Put nuclear technology in space or on the moon, and just as on Earth it can provide a power density unmatched by any other source. But what roles can nuclear power and propulsion play as the world enters a 21st-century space race? That was a key question put to six speakers during the November 14 American Nuclear Society Winter Meeting plenary session “Space: The (Next) Nuclear Frontier.”
Following a brief update on NuScale Power from John Hopkins, the company’s president and chief executive officer, ANS President Kenneth Petersen kicked off Tuesday’s ANS President’s Special Session by recognizing the recipients of Presidential Citations and the Darlene Schmidt Science News Award. Petersen then thanked leaders of the ANS Young Members Group for helping him organize the session and select the focus on space. “I was immediately sold when they pitched space and nuclear,” he said. “There's so much happening in space exploration today. And with each mission, whether it's the moon, Mars, or somewhere else in the solar system, it brings more scientific knowledge but also much more enthusiasm.”
Matt Wargon, a senior nuclear engineer at TerraPower and chair of the YMG, moderated the session and introduced the six speakers who shared their vision for nuclear in space before the Q&A: Bhavya Lal, former NASA associate administrator for technology, policy, and strategy; Tabitha Dodson, program manager for DRACO, DARPA’s Demonstration Rocket for Agile Cislunar Operations; Kate Kelly, director of space and emerging programs at BWXT Advanced Technologies; Steve Squyres, chief scientist at Blue Origin; Jack Goodwin, director of business development for Lunar Surface Systems at Astrobotic; and Tyler Bernstein, CEO of Zeno Power.
Lal: “If we are to survive in the solar system and beyond, we need nuclear power,” Bhavya Lal said. “Getting someplace is only half the challenge. Once we get to those destinations, we need to do stuff, and to do stuff we need power. Remember [the movie] Apollo 13? ‘Power is everything,’ a NASA engineer said.”
Lal asked rhetorically: “Can we do all this exciting science with chemical [propulsion] systems? Of course. Just like horses were perfectly fine transportation. We didn't need to invent cars or airplanes to go across the country . . . but doing so opened up a lot of opportunities.”
Lal then explained how space nuclear prospects can benefit from recent policy changes. “I'm happy to report that in addition to investing in both power and propulsion systems, NASA and the U.S. government are exploring policy changes as well and have made space nuclear a priority,” she said. “I was lucky enough to be part of teams that are lowering the barriers to the use of nuclear systems in space. I was part of the team that developed what's referred to as the National Security Presidential Memorandum (NSPM-20) that restructures how the U.S. government regulates and approves space-based nuclear power system.”
Dodson: Tabitha Dodson emphasized the Defense Department’s desire to maximize capabilities in space and on Earth: “The more power we have, the farther we can go, the longer we can stay in space, the more we can do in space—just as we can do more with bigger ships in the ocean. The navy prefers to have nice big battleships with nuclear reactors. You don't see the navy driving around the ocean with little jet skis,” Dodson said, implying that a nuclear thermal rocket—like the one being tested through DRACO—is to a battleship what a small, electrically propelled satellite might be to a jet ski.
“Before we can launch all these awesome nuclear devices into space and go on our space adventures, we need to figure out a way to fabricate, test, and operate these nuclear devices,” she continued. “I see space as a big nuclear playground. Space is naturally radioactive, it's uninhabited, it's far away from us. Take a nuclear reactor into space far, far away from people, [and] your worries about nuclear safety . . . go way down and you can grow and diversify the kinds of experiments that you can do. The more rapidly you can prototype and build and test something, the more rapidly you can evolve your technology.”
The DRACO team, which includes BWX Technologies as the contracted performer, is taking lessons from the NERVA/Rover program of decades past. “Most of the failures that they experienced were mechanical in nature,” Dodson said. “I think it's somewhere between 60 to 90 percent of the failures were because the reactor was shaken apart in some way from either flow-induced vibrations or phase change from liquid to gas of the propellant from the nozzle to the reflector, and in other places. So we are going to focus on . . . mechanical testing. Kate [Kelly] and I just got back from [BWXT facilities in Lynchburg, Va.] last night. We were there yesterday freezing the design for our first test unit such that it can undergo a series of cold flow tests.”
Dodson and the U.S. Space Force are also thinking about what comes after DRACO. “When it comes to follow-on programs, one obvious major skill gap is that we don't have any nuclear space operators, and that's because we've never launched something like a DRACO before. For dynamic fission systems we need people who are skilled operators, similar to people in the navy. [With] DRACO, we're trying to seed that future workforce.”
Kelly: Kate Kelly explained that BWXT Advanced Technologies is working on several “new nuclear” missions to provide remote power, including in the space domain through participation in NASA’s fission surface power projects; the Air Force Research Laboratory’s JETSON program, which will mature nuclear electric propulsion technology; and “most notably” through DRACO.
“We have a ton of opportunity,” Kelly said. “We can leverage the advances that we've made in manufacturing, particularly in confidence in the ability of our fuel to perform as we need it to in these harsh conditions and for these aggressive program ambitions,” and leverage the policy advances mentioned previously by Lal.
In the nuclear space domain, she continued, “We've been able to take the intersection of these two high-tech industries, and when you merge those together, it creates something really powerful. We're able to pull from a whole new pool of talent that we've been unable to tap into in the nuclear industry. And it's leading to more diverse teams, more innovative teams, and more collaborative teams that are helping us address the problems that we faced in the past with prior nuclear programs.”
Squyres: “The thing that Blue Origin is best known for right now is our New Shepherd launch vehicle,” Steve Squyres said. New Shepherd has made about 20 test flights approximately 100 kilometers up to the Kármán Line [the conventional boundary between Earth’s atmosphere and space] and back down again, using liquid oxygen and liquid hydrogen as propellants.
“Why on earth would we use [liquid hydrogen]? . . . This was a forward-looking strategic decision, because it was known [15 years ago, when] New Shepherd was first designed that there were rich deposits of ice present in the polar regions of the moon. . . . What we can do if we can get to these deposits and mine them is extract H2O, split it via electrolysis, and now we have very capable rocket propellants: oxygen and hydrogen,” Squyres explained.
Working at the lunar poles for exploration, mining, power generation, or electrolysis is a cold, dark challenge. “We don't have a way of providing power to our vehicles in the cold and darkness of these places on the moon unless we have a nuclear source to power us,” he said. Solar powered vehicles would need to expend some of the electricity generated during sunlit hours “just to keep the thing warm enough that it will still be alive when the sun comes up two weeks later. That's not the way to explore. . . . I want to drive around during the lunar night, not just sit there and shiver.”
The moon is “a hard, hard place to work,” Squyres continued, citing once again the cold and dark, the lack of atmosphere that makes cooling difficult for some generation technologies, the need to replace bulky wiring with microwave or laser power transmission, and the dusty environment that requires dust-tolerant connectors.
But Squyres is of two minds. Despite all the difficulty, “the moon is a wonderful place,” he said. Wonderful to a planetary scientist, that is, because “it's a perfect testing ground for some alternate technologies,” like Stirling energy conversion, before those technologies are needed on planets with even tougher working conditions.
Goodwin: “You're not going to have any of this activity, power, mobility, whatever it might be without a grid that is reliable,” said Jack Goodwin, who describes Astrobotic as wanting to provide the “connective tissue” of lunar power systems.
“We're on contract with NASA to provide LunaGrid, the first lunar power grid,” he explained. “We're going to adopt a lot of that power in vertical solar array technologies” positioned at the lunar south pole to maximize sunlight exposure. “That will start the basis of the power grid, and then we'll accept megawatt-scale fission surface power systems . . . they will all go into a grid that is mutually beneficial.”
“At first,” according to Goodwin, the company will look to cover its costs under contract to NASA. “We don't want to gouge NASA, but in the future, we understand there will be different types of customers, different levels, some that one might call premium. . . . So a human habitat base might have a very different demand than an industrial scale in situ resource utilization plant.”
Bernstein: Zeno Power is in the business of developing commercial radioisotope power systems, which Tyler Bernstein describes as “boxes of hot rocks” the “size of microwaves that generate electricity for decades utilizing the heat from decaying radioisotopes.”
They differ from the plutonium-238 radioisotope thermoelectric generators that have been used by NASA and others in space for decades in their fuel—strontium-90—and in the greater need for power conversion efficiency posed by that change of fuel.
“If we can build one that uses an available abundant fuel but in a lightweight form factor, that would open up broad usability to serve this growing need for reliable power in these off-grid regions,” Bernstein said, emphasizing Zeno’s “novel design that increases the specific power of our strontium-90 heat sources.”
The Space Force has contracted Zeno Power to provide electric propulsion on a small satellite, and earlier this year the company also announced a contract with NASA for lunar surface power.
Zeno is seeking customers, and Bernstein asks how NASA can become an “anchor customer” on the moon. “How can NASA start to expand from not just buying payload delivery to the lunar surface but buying energy on the moon, buying the ability to survive the lunar night, buying telecommunications data?” he asked. Bernstein believes those actions by NASA “will help provide that incentive to commercial industry to build and deliver this capability, . . . eventually building a more sustainable commercial market.”
Read more from the 2023 ANS Winter Meeting