Mechanical Design Engineer - Multiphysics Simulation

Subcritical Systems Inc; Austin (TX); On-site; USD 120,000 - 180,000; Full time

Benefits offered by this job

Health insurance

Dental insurance

Vision insurance

Job summary

Subcritical Systems, Inc. in Austin is hiring a hands-on mechanical engineer to design components for an advanced reactor facility and to apply first-principles methods across heat transfer, fluid flow, and structural dynamics.

You’ll drive tasks from requirements to commissioning, and ensure systems meet ASME piping and vessel codes. The role involves FEA in ANSYS, CAD in Siemens NX, and close collaboration with physicists, engineers, and tradespeople to deliver safe, robust energy solutions.

Qualifications

• Bachelor’s degree in Mechanical Engineering or equivalent.
• 3+ years of relevant engineering experience.
• Strong knowledge of heat transfer, solid & fluid mechanics, and structural dynamics.
• Ability to read/interpret mechanical, P&ID, weld and fabrication drawings.

Responsibilities

• Perform engineering analyses including heat transfer, fluid flow, vibration, and stress analysis.
• Utilize CAE tools such as ANSYS and CAD in Siemens NX.
• Define requirements, coordinate with vendors and trades, and support procurement.
• Ensure designs comply with ASME piping/pressure vessel codes.
• Present at engineering and safety reviews.

Skills

3+ years experience

Engineering fundamentals

Cross-functional coordination

Documentation/read drawings

Education

Bachelor’s Degree in Mechanical Engineering or equivalent

Tools

ANSYS

Siemens NX

Job description

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.

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

This is a hands-on engineering role at a small Austin startup building next-generation nuclear energy systems. You'll apply first-principles mechanical engineering, heat transfer, fluid flow, stress analysis, and structural dynamics, to design and deliver components and systems for an advanced reactor facility, working directly alongside physicists, engineers, and tradespeople.

The role spans the full project lifecycle: from defining requirements and running FEA in ANSYS, through CAD in Siemens NX, procurement, fabrication, and commissioning. Systems must be designed to ASME piping and pressure vessel codes in a technically demanding environment.

This is an ideal role for someone who can defend modeling choices in a design review as confidently as they can coordinate with a vendor or a trades team on the floor.

KEY RESPONSIBILITIES

Engineering Analysis & Simulation

• Perform engineering analyses including heat transfer, fluid flow, vibration, and stress analysis.
• Utilize CAE tools such as finite element analysis software (ANSYS) as needed. Maintain proficiency in use of the software so that tasks can be completed in a timely fashion.

Cross-Functional Collaboration

• Work with engineers and scientists in defining requirements, designing, analyzing, fabricating, installing, and testing/commissioning components and systems.
• Present technical status reports and designs at engineering and safety reviews; produce system documentation as needed.

Design & Standard Compliance

• Design systems in accordance with applicable codes and standards, including ASME piping, ASME Boiler and Pressure Vessel Codes, and JLab Pressure and Vacuum System Rules.
• Work with design staff to generate components and assemblies in a 3D CAD tool using Siemens NX.

Procurement & Fabrication Support

• Initiate and support procurement and fabrication of small and large-scale complex components and assemblies. Act as Technical Representative for major procurements:

a. Generate pre-solicitation technical and funding documents.

b. Review and approve submittals and contractor changes.

c. Define inspection requirements; perform/witness inspections and tests.

d. Provide approval of final products and/or services.

Safety

• 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

• Bachelor’s Degree in Mechanical Engineering or equivalent.
• 3+ years of relevant experience
• Strong working knowledge of the underlying engineering: heat transfer, solid mechanics, fluid mechanics, and structural dynamics — not just the software that solves them.
• Sound judgment on mesh, element selection, boundary conditions, and convergence; able to defend modeling choices in a design review.
• Ability to read and interpret mechanical, P&ID, weld, and fabrication drawings, and to produce clean engineering documentation independently.
• Bias for action and ability to coordinate effectively across engineers, scientists, trades, vendors, and executives.

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.