Just Add Water - John Dodd

Humanity has reached out to the stars, an exodus of dehydrated packets waiting to be sent down to any habitable planet with water on it, to start life anew. They are watched over by an AI, programmed to find them safe haven.

Chief Engineer Mara Loganova is reconstituted early to repair a fault the AI can't fix, only to find the ship engaged in a war against a populated world, using weapons it didn't leave Earth with.

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With the AI breaking all of its programmed rules, it becomes frighteningly clear what the ship's new purpose is, and the true battle for the future begins...