Test 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.

Development Test Engineer - Mechanisms

The Development Test Engineer owns the planning, execution, and analysis of tests that turn designs into flight-ready mechanisms. This role sits at the center of engineering, manufacturing, and operations—translating requirements into real-world validation through benchtop, environmental, subsystem, and vehicle-level testing. You will design test stands and write automation software to enable rapid testing to drive iterative design.

This is a hands-on role for engineers who thrive in fast-paced, ambiguity-heavy environments and believe the fastest way to learn is to test real hardware.

Responsibilities

• Translate system and subsystem requirements into test objectives, acceptance criteria, and verification methods
• Own development and acceptance testing for flight mechanisms for Castelion's hypersonic strike missiles
• Design and build complex test stands with integrated load actuators and instrumentation
• Develop automated test software for instrument control, test sequencing, data logging, and analysis; Python is preferred.
• Maintain rigorous configuration control, data management, and test documentation
• Improve test infrastructure, automation, and data quality to increase test cadence and learning velocity
• Support flight tests and rocket motor static fires as required

Basic Qualifications

• Bachelor's degree in Mechanical, Electrical, Aerospace, or related engineering field
• 2+ years of experience developing, integrating, or testing mechanical, electromechanical hardware
• Proficiency with test instrumentation and lab equipment (DAQs, oscilloscopes, power supplies, sensors)
• Knowledge of common sensors like load cells, pressure transducers, LVDTs, encoders
• Strong debugging, troubleshooting, and root-cause analysis skills
• Comfortable working across disciplines in high-ownership environments
• Willingness to support extended hours, weekends, travel, and on-site operations during critical test campaigns
• Comfortable working in fast-moving environments where hardware is the source of truth

Preferred Skills and Experience

• Aerospace, automotive, defense or other high-reliability hardware testing
• Environmental testing: vibration, thermal-vacuum, thermal cycling, shock
• Flight test, range operations, or hardware-in-the-loop (HIL) experience
• Familiarity with requirements verification, qualification evidence, and failure tracking
• Hands-on machining, wiring, soldering, or rapid prototyping experience

What We Value

• Hands-on rigor: deep understanding of systems through direct testing and failure analysis.
• Autonomy and ownership: you don't wait for direction you seek out what needs to be tested and make it happen.
• High standards for reliability, data quality, and test repeatability.
• Systems-level thinking: understanding how actuator behavior affects broader vehicle performance.

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.