Principal Mechanical Design Engineer

In this role, you will lead the design and development of complex mechanical fluid systems that support critical submarine platform functions. You will define system requirements, develop high-integrity engineering solutions, and ensure designs meet demanding performance, safety, and environmental standards. You will work closely with engineering and project teams to support modelling and analysis, technical reviews, and supplier engagement, while contributing to cost estimation, risk assessment, and the resolution of technical challenges across the programme lifecycle. Core duties:

• Lead the end-to-end design and development of complex fluid systems, ensuring alignment with operational, safety, and environmental requirements
• Produce and review engineering deliverables including schematics, P&IDs, calculations, system descriptions, and 3D models
• Perform advanced system analyses (flow, pressure, thermal, transient) to validate performance under demanding conditions
• Select and assess mechanical equipment (eg pumps, compressors, valves, heat exchangers), ensuring compliance with environmental and operational requirements
• Review supplier documentation and ensure integration with system requirements including maintainability and accessibility
• Contribute to technical reviews, hazard studies, and verification and validation activities
• Support resolution of technical issues, design changes, and non-conformances across the engineering lifecycle, This is an exciting opportunity to join the SSN-AUKUS Platform Mechanical Integrated Delivery Team as a Principal Mechanical Design Engineer, acting as a technical specialist for critical compressible and incompressible fluid systems essential to submarine operations. You will take ownership of high-integrity mechanical designs in one of the most demanding engineering environments, working across multidisciplinary teams to develop complex system solutions, influence platform-level decisions and ensure designs meet strict safety, performance and environmental standards. This role offers the chance to contribute directly to one of the UK's most advanced defence programmes. Relocation support may be available for submarine roles, subject to eligibility criteria.
  
  Strong mechanical engineering expertise in fluid systems, with knowledge of fluid dynamics, thermodynamics, and system modelling
• Experience leading the design and development of complex mechanical systems
• Ability to produce and review detailed engineering documentation (P&IDs, calculations, system descriptions, 3D models)
• Experience performing system analysis (flow, pressure, thermal, and transient behaviour)
• Knowledge of equipment selection and integration (eg pumps, valves, heat exchangers) within complex systems
• Experience in technical reviews, verification & validation, problem-solving, and working with suppliers; familiarity with tools such as FloMASTER, CFD, MATLAB or ANSYS desirable
  
  Join BAE Systems and you'll be part of something bigger. As a valued member of our global colleague network, you'll bring your unique skills and perspectives to help pioneer progress and protect what matters most. You'll be trusted to play your part in delivering advanced, technology-led defence, aerospace and security solutions, shaping a safer future for all of us.
From the depths of the ocean to the far reaches of space, there's no limit to where a career at BAE Systems could take you., Please be aware that many roles at BAE Systems are subject to security and export control restrictions. Applicants must meet Baseline Personnel Security Standard, and many roles require higher levels of National Security Vetting, including 5-10 years continuous UK residency depending on the role .