Algodoo

Going through my myriad of spring engines, running them at 240 Hz and actually making them usable.
This one has spinning piston chambers going around an opposite-spinning elipse disc.
The reason for the counter-spinning, with the blue disc going ~half as 'fast' as the green one, is for anti-stalling reasons.

When this one gets going, it really gets going, sitting at a comfortable 26 rad/s (blue), but if it drops below ~15 rad/s, it'll just wind down.

(Assuming using Blue disc for output [but green works too, just other direction])
Hold F for clockwise output,
Hold R for anti-clockwise output.
- Should take about 4 seconds to get up to speed; at that point, release the starting thrusters.