Video: Nuclear Vs Diesel Aircraft Carriers - How do they Compare?

Video: Nuclear Vs Diesel Aircraft Carriers – How do they Compare?

Nuclear diesel aircraft carriers

The nuclear-powered USS Gerald R Ford and the diesel-powered HMS Queen Elizabeth are the latest and most modern aircraft carriers in the world. You may think that being nuclear-powered, Ford-class carriers will be a clear winner as they have virtually unlimited ranges while HMS Queen Elizabeth carriers have a range of only 10,000 Nautical Miles before it needs to refuel.

But even if you discount the food supplies needed for both types of vessels, USS Gerald R Ford would still need to be refueled from time to time with fuel for aircraft that it carries on board. While the unlimited range may seem like an advantage at first, saving money on fuel and resupply runs. The more you look into it, the more you realize that it takes a while, if ever, for the benefits to pay off. Think of a hybrid car, you pay more money for it upfront to enjoy the fuel savings in the long run, but it will take years before it breaks even.

So, let’s take a look at all the advantages and disadvantages of nuclear-powered (Ford-class) and diesel-powered (Queen Elizabeth class) aircraft carriers and try to conclude which one is the better value for money as in the end it’s all about the cost.

Ford-class nuclear carriers are powered by two A1B nuclear reactors which provide 25 percent more power than its predecessor A4W nuclear reactors that are used on Nimitz-class carriers. It’s estimated that each A1B reactor produces 125 Megawatts of electricity, which’s enough to power 25,000 homes. Additionally, each A1B reactor produces 350,000 shaft horsepower which is equivalent to 260 Megawatts. Increased electricity production compared to older reactors means that electromagnetic aircraft launch systems can be used which accelerate aircraft more smoothly and thus put less stress under airframes. In contrast Queen Elizabeth carriers are powered by two 36-megawatt gas turbine alternators, located underneath each island, which by the way is one of the main reasons for the twin island design due to the engine exhaust shafts. There are also four 10-megawatt diesel engines in the middle of the ship. In total, the ship’s power plant produces 112-megawatts of electricity, half of which powers multiple electrical motors that spin the propeller shafts.

You might be surprised to find out that conventional diesel burning power plants are more efficient than nuclear power plants. When you burn diesel, 40 percent of the fuel is turned into useful energy while in a nuclear power plant 33 percent of the fuel is turned into useful energy. This is because conventional power plants can generate steam at a higher temperature therefore providing more force to the turbines, but efficiency is not that important when it comes to nuclear power plants as nuclear fuel is much more energy dense. If you were to run each type of aircraft carrier with 200,000 horsepower, non-stop for one-week, a conventional carrier (HMS Queen Elizabeth) would require over 5 million liters (1,30,000 gallons) of diesel fuel while a nuclear carrier (USS Gerald R Ford) would require just 4 Kilograms (8.8 pounds) of enriched uranium. In other words a nuclear carrier consumes as little as 0.00008 percent of the fuel that conventional carriers do!

So, while on paper nuclear propulsion is less efficient, it still provides much more power in total due to the higher energy density of the nuclear fuel. In fact Ford-class carriers have about seven times the power available compared to HMS Queen Elizabeth class carriers, but to be fair the Ford-class carrier is about 67 percent larger than its counterpart. This energy supply is needed for new power intensive weapon systems, like rail guns as well as new generation powerful radars.

Having more power also means that nuclear-powered carriers can travel faster. In fact Ford-class carriers can travel 5-knots faster than HMS Queen Elizabeth class ships. The faster the ship travels, the more apparent wind it generates meaning it’s easier for aircraft to take off. However in case of Queen Elizabeth carriers wind is not a factor as these ships don’t have catapults and they rely on F-35B aircraft which use short take-off and vertical landing technology.

Now let’s talk about the Range, Fuel Tanks, and Bills!

HMS Queen Elizabeth weighs 65,000 tons and holds 1 million gallons (3,780,000 liters) of F-76 marine diesel for the ship and 750,000 gallons (2,830,000 liters) of F-44, also known as JP-5 Jet fuel for the embarked aircraft. To put this in perspective, the total amount of fuel on a Queen Elizabeth carrier is equivalent to 120 fuel trucks. In 2020, the average cost for both the types of fuel was roughly 3 USD per gallon meaning that it would cost 3 million USD to fuel up the carrier and 2.2 million USD to fill up the planes. A full tank of fuel allows the carrier to travel 10,000 NM at most.

During operations, aircraft carriers, whether nuclear-powered or diesel-powered will consume a lot of aviation fuel, meaning that both types of carriers will need to undergo replenishment at sea at frequent intervals. Moreover, aircraft carriers mostly travel with escort ships which are diesel-powered, meaning there is always a need for fuel tankers. Logistically speaking, it is still harder and slower to refuel a conventionally-powered aircraft carrier compared to a nuclear one as you have to do more frequent replenishments.

Nuclear reactors on carriers have to be refueled only every 20-25 years or so, for instance, USS Theodore Roosevelt underwent refueling and a complex overhaul after 23 years of service. However, it did take four years to complete and cost 2.6 billion dollars. As mentioned earlier, nuclear fuel has a much higher power density, meaning it takes less space to store a given amount of energy. This means that the nuclear-powered Ford and Nimitz-class ships have much more free storage capacity so they can store more jet fuel, weapons, and so on. In fact, on average, nuclear carriers carry twice as much jet fuel compared to their counterparts. The bottom line is that the nuclear carriers make a lot of sense if you are covering a large geographical area, especially something like the Pacific ocean.

Another benefit of nuclear propulsion is that it provides plenty of steam for the catapults that are used on the Nimitz-class carriers. The newer Ford-class carriers, however, rely on electromagnetic aircraft launch systems that don’t require steam but use a considerable amount of electricity. While Queen Elizabeth class carriers don’t currently have any sort of catapults, they may be retrofitted with electromagnetic catapults one day, and the good thing is that they have sufficient spare electricity generation available for it.

The next element worth exploring is the construction time. Some say it takes much longer to build a nuclear carrier compared to a conventional one, for instance, it took 13 years to build the French nuclear-powered Charles de Gaulle aircraft carrier but only eight years to build HMS Queen Elizabeth. However, it took 13 years to build a conventional-powered Russian carrier Admiral Kuznetsov, and only eight years to finish the nuclear-powered carrier USS Gerald R Ford. Having a colossal nuclear industry, talent, and expertise certainly plays a role in how fast one can build a carrier of any type. So, just by looking at the build-time of the aircraft carriers, it’s hard to say which one can be built faster.

Aircraft carriers are expensive (HMS Queen Elizabeth- $4.1 billion, USS Gerald R Ford- $13 billion). However, the nuclear-powered carriers not only carry a higher initial price tag but their operation and maintenance costs are also much higher than the diesel-powered ones. The fuel bill for Queen Elizabeth class carriers and the replenishment at sea cost will add up over time, but it would still be much lower than if the ships were nuclear-powered.

Having a nuclear reactor on a ship is complicated. Traditional land reactors rely on gravity to drop control rods to shut down a reactor, but that is impossible on a moving vessel that can go up and down in waves. The solution is to use a mechanical system to insert rods into the reactor’s core, which adds to the cost. Additionally, a desalination plant specifically for the reactor must be built and maintained in order to provide fresh water for reactor cooling, again raising the expenses.

Some say that nuclear-powered carriers are greener as they don’t produce any CO2, but they do produce nuclear waste, and the disposal of nuclear waste is a big challenge. USS Enterprise was deactivated in 2012 and it took four years just to defuel eight of its reactors. Since 2018, USS Enterprise is stored in Hampton roads until disposal plans can be determined by the US Navy. So, in terms of disposing, nuclear-powered carriers are clearly at a disadvantage when compared to diesel-powered vessels.

Another thing to consider is nuclear safety, due to changes in the nuclear safety standards, the French Charles de Gaulle had to add extra protection all around the reactor as the detectable radiation leakage was above the revised standards. For the US Navy, the argument can be made that nuclear power is safe. For instance, the US Navy operates 103 nuclear reactors on 81 ships, and for more than half a century, there have been no accidents or radioactive releases.

Whenever a nation decides to build an aircraft carrier, there are two more things in play- Politics and Prestige. In 2019, Pentagon decided to cut the aircraft fleet from 11 to 10 and retire USS Truman early instead of letting it undergo a midlife refit, a move that would save more than 30 billion USD over 25 years, as the cost of refueling the carrier was pegged at 3.4 billion USD, and additional billion dollars would be saved each year by not operating the carrier and its air wing. Congress was outraged by such a proposal, and soon thereafter, President Trump ordered the US Navy to keep USS Truman.

American super carriers are unique icons of military power that project dominance in the International waters. No matter the cost, they are not going anywhere anytime soon. In fact US Navy is currently in the process of replacing all 10 Nimitz-class carriers. So far two Ford-class carriers have been completed with one currently under construction and seven more planned.

Going back to answer the original question, which type of carrier is better value for money? We have to say it depends! In case of Queen Elizabeth class carriers, conventional power makes sense as the Royal Navy has limited budget and both carriers are mostly deployed in the Northern Atlantic, making the travel range less of an issue. With regards to the US Navy, nuclear makes sense as the distances that its carriers covers are much larger, especially in the Pacific region, and it’s definitely about the prestige as well. Having 11 nuclear carriers in its fleet, the United States projects its dominance in the international waters.

With regards to which technology is cheaper over the long-term, it is hard to say for two reasons, first of all, when comparing nuclear-powered with the conventionally-powered carriers, it is not exactly an apples to apples comparison as the ships are of different sizes. For instance, Ford-class carriers are 67 percent larger than the Queen Elizabeth class carriers. There are simply no conventionally-powered carriers with displacement of 100,000 tons, so it’s hard to say what the lifetime cost of running that kind of a ship would be. Secondly, no nuclear-powered aircraft carrier has been fully disposed off yet, but one thing is clear, it would be pricey.

What do you think, which type of carrier is better value for money, and does it even matter? Do let us know your views in the comments section. While you think about it, here is an awesome video comparing the nuclear-powered carriers with the conventionally-powered carriers!


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