I think as the main core fails,

the plane will be notified by the sensors,

 

and they would have quite a while before the issue

expands.

 

during those times, the secondary engines can begin working...

 

 

But say, surrounding the battery, how many jet engines,

and... should all of them be functional at the same time...

 

but i guess if something goes wrong and all of them

catches fire... then, it is better to eject it

 

and start relying on the secondary.

 

whether to fold it or not is the question...

 

 

Oh. The shell above the main core can slide downwards,

as would half a cut cylinder,

 

eject the main core,

 

and close itself again - maybe.

 

Maybe because this may not work,

 

if in mid-flight, the air hits the back of the base/wall,

 

where it supported the cylinder in the first place,

 

the plane may flip.

 

But if the plane folds in half, there is no air resistance.

 

 

Ok. So fold, but the jet engines on the wings, they

must activate fast and sustaining while it re-folds into shape....

 

 

That's my guess Mr Musk. You will know better after simulations...