Signs have emerged that China is building a dedicated surface mothership that can launch and recover a large unmanned underwater vehicle directly at sea. If fielded, it could become a platform that expands the operating range and long-duration maritime operating capability of large unmanned underwater vehicles.

On Sept. 19 (local time), IT outlet TechRadar reported that a hull with a different shape from existing Chinese naval ships was spotted at the dock of Hudong-Zhonghua Shipbuilding in Shanghai. The Chinese government has not officially confirmed the vessel’s existence or purpose.

Open-source intelligence (OSINT) experts who analysed the released photos raised the possibility that the ship is a mothership designed to operate a large unmanned underwater vehicle at sea.

A Japanese open-source analyst, Karotas (카로타스), released photos of the hull on Sept. 13. After naval specialist analyst H I Sutton analysed the photos, speculation about the ship’s purpose spread.

Karotas estimated the ship was placed in a dock about 340 metres long, and that the hull is likely about 200 metres long and 30 metres wide. He said the 340 metres refers to the size of the dock where the ship is being built, not the ship’s own length. In the same dock, another separate structure of unconfirmed purpose was also observed being assembled.

Defence outlet Defense Security Asia estimated on Sept. 15, based on satellite imagery, that the hull is about 205 metres long and about 27 metres wide. That is about 672 feet long. It is significantly larger than a typical support ship. The hull is estimated to be smaller than the Essex-class aircraft carriers operated by the U.S. Navy during World War Two, but larger than Independence-class light aircraft carriers.

A key focus is the ultra-large unmanned underwater vehicle that is expected to be carried on the ship. The outlet described it as an "ultra-large unmanned underwater vehicle", and the vehicles discussed in the 35-metre and 45-metre classes are close in size to small manned submarines.

Based on a similar large unmanned underwater vehicle concept previously unveiled by a Chinese shipbuilder, there is also speculation its range could reach about 10,000 nautical miles. That does not confirm the performance of the vehicle to be carried on the ship.

China’s large unmanned underwater vehicles are currently known to have been tested using specially built floating docks. That method is suitable for operating or testing the vehicles at ports, but is seen as having limitations for long-duration operations in distant seas.

In particular, towing an unmanned underwater vehicle as a separate vessel to an operating area can be affected by weather conditions and port infrastructure. If a large mothership carries the unmanned underwater vehicle, it becomes possible to launch it directly at sea and recover it after the mission ends.

Differences could also arise in maintenance and resupply. If the ship provides internal hangar space and maintenance facilities for unmanned underwater vehicles, it could serve as a mobile base supporting long-duration operations rather than simple transport.

For this reason, if the ship is confirmed as a mothership for unmanned underwater vehicles, it could also bring changes to how China operates maritime unmanned systems. If China can deploy and recover large unmanned underwater vehicles in distant seas beyond testing near ports, it could extend operating radius and time on station.

Still, it is difficult to conclude the ship’s exact mission or embarked systems based solely on the information confirmed so far. Chinese authorities have not officially confirmed the ship’s existence or purpose, and the main basis is external analysis based on released photos and satellite imagery.

In particular, the configuration of internal hangar facilities and the types of unmanned underwater vehicles that can actually be carried, propulsion systems and communication methods have not yet been confirmed. More photos or satellite imagery would need to be released during construction to determine its exact nature.

Even so, the roughly 200-metre-class large hull spotted at the Shanghai shipyard is drawing attention as a sign that China may be building a separate platform to operate large unmanned underwater vehicles at sea beyond testing them.