Thermal Engineer (Senior)

Spacecraft represent the most pressing unmet need across the entire aerospace industry. As more launch vehicles come online and the cost to orbit decreases, more companies launching payloads to space continue to emerge.

For the first time in history, this influx of payload companies combined with reduced launch costs has resulted in a massive increase in need for commercial spacecraft platforms, known as satellite buses. These buses hold the payloads of our customers and are flown on launch vehicles.

Apex manufactures these satellite buses at scale using a combination of software, vertical integration, and hardware that is designed for manufacturing. Our spacecraft enable the future of society: ranging from earth observation to communications and more.

We’d love for you to join us on our mission of providing humankind access to the galaxy beyond our planet.

About the Role

Apex is seeking a Senior Thermal Engineer to own the thermal design and performance of our spacecraft from concept through flight. In this role, you’ll solve complex thermal challenges across the vehicle, develop and validate spacecraft level thermal models, and directly influence hardware design and mission performance. You’ll work hands-on with flight hardware and partner across engineering teams to take thermal systems from early design through integration, test, launch, and on orbit operations.

Responsibilities:

• Lead payload thermal design, analysis, and integration from early concept and requirements definition through qualification, launch, and on-orbit operations.

• Own the thermal technical interface with external customers, including requirements definition, interface development, design trades, technical reviews, and resolution of thermal-related issues.

• Develop and maintain spacecraft- and payload-level thermal models using Ansys Thermal Desktop and perform analyses across applicable mission environments.

• Develop and implement advanced passive thermal control solutions, including high-performance heat transport and heat rejection technologies.

• Design and analyze active thermal-fluid systems, including component sizing, system-level performance analysis, and integration with spacecraft thermal architectures.

• Drive thermal design decisions and collaborate with mechanical, systems, avionics, GNC, and other engineering disciplines to ensure vehicle and payload thermal requirements are met.

• Plan and execute thermal subsystem milestones and technical reviews, including SRR, PDR, and CDR.

• Support thermal hardware development, integration, build, and test, including component- and spacecraft-level thermal vacuum testing.

• Correlate test and flight data to thermal models to improve model accuracy and validate thermal performance.

Requirements:

• U.S. Person status is required as this position requires access to export-controlled data.

• Bachelor’s degree in Mechanical Engineering, Aerospace Engineering, or a related field.

• 5+ years of experience in thermal engineering or analysis.

• Experience with thermal modeling and analysis tools.

• Strong understanding of heat transfer and thermal engineering fundamentals.

• Strong analytical and problem-solving skills with the ability to work in a fast-paced environment.

Preferred Qualifications:

• Experience with spacecraft or aerospace thermal systems.

• Proficiency with Ansys Thermal Desktop.

• Experience designing spacecraft thermal control systems.

• Experience with thermal vacuum testing, instrumentation, and data acquisition.

• Experience correlating thermal models with test or flight data.

• Familiarity with spacecraft thermal margin standards and requirements.

• Working knowledge of two-phase thermal control systems.

• Experience with Siemens NX and Teamcenter.

#LI-MO1

Why Join Apex?

Apex believes in creating a work environment that you look forward to embracing every day. Our employees love working at Apex, and we want you to love it too. We're a fast-growing startup that has raised more than $500M in funding, and we invest heavily in our people from day one.

What We Offer For Full-time Employees:

• Shared upside: Receive equity in Apex, letting you benefit from the work you create

• Best-in-class healthcare: 100% company-paid medical, dental, and vision for you and your dependents, plus $100k life insurance at no cost

• Comprehensive PTO package to reset and recharge - starting at 15 days vacation, growing to 20+ days annually, plus 10 paid holidays

• Competitive 401(k) plan with generous matching - 100% match on first 3%, 50% on next 2%

• 8 weeks paid parental leave plus childcare reimbursement up to $350/day for work-related travel

• Daily catered lunch and unlimited snacks to keep you fueled throughout the day

• Vibrant community: Monthly office socials, pickleball tournaments, run club, and gatherings for you and your family

• Your dream desk setup and all the tools you need to be your most productive self

• World-class Playa Vista office with the benefit of in-person collaboration with amazing coworkers and flexibility to integrate work and life

• Real impact opportunity: Work alongside experts from aerospace, new space, and other cutting-edge industries to make a lasting difference

Additional Information:

Compensation ranges are set by role, level, location, and alignment with market data. A candidate's specific level and base pay are determined case by case and may vary with job-related skills, education, experience, technical capabilities, and internal equity. Beyond base salary, full-time hires are also eligible for long-term incentives in the form of stock options, along with medical, dental, and vision coverage and a 401(k) retirement plan.

ITAR Requirements

Apex's work is governed by U.S. export control laws, including the International Traffic in Arms Regulations (ITAR) and the Export Administration Regulations (EAR). To be eligible for this role, applicants must either (1) qualify as a U.S. Person, meaning a U.S. citizen or national, a lawful permanent resident (green card holder), a refugee admitted under 8 U.S.C. § 1157, or an individual granted asylum under 8 U.S.C. § 1158, or (2) be able to obtain the required export authorizations from the U.S. Department of State, the U.S. Department of Commerce, or another applicable U.S. government agency. You can learn more about ITAR here .