About Castelion

Castelion is bringing a new approach to defense development and production: one that focuses on short, iterative design cycles, rapid testing in development, and modern commercial manufacturing strategies for production at scale. We're designing, building, and testing next generation long range strike weapons systems to give America and its Allies a definitive edge and deter future conflicts.

Principal Hardware Test Engineer

We are seeking a Principal Hardware Test Engineer to lead the planning, execution, and analysis of hardware test campaigns across Castelion's missile and vehicle systems. You will own test strategy and execution for major hardware programs, ensuring that system performance is verified through rigorous and repeatable test processes. This role is highly hands-on and collaborative, working closely with propulsion, GNC, electrical, and mechanical engineering teams to translate design intent into validated performance in the field.

Responsibilities

• Lead end-to-end test campaigns for missile and subsystem hardware, from planning and instrumentation through execution and data analysis
• Define and implement test methodologies, metrics, and validation frameworks to ensure technical and programmatic success
• Develop and review detailed test plans, procedures, and acceptance criteria for hardware validation
• Lead root cause investigations and failure analysis efforts, coordinating across disciplines to identify corrective actions
• Direct test infrastructure development, including instrumentation, data acquisition, and telemetry systems
• Provide real-time technical leadership during dynamic test events, troubleshooting anomalies and guiding on-the-fly adjustments
• Drive data analysis and visualization efforts to extract insights and inform design optimization
• Mentor and guide test engineers in execution, technical rigor, and safety discipline
• Communicate findings and recommendations clearly to technical leadership, program management, and external stakeholders

Basic Qualifications

• Bachelors or Masters degree in Mechanical, Electrical, Aerospace, or Systems Engineering, or a related field
• 8+ years of experience in hardware or development testing within aerospace, defense, or other high-performance environments
• Proven experience leading large-scale test campaigns for integrated systems or subsystems
• Deep technical understanding of test instrumentation, data acquisition, and telemetry systems
• Strong data analysis and scripting capability (Python, MATLAB, etc.)
• Demonstrated ability to diagnose complex system-level issues through test data and field observation
• Experience with rapid prototyping and iterative development test cycles

All employees are granted long-term stock incentives as part of their employment at Castelion. All employees receive access to comprehensive medical, vision, and dental insurance, and the company offers four weeks of paid time off per year.

Leadership Qualities

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.

ITAR Requirements:

• To conform to U.S. Government export regulations, applicant must be a (i) U.S. citizen or national, (ii) U.S. lawful, permanent resident (aka green card holder), (iii) Refugee under 8 U.S.C. § 1157, or (iv) Asylee under 8 U.S.C. § 1158, or be eligible to obtain the required authorizations from the U.S. Department of State.

Employment 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.