Senior Mechanical Design Engineer (Structures & Thermal Protection Integration)

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, ownership, and excellence are decisive advantages - and we're building a world-class team to turn bold ideas into real capability.

This is a rare opportunity to join at an early stage, where you'll have significant ownership, collaborate with exceptional teammates, and make a direct, measurable impact on our mission and the future of the company - regardless of your function.

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

Castelion offers a generous benefits package. Please refer to the bottom of our Careers page for more details.

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.

Additional Eligibility Requirements

This position may require access to classified information or restricted U.S. Government sites, systems, or information, as determined by the Company and/or applicable U.S. Government requirements. If the position is so designated, your employment in the role may be contingent upon your ability to obtain and maintain the required U.S. Government security clearance or other government authorization, and to satisfy any citizenship or other eligibility requirements imposed by applicable law, regulation, executive order, or government contract requirements. You will be notified if and when such requirements apply.

Affirmative Action/EEO Statement

Castelion is an Equal Opportunity Employer. We are committed to providing equal employment opportunities to all applicants and employees without regard to race, color, religion, sex, sexual orientation, gender identity, national origin, age, disability, genetic information, protected veteran status, or any other characteristic protected by applicable federal, state, or local law.

Castelion is committed to providing reasonable accommodations to qualified individuals with disabilities throughout the application and hiring process. If you require a reasonable accommodation to complete an application, participate in the interview process, or otherwise participate in the hiring process, please contact View email address on aiapply.co. Requests for accommodation will be considered on an individual basis and handled in accordance with applicable law.

Castelion is committed to fostering a workplace where employment decisions are based on qualifications, business needs, and the ability to perform the essential functions of the role, with or without reasonable accommodation.

EAR/ITAR Requirements

This position requires access to export-controlled information, and as such, employment (or hiring of a contractor) is contingent upon the candidate’s ability to access all applicable export-controlled information without additional export licensing being required by the Bureau of Industry and Security and/or the Directorate of Defense Trade Controls.