Hyliion KARNO Cores Selected for Sea Trials Aboard US Navy's USX-1 Defiant Unmanned Vessel

The US Navy's Office of Naval Research, in partnership with DARPA, has selected the USX-1 Defiant unmanned surface vessel as a candidate test platform for Hyliion's KARNO power generation technology, with initial sea trials funded under an ONR development programme to advance onboard power generation for US Navy vessels. Hyliion will deliver an 800 kW drop-in power system consisting of four 200 kW KARNO Cores in a keel-cooled configuration, designed to demonstrate reliable and low-maintenance power generation for unmanned maritime platforms where onboard servicing is not available.

 

Strategic Significance of the Programme

 

The selection of the USX-1 Defiant as the test platform for KARNO technology places Hyliion's modular power generation system at the centre of one of the US Navy's most strategically significant unmanned vessel programmes. The USX-1 Defiant was developed under DARPA's No Manning Required Ship programme, which challenged traditional naval architecture by designing a seaframe from the ground up with no provision, allowance, or expectation for human presence on board. The power generation system selected for such a platform must meet demanding requirements for reliability, low maintenance, acoustic performance, and scalability, all of which are central claims of the KARNO technology. Successful sea trials would provide a critical proof point for KARNO's applicability in unmanned naval contexts and open pathways to broader adoption across the US Navy's surface fleet modernisation programme.

 

USX-1 Defiant Platform Profile

 

The USX-1 Defiant measures approximately 180 feet in length with a displacement of around 240 metric tonnes and is designed for long-duration autonomous operation in the open ocean, either independently or alongside other naval assets. The vessel has been designed and developed by Serco North America as a full-scale technology demonstrator and is currently undergoing sea trials. The NOMARS programme philosophy behind the platform represents a fundamental departure from conventional naval design, in which crew requirements have historically shaped hull form, volume allocation, and system architecture. By removing all provision for human presence, the design enables simpler hull geometries, improved reliability through reduced mechanical and habitability systems, and increased flexibility in how payload and power systems are integrated.

 

KARNO Core Technology and Operating Principles

 

The KARNO Core is a heat-powered linear generator designed for high modularity, efficiency, and low-maintenance operation. For the US Navy deployment, the KARNO Cores will operate on F-76 marine diesel and demonstrate the ability to supply onboard power for extended durations with a low thermal and acoustic footprint. The system generates direct current power output at 800 Vdc, enabling direct integration with modern ship electrical architectures. The linear generator configuration and the low thermal and acoustic signature are particularly relevant for naval applications, where acoustic quieting is a critical performance parameter for surface and subsurface operations. The DC output architecture also aligns with the direction of travel in naval and commercial vessel power systems, where direct current distribution is becoming increasingly standard as electric propulsion and high-power sensor systems demand more flexible power management.

 

Modular Architecture and Redundancy

 

The 800 kW system will be delivered as four 200 kW KARNO Cores, a configuration that demonstrates the modular scalability of the technology and its inherent redundancy through distributed power generation. For unmanned vessels where onboard fault-finding and repair are not possible, the ability to distribute power generation across multiple independent units is a critical design requirement. If one core fails, the remaining units can continue to supply power, preventing total loss of ship capability. The modular architecture also supports future scalability, allowing operators to adjust power capacity by adding or removing cores without redesigning the power plant. These characteristics address some of the central reliability challenges that have limited the deployment of complex power systems on unmanned platforms.

 

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Land-Based Testing and Development Status

 

Hyliion's KARNO technology is currently undergoing land-based testing and development using simulated US Navy load profiles, providing a controlled environment in which to validate performance before the system transitions to sea trials. The use of realistic naval load profiles during land-based testing is important because shipboard power systems are subjected to demand patterns that differ significantly from stationary industrial generators, with rapid load transients, variable hotel loads, and mission-specific power demands that must all be managed within the specified voltage and frequency tolerances. Successful completion of land-based testing will provide the technical validation needed to proceed to sea trials with confidence in the system's ability to perform under representative operational conditions.

 

Broader Naval Autonomy Context

 

The KARNO sea trials programme sits within a broader US Navy and DARPA effort to modernise surface platforms for autonomous operation, enabling simpler hull designs, improved reliability and survivability, and increased flexibility in payload and power system integration. The development of reliable, low-maintenance power generation systems is one of the foundational enablers of long-duration unmanned naval operations, since the ability to sustain power output without human intervention determines both the endurance and the operational independence of autonomous platforms. As the US Navy continues to expand its investment in unmanned surface and undersea systems, the demand for power solutions with the characteristics demonstrated by KARNO, including modularity, acoustic quieting, and maintenance-free operation, is expected to grow across multiple platform classes.

 

Implications for Unmanned Maritime Power Systems

 

The selection of KARNO technology for ONR-funded sea trials on a DARPA programme vessel signals that linear generator-based power generation has reached a level of maturity warranting serious naval evaluation. Successful trials would validate the technology's potential across a range of unmanned maritime applications beyond the immediate USX-1 Defiant programme, including other unmanned surface vessels, undersea vehicles requiring air-independent power generation, and remote monitoring platforms that require long-duration, low-maintenance energy supply. For Hyliion, the naval programme provides both a rigorous operational testing environment and a commercially significant reference that could support adoption in civilian maritime applications where similar requirements exist.

 

Outlook for the Sea Trials Programme

 

The transition from land-based testing to sea trials on the USX-1 Defiant will provide the first operational validation of KARNO technology in a real maritime environment, exposing the system to the full range of dynamic conditions, vibration profiles, and thermal environments that distinguish sea-state operation from controlled testing. Successful performance across these conditions would demonstrate that the technology is ready for broader naval and commercial evaluation, while any issues identified during trials would provide valuable data for system refinement. The ONR and DARPA backing of the programme reflects institutional confidence in the technology's potential and provides the financial and operational framework needed to advance from development to demonstrated capability.