China’s Secretive 670-Foot Vessel Signals New Era in Undersea Drone Warfare

Satellite images captured in early September revealed an unusual hull taking shape at the Hudong-Zhonghua shipyard in Shanghai. Roughly 205 meters long and 27 meters wide, the vessel bears a passing resemblance to an amphibious transport dock. Yet its internal arrangements tell a different story.

Analysts who examined the commercial imagery concluded it is likely the world’s first dedicated mothership built to carry, launch, recover and maintain giant uncrewed submarines. The assessment comes from open-source naval expert H.I. Sutton, who wrote in Naval News that “by far the most plausible explanation is that it is a special drone submarine mothership.”

China has already tested two distinct extra-extra-large uncrewed underwater vehicles, known as XXLUUVs, near Hainan island. One measures about 35 meters. The other stretches to 45 meters, or roughly 148 feet. Those dimensions dwarf the U.S. Navy’s Boeing Orca XLUUV, which comes in at approximately 26 meters overall. The Chinese designs appear six to eight times larger by volume.

Until now the XXLUUVs depended on specialized floating docks for launch and recovery. Those docks limited operations to areas close to home. A dedicated surface mothership changes the equation. It could ferry the drones across vast distances, keep them sheltered in an internal hangar, perform maintenance at sea and deploy them from open ocean without reliance on shore infrastructure.

The new vessel features a stern well deck measuring around 55 by 13 meters. Unlike conventional well decks on amphibious ships, this one appears open at the bottom. A large cradle supported by 12 vertical jack-up arms can be lowered beneath the hull. The arrangement allows the cradle to submerge, position itself under an XXLUUV and lift the vehicle directly from the water. Recovery works in reverse.

Forward of that well deck sits a large enclosed hangar. Based on the known sizes of the Chinese underwater vehicles, the space could accommodate up to four of the largest models. Or it might hold a greater number of smaller uncrewed systems. Either way the design points to sustained operations far from Chinese ports.

But the vessel itself is not the full picture. It forms one element in a broader, largely undeclared Chinese push into large-scale autonomous undersea systems. Beijing has not commented publicly on the Shanghai construction or the XXLUUV program. That silence leaves analysts to draw conclusions from imagery alone.

South China Morning Post reporters reviewed the same satellite photos taken around September 10. An experienced military imagery analyst, speaking on condition of anonymity, confirmed the presence of a lifting frame or cradle positioned behind the hull in dry dock. That cradle appeared narrow enough to pass through the stern opening. The analyst noted the area inside the opening might lack a floor, allowing the entire assembly to lower vehicles into the sea or hoist them back aboard.

“An unusual vessel taking shape at a Shanghai shipyard has been assessed as a possible mothership for China’s large uncrewed submarines – a capability that, if confirmed, could enable Beijing to operate the drones far from its own coast for sustained periods,” the South China Morning Post reported on September 18.

The timing matters. China has poured resources into unmanned systems across air, surface and subsurface domains. Its progress with extra-large underwater vehicles sets it apart. No other nation has fielded uncrewed submarines approaching these dimensions in operational testing.

American efforts remain more modest. The Orca XLUUV program focuses on vehicles that can carry payloads over long ranges but at a fraction of the Chinese scale. U.S. concepts emphasize modularity and integration with manned forces rather than standalone giant drones. Britain’s XV Excalibur, by comparison, measures only about 12 meters.

Potential missions for the Chinese XXLUUVs extend across the spectrum of naval warfare. Persistent surveillance in contested waters. Mine laying in chokepoints. Seabed mapping and cable monitoring. Even strike capabilities if armed. A mothership multiplies those options by freeing the drones from coastal constraints.

Imagine a task group centered on this vessel operating hundreds of miles from the nearest Chinese base. The mothership remains relatively safe in blue water while its submerged charges probe closer to adversary coastlines. Maintenance crews service the drones between sorties inside the protected hangar. The cradle system permits launch and recovery in moderate sea states without heavy cranes.

Steerable azimuth thruster pods visible in the imagery suggest the ship prioritizes precise low-speed maneuvering. Exactly what operators need when aligning the cradle with a bobbing 45-meter drone. Speed and endurance figures remain unknown, yet the overall size hints at blue-water capability.

Construction at Hudong-Zhonghua fits a pattern. The yard previously built large amphibious assault ships. Its workforce knows how to handle big hulls with complex internal volumes. Yet the unconventional stern arrangement sets this project apart from standard naval production.

Some observers initially speculated the vessel might serve research or civilian purposes. The scale of the hangar and the specialized launch system make those explanations unlikely. “The size and presence of the internal hangar make a civilian or research explanation unconvincing,” Sutton noted in his Naval News analysis.

Recent reporting adds weight to the military interpretation. Defense Security Asia highlighted on September 16 that the configuration could expand Beijing’s undersea surveillance, mine warfare and seabed operations across the Indo-Pacific. The outlet drew directly from the same satellite evidence and Sutton’s assessment.

Similar conclusions appeared across outlets in mid-September. Interesting Engineering, The Independent and others cited the 205-meter length, the 12-arm cradle and the hangar capacity for four large drones. None found official Chinese confirmation. All pointed to the same logical conclusion.

This development arrives as tensions simmer across the Western Pacific. China’s military modernization continues at pace, with new ships, aircraft and unmanned platforms entering service each year. The XXLUUV mothership, should it enter PLAN service, would represent another asymmetric tool designed to complicate adversary planning.

For the U.S. Navy and its partners the implications stretch beyond a single ship. They touch on the future balance of undersea power. Large autonomous vehicles could loiter undetected for weeks, gathering intelligence or laying sensors. A mobile tender allows those vehicles to reposition quickly across theater without revealing their land-based support network.

Questions remain. How autonomous are the Chinese XXLUUVs in practice? What sensors and weapons might they carry? How vulnerable is the surface mothership to detection and attack once it begins operating with its charges? Beijing offers no answers yet.

Still the imagery from Shanghai paints a clear direction. China is moving beyond experimentation with giant underwater drones. It is investing in the logistics and support architecture needed to turn those drones into a deployable capability. The vessel under construction may not look like a traditional aircraft carrier. Its cargo, however, could prove just as disruptive to established naval thinking.

And the pace shows no sign of slowing. Additional satellite passes will reveal more as construction advances. Further testing of the XXLUUVs off Hainan will provide clues about performance. Eventually the mothership will likely leave the yard for sea trials of its own unique launch and recovery systems.

When that day comes, a new chapter in underwater warfare will have begun. One written not with crewed submarines but with their uncrewed, larger-than-life successors and the surface vessels built to sustain them.