Principal Mechanical Engineer Jobs
Principal Mechanical Engineer jobs are open across aerospace, defense, industrial manufacturing, energy, and medical devices, from senior engineer to staff and principal levels, with specializations in structural analysis, thermal systems, and product development. Find a role that fits below and apply directly.
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Showing 5 of 242+ Principal Mechanical Engineer jobs
About Radiant
Radiant is an El Segundo, CA-based company building the world's only mass-produced, transportable nuclear microreactors. The U.S. grid is under growing strain, with power demand accelerating, driving higher utility costs, rising carbon emissions, and interconnection backlogs. Radiant has a solution, transportable, on-site power. Our first reactor, Kaleidos, is 1 megawatt: small enough to be factory-built, transported by land, sea, or air, and deployed wherever power is needed. 1 MW can power 1000 homes for five years. Ship it back and we refuel for a 20 year operating life. We made energy a product that can be used for critical infrastructure like military bases, data centers, hospitals, and remote sites, as well as the commercial main street businesses that keep America running. Founded in 2020, Radiant is under contract to deliver power to the U.S. Army, Navy and Air Force and has signed pre-order agreements with Equinix, with deployments beginning in 2028.
About the Role
Radiant is seeking a Principal Mechanical Design Engineer, Turbomachinery to serve as the Responsible Engineer for the turbomachinery within our nuclear-driven power generation system. This role owns the mechanical design, integrity, and performance of the core rotating assembly at the heart of our 1MW closed-loop Brayton cycle.
You will define and drive the mechanical architecture of high-speed rotating hardware operating at extreme temperatures, pressures, and rotational speeds. As a deeply technical individual contributor, you will set direction for rotor dynamics, structures, bearings, seals, and system integration while working closely with electrical, thermal, and manufacturing teams.
This is a hands-on, high-ownership role focused on technical excellence, sound engineering judgment, and delivering reliable, production-ready turbomachinery.
Responsibilities & Duties:
Technical Ownership & System Architecture
Serve as Responsible Engineer for the turbomachinery mechanical system.
Own the mechanical architecture and design strategy for high-speed rotating assemblies.
Lead rotor dynamics, structural integrity, and life analysis for rotating components and assemblies.
Define and flow down requirements from system-level constraints including thermal, structural, and operational environments.
Make key technical decisions on rotor layout, shafting, bearings, seals, materials, and clearances.
Ensure designs meet performance, reliability, safety, and regulatory requirements.
Establish and uphold standards for mechanical design rigor, analysis quality, and documentation.
Mechanical Design & Analysis
Lead detailed design of turbomachinery components including rotors, shafts, housings, and support structures.
Test and validate turbomachinery, driving model correlation, risk reduction, and performance verification.
Perform and review structural and thermal analysis to ensure integrity under high-speed and high-temperature operation.
Define tolerances, fits, stack-ups, and alignment strategies for precision rotating assemblies.
Partner with electrical engineering on alternator integration, including electromagnetic and structural coupling.
Cross-Functional Integration
Partner closely with turbomachinery aero, motor design, thermal, manufacturing, and test teams.
Ensure seamless integration between turbine, compressor, and alternator subsystems.
Drive clear interface definitions across mechanical, electrical, and thermal boundaries.
Collaborate with manufacturing to ensure designs are producible, inspectable, and scalable.
Engage with suppliers on technically critical components and design decisions.
Prototyping, Testing & Validation
Support assembly, integration, and test of turbomachinery hardware.
Define validation strategies including spin testing, thermal testing, and system-level operation.
Lead root cause analysis and drive design iteration for test failures or performance gaps.
Remain hands-on in hardware bring-up, troubleshooting, and refinement.
Technical Influence
Act as a subject matter expert in turbomachinery mechanical design and rotating systems.
Provide technical guidance and design reviews across the team without direct people management responsibility.
Influence engineering direction through deep expertise, data-driven decisions, and strong judgment.
Contribute to technical roadmap, risk identification, and mitigation strategies.
Required Qualifications & Skills:
B.S. in Mechanical Engineering or related field.
10+ years of experience designing high-speed rotating machinery (turbines, compressors, or similar systems).
Deep expertise in structural analysis and mechanical design of turbomachinery.
Experience with bearings, seals, and high-speed shafting design.
Expert-level proficiency with analysis tools (e.g., ANSYS) and advanced use of NX and Teamcenter for complex design, simulation, and product lifecycle management.
Strong understanding of tolerancing, GD&T, and precision mechanical assembly.
Experience owning hardware through design, build, and test cycles.
Hands-on experience with assembly, integration, and troubleshooting of turbomachinery.
Strong system-level thinking and mechanical intuition.
Excellent engineering judgment and decision-making capability.
Ability to influence without authority across cross-functional teams.
Clear communicator capable of articulating complex technical concepts.
High ownership mindset and accountability for hardware outcomes.
Ability to operate effectively in a fast-paced, first-of-a-kind development environment.
Desired Qualifications & Skills:
Experience with closed-loop Brayton cycle systems or similar energy systems.
Familiarity with high-temperature materials and extreme environment design.
Experience integrating mechanical systems with high-speed electric machines.
Prior experience as a Responsible Engineer for complex hardware.
Experience scaling hardware from prototype to production.
Additional Requirements:
Must be willing to work extended hours and weekends as necessary to accomplish our mission.
Must work 100% onsite at El Segundo HQ.
Benefits and Perks
Stock: Substantial incentive stock plan for all full-time employees.
Medical: 100% up to base silver level plan for employee + 50% dependents, offers up to Platinum plans.
One Medical: Sponsored memberships for employees and their dependents.
Vision: 100% top tier plan coverage + 50% for dependents.
Dental: 100% top tier plan coverage, orthodontia extra, 50% for dependents.
Voluntary life, accident, hospital, critical illness, commuter and FSA/HSA are offered as employee contributed benefits.
8-weeks of paid parental leave for all parents. Additional paid pregnancy leave for CA employees.
Nuclear Engineering Certificate Program: 100% covered educational program with Penn State University, for eligible employees, to rapidly upscale into nuclear.
Daily catered lunch. Free snacks and drinks.
Flexible PTO policy. Remote workday allocation.
Company and team-bonding events, happy hours and in-person camaraderie.
Beautiful El Segundo headquarters close to the Pacific Ocean.
Total Compensation and Benefits
Radiant compensates people for impact and invests in those who continue to raise the bar. Radiant’s full-time new hire compensation package includes base salary, substantial equity grants, and comprehensive health benefits. Total compensation and level are determined through a rigorous evaluation of interview performance, experience, education, and qualifications, and are designed to support continued growth as scope, responsibility, and impact expand at Radiant.
The best of today’s advanced reactor builders don’t wait for job postings. They join the winning team. If that’s you, contact us directly for immediate opportunities: recruiting@radiantnuclear.com.
We are an equal opportunity employer and all qualified applicants will receive consideration for employment without regard to race, color, religion, sex, sexual orientation, gender identity or expression, pregnancy, age, national origin, disability status, genetic information, protected veteran status, or any other characteristic protected by law.
This position involves access to technology that is subject to U.S. export controls. Any job offer made will be contingent upon the applicant’s capacity to serve in compliance with U.S. export controls.
Compensation Range: $200,500 - $314,475
About Radiant
Radiant is an El Segundo, CA-based company building the world's only mass-produced, transportable nuclear microreactors. The U.S. grid is under growing strain, with power demand accelerating, driving higher utility costs, rising carbon emissions, and interconnection backlogs. Radiant has a solution, transportable, on-site power. Our first reactor, Kaleidos, is 1 megawatt: small enough to be factory-built, transported by land, sea, or air, and deployed wherever power is needed. 1 MW can power 1000 homes for five years. Ship it back and we refuel for a 20 year operating life. We made energy a product that can be used for critical infrastructure like military bases, data centers, hospitals, and remote sites, as well as the commercial main street businesses that keep America running. Founded in 2020, Radiant is under contract to deliver power to the U.S. Army, Navy and Air Force and has signed pre-order agreements with Equinix, with deployments beginning in 2028.
About the Role
Radiant is seeking a Principal Mechanical Design Engineer, Turbomachinery to serve as the Responsible Engineer for the turbomachinery within our nuclear-driven power generation system. This role owns the mechanical design, integrity, and performance of the core rotating assembly at the heart of our 1MW closed-loop Brayton cycle.
You will define and drive the mechanical architecture of high-speed rotating hardware operating at extreme temperatures, pressures, and rotational speeds. As a deeply technical individual contributor, you will set direction for rotor dynamics, structures, bearings, seals, and system integration while working closely with electrical, thermal, and manufacturing teams.
This is a hands-on, high-ownership role focused on technical excellence, sound engineering judgment, and delivering reliable, production-ready turbomachinery.
Responsibilities & Duties:
Technical Ownership & System Architecture
Serve as Responsible Engineer for the turbomachinery mechanical system.
Own the mechanical architecture and design strategy for high-speed rotating assemblies.
Lead rotor dynamics, structural integrity, and life analysis for rotating components and assemblies.
Define and flow down requirements from system-level constraints including thermal, structural, and operational environments.
Make key technical decisions on rotor layout, shafting, bearings, seals, materials, and clearances.
Ensure designs meet performance, reliability, safety, and regulatory requirements.
Establish and uphold standards for mechanical design rigor, analysis quality, and documentation.
Mechanical Design & Analysis
Lead detailed design of turbomachinery components including rotors, shafts, housings, and support structures.
Test and validate turbomachinery, driving model correlation, risk reduction, and performance verification.
Perform and review structural and thermal analysis to ensure integrity under high-speed and high-temperature operation.
Define tolerances, fits, stack-ups, and alignment strategies for precision rotating assemblies.
Partner with electrical engineering on alternator integration, including electromagnetic and structural coupling.
Cross-Functional Integration
Partner closely with turbomachinery aero, motor design, thermal, manufacturing, and test teams.
Ensure seamless integration between turbine, compressor, and alternator subsystems.
Drive clear interface definitions across mechanical, electrical, and thermal boundaries.
Collaborate with manufacturing to ensure designs are producible, inspectable, and scalable.
Engage with suppliers on technically critical components and design decisions.
Prototyping, Testing & Validation
Support assembly, integration, and test of turbomachinery hardware.
Define validation strategies including spin testing, thermal testing, and system-level operation.
Lead root cause analysis and drive design iteration for test failures or performance gaps.
Remain hands-on in hardware bring-up, troubleshooting, and refinement.
Technical Influence
Act as a subject matter expert in turbomachinery mechanical design and rotating systems.
Provide technical guidance and design reviews across the team without direct people management responsibility.
Influence engineering direction through deep expertise, data-driven decisions, and strong judgment.
Contribute to technical roadmap, risk identification, and mitigation strategies.
Required Qualifications & Skills:
B.S. in Mechanical Engineering or related field.
10+ years of experience designing high-speed rotating machinery (turbines, compressors, or similar systems).
Deep expertise in structural analysis and mechanical design of turbomachinery.
Experience with bearings, seals, and high-speed shafting design.
Expert-level proficiency with analysis tools (e.g., ANSYS) and advanced use of NX and Teamcenter for complex design, simulation, and product lifecycle management.
Strong understanding of tolerancing, GD&T, and precision mechanical assembly.
Experience owning hardware through design, build, and test cycles.
Hands-on experience with assembly, integration, and troubleshooting of turbomachinery.
Strong system-level thinking and mechanical intuition.
Excellent engineering judgment and decision-making capability.
Ability to influence without authority across cross-functional teams.
Clear communicator capable of articulating complex technical concepts.
High ownership mindset and accountability for hardware outcomes.
Ability to operate effectively in a fast-paced, first-of-a-kind development environment.
Desired Qualifications & Skills:
Experience with closed-loop Brayton cycle systems or similar energy systems.
Familiarity with high-temperature materials and extreme environment design.
Experience integrating mechanical systems with high-speed electric machines.
Prior experience as a Responsible Engineer for complex hardware.
Experience scaling hardware from prototype to production.
Additional Requirements:
Must be willing to work extended hours and weekends as necessary to accomplish our mission.
Must work 100% onsite at El Segundo HQ.
Benefits and Perks
Stock: Substantial incentive stock plan for all full-time employees.
Medical: 100% up to base silver level plan for employee + 50% dependents, offers up to Platinum plans.
One Medical: Sponsored memberships for employees and their dependents.
Vision: 100% top tier plan coverage + 50% for dependents.
Dental: 100% top tier plan coverage, orthodontia extra, 50% for dependents.
Voluntary life, accident, hospital, critical illness, commuter and FSA/HSA are offered as employee contributed benefits.
8-weeks of paid parental leave for all parents. Additional paid pregnancy leave for CA employees.
Nuclear Engineering Certificate Program: 100% covered educational program with Penn State University, for eligible employees, to rapidly upscale into nuclear.
Daily catered lunch. Free snacks and drinks.
Flexible PTO policy. Remote workday allocation.
Company and team-bonding events, happy hours and in-person camaraderie.
Beautiful El Segundo headquarters close to the Pacific Ocean.
Total Compensation and Benefits
Radiant compensates people for impact and invests in those who continue to raise the bar. Radiant’s full-time new hire compensation package includes base salary, substantial equity grants, and comprehensive health benefits. Total compensation and level are determined through a rigorous evaluation of interview performance, experience, education, and qualifications, and are designed to support continued growth as scope, responsibility, and impact expand at Radiant.
The best of today’s advanced reactor builders don’t wait for job postings. They join the winning team. If that’s you, contact us directly for immediate opportunities: recruiting@radiantnuclear.com.
We are an equal opportunity employer and all qualified applicants will receive consideration for employment without regard to race, color, religion, sex, sexual orientation, gender identity or expression, pregnancy, age, national origin, disability status, genetic information, protected veteran status, or any other characteristic protected by law.
This position involves access to technology that is subject to U.S. export controls. Any job offer made will be contingent upon the applicant’s capacity to serve in compliance with U.S. export controls.
Compensation Range: $200,500 - $314,475
See All 242+ Principal Mechanical Engineer Jobs
Find roles that match your experience and apply in just a few clicks.
Find JobsPrincipal Mechanical Engineer Job Market
Who's Hiring
- Northrop Grumman39
- BAE Systems USA20
- Raytheon9
- Dell Technologies9
- Worley7
Top Industries Hiring
- Consulting & Professional Services
- Electronics & Hardware
- Technology & Software
- Automotive
- Manufacturing
What Employers Look For
The qualifications that appear most often in principal mechanical engineer jobs.
- Bachelor's or master's degree in mechanical engineering or a closely related discipline
- Eight or more years of progressively responsible mechanical design or systems engineering experience
- Proficiency in CAD tools such as CATIA, SolidWorks, or NX for detailed design and modeling
- Experience leading design reviews, tolerance analysis, and GD&T on complex assemblies
- Knowledge of FEA and simulation methods for structural, thermal, or dynamic analysis
- Professional Engineer license or active progress toward PE licensure preferred by many employers
Tips for Your Principal Mechanical Engineer Job Search
Tailor your resume for systems ownership
Principal-level hiring managers want to see that you owned full mechanical systems end-to-end, not just contributed to them. Call out specific subsystems you designed, qualified, and saw into production, with clear scope and measurable outcomes.
Apply early to roles that fit
Migrate Mate lists principal mechanical engineer openings from across the United States in one place, so you can find roles that match and apply directly to each listing.
Highlight cross-functional leadership explicitly
Principal roles expect you to influence electrical, software, and manufacturing teams without direct authority. If your resume reads like a solo contributor profile, reframe project bullets to show where you led design reviews, resolved trade-offs, or unblocked other disciplines.
Target postings by program phase carefully
Some companies hire principals for early-stage concept work, others for sustaining engineering on fielded products. Read postings for phrases like TRL advancement, DVT, or sustaining to match your background to the phase where you have the most depth.
Prepare a portfolio of technical decisions you defended
Interviews at this level routinely include a technical deep-dive where you walk through a design decision under real constraints. Pick two or three examples where you made a defensible call under pressure, explained the trade-offs, and lived with the result.
Negotiate scope before negotiating compensation
At the principal level, your reporting line, program ownership, and headcount influence matter as much as pay. Clarify whether the role has actual design authority or is advisory before accepting, so you can negotiate from an accurate picture of the job.
Principal Mechanical Engineer Jobs: Frequently Asked Questions
Which companies are hiring the most principal mechanical engineers?
Northrop Grumman, BAE Systems USA, and Raytheon are hiring the most principal mechanical engineers right now, with openings concentrated in California, Texas, and Utah, based on current listings on Migrate Mate as of November 2026. Aerospace, defense, and industrial equipment manufacturers consistently account for the largest share of principal-level postings.
How many principal mechanical engineer jobs are remote?
About 57% of principal mechanical engineer openings are fully remote or hybrid as of November 2026, which is lower than the broader engineering average given the hands-on nature of the role. Sub-specializations in systems engineering, technical program management, and simulation-heavy analysis tend to offer the most remote flexibility compared to roles tied to lab or production environments.
How do you become a principal mechanical engineer?
Most principal mechanical engineers start with a mechanical or related engineering degree, then spend years building depth in a specific domain such as aerospace structures, thermal systems, or precision mechanisms. Progression typically requires demonstrating ownership of complete design cycles, leading technical decisions across teams, and earning recognition as a subject-matter authority. Many engineers also pursue a PE license or graduate degree to strengthen their candidacy for principal-level roles at larger organizations.
Can you get hired as a principal mechanical engineer without direct principal-level experience?
Yes, but you need to close the credibility gap with evidence of principal-level scope, not just senior-level tenure. Hiring managers look for candidates who have driven a major design from concept through qualification, mentored other engineers, and made independently defensible technical decisions. If your title was senior but your work matched principal scope, make that explicit in your resume and be ready to walk through the evidence in detail during interviews.
What does the principal mechanical engineer interview process look like?
The process typically runs three to five rounds and includes an initial screening call with a recruiter or hiring manager, one or more technical interviews covering design principles, materials, failure analysis, and your domain specialty, and a deep-dive presentation where you walk through a past project in detail. Some companies add a written design exercise or a panel review with cross-functional stakeholders to assess how you communicate trade-offs to non-mechanical audiences.
Where can I find and apply to principal mechanical engineer jobs?
You can find and apply to principal mechanical engineer jobs on Migrate Mate, which lists current openings from employers across the United States. Search the listings to find roles that match your industry background and specialization, then apply directly to each one that fits.
See All 242+ Principal Mechanical Engineer Jobs
Find roles that match your experience and apply in just a few clicks.
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