On last Friday’s episode of Battlestar Galactica, the crew of the Galactica finally ran up against a problem that is the bane of aerospace engineers: metal fatigue. Fatigue can affect anything built with metal that is subjected to stress, but airplanes and spacecraft can be particularly vulnerable. As shown on BSG, metal fatigue starts with tiny cracks you can’t see. Subjected to repeated cycles of stress, these microscopic cracks grow. Left unchecked, they can cause a structural member to fail abruptly, sometimes with catastrophic results.