Senior Thermal Engineer

Next Matter; Torrance (CA); On-site; USD 120,000 - 180,000; Full time

Benefits offered by this job

Equity (long-term)

4 weeks PTO

10 company-paid holidays

Health benefits including medical

Parental leave

Fitness stipend

EV charging on site

Catered meals and fully stocked pantry

Job summary

Castelion is seeking a Senior Thermal Engineer to own the thermal engineering methodology across missile systems. You will define thermal architectures, develop high-fidelity thermal models, and use first-principles analysis, simulation, and hardware testing to ensure our vehicles perform reliably in demanding environments.

You’ll work across aerodynamics, structures, electrical, propulsion, systems, manufacturing, and test engineering to develop integrated thermal solutions from concept through

Qualifications

• BS or higher degree in Aerospace Engineering, Mechanical Engineering, or Applied Physics.
• Strong understanding of heat transfer, fluid dynamics, and high-temperature environments.
• 5+ years of experience in aerospace thermal engineering on rocket, spacecraft, aircraft, or missile programs.
• Experience with electronic unit thermal analysis and control to component junctions.
• Ground testing experience with thermal instrumentation and data acquisition.
• Strong programming skills in MATLAB, Python, or similar for tool development.
• Experience preparing formal documentation.
• CAD experience with SolidWorks or Siemens NX.
• Ability to obtain and hold a U.S. security clearance.

Responsibilities

• Thermal design and analysis of unmanned air vehicles at conceptual, preliminary, and detailed design maturities.
• Define thermal system architectures and material selection strategies for vehicles operating in demanding flight environments.
• Thermal analysis of flight vehicles using standard thermal analysis codes and engineering/hand methods.
• Transient thermal analysis for time-varying mission profiles.
• Ground test planning, execution, and analysis in specialized thermal test facilities.
• Flight test planning, execution, and post-flight thermal data analysis.
• Use first principles and MATLAB/Python models to inform design decisions.
• Collaborate with aerodynamics, structures, electrical, and systems engineers on integrated solutions.
• Present thermal status at formal reviews internally and with customers.
• Prepare formal documentation (specifications, test procedures, technical reports).

Skills

Heat transfer

Fluid dynamics

High-temperature environments

MATLAB

Python

First principles analysis

Modeling & simulation

Team collaboration

Education

BS in Aerospace Engineering

MS in Aerospace/Mechanical Engineering

Tools

SolidWorks

Siemens NX

Thermal Desktop/SINDA

Data acquisition

Job description

Why Castelion, Why Now

Castelion is moving incredibly fast to develop and deliver advanced defense systems at a time when execution matters more than ever. We believe focus and technical excellence are decisive advantages - and we are building a team that can deliver real capability, not just concepts.

This is a rare opportunity to join at an early stage, where your work will directly shape critical systems, influence major technical decisions, and have immediate, real-world impact.

Senior Thermal Engineer

As a Senior Thermal Engineer at Castelion, you will own the thermal engineering methodology across our missile systems. You will define thermal architectures, develop high-fidelity thermal models, and use first-principles analysis, simulation, and hardware testing to ensure our vehicles perform reliably in some of the most demanding thermal environments imaginable.

You’ll work across aerodynamics, structures, electrical, propulsion, systems, manufacturing, and test engineering to develop integrated thermal solutions from concept through flight. Your work will span transient mission analysis, electronic unit thermal management, specialized ground testing, and flight-test instrumentation and data analysis. This role is ideal for an engineer who enjoys moving fluidly between analytical models, real hardware, and flight data—and who wants to directly influence vehicle architecture and design decisions from day one.

Responsibilities

• Thermal design and analysis of unmanned air vehicles at conceptual, preliminary, and detailed design maturities
• Define thermal system architectures and material selection strategies for vehicles operating in demanding flight environments
• Thermal analysis of flight vehicles using standard thermal analysis codes and engineering/hand methods
• Transient thermal analysis for time-varying mission profiles
• Ground test planning, execution, and analysis in specialized thermal test facilities
• Flight test planning, execution, and post-flight thermal data analysis
• Use first principles and MATLAB/Python models to inform design decisions
• Collaborate with aerodynamics, structures, electrical, and systems engineers on integrated solutions
• Present thermal status at formal reviews internally and with customers
• Prepare formal documentation (specifications, test procedures, technical reports)

Basic Qualifications

• BS or higher degree in Aerospace Engineering, Mechanical Engineering, or Applied Physics
• In-depth understanding of heat transfer, fluid dynamics, and high-temperature environments
• 5+ years of experience in aerospace thermal engineering on rocket, spacecraft, aircraft, or missile programs
• Experience with electronic unit thermal analysis and control to component junctions
• Ground testing experience with thermal instrumentation and data acquisition
• Strong programming skills in MATLAB, Python, or similar for tool development
• Experience preparing formal documentation
• CAD experience with SolidWorks or Siemens NX
• Ability to obtain and hold a U.S. security clearance

Preferred Skills and Experience

• MS or higher degree in Aerospace Engineering, Mechanical Engineering, or Applied Physics with focus on heat transfer and fluid dynamics
• Experience with material ablation response modeling in extreme thermal environments
• Knowledge of material degradation and surface phenomena under demanding conditions
• Experience with specialized thermal ground test facilities
• Flight test experience including instrumentation design and post-flight analysisExperience with Thermal Desktop/SINDA
• Experience with manufacturing and assembly of thermal systems
• Active U.S. security clearance

Benefits And Perks

All full-time employees are granted meaningful long-term equity, sharing in the company's significant growth trajectory. We offer four (4) weeks of paid time off, ten (10) company-paid holidays, and comprehensive health benefits - including 100% employee-covered medical and strong dependent coverage, along with dental and vision plans. We also provide paid parental leave to support growing families, a $100 monthly fitness stipend to promote health and performance, and onsite EV charging for convenience. In addition, employees enjoy perks like catered meals, company-covered food during high-demand periods, and a fully stocked kitchen to stay fueled throughout the day.

While this position does not currently require a U.S government-issued security clearance, it may in the near future. Therefore, the ability to obtain and maintain a U.S government-issued security clearance is required. U.S. citizenship is required, as only U.S. citizens are eligible for a security clearance.

Affirmative Action/EEO Statement

Employment with Castelion is governed on the basis of competence and qualifications and will not be influenced in any manner by race, color, religion, gender, national origin/ethnicity, veteran status, disability status, age, sexual orientation, gender identity, marital status, mental or physical disability or any other legally protected status.