Pilot Mike Ryan was played by Paul Jones, former singer of Manfred Mann (1962-1966) who sang "Do Wah Diddy Diddy".
In interviews, Martin Landau praised this episode, stating that this (as well as others such as Earthbound (1975)) were along the lines of where the show's cast and crew wanted the series to go. With Season Two, however, the show was "jazzed up" by a bunch of American minds (ITC New York and Fred Freiberger, who was fresh off of Josie and the Pussy Cats in Outer Space (1972)) who intervened with ideas of how to make the show more commercial, such as inundating it with monsters. Freiberger, as the show's new producer and script editor, proceeded in the twisting of the characters' personalities to suit each action-oriented episode. The actors complained, but Freiberger refused to listen (causing Landau in particular to give up his enthusiasm for the series). In later years, Freiberger admitted that he should have listened to the actors.
Filming took 3 1/2 weeks (January 31st to February 21st, March 25th 1974) instead of the allotted 2 weeks; because of the over-run on this and his direction of the episode "Breakaway", Lee H. Katzin was not asked to direct any more episodes as he had been contracted to do (although one of the reasons for the overlong filming sessions for "Black Sun" was due to ITC's Abe Mandell in New York ordering script changes after he was sent a cut of the filmed episode).
In this episode, it is alluded to that Professor Bergman has a mechanical/artificial heart (hence Koenig and later Bob Mathias remonstrating with him for smoking cigars), although Guardian of Piri (1975) preceded it in the original US running order, making that episode the first to mention it.
The original script was by David Weir in 1973 but was overlong, with enough material for a two-hour episode. It was subsequently edited and reworked by Christopher Penfold, Story Consultant for most of the first season (who added in Koenig's and Bergman's communication with a female deity). According to Gerry Anderson, having "Black Sun" as the title, when the phenomenon was obviously a black hole was due to a black hole only being a theory in 1973.