Given the huge spread of the debris, it must have been a decent sized boom, no? I mean that's got to be 10's of miles wide in this video.
do we know when this video was taken? this could just be ship breaking up during re-entry because it lost altitude control. not necessarily the moment of the primary failure.
the flight termination system is sort of a shaped charge that's designed to rupture the oxidizer and fuel tanks. Even if only a few % fuel remains, it'll be a big boom.
For context, The lower stage reportedly has 150 tons of propellant on board when it lands.
The whole thing (booster et al) is around 1/3 as tall as the Eiffel tower... for context
It wasn't FTS, it just blew up: https://x.com/SpaceX/status/1880033318936199643
That doesn't explicitly say that it wasn't FTS. Activation of the FTS is never scheduled and it results in rapid disassembly. There's speculation that it flew for a significant time after losing telemetry. FTS is designed to activate if it goes off course (if it's still on course, it's better to keep flying).
Yeah, I was wondering if it was FTS. I guess it doesn't really matter as FTS is just designed to intentionally cause the same kind of RUD that happened anyway. The main criteria is a RUD sufficient to ensure pieces small enough to burn up on reentry. From the looks of the explosion from the videos helpfully captured from the ground, the RUD certainly looked sufficient. Given it was 146km up at >13,000 mph, rolling down a window would trigger a sufficient RUD.
At those speeds, temps and pressures exploding into tiny pieces isn't just easy - it's the default. NOT exploding is much harder!