The Hyposlip Travel System was a type of starship engine invented by the Brothers Hop Pyleen. (TV: The End of the World)
One type of engine, the one used in the Hyposlip 500 Lightspeed-Podule, was greatly coveted by other races in the galaxy. Astro-race pilot Skip Pyleen attempted to sell the secrets of the Hyposlip-500 technology to the Rakkonoids, but was stopped by the Tenth Doctor. (COMIC: Death Race Five Billion)