THE Defense Advanced Research Projects Agency (DARPA) and Serco have launched the Defiant, a prototype unmanned surface vessel that was designed from the ground up for fully uncrewed naval operations, reports Fort Lauderdale's Maritime Executive.

The ship has no provisions at all for human occupancy during operation, said DARPA.

The 180-foot, 240-tonne autonomous grey hull is in the water and will now undergo sea trials, beginning in the spring.

Its crewless design has specific advantages, according to DARPA: without making room and allowances for people, there is little in way of a deckhouse, and the vessel has a narrower beam.

This means less construction cost, less weight, better hydrodynamic efficiency, better stealth performance, and a better operating window in rough sea states, according to DARPA.

The prototype is the product of the agency's No Manning Required Ship (NOMARS) programme. DARPA has been running multiple tests to support the operating concept in parallel with construction, including at-sea refuelling for a Defiant-sized vessel.

The US Navy's USV Squadron 1 conducted the test in partnership with DARPA using two experimental unmanned vessels, the crew boat-based Ranger and Mariner.

The design objective is to produce an unmanned ship that has 90 per cent reliability at sea for a year at a time, with minimal human intervention.

Ryan Maatta, marine engineer manager at SERCO and deputy programme manager for DARPA's NOMARS programme, told Naval News that the design could drive "greatly reduced cost per mission hour."

"It's going to put more payload out on the ocean, more mission systems Out on the ocean for much cheaper than the navy does traditionally," he said.