From watching the video, it looks like the engine is running until breakup, which is very sudden. This suggests to me, based on no evidence whatsoever, that:
1. Something went wrong.
2. The onboard automation tried to compensate and kept going in the hope that it wasn't a fatal problem.
3. As soon as it realised it was a fatal problem and the vehicle was lost, it triggered range safety (aka the self destruct system).
If the vehicle had started to topple and broken up due to being pushed sideways through the atmosphere at hypersonic speeds, then I would expect to see much bigger pieces and a slower breakup. As it is it turns from a single vehicle that's obviously in trouble to a cloud of shrapnel very, very quickly. This suggests deliberate destruction (which is the right thing to do).
Although it does seem to take a long time before this happens, and you can see a piece fall off about six or seven seconds before the engines stop. This strikes me as being a lot. Maybe it's not as automated as I thought.
I hope the postmortem is made public once it's done. It'd be fascinating reading.
Edit: I hear a rumour that the bit which fell off was, in fact, the Dragon capsule being ejected. I wonder if it made it down all right? Probably not or we'd have heard about it by now...
Edit edit: According to the press briefing they had Dragon telemetry for 'some period' after the event. So chances are it worked fine until it hit the water. I bet they have boats out looking right now in the hope it survived.
The large object seen leaving the cloud before the final breakup has a distinctly Dragon-looking shape (https://youtu.be/2K030HRTutU?t=2m36s), so it appears to have survived whatever happened basically intact. (This isn't super-surprising, Dragon is a pretty compact structure with a pressure hull, compared to a long and skinny rocket.)
Gwynne stated in the press conference that, to her knowledge, the range safety system had not been activated.
1. Something went wrong.
2. The onboard automation tried to compensate and kept going in the hope that it wasn't a fatal problem.
3. As soon as it realised it was a fatal problem and the vehicle was lost, it triggered range safety (aka the self destruct system).
If the vehicle had started to topple and broken up due to being pushed sideways through the atmosphere at hypersonic speeds, then I would expect to see much bigger pieces and a slower breakup. As it is it turns from a single vehicle that's obviously in trouble to a cloud of shrapnel very, very quickly. This suggests deliberate destruction (which is the right thing to do).
Although it does seem to take a long time before this happens, and you can see a piece fall off about six or seven seconds before the engines stop. This strikes me as being a lot. Maybe it's not as automated as I thought.
I hope the postmortem is made public once it's done. It'd be fascinating reading.
Edit: I hear a rumour that the bit which fell off was, in fact, the Dragon capsule being ejected. I wonder if it made it down all right? Probably not or we'd have heard about it by now...
Edit edit: According to the press briefing they had Dragon telemetry for 'some period' after the event. So chances are it worked fine until it hit the water. I bet they have boats out looking right now in the hope it survived.