Senior Development Test Engineer

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.

Senior Development Test Engineer

We are seeking a Senior Development Test Engineer to drive testing and validation of missile and vehicle systems in a fast-paced, hardware-rich environment. You will be responsible for designing and executing tests, analyzing results, and providing actionable insights that directly inform design and performance optimization. This is a hands-on role that requires technical depth, resourcefulness, and strong cross-team collaboration.

Responsibilities

• Develop test plans and analyze data from testing equipment to validate system performance
• Use advanced analytics tools to process and interpret test results, providing actionable insights for optimization
• Develop and deploy custom software or scripts to enhance testing efficiency and performance evaluation
• Provide real-time support during testing, including tuning and setup adjustments based on telemetry and other feedback mechanisms
• Troubleshoot performance issues and recommend solutions during testing campaigns
• Identify and implement process improvements to enhance test execution and development efficiency
• Clearly communicate technical data, findings, and recommendations to team members across all levels of the organization

Basic Qualifications

• Bachelors or Masters degree in Aerospace Engineering, Mechanical Engineering, Electrical Engineering, Computer Science, or related field
• 5+ years of experience in test engineering or development testing of aerospace, defense, or high-performance hardware systems
• Strong background in data analysis, including the use of tools such as Python, MATLAB, or similar
• Hands-on experience developing test procedures, troubleshooting hardware/software integration issues, and working with telemetry systems
• Ability to write custom scripts or software to automate testing and improve performance evaluation
• Experience working in high-pressure, hardware-driven test environments
• Strong communication skills, with the ability to clearly present complex findings to technical and non-technical stakeholders

Why Castelion

• Opportunity to test and validate cutting-edge missile systems that shape the future of deterrence
• Work alongside a team of A+ players who believe in the mission and want to make a difference
• Be part of a rapidly growing startup where your impact is direct and visible
• Competitive compensation, equity, and benefits package

All employees are granted long-term stock incentives as part of their employment as Castelion. All employees receive access to comprehensive medical, vision, and dental insurance, and the company offers three 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.