Are Aircraft Carriers Obsolete?

2023 February 24 Twitter See all posts

One poorly designed class of ships does not obsolete aircraft carriers.

Are Surface Ships and Aircraft Carriers Obsolete?

In a recent post, I made the assertion that aircraft carriers were still the queens of the ocean and that long-range anti-ship missiles would become less relevant due to inexpensive countermeasures. Many disagreed, specifically citing some posts by Steve Hsu. I'm sure Steve is smarter than me, but I probably know more redneck engineering. Let's look at a carrier example.

The Ballistic Anti-Ship Missile Hypothesis

The idea is that carriers are obsolete because new technology makes them easy to find and allows for accurate anti-ship missiles. Microsatellites will be so numerous that you can't shoot them down, and ballistic missiles like the Chinese DF-21D can get targeting updates from the satellites until they are close enough for their own AI/ML-powered seekers to track the carriers. They'll be going Mach 5+ and can maneuver to make it impossible for defensive missiles to hit them. The aircraft carriers will sink, demoralizing the US.

Then even merchant shipping to US allies will be blockaded by the Chinese shooting ballistic missiles at any blockade runner. Surface navies are irrelevant.

What Does Physics Say?

I think this scenario is plausible from a physics standpoint. There are three minor issues.

First, many sensors will not work at Mach 5 in a dense atmosphere because the skin temperature of the missile will ionize the air, form plasma, and block much of the electromagnetic spectrum. The final closing speeds will have to be something more like Mach 3.

Ballistic missiles and hypersonic glide vehicles aren't powered. So any maneuvering they do will bleed velocity. The juking will be limited, especially when closing on the target in a dense atmosphere.

The energy a DF-21 carries is less than a World War II dive bomber bomb, and one of those could not sink a 20,000-ton carrier unless the crew failed at putting fires out. So one missile might damage a modern 100,000-ton aircraft carrier enough to stop flight operations, but it will likely take many more strikes to sink one. US carriers need their catapults, arrestors, elevators, and power plants to fight. Everything else is extraneous.

A Carrier for the Missile Era

The US Navy is complacent after lacking a competitor for so long. Modern carrier design reflects that. Thankfully physics has little to say about how much a carrier needs to cost. The new USS Ford weighs 100,000 tons. Steel costs ~$700/ton, so the basic materials are only $70 million. Very Large Crude Carriers (VLCCs) are roughly the same size. They cost ~$90 million, barely more than steel and engines. Crew quarters for 5000 sailors, nuclear reactors, radars, catapults, flag accommodations, specialized systems, and general government bloat get you to a $10+ billion ship.

The minimum requirements for a carrier are:

  1. Launch full-size aircraft
  2. Have space for bombs, fuel, and crew

One option is to design carriers without complex systems. Make the deck long enough to launch aircraft without catapults or arresting wires. Use ramps instead of elevators. Put only the most basic radio or radar. Then use cost-effective marine diesel engines instead of high-performance power plants. Don't bother with fuel piping. Small trucks can carry fuel from deep in the ship to the hangar. Having ramps at each end of the runway simplifies traffic control. You don't even need a tower, just a pure flat deck. Forget flag facilities. The admirals can stay on an AEGIS ship if they want fancy screens and wardrooms.

The carrier would be the longest ship in the world at ~1000 meters. The vessel before outfitting would cost ~$300 million if built like VLCCs. Modular construction methods help shipyards complete these ships in less than a year. Crew quarters can be austere to speed construction. Sleeping arrangements would be small cots, there wouldn't be kitchens (eat MREs) or plumbing (use chemical toilets, bottled water, and camp showers topside), and all laundry could be shipped offsite. A typical VLCC only has twenty crew, so most sailors will be the ~1400 it takes to run seven squadrons of aircraft. Active combat will require a few hundred more solely for firefighting and damage repair. Cutting support functions and features reduces the crew significantly.

The ship will be ~3x the size with half the crew, leaving excess space. That allows aircraft to be kept below deck and protected. Crew quarters can move deep into the interior. The ship can fill the cavities surrounding crew and aircraft storage with closed-cell aluminum foam. These foams are fire-proof, absorb energy, and are impermeable to water to prevent flooding.

The design could end up near ~$1 billion with rapid development and construction times once the Navy commissions a suitable dry dock.

Why Do We Need Carriers?

Ships are vulnerable to sustained air attack. Fighters from carriers maintain air superiority and defend the fleet. Their effectiveness in this role is why the Soviets started building long-range anti-ship missiles in the first place. They'd much rather stroll up with glide bombs that cost a fraction of the price and maximize payload. Surface-to-air missiles aren't a great replacement because enemy planes can fly beneath a ship's radar horizon to toss a glide bomb or fire a missile. Fighters can interdict enemy aircraft much further away. Launching fighters and sensor platforms that provide the proper coverage requires carrier-size ships.

Carriers can also host strike aircraft. A carrier air wing can deliver 500,000 pounds of bombs in a single sortie with 50 F-18s. China's long-range anti-ship ballistic missile inventory only has 200,000 pounds of warheads. Carrier aircraft can move a lot of mass.

The Moment of Truth

The Carrier Battle Group

I will make the same two assumptions as Steve. Both sides will have omniscient satellite coverage and very capable AI/ML.

The first goal is to degrade missile seeker performance. Missiles can use radar, infrared, visual, and electronic listening sensors for terminal guidance. A small escort ship could have a powerful jamming suite to spoof the satellite's synthetic aperture radar, jam radar frequencies the missiles use, and degrade satellite-to-missile communication. It is best for it to be separate from the carrier to thwart home-on-jam seekers. Smoke can obscure visual observation, and many aerosols can degrade the infrared spectrum. For good measure, you can spread diesel on the ocean and light it on fire. Chaff can distort any unjammed radar signals. None of these methods are perfect, but they all degrade missile performance. The cost is marginal compared to the billions of dollars a missile salvo would cost. Satellites will monitor China's mainland for launch plumes, giving the carrier group ~15-30 minutes of warning. The carrier crew can launch its planes, drain and park fuel trucks, secure tools in lockers, store munitions, and go to shelters during the missile flight time.

Missiles won't be the only users of AI/ML. Instead of bespoke close-in weapon systems that cost $10 million, you can hook up cheap infrared cameras and iPhone-level computing to 20 mm and 40 mm cannons. You are looking at $100,000 per gun instead. An ideal situation might be spending $100 million to buy 1000 cannons and putting them on a few glorified barges near carriers (but outside of the smoke/aerosols). These guns have a several thousand meter range, providing several long seconds to wreck incoming missiles. And because we have advanced AI/ML, aiming will be very accurate.

When we do the math, fifty $20 million missiles equals a $1 billion carrier. ~100,000 bullets from our guns equal one missile. We can afford to turn the sky black with lead. Our defenses can get off around 50,000 per second. Most CIWSs don't even bother using explosive shells, but that is an option to make the ammo more effective.

Assume China drains its entire inventory of ~200 DF-21D and DF-26 missiles in one salvo. The SM-6 and SM-3s from the guided missile ships will get a few - call it 10%. Our guns will get off 150,000 rounds - almost 1000 rounds per missile - even if the Chinese time the attack perfectly. Any staggering of the missiles increases the rounds per missile dramatically. Of course, some will still probably get through. A portion will be confused by the smoke/aerosol/chaff/fire/jamming countermeasures. Assume a few hit the flight deck of our carriers. They'll punch some holes and get buried in aluminum foam. Maybe they push some damage into the empty hangar.

Thousands of sailors will scurry to put out any localized fires. Then they'll drive some forklifts out of shelters to pick up steel plates, beams, and extra bails of aluminum foam to take up the ramps. They'll cut up damaged deck plate pieces, toss in the foam bails, insert beams, and use hundreds of welders to attach new plates. The crew will repair the damage before the planes need to divert away.

These defenses also work well for drone swarms. Iranian Shaheds would struggle to sneak by the 1000 guns with independent eyes, and their 80-pound warheads would barely dent the paint. The ramps could have blast doors to keep any drones from wandering down toward the planes.

The strike group can carry on and do its job.

Convoy Duty

Hsu also makes claims that this missile system can enact a blockade. Japan, South Korea, and Taiwan will not lie down and die. The first thing to do is organize and nationalize convoys of smaller ships that cost less than the $10-$20 million missiles. Then the convoy can implement the same smoke/aerosol/chaff/fire/jamming countermeasures to improve their chances. And they can bring a few gun barges along. The Chinese will run out of money and missiles before the container ship supply runs dry.

Making the Correct Assumptions

There is a difference between the US Navy needing to shake off a slumber and an actual change in weapon hierarchy. We should be begging the Chinese to pour immense resources into expensive missiles instead of more practical technologies.

There are always countermeasures! The Chinese could try a small first salvo with cluster submunitions to damage the gunboats. Or who knows what other ideas. Then the US would counter that, and back and forth. But they must increase how much mass they are firing down range to overwhelm defenses. That is an expensive proposition when ballistic missiles cost $10,000-$20,000 per pound of warhead, while carrier aviation can deliver smart bombs for ~$100/pound (including aircraft and carrier cost).

A better way to limit ship access from long distances is to drop inexpensive mass from a reusable vehicle, like SpaceX's Starship. But even a technology this powerful will not make surface ships obsolete.

The aircraft carrier is dead! Long live the aircraft carrier!