Then pace the time between detonations to different prime numbers...
There may be hard limits that stop development of technology past a certain point. Like Moore's law coming to an end, but one day we may not have any viable alternatives.
Curiosity killed cat.
I wonder if that would be noticeable over interstellar distances?
https://wattsupwiththat.com/2006/12/08/yottawatts/
Tsar Bomba - 5.3 YW
Sun - 386 YW
39 nanoseconds isn't very long (~39 light-feet).
There is a problem though. Whose time ? Your time, observers time ? Are the bombs moving with the same velocity ?
Relative to the speed of light, where these effects actually become appreciable?
Yes. Hell yes. Basically identical velocities. Signal to noise ratio issues will do in this idea long before relativity has any sort of impact; it's not even close.