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.

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.

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.

• 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

• 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, Solid Works, 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,…