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 Mechanical Design Engineer (Structures & Thermal Protection Integration)

We are seeking a Senior Mechanical Design Engineer to design and deliver critical flight vehicle structures for Castelion's long-range hypersonic strike vehicles. This role is focused on structural systems that interface with and enable the thermal protection system (TPS), including separating nose tip architectures and other high-temperature structural components. You will work hands-on with multidisciplinary engineering teams to design, analyze, build, and validate flight-critical structures in a fast-paced, hardware-driven environment.

Responsibilities

• Design and develop flight vehicle structures, including separating nose tip systems and other components critical to thermal protection system (TPS) performance
• Lead the architecture and detailed design of high-temperature structural assemblies, including joints, interfaces, and load paths across TPS and primary structure
• Perform structural and thermal analyses to ensure performance and reliability under extreme aerothermal, pressure, and dynamic environments
• Work closely with materials, TPS, aerothermal, GNC, and manufacturing teams to ensure seamless integration of structures with vehicle systems
• Develop and analyze separation mechanisms and interfaces, ensuring reliable and repeatable operation under flight conditions
• Conduct tolerance analysis and assess thermal expansion, material compatibility, and interface behavior at elevated temperatures
• Support prototyping, assembly, and hardware bring-up, including troubleshooting and root cause analysis of structural and interface performance issues
• Define and execute qualification and environmental test plans, including thermal, vibration, and shock testing
• Optimize designs for mass, thermal performance, structural integrity, and manufacturability
• Mentor junior engineers and contribute to best practices in high-temperature structural design
• Partner closely with program leadership to make technical trades aligned with mission success

Basic Qualifications

• Bachelor's, Master's, or PhD in Mechanical Engineering or related field
• 5+ years of experience in structural design and analysis for aerospace or high-performance systems
• Strong background in high-temperature structures and materials, particularly in TPS-adjacent or aerothermal environments
• Experience designing separation systems, joints, and structural interfaces for flight hardware
• Proficiency in CAD and analysis tools (e.g., NX, SolidWorks, ANSYS, or equivalent)
• Experience with structural and thermal analysis, including thermal-structural coupling and tolerance stack-up
• Familiarity with materials used in high-temperature environments (e.g., ceramics, carbon-carbon, refractory metals, or similar)
• Experience with hardware build, test, and troubleshooting in a lab or flight hardware environment
• Strong problem-solving mindset, thriving in a fast-paced, hardware-rich, high flight 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.