from the back of the book: Yes, its ROCKET RANGERS, the long-awaited companion volume to TWERPS SPACE CADETS ! With ROCKET RANGERS, your charakter can design, build and fly your own spaceships. New charakter classes include Pilots, Navigators, Gunners, and Engineers ! Complete spaceship combat rules, which integrate man-to-man and ship-to-ship action, are also included. So suit up ! Seal the hatch ! Fire up the engines ! Break out the champagne ! With ROCKET RANGERS, the stars are the limit ! This is an expansion set for the TWERPS Game System. TWERPS Basic Rules (GS 10455) and SPACE CADETS are also required.