Not Even Their Final Form
The classical image of the aircraft carrier remains that set by the Third, Fourth, and even Fifth Oceanic Dominances - from the flush-deck carriers common at the start of the Third, to the V-deckers that dominated its ending, the Fourth, and into the Fifth, the romance of the flattop continues to dominate the popular imagination¹.
But these were not the last generation of carrier designs.
The last and latest generation of aircraft carrier, perhaps best typified by the Daiségei ("Great Whale")-class that began it, was a radical departure from everything that went before, as were the aircraft it carried. Having pushed prior technologies as far as they could go, the Imperial Navy convened its most radical maritime architects to produce a blank-sheet design for the new era. What they produced was extraordinary.
It all started with the catapults.
The development of the previous generations of carriers involved a roughly linear progression in methods of aircraft launch while methods of recovery stood, in essence, still. Designs progressed from STOBAR carriers (in which aircraft were expected to manage their own take-off from the flight deck, and landed to be caught by hook-and-cable arrest systems), through steam-powered catapult launches (CATOBAR), through electromagnetic catapult systems, using similar technologies to the coilgun-based weapons systems being fitted to contemporary battleships.
The Daiségei-class concept originated from one simple idea: what if we put the entire aircraft inside the coilgun²? This would do for recovery what the electromagnetic catapult did for launch, while avoiding the need to make solid dock with a captive cradle on touchdown - a prospect with little appeal to anyone, not least the pilots already familiar with the rigors of carrier landing.
Such a simple concept, at first, floated to simplify the deck machinery and recapture energy from landing aircraft during their deceleration. But one with so many implications.
The Aircraft
The very next step, of course, was to bring the aircraft designers in on the plan. Their joining in on the blank-slate design ushered in a new generation of naval-specific aircraft, whose key novel feature would be familiar to aficionados of modern UAVs and AKVs: replacing the aircraft's keel longeron with an electromagnetic frame running down the centerline at the bottom of the fuselage, made up of independent hybrid-excitation segments - to prevent quench propagation or other cascade failures - each composed of a solid permanent magnet core wrapped in actively-driven superconducting coils.
These coils, each following the well-established coilgun model in which each has an associated accumulator under photonic control, provide the means for the aircraft to couple to the launch/recovery accelerator not merely passively, but synchronously (at the cost of requiring telemetry interlock with the carrier), which in addition to allowing true regenerative operation rather than mere eddy-current braking, permits the accelerator to actively steer and center an incoming aircraft in a manner similar to, on a larger scale, that of maglev rail - allowing a much more flexible landing window, and operation in heavier seas than the original flattop design.
And the active magnetic system would be easy to integrate with the existing aircraft power subsystem, which already made use of radiothermal generation, supplemented by engine-power taps and buffered through multiple superconducting-loop accumulators, to support the aircraft's avionics and hotel load.
This was not without both cost and profit to the overall aircraft design, of course.
The most obvious cost was that it foreclosed on the option to make use of the - then-common in civilian designs - magnetoaerodynamic vortex-jet engines for such aircraft; the difficulties of reliably integrating two complex electromagnetic systems at two critical flight phases were deemed, if not beyond the technology of the time, at least not suitable for attempting at this point. Fortunately, the existing engine combination in use on military aircraft - a combined-cycle nuclear-electric propfan and variable-throat nuclear-thermal ramjet/scramjet remained superior in role, and was designed to be powered primarily by its own internal core, requiring no large additional fuselage powerplant.
A secondary limitation was the need for a continuous keel, which initially was thought to pose potential problems both for the main gear well, and for fuselage weapons bays. For the gear, especially given the reduced load mentioned below and the broad beam of most carriers, this was solved simply by displacing the main gear to the wing roots, conveniently also adjacent to the heaviest loading on, and thus most heavily reinforced part of, the airframe.
Weapons bays appeared more problematic, until on review it was noted that very few weapons of the time required the clean bottom drop called for by deadfall ordnance, and it was decided that the rare exceptions could be offloaded to external hardpoints or specialized vehicles. Actively-guided ordnance could - and in many cases already had, to serve the needs of stealth aircraft - be transitioned to side-bay ejection.
Against this could be set the ability to reduce fatigue in, and thus lighten, the overall airframe, since the load applied to them by the magnetic accelerator was distributed both across much of the fuselage and across a greater span of time. Similarly, the landing gear itself would bear less load, from milder decelerations and gentler touchdowns.
The Ship
But the greatest changes were to the carrier itself. As I have implied above, this generation of carriers were not accounted among the flattops, and for one simple reason: the "runway" of these carriers is not a flat strip, but a tunnel.
Field geometry dictates that you should have coil segments surrounding the aircraft's keel from above, below, and on both sides to avoid asymmetric-force problems and to let the field envelope center the aircraft for smooth acceleration. And the coil structures themselves are heavy; stability concerns dictates that they be low.
Daiségei and her sisters have a flight deck; it is the internal deck within which the tunnel rests, extending through the ship from bow portal to stern portal in a shallow "V", with the elevator system (and, on either side of them, the emergency arrest equipment) in the center. The shallow angles of the tunnel allow landing aircraft to descend on a comfortable glide slope directly into the capture envelope, and boost launching aircraft directly into their climb-out. (And since the tunnel extends all the way through the ship, should deceleration fail and they have a bolter on their hands, the accelerator can switch modes and accelerate them back to flight speed for their go-around.)
The Daiségei-class, designed as fleet carriers, had a pair of launch/recovery tunnels, balanced to each side of the ship's centerline. (Escort carries classes which followed usually made do with one.) In the course of normal operations, this let them launch through the bow portals, into the wind, and recover at the stern, using one tunnel for each for minimal risk; in less normal times, both could operate simultaneously.
The hangar, meanwhile, is buried deep within the hull, and treated to the full flexibility of modern automation: every aircraft stored within an individual cell in a three-dimensional rack, capable of being moved from there to either tunnel, or to maintenance or arming bays, or to a launch queue beneath the tunnel in the course of spotting a strike, as simply as punching in a tail number.
What is the most important thing the carrier gains from these changes?
Resilience.
On a classically designed flattop, the flight deck is both the single most operationally critical and is most vulnerable aspect; deck-penetrating hits, from gun, missile, or drone, can shut down flight ops for hours or longer even if the ship itself survives easily. In this generation of carrier, all the vulnerable equipment needed to arm, spot, and launch aircraft is buried deep within the hull, behind stout belt armor with only the relatively small bow and stern portals exposed. And even they are protected in the type design, with decklets below their emergence housing blast, FOD, and sea-tight doors to close this vulnerable access when not in active use, with accompanying CIWS to guard against enemy attempts to sneak a weapon by.
As for the rest of topside? Very little flat profile at all; Daiségei, true to its name, has an armored "whaleback", whose armor and profile combine to shrug off attempts at potentially-penetrating plunging hits. Since without a flattop's flight deck there is no need for an island, there's only a small superstructure forward to minimize visual and radar profile, followed by a pair of sensor masts, the auxiliary aircraft hangar - which houses the tilt-rotors and tilt-turbines used for resupply, scouting, and ASW and their small VTOL apron, all accompanied by a scatter of point-defense weapons and vertical-cell missile launchers for local defense.
Low-slung, whaleback-armored, weather-hardy, with minimal superstructure and no visible runway at all? They hardly seem like the classic image of a carrier at all, do they?
Yet it was with Daiségei and her sisters that the aircraft carrier design reached its apotheosis.
- The Last Carriers, Commodore Atélen Dallewyl-ith-Dallewyl
- Perhaps the brevity of the Eclipse War, which did not lend itself to fleet actions, was responsible for the greater prominence of the "fighting carriers" in mind and memory - ed.
- Future readers will recognize this as an early form of the system later used by spacefaring AKV carriers.