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.

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.

• 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

• 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, Solid Works, 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

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.

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,…