Harry Turtledove 
Earthgrip 

Jennifer Logan was young, gorgeous, and utterly dedicated to teaching middle English. But to qualify for any decent teaching position, she’d have to make her r sum stand out. Since her specialty was science fiction, she wrangled a berth on a trading ship bound for the stars. Just one trip, she figured, then back to a nice, safe classroom . . . But Jennifer hadn’t fully appreciated her own talent. She had a keen eye, a fresh perspective-and all of science fiction to fall back on when the going got tough!