When Kryten defeated Legion by forcing the gestalt being to mimic a mechanoid's regard for human life, Legion felt compelled to assist the Dwarfers by helping them escape his space station. While he and Kryten dragged the unconscious crew to Starbug, Kryten enquired if Legion had any technology that could assist their pursuit of Red Dwarf.
Legion provided them with a Star Drive, something he had developed during his previous existence as the host to some of the greatest scientists of their generation. Kryten connected the drive to Starbug's engines and told his shipmates that tests he had performed showed it to be fully functional and capable of increasing Starbug's velocity so that they would catch up with Red Dwarf within nanoseconds.
The others were less optimistic, insisting that everything they tried went wrong eventually. Kryten saw this pessimism as counterproductive, since Legion had proved that as a whole the Starbug crew could be exceptionally talented. He tried to rally their support for the drive, saying that if they believed in its ability then it would succeed.
When Kryten activated the device, roughly 1.5 metres tall, the central spherical component lit up and started to spin. This obvious functionality pleasantly surprised the crew... for a few moments. The Star Drive then took off and flew around the engine room before smashing through the bulkhead and rocketing away into Deep Space. This caused the engine room to decompress, blowing the atmosphere into space and forcing the crew to scramble for handholds to prevent themselves being ejected. Kryten was still determined to look on this as a success, since the Star Drive had worked, it just hadn't taken Starbug with it. (RD: Legion)
It was unclear if the Star Drive had never worked properly, if Legion had deliberately given them faulty technology or whether the Starbug crew had simply installed it badly - though given the typical outlook of Red Dwarf, it is possible that all three of these are the case.