SSN-AUKUS Submarine Combat System Details
The SSN-AUKUS attack submarine program is characterized by a tightly integrated, trilateral combat system. This program, which will replace the Royal Navy's Astute-class, is a British-led design despite emphasis on Australian industrial outcomes. The UK's decisions establish the framework for its partners.
The Royal Navy requires a larger, quieter, and more capable hunter-killer submarine for operations in contested environments. Key capabilities beyond the Astute-class will likely include Vertical Launch System (VLS) cells for land-attack missiles and deep integration with uncrewed systems. Easier maintenance and through-life support are also critical requirements. The design prioritizes interoperability and proven systems.
Combat Management System Core
In March 2025, the UK accepted General Dynamics' AN/BYG-1 submarine combat control system as the core control element for SSN-AUKUS. This decision aligns the future Royal Navy submarine combat system with a US-led architecture. However, the freedom to integrate predominantly European sensors and weapons will be maintained. AN/BYG-1 is an open-architecture system currently used by the US Navy's SSNs and the Royal Australian Navy’s Collins-class SSKs.
For the Royal Navy's boats, BAE Systems, the submarine prime contractor, will serve as the combat system integrator. This approach mirrors the UK model seen in Astute and Dreadnought programs, where the shipbuilder holds design authority and integration responsibility. This differs from the US model, where Lockheed Martin integrates combat systems for all submarines.
UK Sovereignty and National Components
- The selection of AN/BYG-1 does not entail outsourcing UK combat system sovereignty. A modern submarine combat system consists of over 40 sub-systems, encompassing sonar, electronic warfare, communications, navigation, weapon control, and tactical decision aids. AN/BYG-1 functions as the core control layer, connecting these elements and enabling weapon employment, while the surrounding sensor and effector suite largely remains a national choice.
- For the Royal Navy, this includes continued reliance on high-end sonar technology from Thales, a long-standing partner for UK submarines. Thales transducers and processing chains are central to Astute-class performance and will be foundational for SSN-AUKUS. A Memorandum of Understanding on submarine sonar cooperation was signed by Thales UK and BAE Systems in September 2025. This preserves European industrial diversity within the system.
Program Milestones and Funding
A major program milestone, the Preliminary Design Review, is scheduled for later this year. Following this, BAE Systems will issue the majority of the combat system design sub-contracts, which will account for most non-nuclear development spending and define the SSN-AUKUS combat system baseline.
Much of SSN-AUKUS’ core design work was advanced under the UK’s SSN(R) program before the AUKUS pact was announced. The agreement internationalized a maturing British program, incorporating US and Australian requirements into an existing UK architecture. Combat system design work for the initial boats is funded by the UK under the Detailed Design and Long Lead Items phase. US-sourced components, including AN/BYG-1, will be procured through established government-to-government channels to avoid delays.
Support and Upgrade Considerations
Future support, upgrade, and testing arrangements are significant for the Royal Navy. Submarine combat systems undergo major refreshes on approximately six-year cycles in US service, driven by evolving threats and technology. Aligning SSN-AUKUS with this rhythm offers operational benefits but also links the Royal Navy to US-led development schedules.
The UK's integrator role, held by BAE Systems, is critical in this context. By retaining responsibility for integration and acceptance, BAE Systems preserves the Royal Navy’s ability to incorporate national requirements, manage divergence, and ensure compatibility with UK-specific weapons like the Spearfish heavyweight torpedo. This model also allows for UK-based testing and shore integration facilities to play a central role, reducing dependence on US laboratories and safeguarding national data.
Program Dynamics and Future Outlook
The combat system represents approximately 15% of the total value of a multi-billion-pound submarine, with through-life support and development potentially exceeding the capital outlay. Lessons learned from early integration challenges and delayed combat system maturity of the Astute-class are expected to benefit SSN-AUKUS, which will leverage a more stable supply chain and closer alignment with US systems. However, this also introduces constraints associated with trilateral cooperation.
From the Royal Navy's perspective, SSN-AUKUS will feature a proven US combat control core, integrated and managed by the UK, and augmented by a sensor and weapons suite reflecting national priorities. This approach aims to provide a potent, interoperable submarine force while maintaining control over sensitive combat systems.