"Office of Naval Research video of the 31 January test of the world's most powerful electromagnetic rail gun at the Naval Surface Warfare Center, Dalhgren. Firing at a 10.64MJ energy level, railgun achieved a muzzle velocity of 2,520 metres per second"
The idea here is to have, in one or two decades, a gun that fires projectiles from a ship as a weapon. From what I have seen on this system (and please comment with a source of more info because I don't know much about this), it will fire a large RV shaped projectile into space. The projectile will then fall back down, on the target. It is supposed to have a much higher range, and great accuracy as well. Ideally it would be a guided projectile with fins or a small rocket and GPS that could put it on target. But how to make electronics survive such acceleration is also a question.
Now my idea would be a shell with an explosive nose that would blow it up right above the target. Inside the shell would be a bunch of small flechettes or BBs. They would hit the target at about mach 5, perhaps even a tad bit more. In other words, like a howitzer beehive round, the M546 APERS-T for example:
This shell held 8,000 small darts. If detonated a few dozens of meters above the target, these darts would show a fair bit of spread, and lose a mach number or two on the way to the target. Even if these objects could only get on target at mach 5, they would destroy tanks and buildings with no problem. In a perfect world, as much of the shell as possible would be made from Uranium. There is simply no metal that works better (tungsten is decent, but has some real flaws). This means mostly the darts inside. But even steel would work just fine, as long as it gets to target fast enough. Above mach 5, even glass or pebbles would do serious damage. Along these lines, I have been thinking about other ways to use high the impact. Could the shell contain some fine powder like aluminum, magnesium, iron, or even perhaps a mix like thermite? By causing rapid burning of the metal powders, the impact might produce a modest overpressure shock wave, but more importantly, I think it would produce a powerful splash of white hot metal, and maybe even a flash of thermal heat?
There remain some real challenges with this plan... Can a 50 lbs shell (similar to the Apers-T above) make it through 400,000+ feet of atmosphere without losing too much velocity? Or would 100 lbs be too heavy for any rail gun of reasonable scale? And can any working parts be made to withstand the substantially higher acceleration forces in a rail gun? These are some of the challenges that have yet to be addressed, in addtion to the most important challenge of all: making rail guns big enough and strong enough to fire large projectiles on a regular basis, without days of maintenance between shots.
Overall, this seems like a great area to investigate. I am still on the fence, and suspect that UAVs and rockets will probably dominate the future of bombing.