Reactor Engineer Jobs in California (NOW HIRING)

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.

Antares is seeking a Reactor Software Engineer to build the software that operates, tests, and interfaces with our first-of-a-kind microreactor and its hardware-in-the-loop environments. This software sits between reactor controls, instrumentation, operator tools, simulations, and external data systems, collecting live signals, streaming telemetry, executing commands, and helping the system respond predictably to off-nominal conditions.

You will work across a codebase where the same controls and interfaces can run in simulation, on a bench or hardware test stand, and eventually against full-scale reactor hardware. In this role, you will help define data is acquired, validated, routed, displayed, and recorded. You will contribute to how commands are scheduled, gated, confirmed, and executed; and how faults are detected, surfaced, contained, and recovered from.

You will partner with controls, electrical, embedded systems, safety, and test teams to design, implement, and validate hardware-facing software for sensors, data acquisition systems, custom electronics, operator displays, simulations, and HIL/HITL environments. Your work will be central to ensuring the reactor can be safely operated, tested, diagnosed, and eventually deployed.

• Develop reactor software for data acquisition, telemetry processing, command handling, state management, fault response, operator interaction, and automated test environments.
• Own features end-to-end, from test specs and interface definitions through implementation, code review, integration, and documentation.
• Build software that can drive both real instruments and in-memory simulations, keeping controls and interfaces consistent across simulation, bench, HIL/HITL, and reactor environments.
• Implement runtime control features such as timeline scheduling, event/gate handling, mode transitions, command validation, command feedback, and telemetry streaming.
• Create and maintain clear software interfaces for hardware adapters, telemetry sinks, DAQs, sensors, controllers, operator tools, and external data systems.
• Implement data validation and quality logic so telemetry can be marked as valid, invalid, stale, unavailable, suspect, or otherwise actionable by downstream software and operator tools.
• Develop fault-aware software behavior, including detection, classification, containment, recovery, reset behavior, diagnostics, logging, and observability.
• Write automated tests that validate real system behavior, including hardware-facing workflows whenever practical.
• Support simulation, HIL/HITL, hardware bring-up, integrated reactor testing, and debugging across software/hardware boundaries.
• Collaborate with electrical, embedded, controls, software, test, and systems teams to define interface control documents, communication schemas, data dictionaries, and integration test plans.
• Participate in design reviews, code reviews, test readiness reviews, and root-cause investigations during hardware integration and deployment campaigns.

• Bachelor's degree in Computer Science, Computer Engineering, Electrical Engineering, Software Engineering, or a related technical field.
• Experience developing clean, maintainable production or project software for hardware-integrated, distributed, embedded, robotics, aerospace, automotive, industrial, or mission-critical systems.
• Software Engineer I: 0-2 years experience
• Software Engineer II: 2-5 years experience.
• Strong Python 3 fundamentals, including typed code, dataclasses or equivalent structured data models, exceptions, testing, and idiomatic code organization.
• Working knowledge of data structures, object-oriented design fundamentals, and software interfaces that are readable, testable, and maintainable.
• Familiarity with concurrent, asynchronous, or multi-process software patterns, such as asyncio, threads, multiprocessing, event loops, IPC, networking, or message passing.
• Experience integrating software with sensors, controllers, DAQs, instruments, power supplies, embedded systems, simulations, or other hardware-facing interfaces.
• Ability to design clear data models, state machines, command flows, and testable system behaviors.
• Strong debugging skills across software, hardware, and system-integration boundaries.
• Experience with Git and collaborative engineering workflows, including pull requests, code review, and technical documentation.
• Comfort working in an environment where requirements evolve through prototype testing, hardware bring-up, and cross-functional design tradeoffs.
• Strong written and verbal communication skills, especially when working across software, electrical, controls, test, and systems engineering teams.

• Experience with hardware or instrumentation software, including DAQs, sensors, serial devices, lab benches, power supplies, controllers, or custom test stands.
• Experience with event-driven systems, command and control software, telemetry pipelines, state-machine architectures, autonomous mode management, or fault-aware system behavior.
• Experience with messaging, networking, or serialization technologies such as MQTT, NATS, DDS, ZeroMQ, gRPC, sockets, publish/subscribe patterns, or custom telemetry buses.
• Experience building simulation, Hardware in the Loop, fault-injection, test automation, or continuous integration environments for hardware-facing systems.
• Familiarity with Linux workflows, containerized environments, and modern Python tooling such as pytest, type checkers, linters, uv, or similar tools.
• Experience with C, C++, Rust, embedded systems interfaces, binary data formats, or C-style data structures.
• Experience developing mission-critical, safety-critical, or high-reliability software for aerospace, robotics, automotive, industrial, defense, nuclear, or medical systems.
• Ability to improve observability through logging, metrics, structured telemetry, diagnostics, and clear failure reporting.
• Experience contributing to formal design reviews, interface control documents, test plans, hazard analyses, or configuration-controlled releases.
• Curiosity about how software meets the physical world and a bias toward integration, readability, and testing over cleverness.

Software Engineer I: 120k-135k

Software Engineer II: 135k-160k

Your actual level and base salary will be determined on a case-by-case basis and may vary based on the following considerations: job-related knowledge and skills, education, and experience.

• 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

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.

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.