As part of its new trilateral pact with the United States and Britain, Australia will build eight nuclear-powered submarines.
The submarines, the leaders stressed, would not be nuclear-armed.
1. How does it work?
A nuclear submarine is powered by one or more nuclear reactors that create energy via the splitting of atoms. The resulting heat is then used to make steam for turbines to generate electricity for both the engine and the vessel's internal computer systems.
A conventional submarine is powered by diesel engines or electrical batteries.
2. What makes it special?
A nuclear-powered submarine has nearly unlimited range, with the onboard nuclear reactor not needing a refuel throughout its 25-year lifespan. The vessel is instead limited by how long the crew can last, which is dependent on consumable supplies such as food.
The reactor also allows the submarine to operate at high speeds for prolonged periods of time. This is unlike a conventional submarine which has to choose between being at top speed for a few hours, or submerged for a few days at a slower speed, as a result of the limited battery capacity.
Nuclear submarines also do not need to access the air above the water surface in order to continue operations, unlike their diesel/electric counterparts. As diesel/electric submarines need to slow down while taking in air, nuclear-powered ones are thus able to maintain both maximum stealth and speed during operations.
3. What are its disadvantages?
While a nuclear submarine does not need to refuel, it comes with a steep upfront cost to the manufacturer. It is estimated that a single Virginia-class submarine costs around US$2.7 billion (S$3.63 billion), about the same as six to seven German Type 212-class submarines.
Nuclear submarines also need a constant flow of cooling water around the reactor during operation, as it leaves a larger heat signature that may be more susceptible to detection by the enemy.
The submarines are also more complicated to maintain and service. This is further exacerbated by the fact that Australia does not have a domestic nuclear power industry to provide the engineers and nuclear physicists required for these vessels.
4. Which countries own nuclear-powered submarines?
Only six nations in the world currently operate nuclear-powered submarines. They are the United States (70), Russia (40), China (19), United Kingdom (10), France (9) and India (3), said the World Nuclear Association, based on 2019 data.
5. When will Australia's nuclear submarines be ready?
The submarines are to be built in Adelaide, the capital city of South Australia. It would take as long as 18 months to work out details of the agreement with the US and Britain, while building and commissioning such submarines can take years, or even decades.
Sources: The Guardian, US Naval Institute