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.
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.
In an interview with Starlog magazine in the late 1970s, Douglas Trumbull revealed that the plot of the movie in the original version of the script was quite a bit different from what was actually filmed. In this version, the Space Freighters were on permanent duty carrying biological domes. When they're finally told to blow the domes and return to earth, it is because the freighters are going to be scrapped. The Freeman Lowell character in this version was an older, more curmudgeonly man who simply doesn't want to return to earth and forced into retirement, so he steals the Valley Forge, "Shoots the rapids" through Saturn's Rings to make it look like his ship is destroyed, and heads off into deep space. As in the filmed version, he reprograms the robots for some companionship, and the subplot involving the plants dying due to a lack of light were involved, but his main interest in the plants was simply as a means of extending his limited food supplies on the ship. In the second half of the film, he receives a signal which he realizes is from an alien ship passing through the solar system, and decides to approach it - humanity's first contact with aliens - around the same time, his superiors on earth have realized what he did, and are trying to re-capture the ship. The last act of the movie was to have been a race against time, with Lowell trying to contact the aliens, and the recovery force trying to re-take the ship. Finally, in desperation, Lowell detaches one of the domes with one of the robots aboard only seconds before he's killed by the forces that have boarded the Valley Forge. The dome drifts off into deep space, where it's spotted by the as-yet-unseen aliens, who board it and find the robot. The robot, unsure what to do, pulls out a snapshot of itself, the other two robots, and Freeman Lowell taken earlier in the film, a "Family Portrait" after a fashion, and shows it to the aliens, who look at it and the robot confusedly, and there the film ends.
The "Saturn sequence" was originally intended to be featured in Stanley Kubrick's 2001: A Space Odyssey (1968), but the technology needed for the visual effects team to do such a sequence was not ready for use.
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)
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.
Several shots of the Valley Forge and its sister ships were later re-used in the television series "Battlestar Galactica," as agricultural ships in the refugee fleet.
The haunting music for the film was written by Peter Schickele, who is known primarily for his classical music parodies under the name of P.D.Q. Bach.
The model of the "Valley Forge" space freighter was 26 feet in length and was constructed with steel, wood, plastic, and over 650 army tank model kits. After filming was completed, the model was placed into storage. However, as the expense to store the model continued to mount, it was later disassembled and destroyed in the mid-1970s. The bulk of the model was sent to a landfill in the Sepulveda Pass next to Interstate 405 in Los Angeles, but several large pieces survived, including at least two of the domes, one of which is in the collection of the Museum of Pop Culture in Seattle, Washington, USA.
'Joel Hodgson', creator of Mystery Science Theatre 3000 (1988), credits Silent Running as a major inspiration for his show.
Released as a double feature with The Andromeda Strain (1971).
In the skinny-dipping scene, the water Bruce Dern is swimming in was actually ice cold. The production saved money by not providing a water heater.
Filmed in February and March of 1971 on a 32-day-schedule.
Although only three "space freighters" are visible ("Valley Forge", "Berkshire", and "Sequoia"), several other freighters are mentioned in radio communications. They are "Yellowstone", "Acadia", "Blue Ridge", "Glacier" and "Mojave" (each freighter is asked to report the final jettisons of their domes). Each freighter's name refers to an American National Park or Preserve.
Bruce Dern has said in interviews he was cast after 17 other actors turned down the role.
The "Odyssey" carts the crew members drive in the film were custom-built on a chassis designed by the director's father.
This movie follows the same basic outline of another environmental movie, Ark (1970). The earth's environment has been devastated. One lone scientist is trying to preserve samples of plant and wildlife under a dome. He comes under attack and the dome is destroyed.
The dome jettisoning sequences were based on Trumbull's viewing of actual footage of Apollo Saturn V rocket stage separations. The miniatures of the dome couplings were 10 inches in diameter, and were filled with mica and compressed air to get the separation effect Trumbull wanted.
Each of the four characters wears a unique "signal flag" patch on his jumpsuit. Not only do the signal flags stand for the initial letter of their respective last names, but they all have other meanings in the naval code, which are somewhat significant to the characters. For example, Lowell's flag "L" means "You should stop your vessel immediately". "B" means "I am carrying dangerous goods or explosives".
External scenes of the ships were also used in the promo for the TV show The Starlost (1973) along with the early instrumental music.
Footage of the three ships drifting through space and the jettisoning of the domes appears in the story "Different Ones" from Rod Serling's Night Gallery TV series. In an usual twist, the TV episode aired December 29th 1971, months before the movie's release date of March 10th, 1972.
Red Dwarf (1988) creators Rob Grant and Doug Naylor cited Silent Running (1972) as one of their influences behind the BBC sci-fi sitcom. In Red Dwarf: D.N.A. (1991), Lister (Craig Charles) tells Rimmer (Craig Charles) and Cat (Danny John-Jules) a story about visiting a botanical garden aboard Red Dwarf after he was dumped by his girlfriend Kochanski.
The Valley Forge was the name of the first starship that the main character of the Robert Heinlein novel Starship Troopers is assigned to shortly before its destruction.
The watering can that Lowell uses belonged to Bruce Dern's deceased daughter Diane.
Some of the actual corporate logos visible throughout the movie include (but are not limited to) Dow Chemical, Coca-Cola, AMF, American Airlines, Rockwell International, and Ditch Witch. Most of the logos can be seen on the storage modules in the main cargo deck. The Ditch Witch can be seen digging a hole.
According to the commentary on the DVD, Douglas Trumbull gave his blessing when George Lucas (who had approached Trumbull about working on Star Wars: Episode IV - A New Hope (1977)) mentioned his desire to create a robot similar to the drones for his film, which became R2-D2. When 20th Century-Fox sued Universal in 1978, claiming Battlestar Galactica (1978) was a ripoff of Star Wars: Episode IV - A New Hope (1977), Universal retaliated by contersuing Fox, claiming Star Wars: Episode IV - A New Hope (1977) was a ripoff of Silent Running (1972).
Bruce Dern plays a botanist in this film. His daughter Laura Dern plays a paleo-botanist in Jurassic Park.
One of the ships is named Berkshire, where director Douglas Trumbull lives.
According to SciFiMovieZone, scenes in the forest environments were supposed to be shot in the Mitchell Park Domes in Milwaukee, Wisconsin. The movie's production budget forced these scenes to be filmed in an aircraft hangar in Van Nuys, California.
The main character, Freeman Lowell, wears a nautical signal flag Lima patch on his uniform. This flag is used for Radhaz/HERO warnings - radiation hazard and Hazards of Electromagnetic Radiation to Ordinance. This may be a foreshadow of later events.