When testing new military technology, there are always risks for the operators. Test pilots suffered appalling death rates in the early days of jet planes, and the MV-22 Osprey suffered a series of fatal mishaps during its development, including 19 dead Marines in a single accident in 2000.
Benjamin Franklin nailed it when he said, "Fatigue is the best pillow." True story, Benny. There's nothing like pushing your body so far past exhaustion that you'd willingly, even longingly, take a nap on a concrete slab.