USX-1 Defiant USV chosen as platform for KARNO power-gen sea trial
NewsMay 19, 2026
AUSTIN, Tex. Hyliion Holdings, which develops modular power plant technology, announced that the U.S. Navy’s Office of Naval Research (ONR) and the Defense Advanced Research Projects Agency (DARPA) have chosen the USX-1 Defiant -- a fully autonomous medium uncrewed surface vessel (USV) -- as a candidate test vessel for Hyliion’s KARNO onboard power-generation technology.
For the USX-1 Defiant sea trials, Hyliion reports that it will deliver a drop-in 800 kW power system consisting of four 200 kW KARNO power-generation cores in a keel-cooled configuration. The modular architecture is designed, say Hyliion officials, to demonstrate reliable, low-maintenance power generation for an uncrewed vessel, where onboard servicing is not available.
The USX-1 Defiant was developed under DARPA’s No Manning Required Ship (NOMARS) program, which aimed to design a seaframe -- a ship without mission systems -- from the ground up with no provision, allowance, or expectation for humans on board as part of a wider Navy effort to modernize the sea service and optimize surface platforms for autonomous operation by way of simpler hull designs, improved reliability and survivability, and increased flexibility in payload and power system integration.
USX-1 Defiant -- designed and developed by Serco-North America as a full-scale technology demonstrator for long-duration autonomous operation in the open ocean, independently, or alongside other naval assets -- measures about 180 feet in length and has a displacement of about 240 metric tons.
Initial sea trials with the Hyliion KARNO onboard power-generation technology are scheduled for 2027 under a development program funded by ONR.
