Why is Australia getting nuclear submarine capability being seen in the context of possible military aggression involving China?

This is primarily because a nuclear-powered submarine gives a navy the capability to far out into the ocean and launch attacks. Unlike conventional submarines, which are generally considered helpful for defensive purposes, the ability of a nuclear-powered submarine to go long distances, at a higher speed, without being detected gives a nation the ability to protect its interests far from its shores.

• In the context of the AUKUS agreement, nuclear-powered submarines will give the Royal Australian Navy the capability to go into the South China Sea, where China is increasingly getting aggressive, to protect its assets and conduct patrols — even though this has not been spelt out by the three countries. The US has in the past shared its nuclear propulsion technology only with the UK, in accordance with the nuclear power sharing arrangement that the two countries have had since 1958.

When US announced this agreement?

• US President Joe Biden announced a new defence pact between the US, UK and Australia on September 15, 2021. The pact known as AUKUS will enable sharing of advanced technologies, expertise in artificial intelligence, cyber underwater systems and long-range capabilities.
• Australian PM Scott Morrison said that the first major initiative under AUKUS initiative will be the delivery of a nuclear-powered submarine fleet for Australia. AUKUS is a partnership where our technology, our scientists, our industry, and defence force all working together to deliver a safer and more secure region.
• The enhanced trilateral security partnership will see Australia build a nuclear-powered fleet of submarines in a joint endeavor with the US and UK with the main focus being on interoperability, commonality and mutual benefit.It is not clear which submarine the Australian government will obtain, but the US navy’s latest design is the Virginia-class submarine. Manufactured by American aerospace and defence company General Dynamics, this submarine has gone through several iterations but is generally powered by a single nuclear reactor and can travel at more than 25 knots. Its crew includes 15 officers and 117 enlisted personnel, and the subs are used both in anti-submarine warfare and intelligence gathering operations.
• The vessel is powered by a 210MW pressurised water nuclear reactor, inside of which the enriched uranium fuel is sealed. The reactor does not have to be refuelled over its 30-year lifespan.
• The submarines are powered by onboard nuclear reactors. These produce energy by splitting atoms to create heat, which is then used to make steam for turbines that generate electricity to power propulsion and its internal systems. To create the steam, the sub draws in seawater and purifies it through a desalination process. Some of this clean water is also used for drinking, the creation of oxygen through hydrolysis and for scrubbing CO2 or other contaminants from the air.

Where these nuclear submarines lack?

• Diesel-powered submarines, the kind that Australia was initially going to build in partnership with French company Naval Group, tend to be smaller and run more quietly. They can easily slip into shallow waters along coasts or in river estuaries where they are harder to detect.

While this has certain advantages, the main drawback is endurance. Diesel-powered submarines need to resurface regularly in order to take on oxygen, vent exhaust and charge their batteries. As a result, they can’t operate in the open ocean for long periods and careful thought needs to be given about where, when and how they can refuel.

Nuclear submarines, on the other hand, are built for endurance. With abundant power, some builds can run almost indefinitely, or at least until something breaks down or the crew runs out of tinned food. The only real limitations are the needs of the crew, who can only last so long in a confined space.

• Because nuclear submarines tend to be larger, one downside is they can’t move into shallow waters, making them more easily detectable. During one war game in 2015, a Russian-built, Kilo-class diesel-powered submarine used by the Indian navy “sank” a US nuclear-powered sub – although the US navy has never acknowledged the sinking.
• Traditionally Australia’s diesel-powered submarines are thought to have been complementary to US powered nuclear subs used by the US, making the recent announcement a surprise.
• Nuclear submarines are also more complicated to maintain and service. Unlike the US and UK, Australia does not have a domestic nuclear power industry, which could provide a highly skilled workforce of engineers and nuclear physicists. Much of the work on the subs will probably have to be done overseas.
• The US Virginia-class submarines typically use highly enriched uranium (HEU) that does not need replacing during the lifecycle of each submarine. Across the world, the US, Britain, Russia and India are the only countries to use HEU in naval reactors. Other countries like France use high-density, low-enriched uranium that will occasionally require swapping out with a replacement source.
• HEU is one of the most dangerous metals on earth and also one of the simplest nuclear materials to work with. These twin traits also make it a security risk over fears rogue states or terrorists might develop a nuclear weapon, or mishaps trigger a serious accident. It is also why it has been targeted under non-proliferation treaties to reduce its use.

Who leased the SSN to India?

         India is among the six nations that have SSNs. The other five are the US, the UK, Russia, France and China. India has had the capacity since it got the Soviet-built K-43 Charlie-class SSN in 1987. Commissioned with the Red Fleet of the USSR in 1967, it was leased to the Indian Navy, and was rechristened INS Chakra. The submarine was decommissioned in 1991. In 2012 India got another Russian SSN on a 10-year lease, called INS Chakra 2. In the mean time, India was working on building its own SSN, and the first Indian nuclear submarine, the INS Arihant, was commissioned in 2016. A second Arihant-class submarine, INS Arighat, was secretly launched in 2017, and is likely to be commissioned soon.

• After it demonstrated the capability to launch nuclear weapons in 2018, the INS Arihant is now classified as a Strategic Strike Nuclear Submarine or SSBN, which means it is a nuclear-powered ballistic submarine.

INS Arihant is important because it completes India’s nuclear triad, which means that the country has the capacity to launch nuclear missiles from land, aircraft, and submarine.

INS Arighat

• INS Arighat is an upgraded variant of the Arihant-class submarine. It is the second nuclear-powered ballistic missile submarine being built by India under the Advanced Technology Vessel (ATV) project to build nuclear submarines at the Ship Building Centre in Visakhapatnam. It has the code name S3.
• The submarine was quietly launched in 2017 and little has been publicly announced about its capabilities and current status. The submarine was originally known as INS Aridman but was renamed INS Arighat upon its launch. As per reports which were released in early 2021, she was to be commissioned in late 2021 alongside INS Vikrant.

INS Arihant

• INS Arihant (Sanskrit: Vanquisher of Enemies), designated S2 Strategic Strike Nuclear Submarine, is the lead ship of India's Arihant class of nuclear-powered ballistic missile submarines.The 6,000 tonne vessel was built under the Advanced Technology Vessel (ATV) project at the Ship Building Centre in the port city of Visakhapatnam.

How nuclear submarine classified by US?

• A nuclear-powered submarine is classified as an “SSN” under the US Navy hull classification system, wherein ‘SS’ is the symbol for a submarine, and ‘N’ stands for nuclear. A nuclear-powered submarine that can launch ballistic missiles is called an “SSBN”.
• Conventional diesel-engine submarines have batteries that keep and propel — though not very fast — the vessel underwater. The life of these batteries can differ, from a few hours to a few days. The newer Air-Independent Propulsion (AIP) submarines have additional fuel cells that allow them to stay underwater for longer and move faster than the conventional vessels. However, the fuel cells are used only at strategic times, when the endurance to remain submerged is needed.
• Both conventional and AIP subs need to come to the surface to recharge their batteries using the diesel engine. The diesel engine also propels the vessel on the surface. However, the fuel cells of AIP can only be charged at on-land stations, not while at sea.
• The great advantage of an SSN is that its nuclear-powered propulsion gives the submarine a near infinite capacity to stay dived. Since it is propelled by a nuclear-powered engine rather than by batteries, it does not have to emerge on the surface at all, except to replenish supplies for the crew.
• SSNs are also able to move faster underwater than the conventional submarines. Added together, these advantages allow a navy to deploy these submarines quicker and at farther distances.