US is always dreaming. Railguns and laser guns will probably dominate their research space for a while (http://www.thedailybeast.com/articles/2015/12/28/how-star-wars-shaped-the-u-s-military.html). Doesn’t that worry you if you are not an American? The railgun technology is already very mature, capable of very high power projection, failing at only one test: durability. The problem is not about the railgun technology itself, but the American material science in general. Here’s the dilemma. If a railgun is not more powerful, why bother? On the other hand, if a railgun is really that powerful, how to make a gun that can fire thousands of shots without breaking down first? US is currently unable to make a durable gun that can handle that kind of power, whether the power source is electromagnetic or not. US needs Armata, a new type of armor that can stand the power of a railgun to construct the body of the gun. You see, Russia needs street-smart while US needs book-smart, but they can’t work together, just like ballet and pop. How about laser guns? You know, photons are too weak. You need mass to do real damage.
There are a few possibilities. Photons can pair with either electrons or protons to increase damage. GE came up with the idea of pairing water with laser to cut steel recently. In the battlefield, you can’t afford to carry that much water with you, unless, of course, you are a warship. A water shield will definitely work better than a laser shield in that case. Here’s the problem when you are a jet fighter. Both electrons and protons will bend too fast in a strong magnetic field, so your enemy can easily get away with a magnetic shield. In fact, a magnetic field is so flexible that you can make it any shape you want, so you might instead want to create a force shield by generating a strong magnetic field around your jet fighter while emitting protons from your fighter’s nose. Since you are already breathing lots of air, it’s not a problem to get lots of protons if power generation is not an issue. In fact, it may still be more effective to simply hit the missile coming to you with a proton gun. Again, this is not a great technology, just because a missile comes with a rocket that can generate a sufficient magnetic shield to block your protons. The best way to escape a missile is still jamming and flaring, but that’s not bullet-proof, either. In any case, when it comes to the battlefield, never underestimate your enemy. Just do your best.
Again, advanced missiles will be impossible to block or escape for decades to come, just because whatever you do against an incoming missile can also be used by that missile against you. Missile range is everything for now. For centuries, soldiers have learned that range is everything, be it an arrow or a bullet. Missile technology has not changed the way battles are fought. That’s good, because there’s no need to rewrite the art of war yet.
So, how can a missile penetrate a water shield with water? You don’t. Stealth and speed are your best friends. It takes time to activate a shield.