Seven Days - A Space Romance — Jill Myles

When science officer Zoey Maldonado heads out to fringespace for a routine astro-archaeology trip, she never imagines that it'll be her last trip. A solar flare is about to take out everything in the solar system â€" including them â€" in one week's time. She's stranded on board a tiny science vessel with no one but a very sexy soldier. A very, very sexy soldier who's interested in passing the time in very naughty ways. After all, what better distraction from impending doom than really great sex?

Kaden's had his eye on his gorgeous science officer ever since they left port. Of course, she's forbidden to a lowly soldier. But when fate deals them a bad hand, he decides that it's time to stop paying attention to regulations and start paying attention to the woman at his side, and make her enjoy every minute they have left…

This novella (~125 pages) includes two doomed (or so they think) people, lots of frisky business, and an interesting use of a Zero-G room.