Senior Mechanical Engineer

About Marathon Fusion

Marathon Fusion is building the engineering technologies needed to scale fusion from breakeven experiments into real power plants. While much of the industry is focused on proving new fusion devices, our focus is on the practical systems that will make fusion deployable at climate-relevant scale.

We develop core fuel cycle and plant-level technologies for stable isotope production, fuel cycle closure, and advanced blanket systems that enable both energy generation and high-value co-products.

Founded in 2023, Marathon Fusion is building the components and systems that will help fusion become a practical, abundant, and reliable energy source for the 21st century.

Culture at Marathon Fusion

We are a startup environment characterized by a need for focus, adaptability and prioritization in a shifting landscape. Thriving in this environment requires excellent proactive communication across roles and backgrounds, the ability to build and maintain trust between team members, and the willingness to learn and develop new skills on the job. We place particularly high weight on each team member's ability to be self-directed.

About Marathon Fusion

Marathon Fusion is building the engineering technologies needed to scale fusion from breakeven experiments into real power plants. While much of the industry is focused on proving new fusion devices, our focus is on the practical systems that will make fusion deployable at climate-relevant scale.

We develop core fuel cycle and plant-level technologies for stable isotope production, fuel cycle closure, and advanced blanket systems that enable both energy generation and high-value co-products.

Founded in 2023, Marathon Fusion is building the components and systems that will help fusion become a practical, abundant, and reliable energy source for the 21st century.

Culture at Marathon Fusion

We are a startup environment characterized by a need for focus, adaptability and prioritization in a shifting landscape. Thriving in this environment requires excellent proactive communication across roles and backgrounds, the ability to build and maintain trust between team members, and the willingness to learn and develop new skills on the job. We place particularly high weight on each team member's ability to be self-directed.

Role Description

As a Senior Mechanical Engineer, you’ll work closely with mechanical engineers, physicists, and technicians to prototype, test, and deploy solutions in the pursuit of advancing the development of the fusion fuel cycle and stable isotope production. We are seeking an engineer with hands-on experience designing and testing electromechanical systems.

This role requires a blend of practical engineering skills and systems level thinking. You will play a pivotal role in the development and iteration of a first of kind isotope separation device through system and component design and hands-on prototyping and testing.

What You’ll Do:

• Lead the iterative design and improvement of an isotope separation system, driving toward robust, scalable deployment

• Prototype, test, and troubleshoot components and integrated systems in close collaboration with other engineers, physicists and technicians

• Develop first-principles understanding of key physical processes and guide improvements based on experimental data and literature

• Document experimental results and decisions clearly to inform design iterations and process development

• Mentor and support junior engineers, fostering technical growth and strong engineering judgment on the team

What You’ll Bring:

• B.S. or higher in Mechanical Engineering or related field

• 5+ years of hands-on experience in design, prototyping, and testing of electromechanical systems

• Experience as a design lead or program lead on a team of Mechanical Engineers

• Demonstrated experience with high vacuum systems

• Familiarity with high voltage equipment and safety practices

• Strong experimental skills and ability to draw insights from physical systems

• Proficiency in mechanical design, including CAD, GD&T, and DFM best practices

• Capacity to learn new technical subjects quickly, collaborate cross-functionally, and consider problems from inter-disciplinary perspectives

• Ability to thrive in ambiguity, drive projects forward, take ownership and flag when results are not moving the needle

• Excellent written and oral communication

Preferred Experience, But Not Required:

• Experience instrumenting and collecting data off your own systems

• Experience working with high voltage or plasma systems

• Proven experience mentoring junior engineers

• Process development experience in experimental R&D settings

• Experience in a start up or a similarly fast paced environment

Compensation and Benefits

Our compensation for this role is a wide range, determined by an evaluation of your experience and qualifications. All compensation packages for full-time employees include equity ownership in Marathon Fusion.

Annual Base Pay

$115,000 to $170,000

Benefits

We offer the following benefits, subject to applicable eligibility requirements:

• Medical, dental, and vision insurance

• Generous paid time off and sick leave

• 401(k) plan with 4% employer match

• Commuter benefits

• Stocked office kitchen

Marathon Fusion considers all qualified applicants equally for employment. We do not discriminate on the basis of race, color, national origin, ancestry, citizenship status, protected veteran status, religion, physical or mental disability, marital status, sex, sexual orientation, gender identity or expression, age, or any other basis protected by law, ordinance, or regulation. If you need assistance or an accommodation during the interview process, please let us know.

Marathon Fusion considers all qualified applicants equally for employment. We do not discriminate on the basis of race, color, national origin, ancestry, citizenship status, protected veteran status, religion, physical or mental disability, marital status, sex, sexual orientation, gender identity or expression, age, or any other basis protected by law, ordinance, or regulation.