Cut it out already.
You have to be pulling our legs*. In all the centuries of human exploration and travel, all the long ocean voyages (Nantucket whalers would take voyages that sometimes lasted up to five years), all the treks to the distant places of the Earth, I have yet to hear of an expedition perishing of sexual deprivation.
If this really obsesses you, it may be that you have a special problem, and might not be the best choice for a long space trip.
*Or pulling on something.