Senior Thermal Design Engineer

Space is the bleeding edge for humanity's next industrial revolution. While reusable rockets have opened the door, true economic transformation requires infrastructure that makes orbit as accessible and reliable as air travel. At Lux Aeterna, we're building that future by developing the first reusable satellite platform with return capability, transforming space from a one‑way street into a two‑way highway for innovation and commerce.

We're seeking an exceptional Thermal Design Engineer to architect and lead the development of our spacecraft’s thermal management system. As our first thermal engineer, you'll bridge the gap between analysis and hardware ownership, solving complex challenges that have profound implications for the future of commercial spaceflight.
This is a unique opportunity to:

• Architect design criteria to drive thermal performance of all subsystems in orbit, during reentry and on the ground.
• Own the design, procurement, build, and test of all thermal control hardware on the vehicle (heaters, MLI, gap pads, radiators, thermal straps).
• Perform hand calculations to iterate through ideas and problems quickly with the structures, avionics, GNC and FSW teams.
• Own the vehicle thermal model in Thermal Desktop.
• Work directly with technical leadership to shape the future of space transportation.
• Support recruiting efforts to grow the engineering team.
• Pioneering Technology: We’re developing the first reusable satellite platform with controlled return capability, fundamentally transforming space from a one‑way journey to a two‑way highway.
• Real Impact: Your work will enable new industries in space manufacturing, research, and logistics while pioneering sustainable space infrastructure.
• Speed & Autonomy: We maintain parallel hardware development streams and empower engineers to innovate rapidly while upholding rigorous aerospace standards.
• World‑Class Team: Work alongside experts from leading aerospace companies and research institutions, building technology that will reshape humanity's access to space.

You’ll lead the thermal design, analysis, and execution of our spacecraft thermal control systems, including:

• Managing technical interfaces with aerothermal teams for reentry analysis.
• Developing and validating thermal models for both orbital and reentry phases.
• Designing thermal management systems for orbital and hypersonic reentry conditions.
• Creating spacecraft thermal control systems for extended orbital operations.
• Leading selection and qualification for thermal management systems.
• Driving execution of development, qualification and acceptance test campaigns.
• Collaborating with mechanical and electrical teams on thermal design criteria.
• Working with vendors to develop custom thermal components and systems.

• BS in Mechanical Engineering or related field.
• 8+ years of spacecraft thermal engineering experience.
• Proven track record designing and qualifying thermal control systems through multiple successful missions.
• Strong understanding of heat transfer, fluid dynamics, and thermal analysis tools.
• Fundamental understanding of mechanical and electrical first principles and design methodologies outside the thermal domain.
• Experience with Thermal Desktop.
• Expertise in spacecraft thermal control techniques and technologies.
• Demonstrated ability to excel in dynamic, high‑stakes engineering environments.

• MS in Mechanical Engineering or related field.
• Direct experience with hypersonic vehicle or reentry system thermal analysis.
• Background in thermal protection system design and testing.
• Experience with aerothermal analysis tools (FIAT, CBAERO or similar).
• Early‑stage startup experience.

Location: Denver, CO. We are onsite 5 days/week by default, but flexible when life requires it.