crewmembers; it only precludes pregnancies. Indeed, they could just decree “no homosexuals” (like the U.S. military does), but that would be a monumental public relations disaster, and fails to address the real problems. (Does NASA want to touch that issue with a 10-foot pole?)
The trouble is, they have to approach it from a behavioural standpoint, because undoubtedly, they are concerned that these sorts of behaviours would affect the crew’s working relationships. And from a medical standpoint (and despite Dr. Williams’ statement in the linked article), there exists the possibility that a pathogen transferred among partners manifests itself strongly in the recepient, during the mission (HSV, for example). In the case of heterosexual relationships, it’s pretty clear that pregnancy is not a viable option during the majority of the mission, and an unwelcome imposition during the last leg of the return, when it might be theoretically possible to avoid an abortion.
As long as the astronauts are housed in an artificial, enclosed space—such as the one on any spacecraft ever built—and working in a small team environment, either NASA’s doctors need to know that the partners are neither a behavioural risk nor a disease risk, or they need to abstain entirely. Hypothetically, with the consent of the crewmembers, the doctors could assemble a matrix of which liasons posed an unacceptable risk of contagion, in order to forbid that contact. Similarly, the psychiatrists would need to make estimates of the likelihood of conflict. If NASA wants to go this route, it seems like married couples have a significant advantage, in that they have a prior history medically and socially, upon which the medical team can rely.
Even so, that’s no guarantee; in fact, there are no guarantees when it comes to a situation like this, because even an official decree of abstinence can still be violated, putting the health of the crew at risk. And people can still have conflicts, even if they’re well-acquainted and not participating in an intimate relationship. Even largely rational people make occasional irrational decisions. The best recipe is to choose people who are (likely) going to put aside their personal differences and mutual attraction, and get on with the job. It’s NASA’s job to attempt to identify those people, and make sure that only they get to participate in the mission. And yet, they can never be completely sure.
I hate to be crass, but “out the airlock” is really the only way to go, because of the risk of disease among the rest of the crew. It’s ridiculous to contemplate an onboard morgue, when space is at a premium. That doesn’t necessarily mean that they need to leave the deceased to float in space, but it would be rather surreal to have a body bag hanging from the side of your spacecraft… And will the next of kin want the corpse, after it’s been freeze-dried, even if there is a convenient way to transport it to Earth after the mission? (Remember, people pay money to have small portions of their ashes placed in a decaying orbit around the Earth; some would consider it an honour to have their whole body disposed of in that fashion…)
It’s going to be fun (in a sadistic sort of way) watching NASA handle these issues in coming years; but maybe some good will come out of the ethical debates. Too often ethics are characterized by political or religous notions that fail to capture the entirety of the situation, and which rely upon the shock value of the issues to drive the discussion; hopefully NASA’s confrontation with these issues will necessitate a more reasoned, scientific approach, to bring some balance to the debate.
