In the near future, US Navy ships will not use explosive cannons. They will destroy targets 160km away with the monster 33-megajoule railgun in the video. In the words of Rear Admiral Nevin P. Carr: This "really changes several games".
Right now, Navy railguns could only reach targets 20km away. The new railgun reaches any target 160km 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 travelling at 100 mph [160km/h] ". Imagine the effect on a target.
According to the program manager at the Office of Naval Research, Roger Ellis, the gun will eventually reach enemy vehicles and structures 320km away with perfect accuracy, using a GPS-based targeting system. Ellis also says that "eliminating explosives from the ship, which brings significant safety benefits and logistical benefits". They just need a constant source of energy in the ship, like diesel engines or a nuclear reactor.
In other words, war has just become greenerer and fasterer and more destructiverer than ever. [Fox News]