Mechanical Design Engineer Jobs in California

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

Castelion is seeking a high-output Senior Mechanical Design Engineer with a full-stack, Responsible Engineer mindset and experience shipping flight hardware. This person will be responsible for critical flight structures and mechanism design and build efforts for Castelion's hypersonic vehicles. The Senior Mechanical Design Engineer will work closely with a fast-moving team of peers and engineering leadership to ensure mission-critical hardware is delivered on time and meets demanding technical performance. A successful candidate will have significant experience delivering high-performance, mass-constrained hardware in a rapid development environment.

Responsibilities

• • Design and Deliver Mission-Critical Hardware: Lead the design, build, and integration of key flight vehicle components such as composite tanks, separation mechanisms, actuators, and control surfaces. Own your systems from concept to flight. Apply fundamentals in statics, dynamics, and modal analysis to justify designs and prove them in test and flight.
  • Drive High-Cadence Design Iteration: Support iterative prototyping cycles every four weeks for key subsystems. Engage in cross-functional design reviews, integrate test feedback rapidly, and evolve hardware through fast-paced learning loops.
  • Build and Maintain Engineering Rigor: Contribute to the development of engineering best practices at Castelion, including CAD standards, documentation practices, and hardware management protocols. Write build documentation and collaborate hands-on with technicians during integration and assembly.

Basic Qualifications

• • Educational Background: Bachelors degree in Mechanical Engineering with 5+ years of professional ME experience.
  • Technical Skills: This role requires broad mechanical domain knowledge, including detailed CAD design of complex parts, tolerance stack up analysis, thermal analysis, structural analysis, and deign-to-cost.
  • Flight-Ready Hardware: Experience designing elegant, manufacturable components optimized for weight, cost, and simplicity; familiarity with coatings, finishes, and composite structures
  • Full-Cycle Development Ownership: Experience bringing hardware designs from initial concept to implementation, production, and successful operations. Ability to maximize speed and value from vendors for company goals during vendor visits or joint development efforts.

Preferred Skills and Experience

• • Bias to Action and Creative Problem Solving. Desire and experience questioning assumptions in ways that lead to break through ideas that are ultimately implemented. Successfully bring in applicable processes/concepts/materials from other industries to achieve efficiency gains. Ability to personally resolve minor issues in development without requiring significant support.
  • High Commitment, High Initiative. A successful candidate will have a genuine passion for Castelion's mission and consistently look for ways to contribute to the company's technical goals and prevent hardware blockers. Ability to work in a fast paced, autonomously driven, and demanding atmosphere. Strong sense of accountability and integrity.
  • Clear Communicator. Proactively communicates blockers. Trusted in previous roles to be voice of company with regulators, suppliers, gate keepers and customers. Capable of tactfully managing relationships with stakeholders to achieve company-desired outcomes without compromising relationships. Emails, IMs and verbal interactions are logical, drive clarity, and detailed enough to eliminate ambiguity.

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 access to classified information or restricted U.S. Government sites, systems, or information, as determined by the Company and/or applicable U.S. Government requirements. If the position is so designated, your employment in the role may be contingent upon your ability to obtain and maintain the required U.S. Government security clearance or other government authorization, and to satisfy any citizenship or other eligibility requirements imposed by applicable law, regulation, executive order, or government contract requirements. You will be notified if and when such requirements apply.

Affirmative Action/EEO Statement

Castelion is an Equal Opportunity Employer. We are committed to providing equal employment opportunities to all applicants and employees without regard to race, color, religion, sex, sexual orientation, gender identity, national origin, age, disability, genetic information, protected veteran status, or any other characteristic protected by applicable federal, state, or local law.

Castelion is committed to providing reasonable accommodations to qualified individuals with disabilities throughout the application and hiring process. If you require a reasonable accommodation to complete an application, participate in the interview process, or otherwise participate in the hiring process, please contact hr@castelion.com. Requests for accommodation will be considered on an individual basis and handled in accordance with applicable law.

Castelion is committed to fostering a workplace where employment decisions are based on qualifications, business needs, and the ability to perform the essential functions of the role, with or without reasonable accommodation.

EAR/ITAR Requirements

This position requires access to export-controlled information, and as such, employment (or hiring of a contractor) is contingent upon the candidate's ability to access all applicable export-controlled information without additional export licensing being required by the Bureau of Industry and Security and/or the Directorate of Defense Trade Controls.