Senior Propulsion Engineer (Rocket Motor Soft Goods)

About the role

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.

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

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
• Ability to obtain and maintain a U.S. government–issued security clearance (U.S. citizenship required)

Benefits

• Meaningful long-term equity for all full-time employees
• Four (4) weeks of paid time off
• Ten (10) company-paid holidays
• Comprehensive health benefits – including 100% employee-covered medical and strong dependent coverage, plus dental and vision plans
• Paid parental leave
• $100 monthly fitness stipend
• Onsite EV charging
• Catered meals, company-covered food during high-demand periods, and a fully stocked kitchen