Tobe Hooper's director's cut was 128 minutes when the film was cut down to 116 minutes, the cuts being mostly scenes set on the spaceship Churchill. The original unedited European version contains more violent and erotic footage which Tri-Star Pictures cut from the domestic US version. It also contains the full Henry Mancini score in place of the occasional Michael Kamen music cues placed at the last minute for U.S. prints. This version is now available on video and runs 116 minutes.
Frank Finlay was not allowed to use a German accent for his role because Mathilda May who had never acted in English was using his voice as a guide in how to act in English. Likewise Michael Gothard was not allowed to do a German accent for the same reason.
Director Tobe Hooper once said of working for Golan-Globus: "Cannon was really a good company to work for...both Yoram [Globus] and Menahem [Golan] loved the movies and the filmmakers and really treated them well. It seemed more, when I was there, like maybe what the old system was like. I miss that kind of showmanship and risktaking.".
After its release, Colin Wilson recalled that author John Fowles regarded the film adaptation of Fowles' own novel The Magus (1968) as the worst film adaptation of a novel ever. Wilson told Fowles there was now a worse one, the film adaptation of "Lifeforce".
This was promoted and filmed under the title "The Space Vampires" (the title of Colin Wilson's novel). However, Menahem Golan and Yoram Globus' Cannon Films reportedly spend nearly $25 million in hopes of creating a full blown blockbuster. They felt that this title made it sound like a typical Cannon low budget exploitation film. The title was changed to "Lifeforce" and it was released in the United States in an edited version which brought in less than half of its production cost.
The role of Kelly, played by Chris Sullivan, was actually 6 roles joined together by Tobe Hooper after he met Sullivan who was initially offered the role of a crew member before they decided that the role should be played by a female.
Mathilda May had to learn her lines phonetically for her audition as the Space Girl because she didn't know any English at the time. Moreover, May learned how to speak English during the six months she spent in England on this film.
The acronym NERVA stands for Nuclear Motor for Rocket Vehicle Application. It represents the device for the jet propulsion of the Churchill space-shuttle. In real life, according to Wikipedia, "NERVA is an acronym for Nuclear Engine for Rocket Vehicle Application, a joint program of the United States Atomic Energy Commission and NASA managed by the Space Nuclear Propulsion Office (SNPO) until both the program and the office ended at the end of 1972".
Nicholas Ball was booked for three weeks but the scheduled time went over because of shooting of the problematic space Vampire Ship scenes because the ship was hard to light and took ages to light. Plus, he has said in interviews that at one point because no one was being paid everybody nearly quit. Ball was on a daily rate.
Henry Mancini had agreed to do the film based on the original concept of a 15-minute essentially dialogue-free opening sequence involving the discovery and exploration of the alien spacecraft and the moving of the three aliens back to the Churchill, for which he composed a tonal "space ballet."
According to Nicholas Ball, who plays the main British Astronaut Derebridge, it was felt that there was too much material in space and that is why a majority of 'The Churchill' space shuttle scenes were deleted.
Cannon tried to get Anthony Hopkins to play Caine who turned it down; then the film company thought they had a deal with Terence Stamp but for some reason that fell through. Michael Gothard screen tested for Caine too but when Tobe Hooper met Peter Firth he offered him the role. Michael Gothard was very annoyed that he had been demoted to a secondary role and friends of his have alleged that the whole business was the catalyst for his deep depression that would cause his death a number of years later.
Tobe Hooper came up with the idea of using Halley's Comet in the screenplay, rather than the asteroid belt as originally used in the novel, as the comet was going to pass by Earth one year following the film's release.
Despite being credited on the US domestic cut, the following actors were deleted from that cut of the film: John Woodnutt, John Forbes-Robertson and Russell Sommers. The Churchill commanding officer Rawlins, played by Geoffrey Frederick, was British, but in post-production it was decided that Patrick Jordan, a US performer, would dub his voice. Also in the US version, some of Frederick's voiceover heard on the Churchill is dubbed.
The Churchill scenes at first took up the first 35 mins of the film. Some 12 mins of these were cut plus some scenes were moved to later in the film and turned into flashbacks all this was done against Tobe Hooper's wishes.
The cast members playing the astronauts exploring the alien spacecraft were suspended on wires forty feet up in the air. Moreover, some days director Tobe Hooper only got a few seconds worth of footage during the shooting of these scenes.
Michael Caine was originally offered the role of Colonel Colin Caine. The role ultimately went to Peter Firth (Source SPX website). If Caine had played the part, he would have portrayed a character with the same last name as his own.
Some British critics were amused by the surname of Sir Percival Hesetine The Home Secretary. There was a very senior cabinet Minister Michael Hesetine in The Thatcher Government at time of production and release.
Brian Carroll who plays one of the Churchill Crew was killed in road accident while the film was in post production. In editing most of his role ended up being cut plus all his lines were cut in the end his role in the film was really an extra.