Silent Running; Retrospective

Silent Running is a 1972 environmentally-themed American post-apocalyptic science fiction film starring Bruce Dern, featuring Cliff Potts, Ron Rifkin and Jesse Vint. It was directed by Douglas Trumbull, who had previously worked as a special effects supervisor on science fiction films, including 2001: A Space Odyssey and The Andromeda Strain.
Plot
In the future all plant life on Earth has become extinct. A few specimens have been preserved in enormous, greenhouse-like geodesic domes attached to a fleet of American Airlines space freighters, currently just outside the orbit of Saturn. Freeman Lowell (Bruce Dern), one of four crewmen aboard the Valley Forge, is the resident botanist and ecologist who carefully preserves a variety of plants for their eventual return to Earth and the reforestation of the planet. Lowell spends most of his time in the domes, both cultivating the crops and attending to the animal life.
Orders come from Earth to jettison and destroy the domes (with nuclear charges) and return the freighters to commercial service. After four of the six domes are jettisoned and blown up Lowell rebels and opts instead to save the plants and animals on his ship. Lowell kills one of his crew-mates who arrives to plant explosives in his favorite dome, with his right knee seriously injured in the process. He traps the remaining two crewmen in the other dome, just as it is jettisoned and destroyed.

Production
The three drones were played by four bilateral amputees,an idea inspired by Johnny Eck, a sideshow performer of the early 20th century who had been born without lower limbs.[citation needed] The 20-pound (9-kg) drone suits were custom-tailored for the different actors. The suits are in Douglas Trumbull's personal collection.
The sound effects, including the drones, were created by uncredited composer Joseph Byrd. They were generated on a modified ARP 2600 synthesizer with added Oberheim Expander Modules