Source: http://feeds.gawker.com/~r/gizmodo/full/~3/359847840/navy-drops-75-million-on-an-emp-generator
As anyone who has seen the Matrix will tell you, an electromagnetic pulse (EMP) can wreak havoc on electronics. You may also know that an EMP is a byproduct of a nuclear blast—which is why the Navy has handed over $7.5 million to L-3 Services, Inc. to build an EMP generator. The device is not going to be used as a weapon, instead it will be used to test the resistance of military systems to specific EMP levels as a preventative measure in the event that a nuclear weapon is detonated in US airspace.
The fear is that a king-sized EMP generated from a nuclear blast detonated in the sky could send this country back to the stone age. Even if the possibility of such a scenario occurring is remote, the Navy doesn't want to take chances. If all goes well, the generator is expected to be completed sometime in 2010. [Defense Industry Daily via Danger Room]
