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This week, the US military christened an experimental, autonomous warship that can operate for months at a time without a crew. The newly-named Sea Hunter was developed by research agency DARPA as part of its ACTUV program — a rather unwieldily acronym that stands for Anti-Submarine Warfare Continuous Trail Unmanned Vessel. The 132-foot vessel is powered by diesel engines and is designed to operate without even human remote control.

The unarmed ship was originally conceived as submarine-hunter, but military planners say it's emerged as a flexible platform that could fulfill many roles. "What we’ve kind of realized over the course of the program is that it’s a truck," ACTUV manager Scott Littlefield told IEEE Spectrum. "It’s got lots of payload capacity for a variety of different missions."

Sea Hunter being christened on Thursday. (Image credit: Deputy Secretary of Defense / Flickr)

Sea Hunter uses radar and an international ship-tracking program known as the Automatic Identification System (AIS) to find its bearings and dodge other vessels. One consideration in implementing the ship's autonomous functions was making its movements seem human-like. Any maneuvers it makes to avoid collisions have to be detectable by crew on other boats, so changes in direction (which are more easily spotted) are preferable to changes in speed that might be just as effective but are less obvious signals.

"You want it to be fairly autonomous so that it can do things like obstacle avoidance on its own without being joysticked around by a person," Littlefield told IEEE Spectrum.

"We're not working on anti-submarine [technology] just because we think it's cool."

The development of this prototype fits the US military's interested in uncrewed vehicles and drones, but also comes at a time when America's naval power is being challenged by China, especially in the South China Sea. Twenty years ago, US aircraft carriers were pretty much an unstoppable force on water, but China's navy has since invested heavily in modern submarines. Peter Singer, a security expert at the New America Foundation, told Reuters: "We're not working on anti-submarine [technology] just because we think it's cool. We're working on it because we're deeply concerned about the advancements that China and Russia are making in this space."

For the Sea Hunter, the next step is two years of testing of the vessel's autonomous abilities. After this, it could be moved to the US Navy's Seventh Fleet in Japan for its first trials. Deputy US defense secretary Robert Work told Reuters: "I would like to see unmanned flotillas operating in the western Pacific and the Persian Gulf within five years." Work also raised the prospect of someday arming vessels like Sea Hunter, but stressed that if this happened, the decision to use lethal force would always be made by humans.

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