You are really missing the point. We don’t need to intercept the missiles at their point of origin, we need to destroy them when in range of the ship. Lasers are do not need an effective range of more than a mile to be very effective for that task, in fact, the point defenses we have no do not have that type of range. Then the rail gun can destroy the launch site.
Among the limitations, according to the research service, is that lasers are not effective in bad weather because the beam can be disturbed or scattered by water vapor, as well as by smoke, sand, and dust. It is also a “line of sight” weapon, meaning that the target has to be visible, so it cannot handle threats over the horizon. And enemies can take countermeasures like coating vessels and drones with reflective surfaces. Navy officials acknowledge that the first prototype weapon to be deployed is not powerful enough to take on jet fighters or missiles on their approach.
To take down a jet or missile, a laser beam would have to be at least 100 kilowatts, the strength “generally considered militarily mature,” says Spencer Ackerman at Wired. At a megawatt of power, a laser “can burn through 20 feet of steel in a second
WATCH: The U.S. Navy shoots down a drone with a laser cannon (This Week )
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If a enemy missile is coming at you at say 1000 mph (a little over Mach 1) and you wait till its only a mile away you only have 3.6 seconds to respond to it before boom.
At that point when its a mile away you better be praying while mounting a lifeboat.
They are using it for those slow moving and unarmored drones. This is a cool sounding PR toy.