Mechanical Engineer

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. Mechanical Engineer Design, build, and test the mechanical components and assemblies that enable Castelion’s next-generation RF sensors. In this role, you will work at the intersection of mechanical, thermal, and electrical engineering to develop electro-mechanical solutions from initial concept through production. You will own the mechanical design of RF sensor circuit card assemblies (CCAs), develop test fixtures that enable rapid integration and validation, and work hands-on with cross-functional engineering teams to turn designs into reliable, production-ready hardware. Responsibilities • Own the mechanical design and development of RF sensor circuit card assemblies (CCAs), ensuring designs meet system-level requirements for fit, function, structural integrity, and thermal performance. • Design, develop, and release mechanical fixtures and tooling required for CCA integration, characterization, verification, and testing. • Create and maintain detailed engineering documentation, including CAD models, drawings, tolerances, material specifications, part numbers, and revision-controlled design records. • Collaborate closely with electrical, thermal, and systems engineers to develop integrated hardware solutions and resolve mechanical design and interface challenges. • Lead mechanical integration, testing, and design verification activities, using test results and integration feedback to drive rapid design iterations and improvements • Identify and resolve mechanical integration issues through hands-on troubleshooting, prototyping, experimentation, and root-cause analysis. • Optimize designs for manufacturability, reliability, and repeatability, accounting for fabrication methods, assembly processes, and production constraints. • Drive mechanical designs from initial concept through prototyping, integration, testing, and production release, taking ownership of technical execution and deliverables. • Continuously improve hardware designs based on test data, manufacturing feedback, and evolving system requirements. Basic Qualifications • Bachelor’s degree in Mechanical Engineering or a related engineering discipline. • 2+ years of professional mechanical engineering experience, preferably in aerospace, automotive, defense, or other hardware-focused industries. • Proficiency in 3D CAD design and mechanical drawing development using Siemens NX, SolidWorks, or similar tools. • Foundational understanding of statics, dynamics, thermal principles, materials, tolerances, and mechanical interfaces. • Experience developing mechanical components, assemblies, prototypes, or fixtures. • Strong attention to detail in engineering drawings, materials selection, part numbers, tolerances, and technical documentation. • Ownership mentality and a willingness to take responsibility, work hands-on with hardware, and learn through rapid iteration. • Ability to collaborate effectively across mechanical, electrical, thermal, and test engineering disciplines. Preferred Skills and Experience • Experience integrating, testing, and validating electro-mechanical subsystems within complex hardware systems. • Familiarity with PCB design concepts, electrical schematics, circuit card layouts, and mechanical enclosure integration. • Experience designing mechanical interfaces, enclosures, mounting solutions, and test fixtures for electronic assemblies. • Familiarity with RF sensors, radar, avionics, or communications systems in aerospace or defense environments. • Working knowledge of manufacturing processes, including machining, fabrication, assembly, and inspection. • Familiarity with engineering documentation, configuration management, and quality standards such as AS9100 or applica ble MIL-STD requirements. • Experience troubleshooting hardware integration issues and incorporating test findings into iterative design improvements. 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.