Was the Peregrine going to miss the moon entirely?

[Ninurta]

Ah, I see now.
I wouldn't of that a leak coukd have pushed it off course like that.
Thanks, that was very thorough.

Here I'm thinking, they miscalculated. 

Yup, it's the same principle as blowing up a balloon and then turning it loose. That's only air inside the balloon, but look what it can do when gravity is overcome by the force of a rapid release. Now imagine that gravity is a much weaker factor than it is here on Earth...

In all honesty, any rocket engine is just, at it's most basic, a "leak". It's a controlled leak to be sure, but a leak all the same. It's only necessary to burn it because the burning increases the release of propellant gasses, which increases their release pressure all other factors being the same.

In this case, a tank rupture is the same as putting an unwanted rocket nozzle in the wrong place, creating thrust in the wrong direction, an unanticipated direction.

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