Senior Simulation Software Engineer, GNC

Senior Simulation Software Engineer, GNC

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This range is provided by Castelion. Your actual pay will be based on your skills and experience — talk with your recruiter to learn more.

$/yr - $/yr

• Stock options

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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 ’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.

We’re looking for a GNC Simulation Software Engineer to design, develop, and maintain high‑fidelity simulation software supporting missile guidance, navigation, and control (GNC) development. In this role, you’ll work closely with GNC algorithm developers, flight software engineers, and test teams to create fast, accurate, and robust simulations that drive system architecture decisions, performance assessments, and mission success.

• Develop and maintain a 6‑DoF missile simulation software platform.
• Build scalable infrastructure to execute, manage, and aggregate data from Monte Carlo campaigns, along with automated performance evaluation tools.
• Ensure appropriate configuration management and shared sources of truth between simulation and flight code.
• Optimize software for real‑time or hardware‑in‑the‑loop (HITL) execution where required.
• Develop robust testing, verification, and documentation practices to ensure reliability and correctness.
• Support flight software integration, pre‑flight analysis, and post‑flight reconstruction.

• Bachelor’s or Master’s degree in computer engineering, computer science, aerospace engineering, or a related field.
• Strong proficiency in C++ or Rust for high‑performance numerical modeling.
• Proficiency with databases and large data structures.
• Familiarity with version control, CI/CD pipelines, and modern software engineering practices.
• Experience with numerical integration, coordinate transformations, and simulation architecture.
• Experience with software integration, specifically linking disparate software modules (e.g., embedding Rust code in C++, Python bindings for C++ libraries).
• Familiarity with GNC concepts in aerospace or missile systems.
• Ability to develop well‑structured, scalable, and efficient code.

• Experience with missile dynamics, aerodynamics, or propulsion modeling.
• Background in Monte Carlo simulation pipelines and statistical analysis.
• Experience with hardware‑in‑the‑loop or real‑time simulation.
• Exposure to sensor modeling (IMU, GPS, radar, seekers) or actuator modeling (TVC, CAS).
• Experience integrating simulations with GNC or embedded flight software environments.
• Experience designing APIs or internal tools for engineering teams.

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

Desire and experience questioning assumptions in ways that lead to breakthrough 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.

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.

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…