The post on Japanese DDHs (helicopter and aircraft carriers) got me thinking about modern naval air defenses. The U.S. Navy Aegis air defense system has been widely adopted in the Free World. I suspect that China's navy has something similar -- perhaps owing much to industrial espionage; I will not cover that in this post. Instead, I'd like to survey the world's Aegis ships.
But first, a definition: Aegis is not a radar, nor is it a computerized combat system. It is properly defined as a combination of the two: an integrated maritime air defense system. Note, too, that the Aegis system has been adapted to use from fixed NATO land-based sites at two locations in Europe; I'll not cover those here.
An excellent Wikipedia article on Aegis:
https://en.wikipedia.org/wiki/Aegis_Combat_System
See the Wikipedia for the origins and history.
The original AEGIS ships were U.S. Navy 27 missile cruisers (CGs; originally designated as destroyers and based on a previous destroyer design) that were commissioned from 1983 to 1994. These ships replaced the previous rotating radar antennas with fixed phased arrays (the SPY-1A) but also retained one rotating long-range air-search radar. The first five ships (CGs 47 to 51) were equipped with twin-arm missile launchers which proved maintenance-intensive. With the end of the Cold War, the Navy retired these five relatively early, leaving 22 Aegis CGs active. With the large numbers of Aegis DDGs commissioned and the passage of time, many of those cruisers have now been retired. 13 ships remain active.
The CGs were supplemented starting in the 1990s with a very large number of slightly smaller Aegis missile destroyers (DDGs) so that at present all active destroyers are Aegis ships. The DDGs were built in several batches designated "Flights".
Flight I: DDGs 51-71, the baseline. Compared to the cruisers, these lack the long-range rotating air search radar, have three rather than four missile guidance radars, one rather than two 5-inch gun mounts, 90 rather than 122 missile launch cells and do not have helicopter hangars. SPY-1D radar arrays.
Flight II: DDGs 72-78. Detailed improvements in systems; while they still lack hangars for helos, they are capable of refueling them.
Flight IIA: DDGs 79-124, 126 and 127. These are slightly larger and are rearranged so as to provide hangars for up to 2 MH-60R helicopters. They also have a slight increase to 96 missile launch cells.
Flight III: DDG 125 and 128-up. These are slightly larger still with a fuller hull form aft and general hull strengthening. They include next-generation SPY-6 radar arrays, along with increased electrical generation and air conditioning capabilities. These destroyers are just now starting to join the fleet.
Destroyers are the jack of all trades in the Navy and these are no exception; A CG and several DDGs escort aircraft carriers, amphibious forces invariably have a couple and DDGs often carry out independent operations as well. The are homeported mostly on the coasts of the U.S. but four DDGs are homeported in Rota, Spain, to provide ballistic missile defense and three are homeported in Yokosuka, Japan. Several are homeported in Pearl Harbor as well.
I fear I have bitten off more than I can comfortably chew, so I will cover non-U.S. Aegis ships in a separate post.
