The US Navy has tested its rail gun at 10 MegaJoules. Railguns will one day become the main armaments on US Navy vessels:
The technology uses high power electromagnetic energy instead of explosive chemical propellants (energetics) to propel a projectile farther and faster than any preceding gun. At full capability, the rail gun will be able to fire a projectile more than 200 nautical miles at a muzzle velocity of mach seven and impacting its target at mach five. In contrast, the current Navy gun, MK 45 five-inch gun, has a range of nearly 20 miles. The high velocity projectile will destroy its targets due to its kinetic energy rather than with conventional explosives.
A very big advantage of kinetic energy weapons is the reduction in size of a warships Achilles heel: the explosives magazine. With a railgun you would not need propellant charges.
The safety aspect of the rail gun is one of its greatest potential advantages, according to Dr. Elizabeth D’Andrea, ONR’s Electromagnetic Railgun Program Manager. Safety on board ship is increased because no explosives are required to fire the projectile and no explosive rounds are stored in the ship’s magazine.
I am not sure I believe you would get rid of all explosives as you might still want to lob an HE shell over the horizon and downwards on a target. If you are firing on a target 200 miles away, you cannot use direct fire unless you intend to blast a tunnel through a whole lot of water. That means the impact velocity on another ship using indirect fire would only be the normal terminal velocity of the falling shell. Nonetheless, the chance of a repeat of the HMS Hood disaster is much decreased.
What I would like to know is: has anyone done the calculations about direct fire at high elevation? Aircraft are naturally one of the targets. One wonders if it could reach out and touch something at a rather higher altitude.
For those unfamiliar with naval battles of WWII, the HMS Hood was sunk by one lucky salvo from the Bismarck that came straight down into the aft magazine. The ship was on the way to the bottom almost before the smoke cleared. There were (I believe) only 4 survivors.
Correction: It was 3 survivors.