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TOMORROW’S AIRCRAFT CARRIERS

BY NORMAN FRIEDMAN

The aircraft carrier has endured for a century because it is so flexible. The future surely belongs to carriers designed to combine that flexibility – that ability to handle so wide a variety of aircraft – with technology that will make them simpler and less expensive to operate, and that will also help defeat whatever new threats they must face. USS Gerald R. Ford was the first of a new class of U.S. Navy aircraft carriers because it seemed that enough new technology existed or was imminent that it was worth re-thinking carrier design. At least for the U.S. Navy, carriers are vital because, despite many attempts, no other kind of ship can project power ashore on a sustained basis. Only a carrier can easily take modern precision weapons on board at sea, and only a carrier’s airplanes can deliver them on a sustained and affordable basis (because they can attack, return, and attack again at will). It also seems that only a carrier’s fighters can effectively protect ships at sea from enemy air attacks using long-range missiles. Surface ships may be able to shoot down the missiles – but unless the enemy’s bombers are destroyed, they can keep coming back until the missiles are exhausted. It takes a carrier like Ford to sustain an air offensive or air defense.

An F/A-18E/F Super Hornet of Strike Fighter Squadron 97 (VFA-97) Warhawks launches from the flight deck of the aircraft carrier USS Gerald R. Ford (CVN 78) during flight operations May 30, 2020. After decades of employing steam catapults, the U.S. Navy is employing the Electromagnetic Aircraft Launch System (EMALS) to launch aircraft from Fordclass aircraft carriers, notable for the lack of steam streaming from the catapult track.

The Ford class is built in about the same hull envelope as the Nimitz and her sisters. The decision was made early in the design process as a way of limiting the ship’s size and cost growth during that process. There was considerable pressure for growth, and it was not difficult to argue that a somewhat larger, more commodious hull would be more efficient. Moreover, the Nimitz design is now about 50 years old. Although it has evolved through at least three versions (Nimitz, Theodore Roosevelt, and Ronald Reagan), the basic internal configuration of the Nimitz class and even its power plant have not changed very much. Naval architects say that the design has exhausted its margins, both of weight growth and of electric power. The basic requirement for the Gerald R. Ford was to restore the capacity for the ship to grow in capability over its expected 50 year lifetime. At the same time, the Navy badly wanted to reduce the high cost of ownership – of operating the ship. Half of that cost is associated with the ship’s crew and the personnel of her air wing. For a nuclear ship, there is also the considerable cost in the refit undertaken when the ship is refueled. The Navy estimated that it would cost $4 billion less in 2017 dollars to operate USS Gerald R. Ford than a Nimitz-class carrier. The new carrier is expected to require 800 fewer personnel in its crew, and 400 fewer in its air wing.

An F/A-18F Super Hornet assigned to Air Test and Evaluation Squadron 23 (VX-23) piloted by Lt. Cmdr. Jamie “Coach” Struck, performs an arrested landing aboard USS Gerald R. Ford (CVN 78). The Ford-class carriers also employ an Advanced Arresting Gear that generates electric power with each trap of an aircraft.

USS Gerald R. Ford is described as more survivable than earlier carriers, which suggests that she has been rearranged internally to incorporate new types of armor and also new types of underwater protection. Hers seems to be the first U.S. carrier design to take fully into account the reality of torpedoes designed to explode under her hull rather than in contact with her side. Large-scale experiments, including the controlled sinking of the discarded carrier USS America, have presumably provided the basis for this redesign. Typically the degree of underwater protection is associated with its volume. A demand for greater protection would therefore increase pressure to make the innards of the carrier as compact as possible. On the other hand, the demand for a greater sortie rate is associated with greater quantities of air weapons, and therefore probably with more voluminous magazines.

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From an engineering point of view, one of the basic factors in future growth margin is power available for the ship’s auxiliaries. In a Nimitz-class carrier, that is a combination of electric and hydraulic power and steam to operate catapults. Over the life of a ship, additional electric generators can be added (with difficulty), but it is almost impossible to add hydraulic power or to increase the capacity of the ship’s steam catapults. In the Gerald R. Ford class, the solution has been twofold. First, all auxiliary power is now electric.

Second, electric-generating capacity is almost three times as great as that in a Nimitz.

The reactors are a fixed element in a ship’s design, so whatever growth margin (in power) is desired has to be designed in at the outset. Ford has a pair of A1B (originally designated S9G) reactors that are smaller than those of her predecessors but generate about 25 percent more power. They require about half as many personnel for operation and maintenance, which is probably a major contribution to overall ship personnel savings (moreover, nuclear-trained personnel are particularly expensive).

Making all auxiliary power electric has the important virtue that power can be switched between various functions, some of them not yet envisaged. For example, it can be concentrated to power future self-defense weapons such as lasers – which seem to be nearly at the point where they can replace conventional close-in antimissile defenses – or railguns. Electric power is also much more delicately controllable – by computer – than hydraulic or steam power. For example, electric catapults can be controlled to provide a power profile that imposes less stress on an airplane being launched. Electric power can also be associated with a more automated approach to damage control (hence greater survivability) based on sensors in the ship’s compartments. The shift to all-electric auxiliaries helps explain the requirement that Ford’s power plant generate three times as much electric power as that of the earlier Nimitz class.

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Until lasers and their ilk enter service, Ford has the standard carrier defensive battery of a pair of octuple launchers for RIM-162 ESSMs (Evolved Sea Sparrow Missiles), shorter-range Rolling Airframe Missiles (RAMs), and Phalanx close-in guns. ESSM is supported by the ship’s CEC (Cooperative Engagement Capability), a link among ships that provides targeting data on incoming missiles and other threats while they are still beyond the ship’s horizon. ESSM can be launched on that basis, considerably extending the ship’s defensive bubble.

The original design requirement to work within the Nimitz-class hull envelope made it essential to save space inside the ship. That made elimination of steam catapults, whose piping and steam chests have always taken up considerable volume, extremely desirable. Ford has electromagnetic catapults, a system called EMALS (Electromagnetic Aircraft Launch System), that are considerably more compact than steam catapults. She also has arresting gear that absorbs the energy of a landing airplane and converts it to electrical power. That also saves space, but it is not as essential to the success of the ship as EMALS.

The demand to make the best possible use of the ship’s limited internal space has been met in part by allowing for rearrangement of non-structural partitions to create or eliminate spaces as needed. That is practicable because all power for these spaces is electrical, available from outlets built into the ship.

As might be imagined, the main change in the way the carrier operates will probably come from the way in which aircraft are used. In the past, the U.S. Navy conducted mass strikes (“alpha strikes”) against single chosen targets on land. Mass was needed to confuse enemy defenses, and also because it took many bombs to ensure a few hits. The carrier flight deck was designed to support the quick and nearly simultaneous launch of many of the ship’s attack aircraft after they had been loaded en masse. There were also single-airplane attacks, and some aircraft did not fly off en masse, but the emphasis was on preparing a flight deck full of aircraft and launching them together. Turnarounds did not have to be very fast. Even with the advent of smart bombs, the need to saturate enemy defenses remained.

The Ford-class aircraft carrier USS Gerald R. Ford (CVN 78), foreground, and the Nimitz-class aircraft carrier USS Harry S. Truman (CVN 75) transit the Atlantic Ocean, June 4, 2020, marking the first time a Nimitz-class and Ford-class aircraft carrier operated together underway. While superficially similar, the Ford-class carriers incorporate improvements in everything from flight deck layout to electric catapults and arresting systems, as well as a new radar, a new nuclear reactor design, and a transition away from hydraulic and steam power to electric power.

Wars in Iraq and Afghanistan demonstrated a very different sort of carrier operation. It proved possible to destroy enemy national air defenses at the outset. GPS-guided weapons could be dropped from outside the range of the remaining enemy defenses. Unlike the smart bombs of the past, they did not require the airplane to keep a laser fixed on the target until the bomb hit. One airplane could hit multiple targets on a single flight. Guided bombs were so precise that masses of airplanes attacking together no longer seemed very important. Instead, what mattered seemed to be how many different targets a carrier’s aircraft could hit in a day. Instead of being launched in a mass and recovered together, a carrier’s aircraft would be launched one by one. It would matter enormously how quickly an airplane could be turned around upon landing, because that would largely determine how many flights that airplane could make each day – how many separate sorties the carrier could generate each day. This point was reinforced in Afghanistan, when the key value of carrier aircraft was that they could be maintained continuously over the battle area to provide troops with air support. This sort of continuous operation requires that some aircraft be serviced and rearmed while others are launched and recovered.

Carriers always had this capability, but it was limited because their flight decks were arranged for an earlier idea of combat. For example, ships had magazines located forward so that weapons (originally, nuclear weapons) could be fed to aircraft on the bow catapults, before they were launched. They could not feed airplanes being serviced or fuelled after having landed further aft.

USS Gerald R. Ford has her island farther aft, leaving more open space, including parking and rearming space, forward. Ford is the latest in a long series of attempts to place the island in the best position for air operations, keeping in mind that the ship is navigated from it, hence those inside it need good visibility. She has three rather than the previous four elevators (two forward of the island, one right aft to port). These elevators are larger than those of the earlier ships. The last previous major flight deck redesign came in the late 1950s, when the island was moved aft, exchanging position with one of the two elevators formerly abaft it. At the same time, the elevator formerly at the fore end of the angled deck was moved aft. These changes were intended to simplify flight deck operation. For example, the elevator at the forward end of the angled deck blocked the two waist catapults. It was a survival of an earlier flight deck arrangement adopted at the start of World War II, when carriers had only bow catapults. The number of elevators and their location reflect the fact that the hangar deck is split into bays (so that, among other things, no weapon or fire can sweep the whole hangar deck). Each bay has to have independent access to the flight deck. Moreover, elevators are spread out fore and aft and to each side so that the ship is harder to put out of action. The change in Ford means that no hangar deck bay will have access on both sides. Presumably that is acceptable because doors between the bays allow such access unless the carrier has been damaged. Much the same goes for catapults, which are paired forward and amidships. Catapult operation is further complicated by the fact that each catapult requires a slot cut into the flight deck – which is the ship’s strength deck, hence cannot be cut crosswise (because the waist catapults are angled, they do reduce deck strength somewhat).

The USS Gerald R. Ford’s compact island structure, incorporating the fixed arrays of the SPY-3 radar, is less than two-thirds the length of a Nimitz-class island.

Reducing the number of elevators and moving the island to the after corner of the flight deck frees space for aircraft parking, servicing, and rearming. The Ford’s flight deck is about 8,000 square feet larger than the final Nimitzclass USS George H.W. Bush (CVN 77). Rearrangement also entails changing the positions of weapons elevators relative to the parking areas. Given the redesigned flight deck, Gerald R. Ford is expected to be able to hit about a third more targets than her predecessor (the numbers are typically given as numbers of sorties per day: 160 to 220 rather than 120 on a sustained 30-day basis, or 270-310 in a four-day surge). It is also argued that future U.S. Navy unmanned aircraft may be somewhat cumbersome as they are maneuvered around the flight deck. More flight deck area will make them easier to operate.

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Moving the island eliminates possible interference with No. 4 (starboard waist) catapult, which launches aircraft at an angle to the two bow catapults. That improves the ship’s ability to launch two aircraft at the same time, a factor in increasing the sortie rate.

A related factor is a rethought weapons area using high-speed elevators. The new weapons elevators will carry more than twice the weight of those aboard the Nimitz class, and there are two more than formerly. The weapons magazine has also been dramatically enlarged (to two deck heights) so that weapons can be stowed fully assembled (“full-up”) rather than broken down. Again, this is a means of increasing sortie rate, as weapon assembly can be a major delaying factor in rearming airplanes for new strikes. Aircraft rearming has been centralized to make it more efficient and to require fewer personnel.

Aviation ordnancemen assigned to USS Gerald R. Ford’s (CVN 78) Weapons Department bring inert training bombs up to the flight deck during flight operations on May 30, 2020. The new high-speed weapons elevators aboard the Ford class carry twice the weight of those aboard the Nimitz class, and larger magazine spaces allow weapons to be stowed fully assembled.

Carrier designers once considered a wider variety of flight deck arrangements, and perhaps their ideas will return. For example, one early, abortive proposal for the America-class LHA was to place her island on the centerline, with angled decks on either side meeting at the bow. One deck (“tramway”) would have operated helicopters, the other STOVL aircraft. The ship would have been about the size of the old Forrestal. The idea was rejected because of its cost, but the concept of multiple launch (and recovery) decks remains interesting, particularly if the point of the design is rapid cycling of individual aircraft. Note that this configuration was considered and rejected when the first U.S. nuclear carrier, Enterprise, was built – but her designers envisaged a very different kind of flight deck cycle. The Enterprise designers also considered a multi-level flight deck (i.e., launching aircraft from hangar deck level), which would have been a throwback to some foreign carrier designs of the 1920s. They probably also remembered that a few U.S. carriers built during World War II had cross-deck hangar deck catapults. In those ships, the idea was to be able to launch aircraft even with a full air group parked at the forward end (the flying-off end) of the flight deck. The hangar deck catapults were used, albeit rarely; they were eliminated to provide space for more light anti-aircraft guns, hardly a consideration in the post- 1945 jet age. The idea in the 1950s was to increase the rate at which aircraft could be launched.

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The size of the island (and of accompanying masts) is set largely by the radars the carrier needs, both to detect enemy aircraft and to control its own. The more separate radars, the larger the island/mast footprint. Since the 1970s, electronically scanned radars, like the one used aboard Aegis ships, have become inexpensive and reliable. They add valuable capability, but they replace earlier radars on a one-for-one basis, and often take up more space. Proposals to install Aegistype radars on carriers failed because of cost. Now the next step in technology, the active array, is entering service on board the Gerald R. Ford class.

In contrast to the rotating radars on board past carriers, Gerald R. Ford has the fixed arrays of the SPY-3 radar built into her more compact island. She has no radar masts at all. The SPY-3 is an active electronically steered array radar (the SPY-1 of Aegis ships is a passive array). In an active array, each element is a miniature radar capable of transmitting and receiving signals. A computer instructs the elements to work together to form transmitting and receiving beams. In contrast to a passive array, an active array is much better suited to dealing with jammers, as it can rearrange its beams to null them out. An active array may also be able to create its own jamming beam(s) while it continues to conduct radar searches. The published list of electronic equipment on board Ford does not include the usual SLQ-32(V)4 carrier jammer, or any other jammer.

The earlier ships carry radars operating at several frequencies (L-, S-, and X-band). Ford was conceived to use a dual-band active-array radar (SPY-3/4) to operate in both X- and S-band, combining the SPY- 3, operating at X-band, with the S-band, volume-search radar for all-weather search capabilities.

Overall, the island of the Ford is less than two-thirds the length of the island on a Nimitz; too, there is no separate radar mast, as there is in a Nimitz. Both the island and the radar mast of the earlier ships contribute heavily to the ship’s radar cross-section, which is why the last two Nimitz-class carriers had their islands extended and their separate radar masts eliminated.

An MQ-25 Stingray test asset conducts deck-handling maneuvers, including connecting to the catapult and clearing the landing area, while underway aboard USS George H.W. Bush (CVN 77). This unmanned carrier aviation demonstration marked the first time the Navy conducted testing with the MQ-25 at sea. Improvements to the deck layout of U.S. Navy carriers will enable the handling of unmanned aircraft on deck.

Many predict that manned attack aircraft will give way to unmanned ones; the F-35 is often described as the last manned fighter. This transition would not change the basic carrier mission, which would still be to project air power from the sea. However, it might dramatically change carrier operating practices, and hence the shape of carriers. Northrop Grumman’s X-47B Pegasus demonstrated that it could operate from a carrier, and with the development of the MQ-25 Stingray unmanned tanker, it seems that unmanned aircraft will be an integral part of any future air wing. The MQ-25 will become the Navy’s first carrier-based unmanned aerial system. It is somewhat smaller than an E-2D Hawkeye, but larger than an F/A-18F, and is planned to relieve the Super Hornets of their aerial refueling task. Along with some intelligence, surveillance, and reconnissance (ISR) capability, the MQ- 25 could extend the range and reach of the carrier’s manned aircraft. The Navy hopes that the MQ-25 will be able to deliver a total of 15,000 pounds of fuel to four to six aircraft at a range of 500 nautical miles (nm). It comprises an initial step in the U.S. Navy’s Manned Unmanned Teaming (MUM-T) concept.

The carrier flight deck would operate with a different tempo, with much longer intervals between launching and, usually, servicing aircraft. If most of the unmanned strike aircraft spent most of their airborne time orbiting, servicing would be intermittent rather than, as now, nearly hourly. Drones would return either when they were about to run out of time between failures, or to reload or refuel. They would be fed one by one into the orbiting mass. Tanker flights to keep the unmanned vehicles in the sky might be more frequent than any others supported by the carrier. It is not clear how fleet air defense would fit into this picture; it might or might not become an unmanned function.

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On the other hand, handling unmanned aircraft on the flight deck would be a very different proposition, because there would be no pilot onboard to maneuver the airplane in response to the hand signals from the handlers, or for that matter to avoid obvious obstacles. Unmanned aircraft may be provided with their own flight deck sensors, or they may be remotely controlled by the handlers. There may be particular challenges in handling both manned and unmanned aircraft together, but they may be eased if the unmanned aircraft have such long effective endurance that they only occasionally affect the flight deck.

Unmanned aircraft could have profound impacts on the carrier. Pilots have to fly daily to maintain their proficiency, e.g. in difficult skills like carrier landing. Unmanned aircraft would fly only when needed. Such a pattern would dramatically reduce the carrier’s need to take on jet fuel, which currently entails an operating cycle as short as three to five days. The carrier might still fuel her escorts, but she would spend much less time in the vulnerable process of taking on fuel. Merely operating at higher average speed would give her considerable protection against non-nuclear submarines, which have low average speeds when submerged. Dramatically reducing aircraft operating hours would also reduce the carrier’s maintenance workload and would probably require far fewer spares for the aircraft. All of these changes would be attractive in a navy trying, as ours is, to reduce the number of sailors.

Moreover, if unmanned aircraft replaced many manned ones, the economics of the carrier would change, perhaps dramatically. The cost of aircraft is now comparable to the cost of the carrier herself; over her lifetime, aircraft may cost twice as much as the carrier. An unmanned strike airplane would not cost any less than a manned one, but there would no longer be a need to buy nearly as many – none would be needed for pilot proficiency training, for example. Fewer air wing personnel would be needed, too, if the unmanned aircraft flew less frequently (because pilots would not be flying them every day to maintain their skills). Critics of carriers often describe them as too expensive, but a dramatic change in their economics might make carriers far more affordable. Right now, the United States does not have as many carriers as it needs to deal with a very unstable world. Anything that made the same carrier capability much less expensive on a shipfor-ship basis would be very welcome.

Stealth is another issue. About 2000, a U.S. Navy design team sketched a truly stealthy carrier, observing that stealth would have carried a high cost (which proved excessive) in aircraft capability. However, signature control might be a more reasonable proposition. A carrier generally operates with escorting destroyers. An attacker must distinguish the high-value target from the others. If the carrier’s signature could be reduced to the point where she might be difficult to distinguish from her escorts (or their signatures turned up to match hers), she might gain considerably.

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Stealth would include changing radar (and communication) usage so that the carrier could not be identified by the special radars she has. For that matter, any ocean surveillance system that detected the carrier in the first place would probably rely on the carrier’s electronic emissions to distinguish her among the mass of large ships at sea at any one time. Previous carriers use a characteristic set of radars to control airplanes waiting to land. In the Ford, these radars, which might well identify the ship to an enemy, are replaced by a system based on GPS: A returning airplane reports its position to the carrier (via a stealthy link) and the carrier commands it to land based on the series of reported three-dimensional positions. None of this broadcasts the carrier’s identity the way the earlier specialized air traffic control radars did. As in earlier carriers, the main air search radar – in this case SPY-3 – is a fallback for air traffic control. The difference is that the active array radar of the Ford class can carry out that function more effectively while searching for air targets that might threaten the ship.

For the U.S. Navy, an important objective in the Ford-class design was interoperability – the new ships should use as many standard components as possible. The shift to greater reliance on electric power contributed to that objective, because it dramatically reduced the number of specialized power converters on the ship. For example, on board previous carriers, and most other ships, pumps driven by the main engines powered a hydraulic system that drove major auxiliaries. The details of the hydraulic system varied from ship to ship, and so did the details of many of the auxiliaries. Electric power means a much greater degree of standardization. The ship’s generators certainly are specially designed, but electric motors throughout the ship can be standardized. Electrically powered pumps need not be specially designed to work with the carrier’s specialized hydraulic system; they can be the same standard pumps that other electric ships have.

An unmanned Boeing MQ-25 Stingray test aircraft, left, refuels a manned F-35 Lightning II, Sept. 13, 2021, in formation flight with an F/A-18F Super Hornet. The MQ-25A Stingray will be the world’s first operational carrier-based unmanned aircraft, providing critical aerial refueling and intelligence, surveillance, and reconnaissance capabilities that greatly expand the global reach, operational flexibility, and lethality of the carrier air wing and carrier strike group.

The U.S. Navy plans at least 10 Ford-class carriers, to replace the 10 Nimitz-class. While there is also current interest in increasing the carrier force back to its previous strength of 12 ships, others have suggested a “hi-low” carrier mix. The question is generally whether there is some less expensive way to provide sustained striking power at sea. Since about 1970, the answer, in numerous studies, has been no: Big carriers are the most efficient and most survivable way to go.

Critics of expensive large-deck carriers like the Ford class have often suggested that the appropriate reaction to high carrier cost is to build much smaller ships operating fewer aircraft, like ones in foreign navies. Smaller carriers are inherently less survivable, and they keep the sea less effectively. That drives up the accident rate and limits the carrier’s ability to launch aircraft. The smaller the carrier, moreover, the more she costs per airplane and also per sortie. If the ultimate value of the carrier lies in its ability to project power – to attack the largest possible number of shore targets – then anything that makes that more expensive is unlikely to be attractive. Under some circumstances, too, a less numerous air wing is far less effective tactically. Below a certain size, moreover, a carrier will be incapable of operating modern catapult-launched aircraft. A review of foreign programs shows that navies that hope to operate such aircraft have been compelled to contemplate building much larger carriers. Conversely, STOVL technology can allow aircraft operations by a small ship, but it is not enough to operate a very few aircraft. For example, the British found that their light Invincible-class carriers could cram about 20 STOVL Sea Harriers on board. That was too few to be effective. The British jumped up to 65,000-ton Queen Elizabeth-class ships mainly in order to accommodate 40 larger F-35Bs, which they considered the minimum effective size for an air wing.

Some critics have suggested that somehow adopting unmanned aircraft can cut minimum acceptable carrier size. That seems unlikely. It takes an airplane of a given size to deliver strikes at useful ranges using weapons capable of destroying typical targets. If the airplane has no pilot, it may be able to handle somewhat higher accelerations and decelerations, in which case the catapult need not be so long, and the arrester gear pull-out allowance can be shorter. The flight deck as a whole can be shortened slightly, but not very much. However, the number of aircraft is set not by the number of pilots but rather by the damage the ship is intended to impose on an enemy – which is the reason for buying it in the first place. Of course, if the carrier has to accommodate both manned and unmanned aircraft (as seems likely) no such economy of flight deck length is possible.

Another issue is survivability. In a world of numerous satellites and unmanned aircraft, how difficult can it be to find a huge ship? Once found, surely it can always be destroyed. The reality is that the ocean is still vast. An enemy’s surveillance systems can still be decoyed, particularly if the carrier’s aircraft can operate from the greatest possible range (allowing her the maximum possible sea room). Too, the carrier and her consorts can beat off many kinds of attack. There is, however, a deeper reality: The point of maintaining a navy is to make it possible to use the sea freely. Free use must entail the protection of surface ships, such as merchant ships, in the face of an enemy’s attempt to deny the use of the sea. If a heavily defended survivable ship like a supercarrier cannot survive, no surface ship can, and the sea can be denied successfully. That is why the future of ships like the Ford-class supercarriers is so deeply bound up with that of the U.S. Navy.