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 (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

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.