In "By Any Other Name," the Enterprise is commandeered by the Kelvans, a group of aliens from the Andromeda Galaxy, who, having subdued most of the crew, set a course for their home planet. Under normal circumstances, this journey would take thousands of years, but thanks to a few modifications to the warp engines, they predict it will take less than three centuries. Of course, Kirk and company are able to retake the ship long before the Kelvans' voyage can be completed, but the advanced engine modifications remain. They are, however, never mentioned again. The Kelvan modifications would have certainly been handy on Star Trek: Voyager. That show began with the title vessel stranded 75,000 light years from Earth, with the return trip estimated to take 70 years at maximum warp. If Voyager traveled as fast as the Enterprise did in "By Any Other Name," however, the journey would have been finished in just nine years.