According to Xinhua News Agency, around 8 a.m. on May 1st, the third Chinese aircraft carrier, the Fujian carrier, cast off from the dock of the Jiangnan Shipyard in Shanghai and set sail for the relevant sea areas to conduct its maiden voyage trial. This sea trial primarily aims to test and verify the reliability and stability of Fujian carrier’s power and electrical systems.
The sea trial of the first electromagnetic catapult aircraft carrier has caused a frenzy on social media, with various jargon and new terms emerging one after another. The discussion about “nuclear-conventional hybrid propulsion” and “extended-range aircraft carrier” seems to be unraveling the two mysteries surrounding the Fujian carrier!
Nuclear-Conventional Hybrid Propulsion: Is it a combination of conventional and nuclear propulsion or a combination of conventional propulsion and electric catapult?
The Fujian carrier’s propulsion system has long been concluded to be conventional, although CCTV and various major official media outlets have not explicitly stated so. This is because the large exhaust ports have essentially revealed that it belongs to conventional propulsion. However, some netizens still believe that conventional propulsion can be combined with nuclear propulsion to provide power for the aircraft carrier, increasing its reliability. However, in reality, the opposite may be true!
The reason is simple: if it’s a nuclear-conventional hybrid, maintenance may cost the aircraft carrier dearly. Firstly, maintaining two power systems requires a significant amount of time. Secondly, because the maintenance cycles of conventional and nuclear-powered carriers gradually diverge, with extensive maintenance time, the majority of the aircraft carrier’s future time may be spent on maintenance. Can such a carrier still be combat-ready? The following figure shows the difference in maintenance cycles between conventional and nuclear-powered carriers as compiled by the US military:
As shown in the chart, initially, both are roughly synchronized, but as time goes on, they start to diverge:
Conventional-powered carrier maintenance mainly consists of the following stages:
0~18 months: SRA (Selected Restricted Availability) (Intermediate Maintenance), duration of 3 months;
21~39 months: SRA (Intermediate Maintenance), duration of 3 months;
60~72 months: COH (Complex Overhaul), duration of 1 year;
The maintenance cycle of a nuclear-powered carrier mainly consists of the following stages:
0~18 months: SRA (Intermediate Maintenance)
21~39 months: DSRA (Drydocking Selected Restricted Availability), major overhaul, duration of 5.5 months;
44.5~62.5 months: SRA (Intermediate Maintenance) duration of 3 months;
84~108 months: COH1&COH2, major overhaul, cycle of 24 months;
Nuclear-powered carriers need to replace nuclear fuel every 24 to 30 years (after half of the service life), with a cycle of approximately 2.5 years, or 30 months. If an aircraft carrier is a nuclear-conventional hybrid, maintenance overlaps only during the first and second overhauls. Apart from these instances, maintenance is staggered between conventional and nuclear power. In other words, the carrier spends most of its time either under maintenance or preparing for maintenance. Under these circumstances, its operational time would be greatly reduced. From this perspective, nuclear-conventional hybrid propulsion is not cost-effective and fails to achieve the desired 1+1>2 effect!
However, some netizens are still not convinced about nuclear power. They believe that the main propulsion of the 003 aircraft carrier might be conventional, but nuclear power is necessary for the electromagnetic catapult, as the energy consumption of the catapult is too high and cannot be sustained without nuclear power. But is this really the case?
The answer is no! Through calculations, the author has determined that the power consumption of the catapult during operation is approximately 60 MW (average power within 3 seconds of ejection). However, there is a 1-minute interval between each ejection. Compared to 3 seconds, only 3 MW of charging power is required. Even with a charging efficiency of only 50%, it would still only require 6 MW. If multiple sets of batteries are installed, only 12~18 MW would be needed, which could easily be provided by a gas turbine.
In terms of maintainability and the fact that the catapult does not need to be operational for extended periods, but only during launch, gas turbines are undoubtedly the most suitable option. Alternatively, two gas turbines could be alternately operated. If a nuclear reactor were used, it would take a considerable amount of time to start up and shut down, making it unsuitable for this purpose.
So, these two questions are already quite clear in the analysis: conventional propulsion, and even the electromagnetic catapult, are conventional, which might disappoint some. However, there’s no need to worry excessively because, compared to nuclear propulsion, there’s hardly any difference in near-sea operations. The difference becomes significant when considering global deployment. So, there’s no need to worry too much.
Extended-Range Aircraft Carrier: Unveiling the Secrets of Full Electric Propulsion
Another interesting claim circulating on social media is labeling the Fujian carrier as an “extended-range aircraft carrier.” Applying the concept of extended range from automobiles to aircraft carriers is quite creative, but in fact, this claim is not entirely unreasonable. From the perspective of this extended range concept, the 003 aircraft carrier, the Fujian carrier, might indeed be an extended-range aircraft carrier!
The concept of extended-range automobiles involves the engine generating electricity to charge the battery while driving the motor to power the vehicle forward. Similarly, an extended-range aircraft carrier involves shipboard main engines (nuclear or conventional with boilers and gas turbines) generating electricity, which is then distributed through the ship’s full electric propulsion system. A significant portion of this electricity will be provided to the main engine propulsion motors, driving the aircraft carrier forward.
This is essentially the concept of shipboard full electric propulsion. However, shipboard full electric propulsion is not so simple because there are significant differences in difficulty in the following aspects:
Firstly, power: aircraft carrier main engines typically have power outputs of 100 to 200 megawatts, which is essentially the power of a large power plant;
Secondly, comprehensive power distribution: there are dozens of auxiliary machines for shipboard main engines in total, all of which are interconnected through a microgrid for unified deployment. The Americans use AC power, which is convenient for conversion, but dealing with various power frequencies and coupled harmonic processing after coupling is difficult. Additionally, AC power storage is challenging, requiring conversion to DC power and then inversion to AC power when used, which has driven the Americans crazy.
Finally, usage: DC power is convenient to use because most electronic devices use DC power, and AC can be converted to DC using IGBC or SiC when needed.
China’s full electric propulsion uses DC power with only voltage requirements and no frequency requirements, making it easy to connect various power sources directly and store energy conveniently. Therefore, the Americans’ shipboard AC propulsion system needs to be rebuilt, and the electromagnetic catapult built on this foundation is quite awkward; China’s development of shipboard DC systems is progressing smoothly, and the stability of electromagnetic catapults is much higher than that of the Ford-class carriers.
So, have you noticed that the discussions among netizens during
the May Day holiday are gradually approaching the truth? It is estimated that before long, more information will be made public to help everyone understand more of the secrets of the Fujian carrier.