Job description

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 (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 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. U.S. citizenship is required, as only U.S. citizens are eligible for a security clearance. 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.

Requirements

Must-haves

Why Castelion, Why Now
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 (Rocket Motor Soft Goods)
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
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
Other Duties

Nice-to-haves

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Platform: manatal
Effort: medium

Benefits

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Dental

Vision

Paid Time Off

Parental Leave