Manufacturing / Mechanical Engineering

Mechanical Engineer Intern (Winter/Spring 2027)
Mechanical Engineering

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.

Winter/Spring 2027 - Mechanical Engineering Internship Co-Op

As an intern, you'll contribute directly to the design, testing, and integration of advanced defense technologies all within a fast-paced, collaborative startup environment where your work has immediate impact.

Assist in the design, analysis, and testing of components for missile subsystems, including propulsion, guidance systems, power electronics, and more.

Support engineering teams with simulations, modeling, and prototyping of critical hardware components.

Conduct research and development tasks, gathering and analyzing data to inform design decisions.

Participate in system integration efforts, helping to assemble and test subsystems in real-world test environments.

Collaborate cross-functionally with engineering, manufacturing, and test teams to ensure project success.

Document design processes, test results, and project progress, contributing to the continuous improvement of our systems.

Attend technical reviews, design meetings, and team briefings to stay engaged with project developments and learn from industry experts.

Gain hands-on experience in aerospace engineering, working on cutting-edge hypersonic missile systems.

Develop your technical skills by working with high-performance teams and state-of-the-art tools.

Learn about the full lifecycle of missile development, from design and prototyping to testing and final integration.

Receive mentorship from experienced engineers and leaders in the aerospace and defense industry.

Currently pursuing a Bachelor's or Master's degree in Mechanical Engineering, Aerospace Engineering, or a related field.

Rising junior, senior, or graduate-level student preferred.

Strong academic record with relevant coursework in areas such as mechanical design, propulsion, power systems, or related fields

Hands-on experience through lab work, projects, or internships is a plus.

Passion for aerospace, defense technology, and innovative engineering solutions.

Experience with hardware design, testing, data acquisition, and analysis.

Familiarity with missile systems, defense technology, or aerospace components.

Strong interest in working in a startup environment with high-impact projects.

Government sites, systems, or information, as determined by the Company and/or applicable U.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. 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 View email address on click.appcast.io 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.

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