Senior Propulsion Engineer (Rocket Motor Soft Goods)

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 Motor Soft Goods) We are seeking a Senior Propulsion Engineer to design and deliver rocket motor soft goods for Castelion's long-range hypersonic strike vehicles. This role is critical to ensuring reliable motor performance, structural integrity, and thermal protection through the design of liners, insulators, inhibitors, and related internal components. You will work hands-on with multidisciplinary engineering teams to design, analyze, build, and validate soft goods systems in a fast-paced, hardware-driven environment. Responsibilities • Design and develop rocket motor soft goods, including liners, insulators, inhibitors, and internal thermal protection systems • Lead the architecture and detailed design of soft goods systems to ensure compatibility with propellant, case materials, and motor operating conditions • Perform thermal, chemical, and structural analyses to ensure performance and durability under high-temperature, high-pressure environments • Develop and optimize material selections and formulations in collaboration with materials and manufacturing teams • Define and manage bonding strategies between propellant, liner, insulation, and motor case to ensure robust adhesion and prevent debonding • Work closely with propulsion, structures, and manufacturing teams to ensure seamless integration of soft goods with overall motor design • Support material processing, fabrication, and quality control of soft goods components • Plan and execute test campaigns, including subscale and full-scale motor testing, and analyze results to drive design improvements • Conduct failure analysis and root cause investigations related to insulation performance, erosion, cracking, or debonding • Mentor junior engineers and contribute to best practices in soft goods design and processing • 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, Materials Science, or related field • 5+ years of experience in rocket propulsion or high-temperature material systems, with focus on soft goods or internal motor components • Strong background in insulation materials, liners, and bonding systems used in solid rocket motors • Experience with thermal protection materials and behavior under high heat flux and pressure environments • Familiarity with propellant compatibility, adhesion, and chemical interactions with soft goods materials • Experience with material processing techniques for elastomers, ablatives, or composite insulation systems • Proficiency in analysis and modeling tools (e.g., MATLAB, ANSYS, or equivalent) • Experience with propulsion testing, data analysis, and failure investigation • 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.