The future of space travel could be nuclear

Robert O’Brien I’m just stepping into the role of director of the center for Space Nuclear Research, which is a Universities Space research association or USRA’s institute. The institute, or the CSNR, was formed in 2004, in partnership with the Department of Energy. We’re focused on working with the talent pipeline, developing a future workforce for the space nuclear industry, which is a very, very focused but strategically important work force that we need to develop for the nation. But in addition to focusing on the town pipeline, we’re also engaged in the development of national programs. And, and really doing all of the above for development of advanced technologies in space, nuclear power and propulsion.

Eric White Yeah. You know, the melding of space and nuclear. It’s not something that my that wasn’t the first place my head went to. Where do things currently stand as far as the use of nuclear energy? Is it to actually power spacecraft or is it used for other methods in space currently, or are you guys still looking into that?

Robert O’Brien So, you know, let’s go back to the origins of the space industry. Wernher von Braun knew that we needed high energy density, power, and propulsion in order to explore the outer solar system. Even to go to Mars. We were looking at, nuclear fission systems to be able to enable human exploration. It’s also an incredibly important technology that you have to explore robotically as well. Being able to close missions in the lifetime of a principal investigator, which normally is unheard of to do 2 or 3 missions in the career lifespan of a P.I., but with the engagement of nuclear technology being able to maneuver faster than ever before, we’ll be able to close those missions and get, you know, a seasoned experience into the science community and, and closing missions that were normally once in a lifetime. And so, this is not a new technology area. This is very much an area that’s been looked at since the dawn of the space age. What we’re doing now is really refining those technologies and stepping out from what we would describe as 1950s and 60s technologies. Which is primarily driven by radioisotope decay, for our nuclear systems to date, the world has changed. The ability to generate enough fuel for those radioisotope systems is proving to be challenging as all the programs closed out and facilities were closed. We’re now looking at systems that are perhaps more storable, being able to assemble technologies that can sit on the shelf and be ready for flagship class missions, and also can be used by the commercial space industry, which is really an exciting new chapter for, for the space sector. Looking at commercial spaceflight both to the moon and beyond. And I think as we look at, exploring systems from a commercial perspective, we’re also looking at prospecting for minerals and materials that we can use for in-space manufacturing and even bringing materials back to Earth to help enrich human life here on Earth, as well. And all of this is going to be possible, using high energy density systems, systems that use nuclear fission for both generation of electricity process heat and propulsion as well. Being able to maneuver without regret. Being agile, and, you know, really enabling new trajectories for spacecraft, that, couldn’t be closed easily or affordably with chemical propulsion. So, a very exciting, chapter, I think, ahead of us using this, this technology. But the main takeaway is we’ve really used nuclear energy already done that successfully since the 1950s for spaceflight. And, you know, we’re now looking at, the next chapter, which is, you know, very safe, efficient systems, that enable human and robotic missions.

Eric White Yeah. You mentioned that term high density. It seems as if. Yeah, it makes sense. Nuclear power is almost tailor made for space because that you get a lot out of a little bit of, fuel. What are some of the drawbacks of, using nuclear power in space? And you had mentioned some of the challenges that you all are running into. As far as getting an efficient and consistent, power source from these, sorts of materials.

Robert O’Brien So as we move into, you know, the next chapter where we’re looking at, technology. Is that robust. We’re looking at materials that can endure at very high temperatures to be efficient. One of the biggest challenges that we face when we’re generating electricity, as one example, is being able to remove the waste heat. And what waste heat means is on the outside or the rejection side of any kind of, cycle. Or if you think about a power conversion cycle like Brayton power or a Stirling engine, some of the most early types of heat engine, you put heat in, but you also do work and have to reject heat. And it’s that heat rejection that is the biggest challenge in terms of mass penalties as we face being able to close a mission design that doesn’t spiral out of control when it comes to mass and mass penalty. So, in order to overcome all of these challenges with rejecting waste heat, instead of using a lot of dead mass, which is essentially a radiator panel, that radiates heat to space. What we have to do is minimize that mass. We have to do that, using the Stefan Boltzmann law, which there’s that term temperature, the power of four. So, in other words, if you can increase the temperature significantly, you can dramatically increase the efficiency of the overall radiator technology and the ability to radiate to space. All of that reject heat. And there were some legacy programs that looked at fission systems. Those systems, looked at, you know, pretty low temperature radiator technology. It was the best that was at hand back, even up through the 1990s through the early 2000. Those temperatures may have been around 500 Kelvin, 525 Kelvin. With some of the legacy programs and those the challenges there is that you need hundreds to kilometers of, square, you know, square area that, that you need to reject heat from. And so, if we can bring temperature up to in the realm of 900 Kelvin to even in the future 1200 Kelvin, where that could be a sweet spot where we’re in the meter squared, not thousands of meters squared. That is really interesting and very exciting because every meter squared has mass attributed to it. And so, if we can keep the square meter down, then we can keep the mass down of the overall system. And remember that that that mass doesn’t do anything but push heat to space. So, it takes away the amount of useful payload that we can put on a spacecraft, instrumentation, even people and essentials for life support so that that’s what we can bring back to a mission if we can bring temperature up. So that means development of new radiated materials and potentially new fuel systems, and even new reactor technologies that work in the realm of 3000 Kelvin. So, lots of exciting work on materials manufacturing side. All of this to say that we need people to solve those problems, and we need the facilities and infrastructure across the nation to, to really develop those new technologies.

Eric White Yeah, we’ll get into the talent aspect of this, in just a second. But I do want to ask, you know, what sorts of research efforts are looking into those things? How do you how do you experiment with this? You know, it’s pretty finicky technology already here on Earth. I can’t imagine, you know, having to conduct sort of these experimental works in space, you know, are there any research efforts that you’re currently involved in, or you have been involved with in the past that look into trying to address those challenges?

Robert O’Brien Absolutely, yes. This is this is where the programmatic side, of the, the technology areas is really, starting to, to pick up a lot of momentum and getting a lot of great results already. If we think about the NASA Space Nuclear Propulsion project, which is run out of the STMD directorate at NASA, this is, a really exciting program that’s been going for several years now, making immense progress with respect to developing new fuels that perform incredibly well at 3000 Kelvin for the nuclear propulsion side, we’re looking at nuclear thermal propulsion and nuclear electric propulsion. One aspect is generating electric to be able to power, thrusters like whole thrusters, ion drives, even technologies like VASIMR where the future looking being able to be very efficient, looking at different power levels. Everything from the kilowatts, megawatts. We’re making great progress, across the industry sectors as well as, within the NASA centers and the Department of Energy, all working together to solve materials problems at those high temperatures. And, you know, 3000 Kelvin for fuel, is over 2500 Kelvin more than, we’re doing today on Earth for fuel systems that, that are looking at, fission technologies and, existing fleet of reactors like the pressurized water reactors and boiling water reactors across the country. So those technologies are a very robust well understood. And they operate in a very safe and low temperature areas. We’re looking at temperatures now that are pushing the boundaries for space exploration, that are pushing the boundaries of the physical or the solid state, if you like. We’re on the verge of melting fuel when it comes to nuclear thermal propulsion, but we do that because we have a robust matrix to encapsulate the fuel. So, we’re looking at technologies like ceramic matrices and ceramic metallic matrices. The matrix itself holds everything together. It maintains a cool geometry as we take the fuel up to 3000 Kelvin. And the fissile material, the fuel itself is embedded in that matrix. Being able to make that material is an area we’ve made immense progress over the last decade in partnership with industry and the national lab capabilities across the country.

Eric White And so, yeah, as you mentioned, this is a huge undertaking, and you are in need of the people and the researchers to do this work. You know, being a nuclear engineer is hard enough. There’s probably not a lot of them to go around. How do you attract a nuclear engineer to say, hey, you know, why don’t you look above the stars for once and instead of focusing on nuclear power here on Earth?

Robert O’Brien Yeah, talking to stars. You know, it’s like there has to be alignment of three stars. We have to align the people. We have to align the infrastructure and capabilities, and we have to align the national priorities, the programmatic strengths. In other words, the budget to be able to resolve and develop the technology and accelerate it to beyond where it was in the 1960s, to where we’re going over the next decade. And so those three things have to be hand in hand. How do you attract people to an industry? Well, there has to be definitely demonstrated evidence. There are jobs on the outside of participating and engaging in a in an education program that will lead to that job. So, in other words, taking a nuclear engineering degree, taking the specialty course credits, or taking the specialty training that allows you to align with, being able to close some of our gaps that we have in the space nuclear powered propulsion arena. That’s really important. So, as we see more and more active programs, companies hiring companies, looking at bidding on programmatic effort for the country, I think this is a really good signal to the future talent pipeline that the area is healthy. It is definitely needed from, both a science and strategic perspective for the nation. And there are places that they can get jobs. And so, now what we have to do, demonstrating the evidence that there’s a job ahead of them, is we have to connect the dots. And that’s where the Center for Space Nuclear Research can really help both on the industry side, the national labs side, the NASA side, but also on the academic side as well. We are an arena that, allows collaboration and affordable collaboration. That’s the other part to say as well, we’re trying to develop people and develop capabilities. We have to and the low TRL sense to that in an affordable way and not, not cost the Earth because these technologies are expensive. The, you know, the real cost of flying, efficient system in space is, you know, is high. However, the return on that investment, the, the long standing, infrastructure, and capabilities and quite frankly, the national leadership that we gain from, from enabling that technology in space is immense. And so, the benefits completely outweigh the cost. So, I think by developing people, alongside the technologies, we’re really going to help push the nation forward. From a leadership perspective.

Eric White Yeah. And bringing the focus back to yourself, you’ve been at this for a while now, in this role, as you know, returning to the Center for Space Nuclear Research. Do you see yourself more as now a facilitator? And rather than being on the actual front lines of research? And, you know, also, if we could get into, you know, what made you want to go towards the space arena when you first got interested in nuclear engineering?

Robert O’Brien So, so I started, actually in the space sector, essentially, I always wanted to support the development of technology for space exploration. I wanted to be part of the space industry or the academic world that was exploring space, trying to develop science and return science to Earth and adding value and enriching life on Earth with, with space technology. I’ve always enjoyed the talent pipeline aspects as well. Growing others and collaborating with others. And I think that’s what’s exciting about this, this role, as I return to it, what brought me into then, space nuclear was really solving a problem that the general science community had. And we were looking at a mission. I was at the University of Leicester collaborate. Rating with a number of schools, including the University of Bristol in the UK and the British Antarctic Survey. We were looking at performing an experiment in Lake Vostok and, in, in, the Antarctic, and we were looking at trying to deploy a system that could be used on Europa to be able to explore the ice under the icy moon, for example. And really that that challenge was, was really compounded with the amount of energy that we can take to enable that mission. And, you know, we’re using chemical energy storage, like even the best technology, like lithium-ion battery technology is, is really, really challenged by temperature. And as you go to very cold or even cryogenic temperatures, the capacity of batteries, the best battery you can build, it’s roughly 30% of its maximum capacity at room temperature. So that was one challenge. So, you have to have large amounts of energy storage in a mission. And essentially the battery can just displace all of the science. So, I was faced with that problem and developing a technology at the University of Leicester that would work in that arena. And, you know, very quickly concluded that the only way to do this would be for nuclear energy. And so, I began studying ways that we could empower, a small robotic system in Europa and, looking for an isotope source that made sense for the UK. And, the UK faced a lot of challenges, in the 90s and early 2000, doing the same thing that we did here in the US, which was demolition and destruction, reduction of capabilities and actual capabilities. Being able to produce isotopes was difficult. What the UK had was the mock stores with americium 241, and I think the community’s going to hear a lot more about americium, and its ability to power space missions in the future with the work that’s ongoing at the University of Leicester and that, you know, we’re interested in supporting commercially here for the US industry needs as well as international needs as well, so that that real problem solving got me into, trying to trying to look for, for sources that that could help us enable space exploration using nuclear power. And, you know, I soon realized that to do big things, we need a lot of power. And so, radio isotopes worked really well at low power, up to about 100W electric. But as soon as we get into the Kilowatts electric, to be able to do that today here in 2024, with current capabilities to produce isotope materials and the commercial, supply chain for radio isotopes, we’re really looking at kilowatts and above as fission and sub kilowatt is enabled with radio isotopes today. And so, both have a bright future ahead. I think both have, a great, set of solutions that they can close, and, yeah, really, really looking forward to, how my experiences can grow other people’s capabilities and interests in this field and then, ultimately support the, the national programs to come.

Eric White Robert O’Brien is the newly appointed director of the center for Space Nuclear Research, part of the University Space Research Association.