FAQ for
Silent Running (1972) More at IMDbPro »

The drones were occupied by bi-lateral amputee actors (i.e., amputated legs) who walked around on their hands in lightweight, specially designed suits built of thin platsic. Director Douglas Trumbull got the idea for the drones by watching a bi-lateral amputee actor in Todd Brownings "Freaks" (1932).

There were four actors; Mark Persons, Steve Brown, Cheryl Sparks and Larry Whisenhunt - three of whom were teenagers. The drones are different heights to accommodate the actors differing physiques. Dewey is smaller than Huey, since Cheryl Sparks (the "Huey" operator) had a longer torso than Steve Brown (the "Dewey" operator), although some drones did share multiple operators.

The robot arm was generally remote controlled by the crew, using either pneumatics or a less effective radio control system. The radio control system for the arm was ineffectual during the location shooting aboard the USS Valley Forge aircraft carrier due to the heavy interference from the steel bulkheads in the ship.