Build Engineer I/II - Space
Confirmed on the employer's own hiring board on Oct 21, 2026. First seen by Alion on Oct 21, 2026. Antares Nuclear scores A on the Alion truth index.
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.
The Antares team hails from SpaceX, the White House, the Pentagon, the Department of Energy, MIT, Rigetti Computing, General Atomics, Relativity Space, Ursa Major, and National Laboratories like Idaho, Oak Ridge, Los Alamos, and Savannah River. Antares has raised over $600M in venture capital from top-tier investors and has hundreds of million-dollars on contract with the military services, NASA, and the Department of Energy.
About the Role
As a Build Engineer I/II on Antares’ Space team, you will turn engineering designs into hardware that advances nuclear power for space missions. You will own development, prototype, and pathfinder builds from planning through assembly, testing, and as-built closeout. Working closely with design engineers and technicians, you will solve hands-on integration challenges and develop repeatable build processes that support qualification and transition to production.
Job Responsibilities
Plan assembly sequences, build flow, and schedules using engineering drawings and CAD models; update models as needed.
Write build procedures and work orders, maintaining accurate as-built records and hardware configuration throughout each build.
Assemble mechanical and fluid hardware using appropriate tools, torque specifications, and hardware selections; support design reviews to confirm adequate safety factors and margins.
Install instrumentation and wiring, perform mid-build checkouts, and support verification, validation, and qualification testing, including test installation, operations, teardown, and post-test inspection.
Design, procure, and build fixtures, handling equipment, and development tooling.
Source commercial off-the-shelf hardware, quick-turn machined parts, and consumables; inspect incoming parts and resolve fit or quality discrepancies before assembly.
Troubleshoot assembly and integration issues, document redlines, and coordinate changes with design owners to preserve requirements, interfaces, and design intent.
Capture lessons learned and incorporate process improvements into build documentation to support repeatable production and handoff.
Maintain a safe, organized build area when working with pressurized systems, high temperatures, and heavy hardware.
Basic Qualifications
Bachelor’s degree in mechanical or aerospace engineering, or a related engineering discipline.
1+ years of hands-on experience building, assembling, or integrating mechanical hardware; internships and hardware-focused student projects qualify.
Ability to read and interpret engineering drawings and 3D CAD models.
Preferred Qualifications
Experience owning a hardware build from planning through completion, including on collegiate rocketry, satellite, or similar project teams.
Proficiency with geometric dimensioning and tolerancing (GD&T) and tolerance stack-ups.
3D CAD experience designing fixtures and tooling; Siemens NX preferred.
Experience writing build procedures, travelers, or work instructions for flight or flight-like hardware.
Hands-on experience with fluid systems, including tube fittings, valves, regulators, seals, precision cleaning, and helium leak checking.
Strong understanding of bolted joints, including torque, preload, and thread locking.
Experience operating manual mills and lathes, with familiarity in welding, brazing, sheet metal fabrication, and additive manufacturing.
Experience installing thermocouples, pressure transducers, and strain gauges, and building basic wiring harnesses.
Experience with high-temperature, high-pressure, and vacuum hardware.
Familiarity with product lifecycle management (PLM) and enterprise resource planning (ERP) systems.
Additional Requirements:
Ability to work long hours and weekends as necessary to support critical milestones
Ability and willingness to work on-site full time
Salary Range:
Mechanical Design Engineer I - $90,000 - $105,000
Mechanical Design Engineer II - $115,000 - $150,000
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 Is - 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.