I think this was the first BE story I've read that had foreshadowing. Please keep up the good work.
Some notes: I wasn't entirely clear on whether Purity was a planet of prudes. The name and the juxtaposition of giving up sex/the obscene spaceship initially made me think that you were playing these people for laughs, but I had an altogether different impression of them, or at least of Sam, by the end.
The story sort of had that warm and fuzzy feeling to it, and I am assuming that you went in this direction due to the feedback on your previous story. IMO, this was a nice change, but for an "erotic" story, maybe the "middle path" would be more appropriate?
Whatever. Please keep writing. It's so much harder to create than to criticize.