Then I read a little further. She wanted to know what happens when artificial gravity generators break down. Not what might happen. What does.
Why that is tragically sad and portends the decline of the genre as we know it, after the jump.
For a hardcore SF nerd, one who grew up with Heinlein and Asimov and Clarke, it was one of those questions that contain so many bad assumptions that they can't be easily answered. We don't know what happens when gravity generators break down, because they don't exist. We have no idea what principle you would use to build a gravity machine in the first place, so the effects of one breaking down are at the writer's discretion. It is, to use that elegant phrase, bolognium. The poster didn't seem to understand the difference between technology that is possible now (nuclear spaceflight); technology that might never exist, but is not conceptually impossible (Bussard ramjets, maybe); technology that outright violates modern physics (FTL travel, and don't nudzh me about those CERN neutrino experiments); and technology for which we don't even have a clue as to how to begin - like direct gravity control.
And even if we did have direct gravity control, no spaceship designer would choose to use a gravity generator that might break down and would always consume energy, instead of simply spinning the enormous ship to generate weight through centripetal force. In short, the newbie (I hope she was a newbie) had no idea why her ship was, well, dumb.
The idea of long space voyages has been explored in dozens of different ways over the last 70 years. The theoretical possibilities have been mapped out over time, and the implications covered pretty thoroughly. It isn't impossible to find something new, but it is impossible if you're not even aware of the previous work that's been done - what the patent office calls "prior art."
But more and more new F/SF writers have come to the field from movies, videogames, TV shows, and comics, media that aren't as well-suited as novels and short stories to teasing out the implications of new ideas. These writers don't know what's come before, and their initial efforts can be as jarring as a karaoke drunk singing an uninvited duet with Maria Callas.
Of course, I have an answer to the problem...