Senior Propulsion Engineer (Rocket Motors)

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, ownership, and excellence are decisive advantages - and we're building a world-class team to turn bold ideas into real capability. This is a rare opportunity to join at an early stage, where you'll have significant ownership, collaborate with exceptional teammates, and make a direct, measurable impact on our mission and the future of the company - regardless of your function. 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 Basic Qualifications • Bachelor's, Master's, or PhD in Aerospace Engineering, Mechanical Engineering, or related field • 5+ years of experience in rocket propulsion design, analysis, and testing for aerospace or defense applications • Strong background in solid rocket motor design, including internal ballistics, grain design, and nozzle performance • Experience with propulsion testing, including static fire test setup, instrumentation, and data analysis • Familiarity with structural and thermal design considerations for high-temperature, high-pressure systems • Proficiency in analysis and modeling tools (e.g., MATLAB, ANSYS, or equivalent) • Experience with hardware build, integration, and troubleshooting in a lab or test environment • Strong problem-solving mindset, thriving in a fast-paced, hardware-rich, high test cadence environment Castelion offers a generous benefits package. Please refer to the bottom of our Careers page for more details. Other Duties 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. Additional Eligibility Requirements This position may require access to classified information or restricted U.S. Government sites, systems, or information, as determined by the Company and/or applicable U.S. Government requirements. If the position is so designated, your employment in the role may be contingent upon your ability to obtain and maintain the required U.S. Government security clearance or other government authorization, and to satisfy any citizenship or other eligibility requirements imposed by applicable law, regulation, executive order, or government contract requirements. You will be notified if and when such requirements apply. Affirmative Action/EEO Statement Castelion is an Equal Opportunity Employer. We are committed to providing equal employment opportunities to all applicants and employees without regard to race, color, religion, sex, sexual orientation, gender identity, national origin, age, disability, genetic information, protected veteran status, or any other characteristic protected by applicable federal, state, or local law. Castelion is committed to providing reasonable accommodations to qualified individuals with disabilities throughout the application and hiring process. If you require a reasonable accommodation to complete an application, participate in the interview process, or otherwise participate in the hiring process, please contact hr@castelion.com. Requests for accommodation will be considered on an individual basis and handled in accordance with applicable law. Castelion is committed to fostering a workplace where employment decisions are based on qualifications, business needs, and the ability to perform the essential functions of the role, with or without reasonable accommodation. EAR/ITAR Requirements This position requires access to export-controlled information, and as such, employment (or hiring of a contractor) is contingent upon the candidate’s ability to access all applicable export-controlled information without additional export licensing being required by the Bureau of Industry and Security and/or the Directorate of Defense Trade Controls.