This article is a collaboration between IEEE Spectrum, the flagship magazine of the Institute of Electrical and Electronics Engineers, and Foreign Policy.

The modern race to build undetectable submarines dates from the 1960s. In that decade, the United States and the Soviet Union began a game of maritime hide-and-seek, deploying ever-quieter submarines as well as more advanced tracking and detection capabilities to spot their adversary’s vessels.

This article is a collaboration between IEEE Spectrum, the flagship magazine of the Institute of Electrical and Electronics Engineers, and Foreign Policy.

The modern race to build undetectable submarines dates from the 1960s. In that decade, the United States and the Soviet Union began a game of maritime hide-and-seek, deploying ever-quieter submarines as well as more advanced tracking and detection capabilities to spot their adversary’s vessels.

That game continues to this day, but with a wider field of players. In the coming months, the U.S. Navy plans to homeport the USS Minnesota on Guam. This Virginia-class nuclear-powered attack submarine is among the quietest subs ever made. Advanced nuclear propulsion like the Minnesota’s gives the vessel a superior ability to operate covertly. More of its kind will be deployed by the United States, the United Kingdom, and Australia to compete with China for influence and military dominance, especially over the Indo-Pacific region.

As part of the landmark deal known as AUKUS (for the initials of its partner states), Australia will acquire, operate, and maintain three to five U.S. Virginia-class subs, each of which will cost about U.S. $4.3 billion; an additional five subs will be a special AUKUS-class built in the United Kingdom and Australia using U.S. nuclear propulsion technology.

In exchange for access to this technological edge, Australia has agreed to make substantial multibillion-dollar investments in the U.S. and U.K. naval shipbuilding industries. The deal could last until at least the 2050s and cost up to $368 billion.

These submarines are expected to assume a deterrence mission against China and its nuclear modernization plans, which include the deployment of submarine-launched ballistic missiles capable of targeting the United States.

The People’s Liberation Army Navy is the largest navy in the world, but it operates only 12 nuclear-powered submarines, a rather small number compared to the 67 attack subs and ballistic-missile subs of the U.S. Navy. And compared to U.S. submarines, their Chinese counterparts are noisy and easily detected.

But it won’t stay that way for long. The U.S. Department of Defense claims that China plans to modernize and expand its submarine forces significantly by 2035, including by producing more stealthy submarines.

Once built, Australia’s first few nuclear subs will be designed to operate for 33 years, until the 2060s, or even longer with lifetime extensions. To shore up its intended strategic advantages, the AUKUS deal also seeks to develop advanced anti-sub technology, consisting of sensor networks and analytics enabled by artificial intelligence (AI).

This technology cuts both ways, though, and ocean transparency is increasing as a result. Some experts even think the game of maritime hide-and-seek could end by 2050.

Meanwhile, AUKUS faces more practical concerns, including a looming shortage of the highly enriched uranium needed to fuel the submarines, growing opposition to the deal’s extravagant cost, and competing submarine designs that are much cheaper and just as capable for certain missions.

So, is now really the right time for nations to be investing hundreds of billions of dollars in submarine stealth?

A Virginia-class submarine under construction at the General Dynamics electric boat shipyard in Groton, Connecticut, on March 17, 2021.Christopher Payne/Esto

In the quest for stealth, naval engineers first have to consider how their vessel might be spotted. Then they can design their submarines for maximum evasion.

There are two key steps to track a submarine, said Scott Minium, a former commander at the U.S. Navy’s Submarine Squadron 15 in Guam who has mentored the commanding officers of seven nuclear-powered subs. The first step, Minium said, is to detect the signature of a potential submarine. The second step is to “classify it based on known signatures to determine if a submarine has been detected.”

Such signatures include the unique noise patterns generated by different submarine classes as well as other identifiers, and they’re essential for detecting and tracking submarines.

Noise is the most critical signature, so engineers working on stealth technology focus on suppressing the sound waves that submarines give off, rendering their movements nearly silent, especially at slow speeds. The thousands of rubberized anechoic tiles that cover the hull of a Virginia-class submarine absorb or distort sound waves coming from passive and active sonar, obscuring the sub’s whereabouts. Similarly, vibration-damping materials reduce the sounds that the engines and turbines transmit to the surrounding waters.

Submarines have long been designed with certain geometric shapes that minimize their radar cross-section—that is, the areas seen by the radar that enable a vessel to be detected. The addition of radar-absorbing materials on exposed parts of a submarine, such as the periscopes and antenna, also helps, allowing........

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