In the near future, US Navy ships won't use explosive cannons. They will destroy targets 100 miles away with the monster 33-megajoules railgun shown in this video. In the words of Rear Admiral Nevin P. Carr: This "really changes several games."
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Right now, Navy railguns could only reach targets 13 miles away. The new railgun reaches any target 100 miles away in six minutes using 33-megajoules of energy, an unprecedented tactical advantage over conventional weaponry like cannons and cruise missiles. To give you an idea of the magnitude of the impact, a megajoule is "roughly equivalent to a 1-ton car traveling at 100 mph." Imagine the effect on a target.
This Navy Electric Railgun Annihilates Targets 100 Miles Away In Six Minutes [Video] (http://gizmodo.com/5711467/this-navy-gun-annihilates-targets-100-miles-in-six-minutes)