Tuesday, July 30, 2013

Those New, Improved "Old" Destroyers

From U.S. Naval Institute News a tale of a "old" class of ships in their new incarnation - make that "vastly improved" new incarnation - "The Heart of the Navy’s Next Destroyer":

USS Chafeee (DDG-90) U.S. Navy photo by Mass Communication Specialist 2nd Class Sean Furey
When the first new Flight III Arleigh Burke-class destroyer enters service with the U.S. Navy in 2019, it will be equipped with a new radar roughly 30 times more powerful than the long-serving Lockheed Martin SPY-1 system found on current Aegis warships. Called the air and missile defense radar (AMDR), the new sensor is expected to exponentially increase the ship’s performance in simultaneously defending the Fleet against both air-breathing and ballistic-missile threats. The key technology that enables such high performance is a semiconductor called gallium nitride (GaN).
In addition to having 30 times the sensitivity of the current SPY-1 radar, the AMDR’s dynamic range will be greatly improved, particularly in areas with lots of interference from other emitters, jammers, and clutter. Another key attribute will be the AMDR’s digital beam-forming capability, which enables rapid horizon-to-horizon surveillance of air targets while simultaneously devoting much more energy toward ballistic missile defense . . .
Another aspect of the AMDR’s performance will be the result of the radar’s active electronically scanned array (AESA) antennas. Unlike the SPY-1, which is a passive phased-array radar with one large transmit/receive (T/R) element, the AMDR will use many thousands of small T/R modules to form its antenna. About a thousand or so T/R modules will be grouped together to form a sub-array. Several sub-arrays will then make up the radar.

The benefit of such a configuration is that it allows for scalability. But it also affords much more precise control of the radar beam—enabling such capabilities as digital beam-forming. It also eases maintenance since the loss of a few modules has a negligible impact on the overall performance of the system.
Small said that the AMDR, even with its advanced capabilities is proving to cost less than originally expected. “Not only are we going to deliver over 30 times the radar capability in sensitivity, we’re doing it for a lot less money than we thought we could even three years ago,” he said.
So, what's not to like? Well, back in March 2013, Bryan McGrath had a few negative vibes in Opinion: Navy Should Avoid a Flight III Arleigh Burke:
The choice of many in the Navy is to create a Flight III DDG-51 variant to house the radar. Essentially, Flight III DDGs would have an entirely new combat system, built around AMDR and allowing each platform to perform simultaneous self-defense and theater ballistic-missile missions, something the current Aegis fleet is challenged to do. The problem is that AMDR will require notable increases in available power, as the sensitivity goals it seeks to meet are a function of both power out and the size of the array. As currently configured, the DDG-51 could not provide either the power required or the cooling capacity necessary to dissipate the heat created by a radar of this size and power. Second, the available real estate on a DDG-51 limits the size of the array available in a manner that sub optimizes the leap-ahead capability that the radar represents. Put another way, the current DDG-51 hull does not have enough power or cooling for AMDR, and even if it did, the room available on the superstructure is insufficient to the task of achieving tactically relevant radar performance.

The Navy’s answer has been to consider altering the DDG-51 in a way that would give it the power and cooling it needs for AMDR (and the power distribution system) while accepting that the array size is sub optimized. This is the Flight III. Some have suggested that a significant lengthening of the hull would be a Flight III feature, though specifics about the concept are not publicly available.

That plan is flawed on several fronts.
AMDR is the key to the whole architecture, and shoehorning it into a technically risky, sub optimally sited platform (the DDG-51) makes far less sense than continuing to build the most successful ship type the United States has ever built (the DDG-51) as is, while concentrating on siting AMDR on a platform with growth margins to ensure it can continue to meet the threat in decades to come.

1 comment:

  1. Anonymous7:35 AM

    While I concede Capt McGrath's point regarding the space limitations on DDG 51 hulls, I diagree with his proposal for DDG 1000, there is simply too much unproven technology involved in it. Either an evolution of the cruiser/destroyer hull forms currently in service or a mod of an existing larger hull would be preferable. I find the LPD-17 variation somewhat intrequeing, kind of a return to the "Sea Control Ship" concept.