Senior Mechanisms Engineer

About the role

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

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
• Ability to obtain and maintain a U.S. government–issued security clearance (U.S. citizenship required)

Benefits

• Meaningful long-term equity
• Four (4) weeks of paid time off
• Ten (10) company-paid holidays
• Comprehensive health benefits - including 100% employee-covered medical and strong dependent coverage, along with dental and vision plans
• Paid parental leave
• $100 monthly fitness stipend
• Onsite EV charging
• Catered meals
• Company-covered food during high-demand periods
• Fully stocked kitchen