How Lessons from SpaceX Will Make Radiant a Reality

Chris Hansen

Chris Hansen, Head of Mechanical Engineering at Radiant and SpaceX veteran, shares his excitement to be at the leading edge of the nuclear “space race.”

My father is a dentist but was always very handy around the house and his practice, fixing equipment and even remodeling his office. When I was a kid, he taught me about construction, plumbing, and electrical. I quickly learned that I loved working with my hands.

During my high school years at Don Bosco Tech, I learned everything from milling, hydraulics, CNC, and design. But early on, I fell in love with manufacturing. That led me to majoring in mechanical engineering at USC. It’s a versatile degree, very hands-on so you end up being a jack of all trades.

For my master’s, I stayed at USC and worked in machining internships during the summers. My goal was to be an engineer that could actually make things. As a T.A., I helped students with fabrication of their senior design experiments. That’s what led me to aerospace.

In 2003, Brian Bjelde and Phil Kassouf – fellow Trojan students then but now SpaceX veterans – recruited me to a little startup to build rockets. Little could I have imagined that my first full-time job would lead to nearly two decades of designing and building hardware systems that would revolutionize access to space. And better yet, that this experience would prepare me to now lead a world-class team designing and building the world’s first portable nuclear microreactor, poised to change the future of another vital industry.

Trial by Fire

When I first joined the structures team at SpaceX, there were only a few dozen of us. Our CEO Elon Musk repeatedly said that two of the biggest risks in rocket design are engine ignition and separation events. I was assigned as the responsible engineer (RE) for two separation events: the stage and fairing separation.

I knew nothing about either, but I had to step up and learn everything from dynamic analysis to the mechanical design to all the testing. SpaceX taught me the importance and the rigor of testing. Unlike most aerospace companies, we handled testing internally to ensure quality control. We did everything you can on the ground over and over and over to verify the vehicle was ready for flight.

For the first few years, I was a team of one, mentored by great engineers with backgrounds at the big aerospace companies and other hardware REs just starting out like me. It was really a trial by fire for all of us. I wore so many hats, even getting involved with structural qualification in both California and Texas.

Those years taught me so much, especially how roles can change over time. I learned how to run tests by myself. Then later how to better onboard new engineers. And finally, how to keep individuals motivated to make the strongest team possible. Towards the end of my time at SpaceX, I was managing a team of 40-50 engineers and technicians. But I was looking for new challenges, and starting to get increasingly curious about climate change.

Enter Radiant

Several people I knew at SpaceX were entering the clean energy field, including Radiant’s CEO & Co-Founder, Doug Bernauer. Doug and I worked closely on the Grasshopper project at SpaceX, building the system that would enable its first vertical landing. Well before I left SpaceX, we talked about Radiant and what he was trying to achieve with his groundbreaking concept for a portable nuclear microreactor. Over the course of a year, it got to the point that I could not get Radiant’s mission off my mind.

I was really captivated by the challenges of reusability at SpaceX. That was always the biggest driver for me. Our team at SpaceX accomplished great things together. I saw the same potential for Radiant. And I felt passionate about dedicating my time to help with current climate conditions on Earth.

Same Building Blocks

I was originally concerned about my lack of nuclear experience. But when Doug and I started digging in, I realized a nuclear reactor comes down to producing heat for a power system. A reactor has a pressure vessel, pumps, valves, piping, heat exchangers, and structural systems. There’s thermodynamics, fluid mechanics and structural mechanics at play. These are the same building blocks that are used across all mechanical engineering – whether you are working on cars, airplanes, rockets, or nuclear reactors.

Like aerospace engineering, nuclear is also all about mass. A portable reactor requires hardware to be as light weight as possible. A reliable, safe reactor requires detailed analysis, rigorous testing, and validation of every aspect of your design and materials. All these concepts and mindsets carried over directly from SpaceX, especially with Doug leading the way.

Regulations are obviously different in nuclear. I no longer have to adhere to NASA specs. So I’ve had to do a lot of learning. But it feels like my time at SpaceX. You dive in and learn from the seasoned veterans.

As the Head of Mechanical Engineering, I am focused on building a team with a wide variety of skillsets, backgrounds, and experiences that strengthen the team as a whole. I push myself and my team to ensure we have the best engineering practices in place. We’ve got to strike the right balance between being an agile startup and documenting things at every step to meet regulatory requirements.

The engineers on my team own their subsystems or components from beginning to end. They focus their time on overseeing every aspect to completion. That ownership is one of the most rewarding aspects of joining Radiant as an engineer.

Our thermomechanical team is currently finishing our biggest test to date with our helium circulator test loop. The helium circulator enables continuous flow of helium as a coolant through our reactor, extracting heat and transferring it to our power generation loop. We are validating our helium circulator’s performance in the test loop, simulating the same temperatures and hydraulic resistance it will see during operation.

The data we collect from this testing directly informs our in-house Digital Twin system that predicts performance of our reactor system. This is a huge milestone for my team and Radiant. We have additional system level tests coming up with the ultimate goal of testing Kaleidos at the Idaho National Lab in 2026.

The Future is Radiant

Our long-term goal at Radiant is to make nuclear power portable and accessible anywhere. We will eliminate super expensive, fixed infrastructure. Just as there are multiple power size choices for combustion engines, Radiant will bring more diversity to power scales in nuclear.

I see many similarities between the origin stories of Radiant and SpaceX, the unknown commercial space startup working with NASA. At Radiant, we are helping drive and determine the path forward for nuclear. We are part of the evolution of an industry. I think of it like the JFK analogy: “A rising tide lifts all boats.” As one company grows, partnering with national labs, universities, government, and regulators, you impact everyone across the industry and eventually, the planet.