Dr. James Gilland on the Promise and Progress of Space Nuclear Propulsion
A conversation with Parallax Advanced Research and Ohio Aerospace Institute Senior Scientist on the scientific frontiers and strategic imperatives of nuclear-powered space travel
“Nuclear propulsion in all its forms offers the next step in human exploration of outer space; humanity just needs to figure out what steps we want to take.”
— Dr. James Gilland As the United States intensifies its ambitions for deep space exploration and a sustained presence beyond low Earth orbit, propulsion technology has emerged as both a limiting factor and an innovation frontier. Traditional chemical systems can only take us so far, constrained by payload mass and mission duration. To break that barrier, federal agencies are revisiting a long-discussed solution: Space Nuclear Propulsion (SNP). In this interview, Dr. James Gilland, senior scientist at the Parallax Advanced Research and Ohio Aerospace Institute (OAI), shares technical insights, historical context, and future considerations for SNP. A recognized expert in advanced electric and nuclear propulsion systems, Dr. Gilland underscores how federal investment, scientific partnership, and nonprofit research engagement can propel this technology from concept to spaceflight reality. Meet the Expert: Dr. James H. Gilland Dr. James Gilland is a Senior Scientist at the Ohio Aerospace Institute, specializing in advanced plasma and nuclear propulsion. With over 30 years of experience, his work spans systems from 300 W to 300 MW—across Hall thrusters, magnetoplasmadynamic thrusters, and plasma wave propulsion concepts. He currently supports NASA’s Solar Electric Propulsion Hall thruster development for Artemis and previously served as the Lead Nuclear Electric Propulsion (NEP) Engineer at NASA’s Nuclear Propulsion Office (1991–1993). He’s held roles on multiple NASA Institute for Advanced Concepts projects and advised on the 2021 National Academies of Sciences, Engineering, and Medicine study on SNP for human Mars exploration. Gilland has lectured at Case Western, Ohio State, and the University of Michigan, and served on numerous NASA panels. He holds an M.S. in Aerospace Engineering from Princeton and a Ph.D. in Nuclear Engineering from the University of Wisconsin–Madison.
What Is Space Nuclear Propulsion? Dr. Gilland outlines two dominant architectures under the SNP umbrella:
1. Nuclear Thermal Propulsion (NTP): A high-temperature nuclear reactor heats a propellant—usually hydrogen—and expels it through a rocket nozzle. It offers significantly greater specific impulse than chemical rockets, improving efficiency for deep space transit.
2. Nuclear Electric Propulsion (NEP): A nuclear reactor generates electricity to power electric thrusters, which accelerate plasma for propulsion. Where NTP has Isp about twice that of traditional chemical rockets, NEP Isp can be up to 10 times higher than chemical. So, the propellant savings is quite dramatic, but this is offset by having to carry a nuclear power system along. NEP is slower to get going but more efficient; the obvious use is slower cargo missions, but NEP can offer faster trip times for very hard missions than anything else currently in use. “It’s all about propellant mass. The higher the Isp, the less propellant you need. Less propellant either means going farther with the same mass—or doing the same mission trip time cheaper.”
Why Nuclear, Why Now? SNP doesn’t just promise technical performance; it unlocks mission architectures that would otherwise be cost- or time-prohibitive.
Human Mars Missions: For a given total mass, NTP, or NEP with a chemical stage, can reduce travel time compared to chemical rockets, decreasing crew exposure to radiation and life-support risk. Even if it’s not “fast” by terrestrial standards, it’s fast enough to make such missions practical and safer.
Sustainable Lunar and Cislunar Operations: In national security and logistics planning, propellant cost is ongoing and exponential. SNP allows for longer-duration and repeatable missions—key to both NASA’s Artemis program and broader defense goals in the cislunar domain.
What’s Working—and What’s Not Dr. Gilland emphasizes progress alongside setbacks:
NTP Momentum: DARPA’s DRACO program aimed to flight-test a prototype nuclear thermal rocket by 2027 using low-enriched fuel capable of 900s Isp—almost double that of chemical propulsion. Jointly funded with NASA, the program received strong congressional support. However, recent programmatic challenges have stalled launch timelines and cast uncertainty on its continuation.
NEP Gap: NEP remains largely unfunded beyond low-power demonstrations. There is a DoD program JETSON (Joint Emergent Technology Supplying On-orbit Nuclear Power) that is looking at nuclear power for satellites, but the connection to propulsion is secondary. There is a recently established USSF Advanced Space Power and Propulsion Institute centered at the University of Michigan; the focus for this is still being determined, primarily by the academic partners. For NASA missions, Dr. Gilland sees untapped potential in NEP, especially for sustainable deep space missions. Megawatt-class NEP systems, which he previously analyzed as part of NASA’s Nuclear Propulsion Office, have yet to see full R&D commitment.
Space Nuclear Power: Current work, such as NASA’s Surface Fission Power program, is progressing—but these technologies are low-temperature and low-power. Scaling them to higher-output, flight-ready systems remains a critical challenge. The challenges facing SNP are both physical and organizational, involving policy, coordination, and infrastructure:
- Fuel Qualification – Modern NASA SNP programs are focused on HALEU (High Assay Low Enriched Uranium) fuels, which require more reactor moderation at temperatures not previously considered.
- Safety Standards – Ground nesting of nuclear concepts has not been performed since the 70s, and regulations have changed dramatically. DRACO originally planned to forgo ground testing of the nuclear engine but started to include it in later planning.
- System integration and materials – design and integration, and testing, particularly of NEP systems, is a challenge
- Regulatory uncertainty around in-space nuclear operations – the operation of an active nuclear source in Earth or cislunar space, particularly in the incidence of returning to Earth, has yet to be defined.
- Lack of sustained agency-level support for high-power NEP
“There’s no shortage of technical ideas. The real challenge is identifying what steps humanity wants to take—and aligning the funding and programmatic will to get there.”
Accelerating the Path to Readiness Dr. Gilland sees federally funded research organizations, universities, and nonprofits like OAI and Parallax as critical catalysts for SNP progress:
- Addressing fundamental unknowns at the elemental level: materials, fluids, plasmas, policy issues.
- Bridging agency and industry gaps with cross-sector collaboration
- Driving early-stage prototyping and Technology Readiness Level advancement
- Acting as “honest broker” SMEs for program development and monitoring
These organizations also create educational, and workforce pipelines needed to scale these complex systems from labs to launchpads. "Non-profits have the ability to focus work across academia, industry, and government agencies to “fill in the gaps” and extend the scope.
Toward a Nuclear-Powered Future in Space Space Nuclear Propulsion offers the rare combination of technical viability, strategic relevance, and scientific intrigue. Its challenges are real—but so are its advantages. For program managers at NASA, DoD, DOE, and other agencies, collaboration with trusted research organizations like OAI and Parallax represents a smart step forward. As Dr. Gilland puts it: “Nuclear propulsion is a ‘next step’ to a variety of goals but defining the goals in the varied contexts of exploration, defense, and commerce are also part of the path.”
*** About Parallax Advanced Research & The Ohio Aerospace Institute Parallax Advanced Research is a 501(c)(3) private nonprofit research institute that tackles global challenges through strategic partnerships with government, industry, and academia. It accelerates innovation, addresses critical global issues, and develops groundbreaking ideas with its partners. With offices in Ohio and Virginia, Parallax aims to deliver new solutions and speed them to market. In 2023, Parallax and the Ohio Aerospace Institute formed a collaborative affiliation to drive innovation and technological advancements in Ohio and for the nation. The Ohio Aerospace Institute plays a pivotal role in advancing the aerospace industry in Ohio and the nation by fostering collaborations between universities, aerospace industries, and government organizations, and managing aerospace research, education, and workforce development projects. More information on both organizations can be found at Parallax and OAI websites.