Senior Mechanisms 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 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 Mechanisms Engineer** We are seeking a Senior Mechanisms Engineer to design and deliver high-performance mechanical actuation systems for Castelion's long-range hypersonic strike vehicles. This role is critical to enabling precise and reliable control surface motion and deployment mechanisms under extreme flight conditions. You will work hands-on with multidisciplinary engineering teams to design, analyze, build, and validate mechanisms such as elevon drive trains and related actuation systems in a fast-paced, hardware-driven environment. **Responsibilities** - Design and develop mechanical actuation systems, including elevon drive trains and control surface mechanisms, for high-speed flight vehicles - Lead the architecture and detailed design of mechanisms, including gear trains, linkages, bearings, and structural components - Perform analysis of loads, stresses, deflections, and dynamic behavior to ensure performance and reliability under extreme environments - Work closely with control electronics, GNC, avionics, and structures teams to ensure seamless integration of mechanisms with vehicle systems - Conduct tolerance analysis, lubrication strategy development, and life/reliability assessments for high-duty-cycle systems - Support prototyping, assembly, and hardware bring-up, including troubleshooting and root cause analysis of mechanism performance issues - Define and execute qualification and environmental test plans, including vibration, thermal, and shock testing - Optimize designs for mass, stiffness, reliability, and manufacturability - Mentor junior engineers and contribute to best practices in mechanism design and analysis - 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 mechanism design, analysis, and validation for aerospace or high-performance mechanical systems - Strong background in gear trains, actuation systems, and precision mechanical design - Experience designing electromechanical actuators (EMAs) for aerospace or similarly demanding applications - Familiarity with motor-driven actuation systems, including motor selection, gear reduction, torque transmission, and position feedback mechanisms - Experience designing control surface drive systems or similar high-load, high-reliability mechanisms - Proficiency in CAD and analysis tools (e.g., NX, SolidWorks, ANSYS, or equivalent) - Experience with structural analysis, fatigue/life assessment, and tolerance stack-up analysis - Familiarity with high-temperature materials, lubrication strategies, and operation in extreme 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 m…