The Fireball XL5 spaceship was designed jointly by Reg Hill and Derek Meddings. Originally the ship and the television program were both to have been called 'Century 21' but Gerry Anderson, inspired by a brand of motor oil called 'Castrol XL', changed the name to Fireball XL5. The XL5 is part of a huge fleet of XL class patrol ships operated by the World Space Patrol. These ships are launched from Space City on a long rail. This was an idea taken from the Russians who originally announced to the world during the 1950s that they planned to launch their early rockets into space this way. The Russians may have been inspired by German V1 'Buzz Bomb' scientists captured from Peenamunde by the Red Army after the war.
Leading the World Space Fleet in 2063 is FIREBALL XL5, an incredible spaceship steered through space by the steady hand of Captain Steve Zodiac. Encountering strange creatures and mysterious phenomena along the way, Zodiac and his crew have their work cut out for them as they patrol the outer reaches of Sector 25.