http://www.digitaljournal.com/article/301451

US Navy gun able to fire projectile at Mach 5, range 200km

Posted Dec 15, 2010 by Paul Wallis
The USN has developed a powerful gun which can fire a mortar-like projectile over 200km. This is a game changer for naval warfare, and gives the USN a lot of standoff capability.
Photograph taken from a high-speed video camera during a record-setting firing of an electromagnetic...
Photograph taken from a high-speed video camera during a record-setting firing of an electromagnetic railgun (EMRG) at Naval Surface Warfare Center, Dahlgren, Va.
U.S. Navy Photograph
The new “gun” is actually a rail gun. One of the few hard products of the old Star Wars program was the Australian rail gun. A rail gun is powered by electromagnetic forces, and can produce a lot of power. The original rail gun looked like a stapler the size of a 20mm cannon with a drum of aluminium strips it tore off and fired like a machine gun.
This thing is much bigger, but it works. Don’t be deceived by the obvious experimental elements in the video. It doesn’t quite do the technical achievement justice. With the range and speed come a lot of requirements for accuracy and weapon reliability. The projectile is non-explosive, which is apparently part of a tactical concept as well as being a very good idea in terms of not firing live rounds in unproven heads in confined spaces.
Tests have been underway since 2008 at the Dahlgren Surface Warfare Centre in Virginia . The issues here include some pretty difficult ballistics and flight stability for the projectile. Mach 5 is about 4 times faster than a bullet, and at that 200 km range, deflections and course are major issues.
The present tests included a 3 megajoule power source, which is described as:
“A megajoule is equivalent to the energy released when a one-tonne vehicle slams into a wall at 160 kilometres per hour.”
(So now we know. That information would be a lot more informative if we knew the mass of the projectile from available publicity, but given the power and range quoted, you can figure it out. Or get three trucks and a surprisingly well informed wall…)
Previous talk was of 64 megajoule systems, which would either be multiple guns, rapid fire or overkill, depending on configuration. Indications are that the lower range is doing the job of providing the grunt for the required performance
Tactically the significance is on a par with iron cannons compared to bronze. The rail guns are likely to be very popular, particularly given the fact that they don’t require complicated ordinance, and their range compares well with a range of missiles. The projectiles are faster than aircraft, and any level of “smart” weapon capability would make them cheap and deadly.
How this system evolves will be interesting. The new gun could dovetail well with the new improved marine power plants and vessel designs now coming onstream as well as the emerging 3D battlefield concepts and technology.
The right software could make the new gun a very effective combat weapon. At Mach 5, software is the best way to monitor the sort of combat system in which this big rail gun would be operating. Modern firepower needs a “same page” system for multiple elements in a combat group. That sort of system is perfect for the Navy, which operates multiple platforms and needs everything integrated on the same page.