"Silent Running" - one of my favourite Sci-Fi movies - released in 1972.
Starring Bruce "Freeman Lowell" Dern and the drones Huey, Dewey, and Louie.
They made a documentary about it's filming...here's Part 1. The rest of the segments can be fund on You Tube if you are interested.
I find these documentary's fascinating myself.
Here's the link:
The Making of Silent Running - Part 1 - YouTube