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June 23, 2025: A Chinese firm recently announced the UUV-300 series of artificial intelligence (AI)-controlled unmanned submarines. Described as a research vehicle, it is primarily used for military activities. China is striving to catch up with the United States in this domain. The U.S. Navy began developing and using underwater drones in the 1950s. These devices also had commercial applications, and civilian versions found many eager customers. The Remus line of drones was particularly popular. China is working to close this gap quickly to support its navy, which is projected to be the largest in the world by the end of the decade.
Meanwhile, the U.S. Navy believes robotic submarines carrying mobile mines would be an effective new anti-submarine warfare (ASW) asset, as the U.S. is already developing some of the necessary ASW technology. This includes Unmanned Underwater Vehicles (UUVs) and mobile mines. Over a decade ago, the Navy adopted civilian underwater UUVs used for ocean monitoring and has employed them for both environmental data collection and wartime submarine operations. With a growing number of civilian and military customers, American UUV developers and manufacturers have been creating new ocean research UUVs with military applications. The latest example is a new class of Extra-Large Unmanned Underwater Vehicles (XLUUVs) capable of diving deeper, carrying a cargo bay for research equipment, and operating autonomously for up to six months. The first of these XLUUVs was the Echo Voyager, developed by Boeing from a research project and ready for testing in 2016. The tests were successful and have involved increasingly complex and fully autonomous operations. In 2019, the Navy ordered four militarized Orca versions of the Echo Voyager for $11 million each.
Both models are 16-meter-long diesel-electric-powered autonomous submarines with a payload compartment 9.1 meters long and 2.6 meters in diameter, wholly inside the pressure hull. Propulsion is provided by battery-powered electric motors, with diesel generators to recharge the batteries when on or near the surface. These XLUUVs have no topside sail and can remain underwater for days because there is no crew to sustain. While submerged, they can move at 14 kilometers per hour and have sufficient generator fuel to travel 12,000 kilometers.
The main difference between Echo Voyager and Orca is that Echo Voyager is built to dive to depths of 3,400 meters, while Orca forgoes this capability but adds additional passive sensors and signal-processing computers to detect other submarines or surface ships. Orca also features an underwater communications system for arming the dozen Hammerhead mobile mines it can place on the ocean floor in areas like the South China Sea. These Hammerhead bottom mines carry an Mk 54 lightweight torpedo, typically used by ASW helicopters and aircraft. The Mk 54 has a range of ten kilometers and a regularly updated guidance system. Hammerhead operates similarly to a larger Cold War-era system that deployed the Mk 48 torpedo. Hammerhead is an encapsulated system equipped with passive sensors to detect and identify submarines and surface ships, targeting specific types, such as diesel-electric submarines larger than Orca.
China is seeking to augment its submarine fleet with these automated unmanned submersibles. Fifteen years ago, China had 62 submarines: 53 diesel-electric, six nuclear, and three nuclear ballistic missile submarines. At that time, the U.S. had 72 nuclear submarines, including 18 ballistic missile submarines, each carrying 20 missiles.
Currently, China has 60 more modern submarines, with additional ones under construction. The fleet includes six Type 094 nuclear-powered ballistic missile submarines (SSBNs), with two more planned. These 135-meter-long, 13-meter-wide vessels have a top speed of 54 kilometers per hour and a maximum operating depth of 400 meters. With a crew of 140, they can remain submerged for months, limited only by food and other supplies. Each Type 094 carries twelve solid-fuel JL-2 or JL-3 ballistic missiles.
Additionally, China operates six nuclear-powered attack submarines, similar to the American Virginia-class. Most Chinese submarines are still diesel-electric, with 48 currently in service. About half have been modified to include Air-Independent Propulsion (AIP), allowing them to remain underwater for weeks at a time.