There is no single interceptor that is more important in the modern fleet defense than time. The faster a ship sensors can locate, categorize and track a convoluted blend of air and missile targets, the greater choices commanders have to allocate engagements to a formation and the fewer assumptions they need to make about their responsiveness to last-second reactions. The actual value of that operational cushion is the fact that the AN/SPY-6 family is the first to enter the mass production into the broad service usage of various U.S. Navy ship classes.
Shipboard, S-band, active electronically scanned array (AESA) 3D radar is SPY-6, which is meant to be the successor of long-standing SPY-1 family in the Aegis ecosystem, beginning with the Flight III Arleigh Burke class destroyers. In contrast to the previous arrays which were more or less conventional, “fixed size, fixed capability”, SPY-6 is designed to a modular architecture allowing the Navy to add and remove sensor power and aperture without necessarily abandoning a common bus of hardware and software.
The radar itself is based on its own building block, the Radar Modular Assembly (RMA), which is a self-enclosed box, a two-foot cube, which could be stacked in arrays of various sizes. In the Flight III destroyer design, the four fixed faces have 37 RMAs each to cover all of 360 degrees, a design described in a 2019 overview of the design logic and scaling of the system. This modularity is the same basis of other variants rotating and fixed which are designed to topple amphibious ships, carriers, and frigates, in which the topside real estate and power margins can differ considerably.
The importance of that scaling flexibility is that the performance increase in SPY-6 is directly connected to its materials and power density. The transmit/receive modules of the system incorporate gallium nitride (GaN), which has stronger power densities than the previous gallium arsenide period and enables more radar energy to be put out of a similar footprint. The design impact is not insignificant: SPY-6 is reported to consume approximately two times the electrical power of the last generation, and generate over 35 times the radar energy with a ratio that compels ship designers to increase the margins of both power production and cooling, particularly on retrofit or retrofit-upgraded hulls. That is, radar performance ceases to be an “electronics” issue any longer; it becomes a ship-integration issue.
Claims on sensor performance have been typically boiled down to one headline figure, however, the increase of SPY-6 is more appropriately viewed as a combination of sensitivity, capacity and software. SPY-6 is routinely quoted as being 30 times more sensitive than SPY-1 in its intended shipboard applications, and has the capacity to process more than 30 times the targets simultaneously. That combination is made specific to the problem set of the time: high-density raids, littered littorals, the necessity of holding a large number of high-quality tracks simultaneously without the radar “dropping” objects as priorities change.
There is also the structure of SPY-6 as a radar “family” as opposed to a single array. This baseline architecture comprises a volume search S-band radar and X-band horizon search and precision tracking radar which are synchronized with a Radar Suite Controller. The X-band function of Early Flight III aircraft has an interim solution, combining SPY-6 with an existing rotating sensor followed by a more capable X-band radar at a later point of the production run, a feature that highlights the truth that modernization of sensors is often accomplished in stages rather than just a single cutover.
One of the more impactful characteristics is when lots of ships convey congruent sensors and software. In SPY-6 there are distributed sensing ideas which permit it to form networks wherein separated platforms can collaborate one node focusing on transmit, another focusing on receive and they can form a bistatic-like geometry which can enhance detection and tracking in manner which a single ship can not duplicate. The long-term consequence is that the performance of radar is increasingly conditioned by the capacity of the fleet as a whole to share data and control emissions rather than the actual capacity of any particular hull.
This is all in an on board environment where competing emitters and vulnerable electronics are present and electromagnetic compatibility can determine the success of the sophisticated sensors and networks. Both top-mounted installations and their high power radars, and the ubiquity of digital systems, increase the significance of disciplined EMI control, shielding and systems engineering, which is reflected in technical literature on electromagnetic interference and compatibility on shipboard. In the case of SPY-6 that fact cannot be separated out of its promise: a radar that transforms fleet defense not by allowing ships to see farther, but by allowing them to act and to do things earlier, in concert, and at scale.
