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
3+ 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.