The World Space Patrol has a fleet of at least 30 separate patrol ships in this class (an XL30 is referred to one episode), however it is Fireball XL5 that we're most familiar with. When taking off from Earth, the ship uses a mile-long launch rail to build up velocity. It separates from its rocket boosters just as the rail ends with a 40-degree incline, or sky ramp, sending the ship skyward. When arriving at its destination, the main part of the ship remains in orbit, with the winged nose cone (known as Fireball Junior) landing on the planet.
Set in the year 2062, Fireball XL5 was produced in 1962 by Gerry and Sylvia Anderson. A black and white TV series, it ran for one season.
Note: initial development of this new show was under the name 'Nova X 100'. Before filming started the name was changed by Anderson, based this time on a popular brand of motor oil — Castrol XL. A change in phonetics created the name 'Fireball XL', with a '5' added for good measure as the name 'seemed a little flat without the numeral'.