Senior, Thermo-Mechanical Design Engineer - Reactor Cavity Cooling Systems

About Us At Antares, our long-term mission is to make clean energy abundant from Earth to the Asteroid Belt. We’re fueled by the belief that advanced nuclear energy can strengthen our military, solve the climate crisis, elevate global living standards, and expand humanity's presence in outer space. To achieve our mission, we’re building mass‑producible, inherently safe, deployable microreactors that can be used terrestrially, underwater, and in space. Formed in 2023, the Antares team hails from SpaceX, The White House, MIT, Rigetti Computing, The Air Force, General Atomics, Relativity Space, Ursa Major, and National Laboratories like Los Alamos, Idaho, and Oak Ridge. Antares has raised over $130M in venture capital from top‑tier investors and has over $13M in government funding. About the Team As a Senior, Thermo‑Mechanical Design Engineer, you will be the Responsible Engineer (RE) for the Reactor Cavity Cooling System (RCCS), leading the design and analysis of a critical deployment system. You will be responsible for the thermal, mechanical, and piping design of the RCCS, ensuring the reactor cavity and surrounding structures remain within design temperature limits, while minimizing wasted thermal power. This role involves thermal‑fluid analysis, piping and structural sizing, filtration system design, and integration of piping, supports, stacks, and cavity components. The ideal candidate has expertise in thermal‑fluid systems, HVAC, piping, and structural design, and enjoys solving multidisciplinary engineering challenges in a highly constrained design environment. Roles and Responsibilities Perform thermal‑fluid, mechanical, and structural analyses to support the sizing, layout, and optimization of cooling system components, including piping, ducts, stacks, supports, filtration equipment, and reactor cavity structures. Define system architecture, operating limits, design margins, and control strategies to ensure reliable performance across all operating conditions. Develop design documentation, including engineering calculations, system specifications, interface definitions, design reports, and technical justifications to support licensing and design reviews. Support the design, fabrication, and execution of component and system‑level testing by developing test articles, test stands, instrumentation plans, and validation procedures to demonstrate system performance and life‑cycle reliability. Coordinate cross‑functionally with reactor systems, structures, licensing, manufacturing, procurement, and operations teams to ensure successful integration of the RCCS into the overall plant design. Support supplier selection, technical evaluations, design reviews, and resolution of manufacturing and installation issues. Present technical work at internal and external design reviews and provide engineering leadership throughout the design, analysis, testing, and deployment lifecycle. Basic Qualifications Bachelor's degree in Mechanical Engineering, Aerospace Engineering, Nuclear Engineering, or a related engineering discipline with an emphasis on thermal‑fluid sciences, heat transfer 5+ years of professional engineering experience in the design, analysis, or development of thermal‑fluid, HVAC, heat transfer, or cooling systems. Experience performing engineering analyses including thermal, fluid flow, and structural calculations to support component and system design. Demonstrated ability to work effectively on multidisciplinary engineering teams and communicate technical concepts to a variety of stakeholders. Preferred Skills & Experience Master's degree or higher in Mechanical Engineering, Aerospace Engineering, Nuclear Engineering, Thermal Sciences, or a related discipline. Experience designing or analyzing natural circulation, buoyancy‑driven, or convective heat transfer systems using CFD or multiphysics simulation tools. Demonstrated expertise in HVAC or industrial ventilation system design, including equipment selection, ducting, filtration, airflow management, and system performance testing. Proficiency with engineering analysis and simulation tools such as ANSYS, COMSOL Multiphysics, or equivalent finite element (FEA) and computational fluid dynamics (CFD) software. Knowledge of materials and structural design considerations, including material selection for heat transfer applications, thermal stresses, creep, corrosion, and environmental degradation. Experience designing systems in accordance with ASME Boiler & Pressure Vessel Code, ASME B31 piping codes, or other applicable mechanical and structural design standards. Experience serving as a technical lead or Responsible Engineer, coordinating multidisciplinary engineering activities from concept development through testing and deployment. Additional Requirements Ability to work long hours and weekends as necessary to support critical milestones. Location We are located in Torrance, CA in a 322,000 square foot, brand new facility featuring large open spaces for team collaboration, R&D, and production, as well as easy access to the 405, 105, and 110 freeways. Our facility is in the heart of Los Angeles' vibrant emerging tech ecosystem alongside many other high growth startups and enterprises. Culture At Antares, we like to specifically tie each role to our founding document’s set of values–here are the top five cultural values we think you should believe at your core to be successful: Think in Systems - Energy and Defense are complex ecosystems with numerous stakeholders with competing priorities, conflicting policies, perverse incentives, and emergent and path‑dependent properties. First principles thinking alone is insufficient. Think probabilistically and then take action. “If you want to be certain, then you are apt to be obsolete.” Over‑optimizing the components often degrades the system Obsess over the End User - The customer and end user are often not the same. We will never build globally competitive commercial products if we lose sight of our end users and their entire interaction with the product life cycle Be Unconstrained by Convention - Our only limits are the laws of physics. Many, even experts, will say what we are working on is impossible. They said the same about SpaceX reusing rockets. Generationally impactful companies, by definition, must accomplish the seemingly impossible. If it were easy, it would have already been done. Never shy away from a solution because it has never been tried before, and never choose to do something because that's “how it's always been done” Go Where the Work I's - Never miss a chance to meet a customer, user, or stakeholder face to face, even if that means hopping on a plane. If you can’t make it, find a teammate who can channel your intentions and go in your place. Deep work can be done from anywhere, but we believe teams are built in person, and aim to maximize our time together Operate in the Grey - Embrace nuance in pursuit of truth. Question every fundamental assumption Equal Opportunity Antares is an Equal Opportunity Employer. Employment decisions are based solely on merit, competence, and qualifications, without regard to 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. ITAR Requirements 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. Learn more about the ITAR here. #J-18808-Ljbffr Antares