Rocket "engines" aren't like engines in your car. The bell and the plumbing for it is the engine. There's not too many moving parts besides a pump. Any sort of

Rocket "engines" aren't like engines in your car. The bell and the plumbing for it is the engine. There's not too many moving parts besides a pump. Any sort of damage to the bell can cause a failure. The bells are cooled by pumping super cold fuel over them, a rock hitting those thin lines of fuel could rupture a line, or divert on causing a failure in the bell which eventually (seconds) ends in an engine rich fuel mixture.