The Jupiter 8 was named after Jupiter, one of 892-IV's Roman gods. Described as "Royal Comfort" and "unexcelled in its field," it had a conventional internal combustion engine with 456 horsepower, a super-flow automatic transmission, a super-glide suspension system, and super-grip white sidewall tires.
One such Jupiter 8 was viewed by the crew of the USS Enterprise in a television news footage upon entering orbit of 892-IV. The car was parked in front of a building where the Roman Empire police were arresting several dissident slaves.
Later, once on the surface of 892-IV, James T. Kirk was reading an advertisement in The Gallian, which described the Jupiter 8's features. This led the Enterprise landing party to determine that the Jupiter 8's power source was, in part, a cause for the planet's smog. (TOS: "Bread and Circuses")
The Jupiter 8 was in reality a custom aluminum show car called "The Reactor", which was designed by Gene Winfield and completed in 1965. The Reactor was based on a 1956 Citroën DS chassis and powered by a Chevrolet Corvair engine. The hand-built car featured electronically-operated doors, hood and roof. It was painted metallic green. The car was toured around the United States at various car shows to display Winfield's custom work abilities. The car was later used in the 1968 Mission: Impossible episode, "The Freeze" (which also referenced the drug cordrazine), the Bewitched episode "Super Car", and on Batman, "in an outlandish disguise" as the Catwoman's car. (Starlog #53, December 1981, p. 29)
Its fleeting appearance as the Jupiter 8, warranted the shooting of a number of publicity shots, published in several automobile magazines, with William Shatner in the guise of Captain James T. Kirk, posing with and in the car.
Not long after building the Reactor and getting into the Hollywood scene, Gene Winfield went to work for AMT, which were contracted to construct the shuttlecraft Galileo and the Klingon battle cruiser models, and for which Winfield was responsible as head of the Speed & Custom Shop, the AMT subsidiary where the construction took place.
The Reactor still exists and was featured in the 2005 Bilsport Performance and Custom Motor Show in Jönköping, Sweden. The actual supercar is now a part of Darryl Starbird's National Rod and Custom Hall of Fame museum in Afton, Oklahoma.