Castelion was founded to restore America’s ability to field advanced weapons at speed and scale. Inspired by the engineering urgency of the WWII and Apollo eras, we combine rapid iteration, vertical integration, and scalable manufacturing to deliver affordable, high-performance strike systems. Our mission: rebuild industrial agility to strengthen national security and outpace evolving threats. About the Role: 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. Requirements 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 Benefits Employee Equity: Meaningful equity for all full-time employees - share value has increased 150x in three years Personal Time Off: Four (4) weeks of paid time off to unplug, reset, and come back sharp—velocity matters, burnout doesn't Company Paid Holidays: Ten (10) company paid holidays Medical: We offer plans at 100% employee covered and 80% of dependent coverage Dental & Vision: We cover 90% employees and 80% for dependents to ensure you and your family have access to quality preventive and ongoing care FSA/HSA: To support long-term health and financial resilience, we offer FSA and HSA options that allow employees to set aside pre-tax dollars for eligible medical and dependent care expenses Retirement: 401k plan offered to support long term financial growth along side high-impact, high-velocity work Paid Parental Leave: We support growing families with meaningful time to bond and recover. Birthing parents are eligible for up to 10 weeks of paid leave, while non-birthing parents may take up to 4 weeks of paid leave. This time can be used for pre-natal care, pregnancy, childbirth, and related medical needs—ensuring every parent has the support they need during this important life moment.8-weeks of paid parental leave for all parents. Additional paid pregnancy leave for CA employees Meals & Catering: Frequently catered lunches and team meals, plus company-covered meals when extra time or effort is required Snacks & Beverages: Fully stocked kitchen with unlimited snacks and drinks to keep you fueled throughout the day Performance & Fitness: $100 monthly fitness stipend to support peak performance and health, both inside and outside of work EV Charging: Onsite electric vehicle charging available for employees