Senior Mechanical Engineer

The Role As a Senior Mechanical Engineer within the Mechanical Department, you will own the design and execution of complex mechanical subsystems that directly influence the economics, reliability, and scalability of our core technology. This role spans early-stage R&D through NPI and site-scale deployment, requiring strong engineering fundamentals, sound judgment, and a bias toward practical, manufacturable solutions. You will be expected to challenge assumptions, rigorously evaluate tradeoffs, and push the boundaries of design and manufacturing while maintaining a clear focus on cost, reliability, and long-term operability. This is a high-ownership individual contributor role with significant technical leadership and cross-functional influence. What You’ll Do Own end-to-end design of complex mechanical subsystems, from requirements definition and concept architecture through validation, production ramp, and deployment Drive subsystem performance across cost, reliability, manufacturability, and serviceability, with direct impact on $/ton CO₂ economics Design low and high-volume components using a variety of manufacturing processes, including sheet metal stamping, casting, roll forming, and extrusions Lead design trade studies using first-principles analysis, data-driven methods, and sound engineering judgment Design and develop product-level test equipment, fixtures, and validation strategies to support Design for Reliability (DfR), including accelerated life testing, stress testing, and failure-mode–driven validation to ensure robust subsystem and system performance over the intended service life Partner closely with suppliers, equipment operators, manufacturing, and supply chain teams to ensure designs are robust, scalable, and production-ready Generate and review detailed 2D drawings with proper GD&T, aligned with production and inspection standards Support rapid prototyping and iterative development cycles while maintaining a clear path to NPI rigor Act as a technical leader within the team by mentoring peers, driving best practices, and raising the bar for engineering quality What You’ll Bring 5+ years of experience designing and delivering products through the full lifecycle, from concept to production Strong passion for product design and solving complex engineering problems with simple, robust solutions Excellent engineering fundamentals, with the ability to apply first principles, modeling, and data to real-world design decisions Experience applying Design for Reliability (DfR) principles, including failure mode identification, reliability modeling, accelerated life and stress testing, and translating test results into durable design improvements Experience with engineering analyses such as reliability modeling, tolerance analysis, FEA, fatigue analysis, and root cause analysis Demonstrated ability to lead technically complex projects or subsystems with minimal supervision Proven track record of working cross-functionally to balance competing requirements and constraints Experience producing clear, accurate drawings and specifications suitable for manufacturing and inspection Strong sense of ownership, accountability, and follow-through—delivering high-quality work on schedule Bonus Points Hands-on experience designing sheet metal (stamping, press brake), weldments, and plastic parts (e.g., injection molding, thermoforming) Background in random vibration and fatigue testing, metallurgy, material and test standards Experience managing development in a product lifecycle management system (PLM) Comfort operating in both fast-paced R&D environments and the structured rigor of NPI execution Experience using NX in a production or industrial context You don’t have to have every listed requirement and skill to be a great fit. If you are passionate about this opportunity and think you have the skills to succeed, please apply! Our Commitment to Diversity, Equity, and Inclusion We encourage you to apply if you identify as Black, Native Hawaiian or Pacific Islander, American Indian or Alaskan Native, Hispanic or Latino, LGBTQ+ – or with any other underrepresented group – even if you don’t tick all the boxes in the description below. Perks and Benefits for Eligible Employees Excellent health, dental and vision insurance covered up to 100% by Heirloom. FSA option. 16 weeks paid parental leave for all Heirloom employees. Generous stock options. Unlimited PTO for exempt (salaried) employees & 120 hours for full time non-exempt (hourly) employees. 401(k). Monthly health and wellness reimbursement. Annual education and conference budget. Our Principles Radical Honesty. We strive to foster an inclusive environment premised on transparency and respect. We push for excellence, yet always remain thoughtful when challenging each other. Persistent Optimism. We show up to work with optimism and don’t shy away from a challenge. We recognize that the ambitious nature of our mission requires hopefulness, dedication, and persistence. Maximize Learning. Compounding knowledge is our key to victory - we continuously hone our crafts, seek the fastest paths to improve, and are quick to absorb and apply new insights. Why you should join Heirloom We are solving the challenge of our generation. Climate change is an existential threat, and we need as many of the world’s motivated minds as possible to help. There is no greater challenge or opportunity than fighting climate change. We are a world-class team. We are engineers, scientists, and concerned humans from a variety of backgrounds and experiences who are pooling our knowledge and skills to collectively build a more equitable, prosperous future for all. We remain united, resilient, and optimistic. We recognize the magnitude of the challenge ahead of us, yet believe that we can contribute to mitigating the worst effects of climate change. It won’t be easy, but we won’t quit. We are backed by credible climate partners. We’re well funded by investors from Breakthrough Energy Ventures, Ahren Innovation Capital, Carbon Direct, Microsoft, Lowercarbon Capital, ARPA-e and the National Science Foundation. Our early customers include Stripe, Shopify, and Klarna, and we’re building durable partnerships that enable us to tackle this decades-long problem.