SciFi: Rich Protagonist Secretly build giant Tungsten rod in space to destroy super computer... Maybe AI?

[Dustin]

I remember the story barely from a few years ago when a rich man creates a giant Tungsten rod held in space to destroy a certain location on earth if he loses control of himself or a super computer I believe. He has to do it secretly so the AI doesn't know how to stop the failsafe in the event it figures out his plan... This is about all I remember it was an audio book so I didn't pay close enough attention.