Under an ambitious NASA program called Project Rover, which ran from 1955 to 1972, Los Alamos Scientific Laboratory diversified its mission and made serious efforts to develop nuclear-powered rockets.
At Los Alamos, the Nuclear Rocket Propulsion (N) Division was a hotbed of activity for nuclear engineers like Clay Watson, who worked on the program from 1963 to 1972. He was an expert in reactor physics.
“It was a large program, perhaps the largest-single program in the history of the Lab depending on the measure,” according to Lab historian Alan Carr.
Although nuclear-powered rockets didn’t pan out, today’s Mars Exploration Rovers are the result of many years of nuclear reactor development and the contributions of individuals like Clay.
As told by Clay Watson
Editor’s note: At age 85 and living in Pagosa Springs, Colorado, in 2018, Clay reflected on the highs and lows of the Los Alamos nuclear rocket program — and contemplated the future of Mars exploration, as NASA revived the dream of nuclear-powered spacecraft to reach the red planet. This oral history was edited for clarity and brevity. He died May 4, 2023, at age 90.
I joined Los Alamos only because I was on the rover program. They wanted to hire me to work on weapons, and I said, “No, I’m here to work on Project Rover.”
In those days, that was a big program. We did all the nuclear stuff, both inventing and — even more than that — testing, trying to figure out why things work and why they don’t work.
‘You're going to blow up the world'
One of the big deals that the so-called experts would say is, “You’re going to blow up the world!” That is just fundamentally not so.
Some of the world’s most complex computer programs were used to try to analyze what was going on in these nuclear reactors before something happened that you didn’t like. All the effects of phenomena when you’re building real nuclear reactors were at least three dimensional.
We ran computer programs that could predict these things. I did analysis of the gamma ray and neutron environments for things like where did heating occur, and what does it have to do with the nuclear control rods. I did the early Monte Carlo work on that. Monte Carlo is a way to do 3D calculations.
Computers were absolutely essential in all of my work out there. The computers were first-rate people, not machines, and my job was to tell them what to compute and how.
Experiments were done to prove the calculations or improve the calculations. We had to build things to test because you couldn’t calculate it adequately and show other people it can’t blow up and be dangerous. It’s not a weapon. It can’t be a weapon.
A team was assigned the task of coming up with the worst-case scenario to be tested in a remote location at the Nevada Test Site near Jackass Flats. The tongue-in-cheek name assigned to this test was Transient Nuclear Test, or TNT. It was the last Kiwi test.
So, what we did was build one of these reactors and make it go as fast and blow up as much as possible. Throw the control rods out and see what happened. The experiments contributed to the analysis of the physics, which showed that the idea that nuclear reactors are going to explode is nonsense.
Kiwi tests
I was involved in the Kiwi tests (Project Rover’s first series of nuclear engines).
You have to imagine a complex test cell with a device sitting on top of it to run big tests. I remember being up on a 24-foot-tall cherry picker bucket in the air. I had to hop around the test cell a lot. I had a bunch of wires in these little holes in the reactor — by the way, I had the world’s only enriched U-238 material, which I got from Oak Ridge, to make these wires that would respond to the reactor core that was down there. I had to get special permission to stick anything in that core.
I’m on the cherry picker looking down on the core of the reactor and below were a bunch of people running around working on it, and all of the sudden this siren goes off. The cherry picker driver thought it was a nuclear criticality siren, and I thought he was going to jump out, so I told him to relax because I was sure it was a false alarm. We went down about halfway, and he said, “Oh, it’s just the hydrogen alarm.” At that point I wanted to jump out of the damn bucket. “Get us down from here!”
(Clay was afraid of a potential hydrogen explosion that might have occurred — but didn’t.)
Project Rover's demise
There was no alternative but to build one and go to Mars. They could have taken men to Mars and kept them there for two or three months and then come back. Oh, I would have liked to see it go ... But Congress decided that it’s too expensive and we’re not going to do it. There was no question by that time the country had more important things to do, at least in their minds.
Roughly 1,000 Los Alamos staff had to find new work, and the Nuclear Rocket Development Station at Nevada Test Site was shut down.
In between Project Rover and the Strategic Defense Initiative (SDI), I worked on 17 different projects at Los Alamos. For SDI (aka “Star Wars”), I worked on directed energy beams, analyzing and running calculations on what is, what could be, what should be and how they compare.
The whole idea of the Laboratory is not to provide careers for people; it’s to push the country forward and even the world forward. The Laboratory is the country’s laboratory, doing things that industry or other people can’t or won’t.
Project Rover's legacy
A broad spectrum of modern technology come from Project Rover. For example, materials work, including graphite and carbon work.
Also, liquid hydrogen was a two-liter weird thing, a lab curiosity in the beginning, but by the end of the Project Rover we had 250,000-gallon dewars.
Other modern technology started with Project Rover — you wouldn’t believe that it started there but it did, just like an awful lot of really far-out research projects.
Musings on the future of atomic space travel
Editor’s note: Los Alamos still has some of the world’s leading experts in nuclear reactor design. NASA chose Los Alamos to design a small nuclear reactor called Kilopower. Kilopower could one day power a colony on Mars or other planets. When asked about the future of atomic space travel, Clay sounded a little exasperated. He showed his loyalty to the Project Rover legacy.
Los Alamos still has some of the world’s leading experts in nuclear reactor design. NASA recently chose Los Alamos to design a small nuclear reactor called Kilopower. Kilopower could one day power a colony on Mars or other planets.
When asked about the future of atomic space travel, Clay sounded a little exasperated. He showed his loyalty to the Project Rover legacy.
I wish you’d listened to us 40 years ago — but OK, that’s life.
There are lots of other options beside nuclear-powered engines, but they either won’t work or they would cause the mission to take too long.
I think the idea of going there (to Mars) is still good because it will lead you places that are probably good. For that matter, so did going to the moon.
Now to go to another star? No, no, no. God won’t let you, or whoever is running the universe.
Stepping into his father's shoes
Clay’s son, Scott Watson, worked as an electrical engineer in the same Los Alamos group his father did, now known as NEN-2, the Advanced Nuclear Technology group. Though some of Scott’s NEN-2 colleagues were involved with space reactor research, his main focus with that group was radiation detection and imaging. (Scott is now working in Complex Response Solutions, A-5.) Some of his earliest childhood memories were of the famous Apollo Project sending men to the moon between 1969 to 1972.
“Growing up in Los Alamos, I loved hearing about the less famous but equally significant Project Rover, where nuclear rocket engines were built and successfully tested as a way to enable manned exploration to Mars,” Scott said.
He remembers hearing nuclear rocket stories as a young boy whenever the close-knit N-2 poker club met at his house — an elite group that included George Grover, Gordon Hanson, Dick Malenfant, Hugh Paxton and others. He admired the Kiwi and Phoebus nuclear rocket engines on display outside the old Los Alamos Scientific Museum.