Senior Mechanical Design Engineer; ACS Systems) Torrance, CA; Rio Rancho, NM Leviathan Engineering

• Long Range Strike Systems

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.

Senior Mechanical Design Engineer (ACS Systems)

We are seeking a Senior Mechanical Design Engineer to design and deliver attitude control system (ACS) hardware for Castelion's long-range hypersonic strike vehicles. This role is critical to enabling reliable propellant storage, flow control, and thrust generation for precise vehicle control. You will work hands‑on with multidisciplinary engineering teams to design, analyze, build, and validate ACS tanks, valves, thrusters, and integrated assemblies in a fast‑paced, hardware‑driven environment.

Responsibilities

• Design and develop ACS hardware, including propellant tanks, valves, thrusters, and associated fluid system assemblies
• Lead the architecture and detailed design of pressure vessels, fluid lines, mounts, and integrated ACS packaging within the vehicle
• Perform structural, thermal, and fluid analyses to ensure performance and reliability under extreme pressure, temperature, and dynamic environments
• Work closely with propulsion, GNC, avionics, and structures teams to ensure seamless integration of ACS systems with vehicle architecture
• Conduct tolerance analysis, sealing strategy development, and leak‑tightness assessments for high‑pressure systems
• Support prototyping, assembly, and hardware bring‑up, including troubleshooting and root cause analysis of system performance issues
• Define and execute qualification and environmental test plans, including pressure, vibration, thermal, and shock testing
• Optimize designs for mass, reliability, manufacturability, and ease of integration
• Mentor junior engineers and contribute to best practices in mechanical and fluid system design
• 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 mechanical design for aerospace or high-performance fluid/propulsion systems
• Strong background in pressure vessel design, fluid systems, and high-pressure component integration
• Experience designing tanks, valves, thrusters, or similar propulsion or ACS hardware
• Familiarity with sealing methods, leak detection, and cleanliness requirements for high‑reliability fluid systems
• Proficiency in CAD and analysis tools (e.g., NX, Solid Works, ANSYS, or equivalent)
• Experience with structural analysis, thermal analysis, and tolerance stack‑up analysis
• Familiarity with high-temperature materials 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

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…