Supercarriers vs. Assault Ships: Does Size Really Matter in Naval Power?

The importance lies in size—not necessarily implying bigger is better, but a larger aircraft carrier does grant more space for aviation operations. In the military context, the aircraft carrier stands out as the most massive and weighty piece of equipment.

The magnitude of an aircraft carrier significantly influences how it is perceived and respected. While officially, the US Navy has 11 aircraft carriers, there are an additional nine aircraft-carrying ships in its fleet, known under a different designation. These ships are referred to as Amphibious Assault Ships, and as the name suggests, they differ significantly from the traditional supercarriers.

Now, you might wonder why the United States employs two distinct types of aircraft carriers, assigns them to separate military branches, rarely coordinates their operations, and why doubling the size of a ship doesn’t result in a doubled internal volume. The answers to these intriguing questions might surprise you! Comparing these two carriers reveals a clear difference in size, raising the question of how much bigger one is and the implications of this contrast.

On average, American supercarriers stretch about 1,092 feet long, while amphibious assault ships are typically around 850 feet long. Although the disparity may not appear substantial when considering the flight decks alone, it holds significant meaning regarding the intended function of each vessel. Amphibious assault ships utilize their decks more as landing pads rather than runways, limiting the types of aircraft that can operate on them to those capable of vertical take-off and landing, such as the F-35B, AV-8B Harrier, V-22 Osprey, and various helicopters.

Consequently, these ships are officially designated as LHD or LHA, which stands for Landing Helicopter Dock or Landing Helicopter Assault. Their aviation wing’s primary mission is to offer short-term support to smaller landing craft and ground forces nearby since helicopters and Harriers lack the range to maintain constant airspace dominance.

In stark contrast to the usage of the US Navy’s supercarriers, which resemble floating airports more than traditional ships, Nimitz or Ford-class carriers boast an extended deck space that enables them to launch heavier fixed-wing aircraft such as the F-18 Hornet and E-2 Hawkeye in addition to the aircraft launched by amphibious assault ships. These larger aircraft play crucial roles in achieving air dominance, carrying out reconnaissance and electronic warfare in contested airspaces, and providing continuous support to ground forces, solidifying the supercarrier’s long-term mission capabilities.

However, the significance of these ships goes beyond their surface features. The length of a vessel directly impacts its most critical physical property: volume.

The substantial difference in volume between supercarriers and LHDs (Landing Helicopter Docks) significantly influences every aspect of their missions. For instance, larger ships move through the water more efficiently, a seemingly counter-intuitive observation attributed to the square-cube law. Essentially, when an object’s dimensions increase, its volume expands faster than its surface area. Consequently, doubling the size of a ship doesn’t merely double its volume but increases it eightfold. Scaling up ships magnifies their volume, affecting their displacement or buoyancy more than their surface area, which determines the resistance or friction experienced in the water.

Hence, despite the mere 340-foot difference in ship length between supercarriers and LHDs, the former’s greater overall volume grants them superior water efficiency by reducing surface friction proportionally. This efficiency translates into better fuel and energy consumption for larger vessels while exponentially increasing their capacity to carry aviation fuel and supplies. As a result, supercarriers can extend their mission duration significantly, requiring less frequent underway replenishment compared to LHDs.

Moreover, the substantial difference in volume allows supercarriers to carry around 375,000 cubic feet of mortar, whereas amphibious assault ships can only manage about 16,000 cubic feet. This means a supercarrier can sustain two weeks of continuous operations at total capacity without requiring restocking munitions. In contrast, an amphibious assault ship would deplete its fighting capability within one week with only six aircraft. However, it is essential to acknowledge that an Amphibious Ready Group, comprising three ships, can remain self-sufficient for 15 days of continuous operations.

While the size advantages of supercarriers are undeniable, it is crucial to recognize that bigger is not always better. Sometimes, smaller vessels can perform specific tasks more effectively. For instance, the LHD carriers may have a much smaller carrying capacity than supercarriers, but they excel in deploying forces above and below the deck. This is due to their sound deck, an internal housing bay capable of accommodating three hovercraft, 12 Mechanized Landing Crafts, or 40 Amphibious Assault Vehicles, depending on the mission.

The LHDs’ versatility, combined with the variety of Vertical Take-Off and Landing (VTOL) aircraft they can deploy, makes them better suited for quick reaction missions with smaller yet more intense operational timelines. In conclusion, choosing between supercarriers and LHDs depends on the specific functional requirements and objectives.

In 2016, the US carried out airstrikes in Libya to support the UN-backed Tripoli government. To avoid committing a full-sized supercarrier, the Navy utilized the amphibious assault ship, USS Wasp, for continuous strikes as part of Operation Odyssey Lighting. This proved to be a cost-effective approach, as the smaller vessel was well-suited for the scope of the operation.

It’s important to note that although the LHD class of ships, like the USS Wasp, possess landing decks, they were never intended to function as aircraft carriers. Their primary mission is transporting and supporting Marine Expeditionary Units, enabling successful landings, and securing beachheads. These Marine Expeditionary Units are versatile and agile, akin to the Swiss Army knife of the US Military. They can handle diverse tasks, ranging from humanitarian missions after natural disasters to engaging adversaries to buy time for the US Army or Air Force to mobilize and respond. For instance, during the withdrawal from Afghanistan, the first two battalions deployed to Kabul comprised Marines.

LHDs are not well-suited for long-term operations far from shore, making them more aligned with the mission of the US Marine Corps rather than the US Navy. Despite being operated by the Navy, these ships predominantly house over 2,700 Marines, with only a tiny fraction of sailors on board. As a result, the Marine Corps specializes in using these vessels, with all pilots being Marines, not sailors. This makes amphibious assault ships function more like floating Marine bases than the conventional airports associated with supercarriers.

Due to their distinct designs and roles, supercarriers and LHDs rarely patrol together. Supercarriers always travel with a complement of cruisers and destroyers to provide protection and a submarine for patrol duties. With the US Navy phasing out cruisers responsible for airspace control around carrier strike groups, destroyers will assume that role in the future.

Supercarriers heavily rely on underway replenishment to avoid the need to dock at ports for supplies. Acting as fleet command centers, they have an admiral on board who commands the surrounding ships in the strike group. Conversely, LHDs function independently and primarily focus on transporting Marine units from one location to another. When an LHD reaches its destination, it often resupplies at a nearby port rather than through replenishment at sea, although that option is available for more extended missions.

Amphibious assault ships are designed to project land forces, while supercarriers are built to project airpower. Despite this clear distinction, they are frequently compared due to the introduction of the American class Landing Helicopter Assault Ships (LHA) into the US Navy’s fleet. These LHAs brought two significant changes, starting with their larger size.

The America-class LHAs have a displacement of approximately 45,000 tons, surpassing even the French aircraft carrier Charles de Gaulle. Moreover, two of these LHAs were optimized for flight operations, sacrificing their sound deck to accommodate more aircraft, spare parts, weapons, and fuel. Their primary focus is carrying F-35B Lightning aircraft, earning them the “Lightning Carriers.”

As these new LHA ships blur the line between assault ships and traditional aircraft carriers, it raises the question of why both types coexist if advanced aircraft technology can make smaller landing decks more effective.

The answer is relatively straightforward—it’s about using the right tool for the job. Sometimes, a massive sledgehammer is needed to break something down, while other times, a simple ball-peen hammer suffices to drive in a nail. The cost of operating aircraft carriers is astronomical, with LHDs costing around two billion dollars, LHAs at 3.4 billion dollars, and supercarriers exceeding 13 billion dollars to build. Additionally, the annual operating cost of a supercarrier is close to one billion dollars. Thus, the US Navy and Marine Corps seek creative ways to enhance force projection without straining their budget.

This emphasis on having the right tool for each task is not driven by a size problem or an attempt to overcompensate with larger ships. Instead, it reflects the pragmatic approach of seeking efficient, cost-effective solutions to meet specific military objectives.

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