Battery Modeling Simulation Engineer Jobs in Brea, CA

Spacecraft represent the most pressing unmet need across the entire aerospace industry. As more launch vehicles come online and the cost to orbit decreases, more companies launching payloads to space continue to emerge.
For the first time in history, this influx of payload companies combined with reduced launch costs has resulted in a massive increase in need for commercial spacecraft platforms, known as satellite buses. These buses hold the payloads of our customers and are flown on launch vehicles.
Apex manufactures these satellite buses at scale using a combination of software, vertical integration, and hardware that is designed for manufacturing. Our spacecraft enable the future of society: ranging from earth observation to communications and more.
We'd love for you to join us on our mission of providing humankind access to the galaxy beyond our planet.
About the Role
As a Simulation Engineer, you will be responsible for developing closed-loop spacecraft test platforms - such as six degrees of freedom simulation platform (6DOF), software-in-the-loop (SITL) and hardware-in-the-loop (HITL) - and executing simulation testing strategies to validate and verify the performance, functionality, and reliability of satellite systems. Your expertise and attention to detail will play a critical role in ensuring the successful deployment and operation of Apex's satellite buses.
In this role, you will collaborate with multidisciplinary teams of engineers and technicians to design, implement, and integrate realistic test environments using simulation and emulation tools. We are looking for motivated engineers who are eager to solve complex problems with a focus on practicality and scalability, and who thrive in a dynamic, fast-paced environment.
Responsibilities:
• Own closed-loop spacecraft simulation platforms from initial design to deployment
• Develop and maintain core simulation capabilities such as scheduling, data routing, diagnostics, configuration, and Monte Carlo capabilities
• Develop and maintain simulation models, emulators, and hardware/software interfaces with units under test
• Collaborate with cross-functional teams to define test requirements, test procedures, and execute tests
• Analyze test data, identify trends, and generate meaningful insights for test results and model improvements
• Develop tools to automate simulation workflows, enable data analysis, and produce test reports
• Debug complex closed-loop interactions between units under test and simulation
• Help shape long-term technical architecture and roadmap for our simulation platforms
Qualifications:
• U.S. Person status is required as this position needs to access export-controlled data.
• Bachelor's degree in Computer Science, Computer Engineering, Electrical Engineering, Aerospace Engineering, or a related field. Master's degree is a plus.
• 3+ years of experience developing closed-loop simulation tools e.g. 6DOF, SITL, PITL, HITL
• Strong proficiency in programming languages such as C/C++, Rust, Python.
• Comfortable operating and developing within Linux environments
• Familiarity with standard software development practices, including testing frameworks, Docker, CI/CD pipelines, and agile development
• Experience designing, implementing, and validating physics-based simulation models for closed-loop systems
• Experience emulating and integrating virtual sensors, actuators, and test equipment with serial interfaces, network interfaces, and conventional I/O interfaces
• Experience with data analysis techniques, automation tools, and pipeline development
• Strong analytical and problem-solving skills with keen attention to details
• Excellent verbal and written communication skills
• Proven ability to work independently and take ownership of technical deliverables
• Proven ability to work in a fast-paced and dynamic environment while delivering results
Preferred Qualifications:
• Experience in aerospace or satellite industry
• Knowledge of satellite subsystems such as sensors, actuators, controls, communications, and power
• Experience engineering complex systems that require precise timing, deterministic execution, and high performance, such as real-time and HPC systems
• Experience developing and maintaining complex build systems, virtual test environments, and CI/CD
• Knowledge of embedded Linux operating systems and/or real-time operating systems
Why Join Apex?
Apex believes in creating a work environment that you look forward to embracing every day. Our employees love working at Apex, and we want you to love it too. We're a fast-growing startup that has raised more than $500M in funding, and we invest heavily in our people from day one.
What We Offer For Full-time Employees:

• Shared upside: Receive equity in Apex, letting you benefit from the work you create
• Best-in-class healthcare: 100% company-paid medical, dental, and vision for you and your dependents, plus $100k life insurance at no cost
• Comprehensive PTO package to reset and recharge - starting at 15 days vacation, growing to 20+ days annually, plus 10 paid holidays
• Competitive 401(k) plan with generous matching - 100% match on first 3%, 50% on next 2%
• 8 weeks paid parental leave plus childcare reimbursement up to $350/day for work-related travel
• Daily catered lunch and unlimited snacks to keep you fueled throughout the day
• Vibrant community: Monthly office socials, pickleball tournaments, run club, and gatherings for you and your family
• Your dream desk setup and all the tools you need to be your most productive self
• World-class Playa Vista office with the benefit of in-person collaboration with amazing coworkers and flexibility to integrate work and life
• Real impact opportunity: Work alongside experts from aerospace, new space, and other cutting-edge industries to make a lasting difference

Ready to join a team where your contributions matter and your future is bright? Let's build something extraordinary together.
Equal Opportunity Employer
Apex Technology, Inc. is an Equal Opportunity Employer. We celebrate diversity and are committed to creating an inclusive environment for all employees. Candidates and employees are always evaluated based on merit, qualifications, and performance. We will never discriminate on the basis of race, color, 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.