Reliability Engineer Intern Jobs in California (NOW HIRING)

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.

Electrical Engineer Intern - Fall 2026 (Avionics)

Castelion is seeking motivated and talented Electrical Engineering Interns for Fall 2026. You'll help design, build, and test the electronics and hardware that drive our advanced missile systems. From architecture and schematic design to board bring-up and validation, you'll own real hardware projects alongside experienced hardware, firmware, and systems engineers. You won't be doing throwaway work. Your contributions will directly support rapid prototyping and real-world flight tests.

Key Responsibilities

• Take ownership of circuit board design from specification and architecture through schematic, layout collaboration, bring-up, and validation
• Design and integrate analog and digital circuits, processors, sensors, and power electronics
• Collaborate cross-functionally with PCB layout, firmware, mechanical, systems, and test teams
• Rapidly iterate hardware designs as system requirements mature
• Document design decisions, calculations, schematics, validation results, and learnings clearly
• Support system bring-up, debug, and test campaigns in the lab and on hardware-in-the-loop benches

Basic Qualifications

• Currently pursuing a BS or MS in Electrical Engineering, Computer Engineering, Mechatronics, or a related field
• Strong understanding of analog and digital circuit design principles
• Experience with PCB component selection and schematic design
• Familiarity with PCB bring-up and debugging
• Some exposure to MATLAB, Python, C/C++, or other tools for modeling and analysis
• Basics of serial communication protocols (CAN, Ethernet, SPI, I2C, etc.)
• U.S. Person status required (due to ITAR regulations)

Preferred Skills and Experience

• Prior project or internship experience designing and testing PCBAs for aerospace, robotics, automotive, or other high-reliability applications
• Familiarity with mixed-signal design, power electronics, or RF systems
• Strong interest in working in a startup environment with high-impact projects.

You'll leave with

• Real experience designing and testing electronics that power flight systems
• Hands-on exposure to rapid prototyping, lab bring-up, and system integration
• Mentorship from engineers who build mission-critical defense hardware
• A clear path to develop into a future leader in advanced aerospace and defense engineering

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. The 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, the applicant must be a (i) U.S. citizen or national, (ii) U.S. lawful, permanent resident (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.

Why Castelion

At Castelion, you'll be part of a mission-driven company where every project matters. Our interns don't just observe, they contribute meaningfully to the success of our programs. This is a unique opportunity to work at the cutting edge of aerospace engineering while developing the skills and experience that will help you grow into a future leader in the field.

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.

This internship is paid at an hourly rate of $35 per hour. Compensation may vary based on experience and education level. For non-local interns, housing or relocation stipends may be available to help offset temporary living expenses.