Sometimes, everything really IS rocket science.
Even for NASA, nothing in life is a given, no matter how many successes, and no matter how high the zenith or how far the apogee.
Witness the crash of a moon lander in a recent test, an embarassing oops! after so many wins, the most recent -- and perhaps most extraordinary in some time -- the safe landing of the one-ton rover Curiosity on Mars.
No surprise: Building knowledge, and finding your way along in the dark, is slower than running down familiar routes in broad daylight. It's especially true, out on the edge, where no one has been before.
Starting a path is a lot trickier than following a rut.