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 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 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 Motors)
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
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
Other Duties

Nice-to-haves

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Platform: manatal
Effort: medium

Benefits

Benefits detected in the listing.

Dental

Vision

Paid Time Off

Parental Leave