Senior Mechanical Design Engineer (RF Systems & Radomes)

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 (RF Systems & Radomes) We are seeking a Senior Mechanical Design Engineer to design and deliver RF-critical structures and packaging for Castelion's long-range hypersonic strike vehicles. This role is focused on radome development and RF subsystem integration, ensuring structural integrity and thermal survivability while preserving RF performance. You will work hands-on with multidisciplinary engineering teams to design, analyze, build, and validate radomes and RF packaging solutions in a fast-paced, hardware-driven environment. Responsibilities • Design and develop RF-transparent structures, including radomes, windows, and associated support structures for high-speed flight vehicles • Lead the architecture and detailed design of RF subsystem packaging, including mounting, alignment, and environmental protection of antennas, seekers, and electronics • Perform structural and thermal analyses to ensure performance and reliability under extreme aerothermal, pressure, and dynamic environments • Work closely with RF, avionics, materials, and thermal teams to ensure designs meet RF performance requirements (e.g., transmission, reflection, boresight error) while maintaining structural integrity • Develop and analyze interfaces between radomes, TPS, and primary structure, including sealing, attachment, and thermal isolation strategies • Conduct tolerance analysis and assess alignment sensitivity and deformation impacts on RF performance • Support prototyping, assembly, and hardware bring-up, including troubleshooting and root cause analysis of structural and RF performance issues • Define and execute qualification and environmental test plans, including thermal, vibration, and RF testing • Optimize designs for mass, thermal performance, RF transparency, and manufacturability • Mentor junior engineers and contribute to best practices in RF structure and packaging 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 mechanical design for aerospace or high-performance systems • Experience designing radomes, RF-transparent structures, or packaging for RF/antenna systems • Familiarity with RF performance considerations such as dielectric properties, insertion loss, and boresight error • Strong background in structural and thermal analysis for extreme environments • Proficiency in CAD and analysis tools (e.g., NX, SolidWorks, ANSYS, or equivalent) • Experience with tolerance stack-up, alignment, and precision assembly design • Familiarity with materials used in RF applications (e.g., ceramics, composites, low-loss dielectrics) and high-temperature environments • 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 hr@castelion.com. 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.