Senior Mechanical Design Engineer (ACS Systems)

Senior Mechanical Design Engineer (ACS Systems)Rio Rancho, New Mexico, United StatesWhy Castelion, Why NowCastelion 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 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.ResponsibilitiesDesign and develop ACS hardware, including propellant tanks, valves, thrusters, and associated fluid system assembliesLead the architecture and detailed design of pressure vessels, fluid lines, mounts, and integrated ACS packaging within the vehiclePerform structural, thermal, and fluid analyses to ensure performance and reliability under extreme pressure, temperature, and dynamic environmentsWork closely with propulsion, GNC, avionics, and structures teams to ensure seamless integration of ACS systems with vehicle architectureConduct tolerance analysis, sealing strategy development, and leak-tightness assessments for high-pressure systemsSupport prototyping, assembly, and hardware bring-up, including troubleshooting and root cause analysis of system performance issuesDefine and execute qualification and environmental test plans, including pressure, vibration, thermal, and shock testingOptimize designs for mass, reliability, manufacturability, and ease of integrationMentor junior engineers and contribute to best practices in mechanical and fluid system designPartner closely with program leadership to make technical trades aligned with mission successBasic QualificationsBachelor's, Master's, or PhD in Mechanical Engineering or related field5+ years of experience in mechanical design for aerospace or high-performance fluid/propulsion systemsStrong background in pressure vessel design, fluid systems, and high-pressure component integrationExperience designing tanks, valves, thrusters, or similar propulsion or ACS hardwareFamiliarity with sealing methods, leak detection, and cleanliness requirements for high-reliability fluid systemsProficiency in CAD and analysis tools (e.g., NX, SolidWorks, ANSYS, or equivalent)Experience with structural analysis, thermal analysis, and tolerance stack-up analysisFamiliarity with high-temperature materials and operation in extreme environmentsExperience with hardware build, test, and troubleshooting in a lab or flight hardware environmentStrong problem-solving mindset, thriving in a fast-paced, hardware-rich, high flight cadence environmentOther DutiesPlease 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 PerksAll 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, employees enjoy perks like catered meals, company-covered food during high-demand periods, and a fully stocked kitchen to stay fueled throughout the day.While this position does not currently require a U.S government-issued security clearance, it may in the near future.

Therefore, the ability to obtain and maintain a U.S. government–issued security clearance is required. U.S. citizenship is required, as only U.S.

citizens are eligible for a security clearance.Affirmative Action/EEO StatementEmployment with Castelion is governed on the basis of competence and qualifications and will not be influenced in any manner by race, color, religion, gender, national origin/ethnicity, veteran status, disability status, age, sexual orientation, gender identity, marital status, mental or physical disability or any other legally protected status.