The three drone robots Huey, Dewey, and Louie (named after Donald Duck's nephews) were operated by four multiple-amputee actors: Mark Persons, Steve Brown, Cheryl Sparks, and Larry Whisenhunt.
To keep costs down, Trumbull hired college students for modelmaking and other such special effects work. One of them, John Dykstra, went on to a distinguished special effects career of his own.
Douglas Trumbull says that he learned how to be a director while working on this film, as he had no training or experience in the job.
After the success of Easy Rider (1969), Universal Studios hit upon the idea to let young filmmakers make "semi-independent" films for low budgets in hopes of generating similar profits. The idea was to make five movies for low budgets (one million dollars or less), not interfere in the filmmaking process, and give the directors final cut. The movies were: this movie, The Hired Hand (1971), The Last Movie (1971), Taking Off (1971) and American Graffiti (1973)
The decommissioned Essex-class aircraft carrier "Valley Forge," a veteran of Korea and Vietnam, served as the interior of the space freighter "Valley Forge." The flight control area and hangar deck of the carrier were modified and painted to represent the space freighter in the film. The carrier was scrapped after filming was complete.