How British Science Fiction Changed the World, describes Robert as a "very English homage" to the character Robby the Robot from the 1956 film Forbidden Planet. Effects and music After working on the Andersons' earlier productions as a contractor, effects director Derek Meddings became a full-time employee of APF and formed his own unit with Brian Johnson as his assistant. According to Meddings, some of the more action-packed episodes featured as many as "40 to 50" effects shots. The rotating Space City control tower, whose filming model was made of wood and card, was inspired by contemporary revolving restaurants. Fireball XL5 was the first TV series to employ front projection-based visual effects. The XL5 spaceship was designed by associate producer and former APF art director Reg Hill. Three models were made: a version, which was used for close-up shots, and two smaller ones measuring and . XL5s rocket sled launch was based on rumoured Soviet plans to fire craft into space on a track ending in a ramp. Although the 1951 film When Worlds Collide had featured a similar concept, Gerry Anderson denied that XL5s launch method was copied from this. During the filming of the launch sequence, XL5 was pulled down its rail on wires by a technician running along a platform above the set. Fast cutting was employed to conceal the shaking of the model. Some of the series' rocket sound effects were created by recording a jet plane at a nearby airfield. The Jetmobiles – personal hovercraft that the XL5 crew use to explore the surfaces of planets – were conceived as a way of limiting the number of scenes that showed the characters walking, thus helping to conceal their lack of realistic articulation. Originally the vehicles were to have been rocket-powered; however, tests with miniature explosives proved too destructive so the method of propulsion was changed. The characters of APF's later series Stingray and Thunderbirds use vehicles similar to the Jetmobiles. The opening theme music features saxophones as well as series composer Barry Gray's first use of an Ondes Martenot. The closing theme song – "Fireball", arranged by Charles Blackwell and performed by Don Spencer – was a minor hit in the UK. It spent 12 weeks in the country's music charts, peaking at number 32 in March 1963. Broadcast and reception Fireball XL5 was the only Anderson series to be sold to a US network: