About the job Senior Propulsion Engineer 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 The Senior Propulsion Engineer plays a critical role at Castelion, owning the design of solid rocket motor primary and secondary structures as well as key propulsion components. This position is central to our ability to deliver at speed and scale, with a strong emphasis on driving technically sound designs that meet aggressive schedule, affordability, and production goals. Responsibilities Translate project objectives into cost-effective designs that can be produced at scale - the Castelion way. Spearhead the creation of innovative solid rocket motor designs, demonstrating autonomy even with limited expert guidance. Actively engage in the assembly, testing, and troubleshooting of prototypes and production builds, providing expert guidance as necessary. Use our rapid iteration cycles to validate product performance and facilitate necessary design adjustments. Produce, evaluate, and authorize CAD models and drawings, adhering to internal standards and

ASME Y14.5-2009

guidelines. Provide thorough assessments and resolutions for any discrepancies in hardware, including supporting analyses when required. Collaborate with supply chain to ensure seamless support and adapt designs to mitigate availability risks and time delays. Basic Qualifications Bachelor's or advanced degree in aerospace engineering, manufacturing engineering, materials engineering, mechanical engineering or physics. 5+ years of mechanical or fluids design, analysis, or build experience (student project team, university rocketry club and internship experience counts). Effective communication skills are crucial for collaborating with cross-functional teams, presenting design concepts, and documenting work. Preferred Skills and Experience Proficient in test methods/setups, with the ability to conduct trade studies using engineering fundamentals to make informed recommendations, even with limited information. Extensive experience working with aerospace materials (including metals, plastics, and composites) and a solid understanding of spacecraft and/or launch vehicle propulsion systems and fluid components. Skilled in CAD software (NX 8.5 or similar packages like PTC Creo, CATIA) with expertise in geometric dimensioning and tolerancing (GD&T) per

ASME Y14.5-1994.

Relevant experience with rocket motors, solid propulsion elements, and structural interfaces, including knowledge of insensitive munitions protocols and practices. Hold a Master's degree or PhD in a technical discipline such as mechanical or aerospace engineering. Hands-on experience supporting rapid product development, including designing hardware for high-rate production in alternative non-aerospace domains. Currently hold an active DoD Secret Security Clearance or higher. Additional Requirements Willing and able to work extended hours and/or weekends with minimal notification to meet critical deadlines leading up to major milestones. Able to travel up to 30% on an ongoing basis 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. Benefits And Perks All full-time employees are granted meaningful long-term equity, sharing in the company's significant growth trajectory. We offer four (4) weeks of paid time off, ten (10) 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 fitness stipend to promote health and performance, and onsite EV charging for convenience. In addition, employees enjoy perks like catered meals, company-covered food during high-demand periods, and a fully stocked kitchen to stay fueled throughout the day. While this position does not currently require a U.S government-issued security clearance, it may in the near future. Therefore, the ability to obtain and maintain a U.S. government-issued security clearance is required. Affirmative Action/EEO Statement Employment with Castelion is governed on the basis of competence and qualifications and will not be influenced in any manner by race, color, religion, gender, national origin/ethnicity, veteran status, disability status, age, sexual orientation, gender identity, marital status, mental or physical disability or any other legally protected status.