Movement
Image source: Space Settlements: A Design Study, chapter 5 (1975), NASA.
This is like looking at an engine sideways through time, seeing the whole flow round and round. It’s from a 1975 NASA paper about building a sustainable paper, so it describes a closed-loop. Notice that there’s no intake or exhaust here, so it’s not quite like the internal combustion engine.
But you can see ‘animals’ and ‘person’ as blocks in there, so you can imagine the power output to be things like ‘human endeavour’ and ‘meat’. Those are side-effects of this self-perpetuating system. I like that humans are included in the system.
Okay, two more.