A Carrier That Only Launches Cruise Missiles
This is a quick post on a proposal to find a low cost replacement for expensive aircraft carriers and their equally expensive escorts. Carrier battle groups cost billions of dollars a year to operate, but they are incredibly useful in war time situations. Ideally, you would only pay for aircraft carriers when you need them. However, a carrier takes a long time to build, and crews need constant training to function properly in a war time environment. You have to spend billions of dollars a year for the option of having a carrier battle group available when war breaks out. In other words, owning and operating an aircraft carrier is a very expensive form of insurance, but with a low deductible. The ownership cost of a carrier in wartime and peacetime are about the same, as most of the costs of owning and operating an aircraft carrier are fixed. Construction, crew and maintenance costs stay about the same year in and year out. During a war, you would spend more on fuel and munitions, but these represent a small share of the overall expense of operating a modern carrier battle group. To keep things simple, this exercise assumes that a US Navy carrier battle group costs $7 million a day to operate, or $2.6 billion a year.
It is useful to look at carrier costs in terms of targets hit. We use a carrier to get aircraft close enough to strike targets that are out of range of land bases accessible to the United States. Dividing the costs of operating a carrier battle group by the number of targets that battle group can hit is a useful metric for looking at aircraft carrier alternatives. The table below looks at this metric for two likely scenarios: a prolonged, low intensity conflict in which Navy jets drop lots of lower cost munitions like smart bombs, and a short, intense conflict with a peer competitor in which Navy jets fire lots of expensive standoff weapons. The numbers are outlined below. As you can see, the cost per target for the low intensity conflict is a lot lower than the unit cost for the high intensity conflict (see the numbers in the blue row). Note that annual operating costs are the same for both scenarios at $2.6 bn a year. This includes the carrier, its escorts and the air wing.
The challenge is to create a ship that has lower annual operating costs than a carrier battle group AND roughly matches the cost per target hit. This would allow the Navy to spend less in peacetime while being able to economically carry out the same volume of air strikes in war time. One option would be to build a surface ship that can launch lots of cruise missiles. Cruise missiles are accurate enough to perform most of the missions currently assigned to manned carrier aircraft and drones. Cruise missiles also have a range advantage over manned aircraft: a cruise missile has a range of 1,500+ miles, while manned aircraft have a ~500 mile combat radius. The one drawback to using cruise missiles is their high cost. At $1.5 million each, they are extremely expensive, especially since you only get to use one once. To put this on context, a smart bomb costs about $30,000. A modern 4 or 5G fighter costs $25,000 per hour to operate. Hitting a target with a smart bomb from a carrier launched aircraft probably costs <$100,000. You can see the relatively low cost of smart bombs in the Prolonged, Low Intensity Conflict Scenario outlined above. If you can get the carrier to within ~300 miles of the target, it really does not make sense to use a cruise missile. If you assume that the US is going to need to support low intensity operations in prolonged military engagements like Afghanistan and Iraq, you need some kind of fixed wing carrier capability.
Modern Carriers Are Basically Cruise Missile Launch Platforms
A fight with a peer competitor with modern air defenses and the capability to sink carriers operating hundreds out to sea is a completely different set of economics. In this kind of war, carriers are probably operating far from the enemy coast to avoid enemy anti-ship weapons. Being within 500 miles of the territory of an enemy with some combination of stealthy aircraft, modern anti-ship missiles, AIP submarines and hyper accurate intermediate range ballistic missiles puts an aircraft carrier in real danger of being hit and disabled or sunk. To avoid these weapons, we have to assume that the carrier launches aircraft at 1,000+ mile ranges. To avoid the advanced air defenses of the enemy, carrier aircraft will rely on guided standoff weapons with 500+ mile ranges. These kinds of weapons are basically cruise missiles. They use the same guidance technology, have comparable ranges, and have comparable costs. The high cost of stand off weapons, and the lower probability that they destroy their target, are the main reason that the cost of hitting a target is so much higher in a hypothetical conflict with a peer competitor. You can see the difference in the cost between the low intensity and the high intensity conflict in the chart above. The cost to hit a target in a high intensity conflict is 10x higher than a low intensity conflict.
Of course, the odds that the US gets into a shooting war with another country that can sink a carrier are very low. However, the US does need to invest in the kind of war fighting capabilities that can credibly deter such a country from attacking the US or its allies to keep those odds low. The price of this deterrence is $2.6 billion a year, and if a war did break out, the carriers would essentially be a launch platforms for cruise missiles. Why not find a way to lower the cost of that deterrence by building a class of ships that only fires cruise missiles?
The Drawbacks of Arsenal Ships
The US Navy has lots of ships that can launch cruise missiles from vertical cells embedded in their decks. However, these ships typically have less than 100 of these cells, they cannot reload the cells at sea, and even if they could reload, they have no place to store large numbers of spare cruise missiles. Furthermore, these cells also house the missiles needed to defend ships from air attacks. A carrier replacement would need to be able to launch 300+ missiles to match a carrier’s rate of sortie generation. A modern destroyer operating in a high threat environment would probably put to sea with a maximum of 50 land attack cruise missiles.
The US Navy has also explored building large ships with lots of vertical missile cells. These kinds of ships are typically referred to as arsenal ships. The problem with vertical launch cells is that they take up a lot of deck space. This means that there is little room on deck for other kinds of missions. For this reason, any ship relying on vertical launch tubes will also have issues with reloading at sea. Any deck space used for a crane system that can reload the VLS cells reduces the number of cruise missiles the ship can fire. A helicopter pad that can land replacement missiles from a resupply ship would also reduce the deck space available for VLS cells. Reloading would also require a bigger crew, which means missile cells would compete for below deck missile space with berths, food storage and freshwater. Strike length missile cells push deep into the hulls of modern war ships, limiting storage space below deck. If you stack anything on top of a VLS cell, you render the cell useless.
This inability to reload VLS cells at sea really reduces an arsenal ship’s ability to strike targets. Let’s assume that you have an arsenal ship with 500 VLS cells, and this ship must travel 2,000 miles from a friendly port to a position from which it can hit its targets. At a cruising speed of 20 knots, it would take the arsenal ship eight days to get to its station and back to port to pick up a new load of missiles. This works out to a rate of 60 missiles per day, which is rather low, and most of the time the arsenal ship would be out of range. A peer competitor with satellites, submarines or plain old port watchers would know when the arsenal ship left port. Air defense command would know to expect cruise missile strikes in 96 hours. This really limits the utility of an arsenal ship in a high intensity conflict.
Why Not Launch Cruise Missiles Like Carrier Aircraft?
What the Navy needs is a ship that can fire a lot of cruise missiles AND reload at sea to maintain that rate of fire over long periods. Such a ship would need lots of deck space to accommodate helicopter landing pads and hangers. Like a modern aircraft carrier, a cruise missile carrier would continuously replenish its stock of weapons while at sea. If a carrier had to return to port to pick up more aviation fuel and bombs every time it ran out, it wouldn’t be a very effective weapon. Carrier battle groups have specialized cargo ships that keep carriers resupplied at sea. A cruise missile carrier would rely on the same supply infrastructure.
Instead of a vertical launch system, the cruise missile carrier should store spare cruise missiles below decks, and have a launching system that can be reloaded quickly at sea. A telescopic erector launcher is one option. A maglev rail that can accelerate a cruise missile past its stall speed would be another option. The maglev launch rail option has the advantage of being able to launch cruise missiles without a solid fuel booster. This saves on cost and storage space. With some below deck automation of cruise missile handling, the rate of fire from a pair of maglev launchers could rival the launch rates of vertical launch systems. The ship below envisions using both systems.
This ship would feature:
- 2 hanging maglev rails that can accelerate cruise missiles to their launch speed without the need for solid fuel boosters
- A cruise missile hanger that can accommodate 500+ land attack cruise missiles
- An automated crane system in the cruise missile hanger the moves cruise missiles
- Three cruise missile telescopic erector launchers
- A helicopter hanger that can accommodate up to six medium sized helicopters
- MK56 VLS for Evolved Sea Sparrow surface to air missiles and decoys
- Landing spots for two medium sized helicopters
- A 200 foot tall mast with an infrared search and track array at the top
- Two high frequency surface wave radar arrays on either side of the superstructure
This is a ship that should not cost much to build or maintain. It would be 550 feet long, and 60 feet wide, so about the size of a Spruance class destroyer or a modern landing platform dock ship. There are not many sophisticated sensors or equipment, which should keep the cost down. A ship like this could easily cost less than $750, and operating costs would be equally low. The major expense during wartime would be the cost of the actual cruise missiles. The economics of operating such a ship during a low intensity and a high intensity conflict are outlined below. As you can see, such a ship has massively lower peace time operating costs, and matches the per target hit cost of a carrier battle group operating in a high intensity conflict. In other words, a cruise missile carrier provides the war fighting capabilities you need in a high intensity conflict without the massive peacetime costs.
A Modern Escort Carrier
Unlike an arsenal ship, a cruise missile carrier would also be useful in non-strike missions. The large helicopter hanger and generous flight deck gives the ship the flexibility to handle most low intensity missions. In the absence of VLS cells, there would be plenty of room below deck to accommodate a company of marines or special forces. The racks needed to store cruise missiles could be removed, and the cruise missile hanger could be used to accommodate other kinds of cargoes. The cruise missile telescopic erector launcher could be swapped out for a multiple launch rocket system to support shore operations. With three MLRS mounts and a mix of transport and attack helicopters, a cruise missile carrier could quickly become a versatile amphibious warfare platform.
This ship can also defend itself. The MK56 VLS system provides lots of room for medium range surface to air missiles, and the cruise missile carrier can accommodate plenty of helicopters with AESA radars for airborne early warning duty. The LACM TELs could be swapped out for box launchers that can accommodate a long range surface to air missile like the RIM-174 Standard ERAM. A surface to air missile with a 150 mile range would provide as much protection as a fixed wing combat air patrol. The large hanger and landing pad would also be big enough to accommodate some sort of future vertical takeoff and landing drone that can launch air to air missiles. If the UAV is light enough, it could even be launched from the maglev cruise missile launchers, and land on the helicopter pad.
The IRST mast and the high frequency surface wave radar also give this class of ship unique capabilities. At 200 feet above the horizon, an infrared sensor should be able to detect low flying anti-ship missiles at 20+ miles from the ship. This advance warning would offer critical seconds of time to launch SAMs and decoys. IRST sensors are proven, low cost, low maintenance off-the-shelf technology. Its the height of the mast that makes the real difference.
The high frequency surface wave radar is a bit more speculative. Only a few ship based over the horizon radar systems have ever been deployed, so we don’t really know how well they will actually perform. However, HFSW radar does offer the ability to detect low flying targets over the horizon. It could help offset the lack high flying, fixed wing airborne early warning aircraft. You can read more about HFSW radars by clicking on the link below.
Download a description of the Sanders test of ship based HFSW radar