NavList:

Lu Abel, you wrote of disabling GPS:
"which means taking out 28+ satellites"

Not necessarily! All you have to do is upload bad data to the satellites. Here's how: you go through that hacked 'Ashley Madison' database and you find some Mr. Nobody programmer who works for the Air Force in the "ground segment" of GPS. You threaten Mr. Nobody with blackmail, using your best "Bond villain" voice in audio email attachments, promising that Mrs. Nobody, as well as his kids, mom, dad, and all of Mr. Nobody's Facebook friends will find out that he's been very naughty unless he agrees to add a little code to the daily update system for GPS. This code will include a 'time bomb' that will go off whenever the designers wish which could disable the whole system for twelve hours. The idea here is that we can hire good, honest people to work on critical infra-structure, but we can't make them permanently incorruptible. Everyone can be bought. And notice that we can pull off this diabolical crime entirely from the safety of a basement in Moldova or Myanmar or Merrimac, Massachusetts. No superpower --or even super-villain-- reserves of wealth and power are required. You can try this at home.

Frank Reed
PS: Don't try this at home.