Thanks Peekay4. That explains why the ship was upside down and going backwards in the photos. It pitched end over end, ripping off the tail feathers and the delta wings. Those parts and a glowing piece, presumably the motor, are visible. The lighter pieces are trailing the fuselage, and the heavier motor is some distance ahead.
BTW, I looked up the term "fuel grain" as used in rocket motors. It refers to the entire cylinder-shaped mass of solid fuel.