But something you really really want ... even 30 minutes after launch. You do not want a bang when you were expecting silence, nor silence when you were expecting a bang.

One would hope so. "Command And Control" is worth a read; it reviews the history of nuclear weapons, focusing mostly on their safety record. (Spoiler alert: it's bad.)

http://www.amazon.com/Command-Control-Damascus-Accident-Illu...

Just like any weapon, you want it to be safe and reliable - specially nuclear missiles.