The question What is the largest delta-v ever produced in space from mechanically stored energy? asks of course about the delta-v produced, but here I'm asking about the largest amount of stored energy.
Here's an example of a big spring pushing the first and second stages of an Antares rocket apart, from Scott Manley's video The Antares Rocket - NASA's Less Famous Ride To The Space Station:
As another example there is a Falcon 9 "pusher"; a central rod from the first stage that extends through the nozzle of the 2nd stage engine and pushes on the back of the combustion chamber. For more see
- Falcon 9 2nd stage pusher; how far does it continue to extend as it accelerates separation?
- Why is the Falcon 9 upper stage tumbling so much after separation? (SES-10)
Question: What is the largest energy stored in a spring or other mechanical device ever put in space? Ideally this should be intentionally stored mechanical energy.