This month the USS Forrestal (CV-59), the first of the post-World War II aircraft carriers, was towed to the shipbreakers. She was nearly 60 years old, a remarkable lifespan for a steel warship. Commissioned in October 1955, she was decommissioned in September 1993 after 38 years of active service. That figure in turn is dwarfed by the 50-year active lifetime of the later, larger carrier Enterprise (CVN-65). The reason these ships last so long—and are so enduringly useful—is that they are fundamentally modular, so much so that we take that aspect for granted. Their weapon system is largely, though not entirely, the aircraft they carry, which are replaced as they age and become obsolete. Modularity is not complete; some shipboard systems (particularly command and control and maintenance) also have to be replaced to make full use of more modern aircraft. However, the evolution of carrier aircraft has been spectacular.
The Forrestal began life in an era of subsonic jet fighters using analog electronics and short-range weapons. Attack meant either a nuclear strike by a few aircraft flying independently, or a massed alpha-strike against a single target. When the ship was retired, her fighters included F-14 Tomcats armed with long-range air-to-air missiles tied into a fleet digital system that tapped space-based assets to track adversaries far beyond the horizon. Attack aircraft had precision weapons: they could strike individually, generally from beyond the target’s air-defense horizon (as they did during the first Gulf War in 1991). Between birth and retirement were at least four generations of carrier aircraft. The Forrestal herself was rebuilt under the Service Life Extension Program, but the effort required was limited in that her basic aircraft launching and recovery facilities—the ones that determined what modules (aircraft) she could handle—did not have to change.
The Key to Modernization
Modular warship design is often advocated as a way of building vessels that do not require frequent replacement due to obsolescence. Perhaps it is time to ask what lessons the aircraft carrier has to teach about that idea, and what is required to make a ship last as long as a carrier. It is not just that carriers are so large and therefore so expensive that a sane navy keeps them as long as it can. In 1945 both the U.S. Navy and the Royal Navy operated fleet carriers. Both had enjoyed great success using such ships and saw carriers as the future core of their fleets (both also faced opposition by land-based air forces).
The U.S. Navy ended the war with 24 Essex-class fleet carriers and 3 new Midways. The British ended the war with 6 armored-deck fleet carriers, which had shown enviable survivability in the Pacific. Yet the U.S. Navy managed to keep most of its big carriers in service through the 1970s. Only one of the British ships, HMS Victorious, survived in service for long, and only thanks to what the British considered an outrageously expensive (and lengthy) reconstruction. Obviously the difference was due in part to greater resources on the U.S. side, but that was hardly the whole story.
American carriers were much better suited for operating new kinds of aircraft because their hangars were far more capacious (and, from a structural point of view, they were far more adaptable). With hangars integral to their hulls, the British carriers had to be ripped apart to give them the extra space required to accommodate new types of aircraft. That is why postwar plans to rebuild all six fleet carriers were quickly cut to one ship. The U.S. carriers were also rebuilt, but their design made the process far less painful. The longest-lived of the lot, the USS Midway (CV-41), was not decommissioned until 1991 (a 46-year active life span). The only naval aircraft of her era that she did not operate was the F-14 Tomcat. She never required the sort of gutting that made the reconstruction of HMS Victorious such a nightmare.
For carriers, modularity didn’t just mean that aircraft could simply be swapped in and out; it also meant the ability to change the mix at will. In that sense the great lesson of aircraft carrier operation has been that numbers and flexibility matter a great deal. During World War II, for example, U.S. carrier air wing composition changed radically between 1941-42, when attack aircraft were paramount, and 1945, when the first requirement was to cram as many fighters as possible on board to fight off kamikazes. This required absolutely no structural change in the carrier. That would seem to be a fair definition of modularity.
Similarly, in the early 1970s, CNO Admiral Elmo Zumwalt Jr. decided that U.S. carriers should be able to “swing” between different warfighting roles. That is why the earlier CVA (attack carrier) designation was scrapped in favor of CV or CVN (carrier). The idea was that at times sea control would be paramount; at others the carrier would emphasize strike capability. In both cases the types of aircraft would be the same, but the mix would change considerably.
Modularity offered the capacity to modernize because it was relatively easy to adapt a large carrier to new types of aircraft. The World War II-era carriers were retired because of hangar and flight-deck limits, not necessarily because the hulls were worn out. The Forrestal established new limits, mainly because she was designed around a new-generation long-range strike aircraft, the A-3 Skywarrior. It turned out that her big angled deck and powerful steam catapults sufficed for many other advanced aircraft, such as the F-14. Current carriers are lineal descendants, adding such features as nuclear power and digital combat systems.
The littoral combat ship (LCS) is designed to accommodate a single module. Like a carrier aircraft, the module generally consists of a vehicle the ship launches coupled to supporting infrastructure on board the ship. No previous surface combatant has been conceived in this way, and the original promise that ships were merely “seaframes” whose modules could and would be changed out as needed has not been completely met. However, the idea that an LCS can be modernized by changing its modules over time is still inherent in the concept. In effect an LCS is an aircraft carrier (of modular unmanned systems), although it differs from that successful platform in that it accommodates only one module at a time. The attempt to minimize manning runs afoul of the need for what, in aircraft carrier terms, would be deck-handling personnel for the part of the module the LCS is intended to launch.
Adapt and Survive
The comparison suggests that the modules themselves are much more important than the LCS designed to accommodate them. U.S. carriers lasted decades because they could operate numerous modules of mixed types, and because they could change both the mix of types and the types themselves over time. The wartime British armored-deck carriers were far less adaptable and had to be discarded, at considerable expense in terms of wasted resources. The hope is always that the carrier will last over the lifetimes of several of the modules. That makes it affordable to build large warships.
Sheer size buys lifetime in other ways. Active ships spend their lives being beaten up by the sea. The larger the ship, the more she can withstand before maintenance becomes impossible. The U.S. Navy gained considerably by building larger vessels in every category than its contemporaries during World War II. They lasted longer and were more suited to modernization. The carriers retained full capability the longest.
Size also often buys survivability in battle. The larger the ship in comparison with the weapons deployed against her, the smaller the proportion of ship each hit can damage. Modern warheads are not very large; they do not sink even a small ship with a single shot. Current technology can help. It used to be that any hit would wipe out electronics and, often, power. Now electronics are much more rugged and can be distributed and modular, linked by multiple data buses. Primary electric power can be (but is not yet) produced in multiple places on board a ship. Even propulsors can be duplicated, if they need not be connected to propeller shafts. The podded motors on board many cruise liners show what can be done.
All of these possibilities become more practical in a larger ship. It can be argued, incidentally, that a ship capable of surviving multiple hits that can still fight can get by with a less capable air-defense system than one that cannot survive a single hit. In this sense, size may actually reduce ship cost; it simplifies construction and modernization, because all parts of the vessel are far more accessible.
In a modular ship, there is obviously a relationship between the effective range of the modules and the number of ships needed for some given task. Larger ships will be built in smaller numbers, so the question is whether the modules on board (aircraft or other things) balance the reduction in numbers. The U.S. Navy certainly learned to make such choices when it faced a dramatic reduction in the number of carriers it could operate after World War II. History suggests that it chose wisely. We have the opportunity to use that history to inform the development of the other kinds of modules we can now envision.