Mechanical Design Engineer II - Reactivity Controls
- Salary
- $115K - $185K
- Level
- Mid
Not stated in the posting: work type, visa.
Open. First seen 2 October 2026.
About the role
About Us
Antares's standard text
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 the Responsible Engineer for Reactivity Controls – Mechanical, you will lead
the design, development, testing, and validation of the mechanical systems that
govern reactor reactivity and ensure the safe operation of the reactor. You will
architect and build the mechanical mechanisms that interface with electrical and
software subsystems, collaborating closely across disciplines to define system
architecture, requirements, and documentation.
The ideal candidate has a strong track record in designing and developing
precision control mechanisms, preferably with experience in robotics or
electromechanical systems. You will also contribute to system-level architecture
trade studies and support the evaluation and selection of key vendors.
Roles and Responsibilities:
- Design, build, and test the reactor’s control mechanisms, hardware and
assemblies.
- Concept and develop custom actuation solutions, including mechanisms,
linkages, interfaces, and instrumentation.
- Define design criteria, requirements, system architecture, and
verification/validation test plans.
- Collaborate closely with cross-functional teams across thermal, structural,
neutronics, controls, and simulation disciplines.
- Engineer components for high-temperature, high-stress, and radiation
environments using metals, ceramics, and other advanced materials.
- Perform design-for-manufacturability (DFM) assessments and execute
tradeoffs across performance, cost, schedule, and risk.
- Conduct mechanism trade studies, document findings, and present
recommendations to senior leadership
Basic Qualifications:
- Bachelor's degree in engineering
- 3+ years of experience in a full-cycle design engineering roles,
encompassing hands-on experience with CAD, analysis, build and test
- Experience with kinematic synthesis, pneumatic/hydraulic actuation,
mechatronics and instrumentation
- Experience with FMEA including structure strength, stability and fatigue
failure modes
Preferred Skills & Experience:
- Master's degree in engineering
- 1+ years of experience in a full-cycle design engineering roles,
encompassing hands-on experience with CAD, analysis, build and test
- Experience in the Nuclear, Aerospace, or Robotics industries
- Experience in a demanding fast-paced development environment
- Experience with design engineering tools such as NX, ANSYS or Femap, and
other product lifecycle software
- Experience with engineering scripting languages such as Python and
MATLAB
Additional Requirements:
- Ability to work long hours and weekends as necessary to support critical milestones
Antares's standard text
Location
- We are located in Torrance, CA in a 145,000 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.
Salary Range
- Mechanical Design Engineer II - $115,000 - $150,000
Culture
Antares's standard text
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
Antares's standard text
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.
What this role asks for
Particular to this role
MATLAB
Rare in Antares's other 69 open postings.
Standard for software engineering roles
Python
Common in software engineering postings at any company.
78% of this description is written for the role. The rest is Antares's standard text, folded away below.
Read against Antares's other open postings on this site.
The team: Mechanical Engineering HIRES STEADILY
This role is one of 6 open in Mechanical Engineering. 1 was posted in the last 30 days and the oldest in August: a team that hires all year rather than one being built.
WHAT THE TEAM WORKS WITH, ACROSS ITS POSTINGS
ANSYS (6 of 6), FEA (4 of 6), AWS (2 of 6), MATLAB (2 of 6), Python (2 of 6)
OTHER ROLES ON THIS TEAM
- Thermo-Mechanical Design Engineer - Reactor Cavity Cooling Systems posted Oct 9
- Structures Engineer II posted Sep 11
- Senior Structures Engineer posted Sep 11
- Senior Mechanical Design Engineer - Reactivity Controls posted Aug 27
- Mechanical Engineer - Electronics Packaging posted Aug 11
From the team and dates on Antares's own job board.
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