We are looking for a Senior Avionics Test Engineer with 3-8 years of experience to own the end-to-end test environment for flight-critical avionics hardware at a rapidly scaling hypersonics company. You'll be the person who builds the test infrastructure from the ground up — designing test racks, fixtures, harnesses, and automated test systems for hardware like motor controllers, flight computers, instrumentation LRUs, and ignition safety devices. This is not a role where you execute someone else's test procedures; you're figuring out how to test the hardware, designing the architecture, selecting instrumentation, and scaling it all the way from development through vehicle integration and flight. Castelion's avionics hardware is the brain of the missile system, and you'll ensure every board works flawlessly before it flies.
What will you be doing?
Building test environments end-to-end — designing test racks, ATE systems, fixtures, harnesses, and HIL environments for avionics hardware
Owning test development from component-level through vehicle integration-level for systems including motor controllers, flight computers, instrumentation LRUs, and switches
Automating and scaling test procedures to support production growth as the company scales
Debugging hardware anomalies, leading root-cause investigations, and collaborating with avionics hardware engineers to refine designs based on test results
Driving qualification and environmental testing campaigns (vibration, thermal, EMI) for flight hardware
Castelion is a modern defense production company building long-range hypersonic strike systems to address a critical national security gap. Founded in 2021, Castelion was created in response to the recognized need for the United States to rapidly develop hypersonic capabilities to remain competitive with near-peer adversaries and deter future conflicts.
The company operates under the philosophy of "Peace through Deterrence" — building the weapons systems that ensure conflicts never need to happen. Castelion is one of the few companies in the hypersonics space that has moved beyond concepts to actual production deliverables, with government contracts across multiple branches of the military and a $23M+ Navy order for 50 units in calendar year 2027.
Backed by over $469M in funding from top-tier investors including Andreessen Horowitz, Lightspeed Venture Partners, and General Catalyst, Castelion is scaling rapidly. The company is building what it anticipates will become the preeminent hypersonics campus in the country — including a $150M, 1,000-acre solid rocket motor manufacturing facility in Rio Rancho, New Mexico, alongside its headquarters in Torrance, California.
Castelion's culture is defined by technical excellence, ownership, and velocity. Engineers own meaningful subsystems on the vehicle and are responsible for driving their success. The company follows a responsible engineering model inspired by SpaceX, where individuals choose the highest-value work and are empowered to cultivate resources and partnerships to deliver results. The engineering bar is exceptionally high — attracting elite talent who want to be surrounded by other elite talent.
Salary
$150,000 - $200,000
Location
Torrance, United States
Experience
3+ years
Total raised
$464M
Last stage
Growth
Investors
No applications, no recruiter spam. Just the intro.
A few questions to make sure this role is the right shape for you. Two minutes.
I write the intro, send it to the founder, and handle the back-and-forth.
If they’re a yes, I book the chat. You show up — that’s the whole job-hunt.