Senior Structures & Composites Engineer; Rocket Motor Cases

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.

We are seeking a Senior Structures & Composites Engineer to design and deliver high-performance rocket motor cases for Castelion's long-range hypersonic strike vehicles. This role is critical to enabling lightweight, high-strength propulsion structures capable of withstanding extreme pressure and thermal environments. You will work hands‑on with multidisciplinary engineering teams to design, analyze, build, and validate composite and metallic motor case structures in a fast‑paced, hardware‑driven environment.

• Design and develop rocket motor case structures, including composite over wrapped pressure vessels (COPVs) and filament‑wound composite cases
• Lead the architecture and detailed design of motor cases, including load paths, interfaces, domes, bosses, and attachment features
• Perform structural analysis of pressure vessels under internal pressure, thermal loads, and dynamic environments to ensure performance and reliability
• Develop and analyze composite layups, fiber orientations, and manufacturing approaches to optimize strength, stiffness, and mass
• Work closely with propulsion, materials, manufacturing, and test teams to ensure seamless integration of motor cases with propulsion systems
• Support material selection, processing, and characterization for composite and high‑temperature materials
• Conduct failure analysis and root cause investigations, driving design improvements and risk reduction
• Define and execute qualification and environmental test plans, including pressure testing, proof/burst testing, and vibration testing
• Support prototyping, fabrication, and hardware bring‑up, including troubleshooting manufacturing and structural performance issues
• Optimize designs for mass efficiency, manufacturability, and operational reliability
• Mentor junior engineers and contribute to best practices in composite and pressure vessel design
• Partner closely with program leadership to make technical trades aligned with mission success

• Bachelor's, Master's, or PhD in Aerospace Engineering, Mechanical Engineering, or related field
• 5+ years of experience in structural and composite design for aerospace or high-performance pressure vessel applications
• Strong background in composite materials, including filament winding, laminate theory, and failure criteria (e.g., Tsai‑Wu, Hashin)
• Experience designing pressure vessels, COPVs, or rocket motor cases for high-pressure applications
• Proficiency in structural analysis tools (e.g., ANSYS, Abaqus, NASTRAN, or equivalent)
• Familiarity with manufacturing processes for composites, including winding, curing, and inspection methods (e.g., NDI/NDT)
• Experience with proof/burst testing and structural validation of pressure vessels
• Experience with hardware build, test, and troubleshooting in a lab or production environment
• Strong problem‑solving mindset, thriving in a fast‑paced, hardware-rich, high test cadence environment

Please note this job description is not designed to cover or contain a comprehensive listing of activities, duties or responsibilities that are required of the employee for this job. Duties, responsibilities and activities may change at any time with or without notice.

All full-time employees are granted meaningful long-term equity, sharing in the company's significant growth trajectory. We offer four weeks of paid time off, ten company‑paid holidays, and comprehensive health benefits - including 100% employee‑covered medical and strong dependent coverage, along with dental and vision plans. We also provide paid parental leave to support growing families, a $100 monthly…