Senior Propulsion Engineer (Rocket Motors)

About the role

Why Castelion, Why Now Castelion is moving incredibly fast to develop and deliver advanced defense systems at a time when execution matters more than ever. We believe focus and technical excellence are decisive advantages - and we are building a team that can deliver real capability, not just concepts. This is a rare opportunity to join at an early stage, where your work will directly shape critical systems, influence major technical decisions, and have immediate, real-world impact.

Senior Propulsion Engineer (Rocket Motors) We are seeking a Senior Propulsion Engineer to design, build, and test rocket motor systems for Castelion's long-range hypersonic strike vehicles. This role is critical to delivering reliable, high-performance propulsion across all mission phases. You will work hands-on with multidisciplinary engineering teams to develop solid rocket motors and associated hardware from concept through flight test in a fast-paced, hardware-driven environment.

Responsibilities

• Design and develop rocket motor systems, including grain geometry, case structures, insulation, and nozzle assemblies
• Lead the architecture and detailed design of propulsion hardware to meet performance, structural, and thermal requirements
• Perform internal ballistics, thermal, and structural analyses to ensure motor performance and reliability under extreme operating conditions
• Work closely with structures, thermal, GNC, and manufacturing teams to ensure seamless integration of propulsion systems with the vehicle
• Support propellant selection, processing, and characterization in collaboration with materials and manufacturing teams
• Plan and execute static fire tests and development test campaigns, including instrumentation, data collection, and post-test analysis
• Conduct failure analysis and root cause investigations, driving design improvements and risk reduction
• Define and execute qualification and flight test plans, translating results into system-level improvements
• Optimize designs for performance, mass, manufacturability, and operational reliability
• Mentor junior engineers and contribute to best practices in propulsion system design and testing
• Partner closely with program leadership to make technical trades aligned with mission success