Gerry Anderson has said in interviews that he had to shoot all the important stuff with Patrick Wymark and Ian Hendry in the mornings because both were heavy drinkers, and would go for "liquid lunches" and not be able to do much in the afternoons.
Many of the sets, costumes and vehicles (and even some of the cast members) were reused in Gerry Anderson's TV series UFO (1970).
When considering casting for the TV series Space 1999, Gerry and Sylvia Anderson did consider real life married couple, Roy Thinnes and Lynn Loring, who appear in this film. However Sylvia in particular thought that Thinnes hadn't behaved particularly well during production, acting like a diva at times. Put off by the experience Space 1999 ended up casting another real life American couple, Martin Landau and Barbara Bain. Sylvia said many years later that decision was also problematic with both Landau and Bain demanding superstar treatment and throwing their weight around the production.
Lynn Loring, real-life wife of Roy Thinnes, replaced Tisha Sterling, who had to withdraw because of illness.
All of the computer sound effects are actually the sounds of a Strowger telephone exchange.
Robert Parrish: [Rolls Royce ] The Phoenix spacecraft is powered by a reactor manufactured by Rolls Royce. Given the company's involvement in the Valiant Class nuclear submarine program, this is an entirely feasible scenario for the near future depicted in the film.