Simulation Engineer Jobs in Sunnyvale, CA (NOW HIRING)

About Commonwealth Fusion Systems:

Commonwealth Fusion Systems is on a mission to deliver the urgent transition to fusion energy.

Combining decades of research, top talent, and new technologies, we’re designing and building commercially viable fusion power plants. And we’re working with policymakers and suppliers to build the energy industry of the future.

We’re in the best position to make it happen. Since 2018, we’ve raised nearly $3 billion in capital, making us the largest and leading private fusion company in the world.

Now we’re looking for more thinkers, doers, builders, and makers to join us. People who’ll bring new perspectives, solve tough problems, and thrive as part of a team.

If that’s you and this role fits, we want to hear from you.

Join the power movement as a Staff Modeling and Simulation Engineer

We’re looking for a Staff Modeling and Simulation Engineer to join our design team to help build next-generation hardware. In this role, you will serve as a lead technical expert for advanced simulations, driving the predictive validation of complex hardware systems.

This role requires a high-level practitioner in multi-physics simulation who can comfortably model complex interactions across thermal, structural, fluid flow, and chemical regimes. If you enjoy solving deeply complex physics problems, applying rigorous modeling standards, and working in a collaborative, fast-paced environment to deliver first-of-a-kind hardware, this is your opportunity to make an impact.

• Execute Simulation and Modeling: Lead advanced Finite Element Analysis (FEA) and Computational Fluid Dynamics (CFD) for advanced processing equipment
• Run Multi-Physics Analysis: Build, run, and evaluate highly coupled simulations covering structural mechanics, high-temperature thermal management, fluid/gas flow dynamics, and chemical reaction kinetics
• Apply Engineering Best Practices: Implement engineering workflows for simulation data management, mesh convergence criteria, and rigorous verification and validation (V&V) protocols using physical test data
• Drive Design Reviews: Provide analytical leadership during technical design reviews, verifying structural margins, thermal stress distributions, and flow uniformity to guide design choices
• Collaborate & Interface: Partner closely with cross‑functional teams, including Mechanical Designers, Electrical Engineers, Materials Scientists, and Chemical Specialists, to translate simulation insights into actionable hardware modifications
• Project Accountability: Own and report on modeling milestones, timelines, and computational resources to stakeholders, ensuring on‑time and in‑spec delivery
• Mentor Talent: Coach and mentor junior engineering staff on modeling methodologies, simulation accuracy, and the practical application of finite element principles to real‑world hardware
• Get Things Done: Act with speed to solve critical engineering bottlenecks, validating design optimization paths from concept through prototype deployment

• Education: Master’s or PhD degree in Mechanical Engineering, Aerospace Engineering, Physics, or a related field with a heavy focus on computational mechanics and multi-physics modeling
• Experience: 10+ years of experience in simulation and predictive analysis of complex R&D systems
• Software Mastery: Advanced, hands‑on expert in ANSYS, COMSOL Multi‑physics, or equivalent high‑end FEA/CFD simulation platforms
• Multi‑Disciplinary Analytical Expertise: Proven track record of successfully running coupled simulations (e.g., fluid‑structure interaction, thermal‑structural behavior, and chemical reaction modeling)
• Empirical Correlation: Ability to bridge the gap between virtual models and the shop floor by validating simulation results against physical test metrics like strain gauge data, thermal imaging, and flow sensors
• Leadership: Demonstrated ability to influence hardware design direction through analytical data and lead cross‑functional initiatives in a matrixed environment

• Standards Knowledge: Familiarity with applying industry codes to simulation‑driven design validation
• Motion & Dynamics: Experience running transient dynamic simulations or modeling precision motion systems in extreme thermal environments

• Ability to lift up to 25 lbs occasionally
• Perform activities such as stooping, climbing, standing, sitting for extended periods of time
• Willingness to travel or work required nights/weekends/on‑call occasionally
• Dedication to safety to mitigate industrial hazards that may include heat, cold, noise, fumes, strong magnets, lead (Pb), high voltage, high current, pressure systems, and cryogenics

$130,000 - $200,000 a year

Salary range for this full‑time position + equity + benefits. The actual salary will depend on level, location, qualifications, and experience. The range displayed on each job posting reflects new hire salaries for the position across all US locations.

Benefits include:

• Competitive compensation with equity
• 13 Company‑wide Holidays
• Flexible vacation days
• 10 sick days
• Generous parental leave policy
• Health, dental, and vision insurance
• 401(k) with employer matching
• Professional growth opportunities
• Team‑building activities

At CFS, we excel in fast‑paced environments, driven by our values of integrity, execution, impact, and self‑critique. As we grow, we’re eager to bring on mission‑driven folks who offer diverse perspectives and fresh ways to tackle challenges.

We value diversity deeply and are proud to be an equal opportunity employer by choice. We consider all qualified applicants equally, regardless of race, color, national origin, ancestry, citizenship status, protected veteran status, religion, physical or mental disability, marital status, sex, sexual orientation, gender identity or expression, age, or any other basis protected by law.

This role requires compliance with U.S. laws concerning the export of controlled or protected technologies or information (collectively, “Export Control Laws