Originally Posted by
Just This Once...
Aside from the imagination, anti-ship ballistic missiles are recognised as a credible threat. The sensor/targeting systems tend to be multispectral these days to provide both all-weather capability and anti-jam capabilities. Back in the 70's the US mastered the art of terminal manoeuvring and active radar homing on the Pershing II missile, but time and technology has marched on.
Regarding the movement of a CVN - well in truth they really don't move all that much when compared to the inbound speed. At say 13m/s it takes around 25 seconds for the stern of a cruising CVN to pass over the same spot vacated by the front of the flight deck. The maximum lateral displacement it can achieve in that time is also not a lot.
By contrast the kinetic penetrator of the inbound weapon can be nudging 7000m/s (over 13,000kts) making a CVN look almost stationary, with just a small amount of lead to calculate. The other concerning aspect of such speed is that even a direct hit from an intercepting missile may do little to influence the final trajectory - in the same 25 seconds that it took the ship to move its own length the inbound will complete its final 75 miles. Of course, MIRVs complicate matters further.
Keep in mind that the very characteristics you cited above make for a very difficult and complex system. A hyperspectral targetting system that can reliably function through the heat of reentry is very difficult to design and build. To put 7000m/s in perspective, the muzzle velocity of the high velocity kinetic penetrator of a 120mm tank gun is less than 1,700m/s, or less than one fourth the speed of your ballistic missile penetrator. Maximum effective range of the tank penetrator is 3000m. That's a function of loss of kinetic energy AND targeting precision with range. This means your hypothetical multispectral targetting system needs to be orders of magnitude more precise than the tank's targeting system while trying to see thru the heat of re entry and subsequent flight at 7000m/s, all while resisting defensive EW.
As for intercepting such a system, the point is to intercept the re-entry vehicle which contains the sensors, computer systems, and manuevering systems, not the (presumably inert) penetrator. The Aegis system and Block 3 SM missiles can do a midcourse intercept (exoatmospheric), but that would likely require an Aegis ship stationed along the flight path between the launcher and carrier. The Block 4 can do an intercept during re-entry.
As for the speed of the CVN, that is indeed negligible for the terminal phases of the intercept. But the missile's total flight time is measured in tens of minutes. A carrier moves at roughly 1km/minute. Thus it is 10 to 20 km from its position relative to when the missile was fired. That's a pretty large expanse of ocean to search (over 1200 sq km) in a very short time as it re-enters and will require very robust maneuvering of the re-entry vehicle to make the intercept. This is a very very different and much much more complex problem than the one the Pershing system designed and built to solve. After re-entering, the Pershing MARV did a 25G pull up and a 30nm glide to the vicinity of its target. There was not a lot of kinetic energy left after the glide and great precision was not required since it had a W85 "dial a yield" nuke warhead.
I'm
not saying taking out a carrier using a ballistic missile is not possible. They are indeed a real threat. But it is a much more difficult and complex problem than most folks realize. And assuming a nation did that successfully, the US would remain very capable of a devastating retaliation without resorting to nukes. They are essentially an effective area denial weapon. But so are mines. The mines are much much cheaper, but have the disadvantage of denying friendly as well as enemy entry into the area.