The Accidental Time Cadet — Mel Gilden

It should be a routine mission for Space Academy Cadets Raymond Hunt and Longwood Jan. Fly their System Guard scout ship to an asteroid called the Nugget, pick up Doctor Eignbergen and his newest invention from his isolated lab, and ferry him back to Earth-what could go wrong? When Doctor Eignbergen shows Hunt and Jan what he and his assistant have been working on for the past ten years, they can hardly believe it: a time machine! Along with rescued space prospector Bernadette Garley, Hunt and Jan accidentally trigger the machine and end up on Earth in 1955, where they must stop Garley from changing history and destroying the System Guard before it even begins!