Software Engineer

Software Engineer

Engineering Design Automation • Austin, TX (open to split time) • Full-Time

About Subcritical Systems

Subcritical Systems is a venture backed advanced particle accelerator manufacturing company based in Austin, Texas, developing a next-generation accelerator-driven systems for power production from subcritical fission, semiconductor manufacturing, medical isotopes and in the future waste transmutation. We are a growing company with an aggressive timeline and a target of commercial power production by 2028.

This is a rare opportunity to do work that matters at the intersection of nuclear physics, advanced manufacturing, and frontier software, on a timeline that is real and a mission that is urgent.

The Role

We are building internal tooling to dramatically accelerate the design-to-construction pipeline for complex engineered systems. You will be a core contributor/ leader on a five-person engineering team, working at the boundary of software and mechanical design. Your primary focus will be developing and extending our internal CAD automation platform- a system that generates and validates complex 3D assemblies programmatically, enabling our mechanical designers and engineers to iterate orders of magnitude faster than traditional CAD workflows allow.

You will integrate advanced AI tools into this workflow, solve hard geometry and data modeling problems, and own major parts of the software stack end-to-end. If you have ever wanted to build software where the output is a physical machine that generates clean energy, this is it.

What You’ll Do

• Develop and maintain our in-house CAD automation platform, which generates parametric 3D assemblies (geometry, tolerances, bill of materials) from structured design inputs.
• Build software interfaces between our design toolchain and standard engineering formats (STEP, IGES, manufacturing packages) for handoff to construction and fabrication partners.
• Integrate large language model APIs and AI-assisted tooling into the design and review workflow to accelerate iteration and reduce manual engineering hours.
• Collaborate daily with mechanical designers and nuclear engineers: translate complex physical constraints into software logic, and surface software capabilities that unlock new design approaches.
• Own the reliability and performance of design automation pipelines that directly gate our construction schedule.
• Contribute to internal tooling infrastructure: version control for design artifacts, automated validation and consistency checking, and documentation generation.
• Work in a small team where ownership is real and scope is broad—you will wear multiple hats and your contributions will be directly visible in our engineering output.

What We’re Looking For

Required

• Strong software engineering fundamentals: Python and/or TypeScript, clean architecture, version control, testing.
• Experience building tools used by domain experts (engineers, scientists, designers)—you know how to translate expert knowledge into reliable software.
• Comfort working with geometry, spatial data, or engineering file formats (CAD, STEP, mesh, simulation outputs).
• Track record of shipping in resource-constrained environments: startup, early-stage team, or solo ownership of a complex system.
• Excellent communication with non-software collaborators—you can explain a technical constraint to a mechanical engineer and absorb domain knowledge quickly.
• High agency: you identify problems, propose solutions, and execute without needing a detailed spec.

Strongly Preferred

• Experience as a founder, co-founder, CTO, or early technical hire at a deep-tech, hardware, or engineering-software startup.
• Familiarity with LLM APIs and prompt engineering as practical tools for accelerating engineering workflows.
• Background in or exposure to mechanical engineering, manufacturing, or technical design review processes.
• Experience with CAD systems (OpenCascade, FreeCAD, Fusion, SolidWorks, or similar) or geometric modeling libraries.
• Prior work on systems with physical-world consequences: robotics, aerospace, energy, biotech, advanced manufacturing.

The Team & Environment

You will join a dedicated small engineering team embedded within Subcritical Systems, with a mix of mechanical designers, nuclear engineers, and software builders. There is no bureaucracy. You will interact directly with company leadership and your feedback shapes how we work.

The primary location is Austin, Texas. We are open to candidates who prefer to split their time between Austin and another location, or who are willing to relocate.

We are in an accelerated phase of engineering development with a hard target date for power production. The work you do here will have a direct and measurable impact on when we deliver. If you have been waiting for a deep-tech opportunity where the stakes are real, the team is sharp, and the timeline is now, this is it.

Compensation & Benefits

• Competitive salary commensurate with experience.
• Meaningful equity.
• Health, dental, and vision benefits.
• Direct access to leadership and the ability to shape how the company builds and ships.
• The chance to work on one of the most consequential clean energy projects of the decade.

How to Apply

Apply on Linkedin and can send additional information on your background to careers@subcritical.com. We are most interested in what you have built, what you have shipped, and what drew you to this kind of work. A portfolio, GitHub, or specific project examples are welcome and encouraged.