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About the job

ABOUT SUBCRITICAL SYSTEMS

Subcritical Systems, Inc. is a venture-backed startup in Austin, Texas building the accelerator driven systems and the only US commercial manufacturer of accelerator cavities. What Space X did for rockets, we plan to do for accelerator cavities and commercialize across applications of power production, medical isotopes, semiconductors and waste transmutation.

We are in the process of building the Energy Amplifier — a novel nuclear fission system in which a particle accelerator drives a subcritical core, making meltdown physically impossible for clean power production. Due to its inherent safety, our system has a more streamlined licensing process. Our founding team includes successful entrepreneurs with a track record of building several multibillion dollar companies in deep-tech, and scientists who were leading U.S. national labs with deep experience in accelerator & nuclear technologies.

We are actively hiring to expand our team as we work toward licensing, regulatory submissions, and construction of our first energy amplifier. More information is available at subcritical.com.

ROLE SUMMARY

The Mechanical Engineer – Pressure Systems leads design, development, and deployment of large cryogenic pressure and test systems for SSI's superconducting accelerator hardware, with a strong emphasis on pressure, leak, and fluid systems design and safety. Engineering models, design constraints, and validation criteria feed into ATLAS, Subcritical's agentic platform for rapidly solving hard engineering problems, to support pressure systems design and analysis.

KEY RESPONSIBILITIES

Lead and support the design, development, and deployment of large cryogenic pressure and test systems for superconducting accelerator hardware, with a strong emphasis on pressure, leak, and fluid systems design, using ATLAS-enabled workflows under close engineering oversight.

Develop, build, and execute complex analyses to verify system functionality, performance, and safety for cryogenic pressure systems hardware, incorporating validated models into ATLAS.

Conduct technical risk assessments and support hazard analyses, safety reviews, and test readiness reviews for critical design development activities, ensuring ATLAS-assisted outputs meet the same safety bar as conventional engineering.

Diagnose, troubleshoot, and resolve technical issues with designs and analyses.

Utilize engineering analysis, modeling, simulation, and test tools to evaluate system behavior, predict performance, and validate designs, including ATLAS-generated design concepts.

Lead and contribute to reviews, data analysis efforts, and the creation of comprehensive test reports and technical documentation.

Perform all job functions in a safe and responsible manner and encourage the same in fellow employees. Take a proactive view of safety.

QUALIFICATIONS

Required

Master's degree in mechanical engineering or equivalent. PE certification desired.

7+ years of relevant experience, or 15+ years of professional experience.

Hands on experience building, testing, assembling and designing cryomodules.

Strong expertise in pressure systems and leak testing, including hands-on leakage and pressure testing.

Practical knowledge of ASME BPVC, ANSI standards, and US cryogenic pressure systems requirements.

Experience with nondestructive testing and leak testing techniques, including helium mass spectrometry leak testing.

Ability to perform engineering analysis, modelling, simulation, and interpretation of test data to evaluate system behavior and performance.

Ability to read and interpret mechanical, P&ID, weld, and fabrication drawings, and to produce clean engineering documentation of your own.

Bias for action and able to coordinate effectively across engineers, scientists, trades, vendors, and executives, including comfort operating within AI-assisted platforms like ATLAS.

Preferred

Experience developing test procedures, acceptance criteria, and technical documentation for regulated pressure equipment.

Experience with computational engineering, design optimization, automation, or AI-enabled tools such as ATLAS, including translating engineering requirements, safety constraints, and codes into computational workflows.

Ability to critically evaluate AI-generated engineering outputs and apply appropriate engineering judgment, verification, and physical validation, working comfortably in a rapid-development environment where testing, simulation, and AI-assisted iteration occur in parallel.

BENEFITS

We offer health, dental, and vision insurance.

LOCATION & WORK POLICY

This role is fully in person in Austin, Texas. Our facility is located next to Austin Airport.