Mechanical Integration Engineer Jobs in California

Castelion is moving incredibly fast to develop and deliver advanced defense systems at a time when execution matters more than ever. We believe focus and technical excellence are decisive advantages - and we are building a team that can deliver real capability, not just concepts.

This is a rare opportunity to join at an early stage, where your work will directly shape critical systems, influence major technical decisions, and have immediate, real-world impact.

As a Weapons Integration Engineer you will be part of the team that ensures Castelion weapon systems integrate seamlessly with ground launchers, tactical/multi‑role aircraft, and future systems. You will own platform integration efforts from early concept and capability studies through prototype development, test, and operational deployment - collaborating with propulsion, avionics, GNC, software, flight test, and manufacturing teams to deliver mission‑ready solutions.

• Weapons Integration Engineer
• Sr. Weapons Integration Engineer
• Weapons Integration Engineer, Mission Systems
• Weapons Integration Engineer, Airworthiness & Certification
• Weapons Integration Engineer, Launcher & Platforms
• Weapons Integration Engineer, Special Programs (TS/SCI required)

• Serve as the primary technical liaison between Castelion and government customers, platform manufacturers, and other external stakeholders to ensure alignment between mission requirements and system designs.
• Support development of advanced weapon concepts and technologies, with emphasis on missile integration for ground launchers and tactical aircraft.
• Develop, maintain, and execute fast‑paced integration plans and schedules to deliver and field weapon systems.
• Lead mission planning, verification, and test efforts (including live‑fire and flight tests): pre‑test analysis, real‑time mission support, and post‑test evaluation and reporting.
• Review and assess interface specifications, drawings, and design documents for functional, electrical, software, and physical interfaces; identify and close interface gaps.
• Collaborate across internal engineering teams (propulsion, avionics, GNC, software, flight test, manufacturing) to perform design trades and optimize overall system performance with a focus on platform compatibility.
• Develop and coordinate technical specifications, integration documentation, and certification/supporting artifacts required for customer acceptance and regulatory compliance.
• Represent Castelion at customer meetings, design reviews, test campaigns, and demonstrations.
• Ensure contract deliverables meet customer requirements, schedule, and quality standards.

1. Mission Systems Integration

   Define and integrate mission‑level capabilities by translating operational requirements into system performance. Includes mission planning, CONOPS development, fire control integration, and software development to deliver mission‑ready weapon systems.

2. Airworthiness & Certification

   Ensure systems meet safety, regulatory, and platform certification requirements. Includes development of airworthiness strategies, compliance with military standards, and coordination with government certification authorities. Lead qualification efforts and guide systems through safety review boards (WSESRB, JS‑WSR, FISTRP, AISSRB, SSSTRP), as well as Seek Eagle, NAVAIR Airworthiness, and related certification processes.

3. Launchers & Platform Integration

   Lead integration of weapon systems with tactical aircraft, ground launchers, and emerging platforms. Define and validate mechanical, electrical, and software interfaces while coordinating with platform manufacturers and external partners. Includes hands‑on prototype development, integration hardware, test equipment, and travel to customer sites.

4. Test & Evaluation (T&E)

   Plan and execute ground and flight test campaigns, including live‑fire events. Responsibilities include pre‑test analysis, real‑time mission support, post‑test data analysis, and rapid iteration based on results. Conduct fit checks, system validation, and integration verification activities.

5. Logistics, Fielding & Operational Support

   Support transition from development to operational deployment. Includes fielding strategies, sustainment planning, user coordination, and ensuring mission readiness in real‑world environments.

• Bachelors degree in aerospace, mechanical, electrical engineering, physics, or related technical field.
• 2+ years experience in systems engineering, mission/weapon integration, or related roles within defense or aerospace.
• 2+ years experience in technical project management or weapons system development.
• Hands‑on experience with launch vehicles, weapons systems, system integration, or aerospace defense platforms.
• Experience working with the DoD or other national security agencies.
• Strong analytical skills: ability to synthesize complex technical information and communicate effectively to engineers and non‑technical stakeholders.
• Ability to obtain and maintain Top Secret/SCI clearance.
• Ability to travel up to 25% for customer meetings, test campaigns, and program execution.

• Masters degree in a relevant technical field.
• Hands‑on experience with hypersonic weapons, missile defense, or platform integration.
• Strong background in mission design, development, integration, and test for missiles, spacecraft, or similar systems.
• Demonstrated success integrating weapons or sensors with tactical aircraft and/or ground‑based launch systems.
• Active Top Secret/SCI clearance preferred.

• Ability to put in extended hours, including evenings and weekends, when required to meet aggressive timelines.
• This role is based in Torrance, CA and requires full‑time onsite presence.

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.

All full‑time employees are granted meaningful long‑term equity, sharing in the company’s significant growth trajectory. We offer four (4) weeks of paid time off, ten (10) company‑paid holidays, and comprehensive health benefits – including 100% employee‑covered medical and strong dependent coverage, along with dental and vision plans. We also provide paid parental leave to support growing families, a $100 monthly fitness stipend to promote health and performance, and onsite EV charging for convenience. In addition, employees enjoy perks such as catered meals, company‑covered food during high‑demand periods, and a fully stocked kitchen to stay fueled throughout the day.

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.

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.