When I was a kid, we drove up I15 in southern Idaho. There was one place where we topped over this rise, and the road was straight for miles. Way down there in the distance there was an overpass across the interstate. I remember wondering how my dad could aim the car precisely enough to go under that overpass way out there. Now, as an adult, I understand. He didn't aim it that precisely. He steered along the way.
But if you don't steer along the way, and you're off half a degree, say, and you go blind 10 miles out, you miss by 10 miles times sin(1/2 degree), which is 0.09 miles, which is 460 feet. I don't know what the effective radius of an anti-ship missile is, but 460 feet seems to me to be a rather long distance.
That's assuming you just have to worry about aiming accuracy. You could also have things like wind gusts. And the ship could be not just moving, but maneuvering.
Suppose a Mach 2.5 (850 m/s) missile aiming at you. You blind it 4km out (about the same distance as Phalanx can engage) (suppose its sea-skimming so coming right onto your side). It takes 4.7 seconds to impact you. A DDG-51 is 150 meters long. If it was aiming center of mass, you need to induce a 75 m change in relative position in 4.7 seconds to cause a miss. This can be accomplished by like 6.8m/s^2 acceleration. Ok, so thats like 0.7G, super won't work.
But say its subsonic (mach 0.9... so like 300 m/s). Now your talking like 13.3 seconds to impact, and now need like 0.85 m/s^2 acceleration to induce a clean miss. Ok cool, that has some utility.
Oh, and totally, its a stop gap. But it's still useful to learn things like... how do gimballed laser systems behave on a ship? What type of maintenance is required? What unexpected interference is induced?
