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.”

Ultra Safe Nuclear (USNC) announced on October 17 that it had been awarded a contract by NASA to develop and mature space nuclear thermal propulsion (NTP) systems to advance the nation’s cislunar capabilities. Under the contract, USNC says it will manufacture and test proprietary fuel and simultaneously collaborate with its commercial partner, Blue Origin, to mature the design of an NTP engine optimized for near-term civil science and cislunar missions.

BWX Technologies announced today that it has been selected to supply the nuclear reactor and fuel for the Defense Advanced Research Projects Agency’s Demonstration Rocket for Agile Cislunar Operations (DRACO) program—the goal of which is to demonstrate a nuclear thermal propulsion (NTP) engine in orbit.

Miguel Alessandro Lopez

At the University of Rhode Island, I initially enrolled as a candidate for an accelerated track to earn bachelor’s and master’s degrees in mechanical engineering, with a minor in nuclear engineering. My objective was to concentrate on reactor power design and join efforts to make nuclear energy safer, more efficient, and less stigmatized.

My plans changed after I attended a guest presentation on high-performance nuclear thermal propulsion (HP-NTP) led by Michael Houts, manager of NASA Nuclear Research at Marshall Space Flight Center. He posted his email address on one of the last slides, so I took a chance and contacted him about potential research opportunities and thesis work. As it turned out, that one little email ultimately led to four NASA-sponsored design projects at URI—two are complete, and two are in progress—as well as my thesis. My research has been on HP-NTP, specifically the centrifugal nuclear thermal rocket (CNTR) design. In that design, liquid uranium is heated to extremely high temperatures in a cylinder that is rotated between 5,000 and 7,000 revolutions per minute as liquid hydrogen passes through the center of the cylinder, where it is heated and expanded, exiting as a propellant while the liquid uranium is retained by centrifugal force.

NASA and the Defense Advanced Research Projects Agency (DARPA) have announced they will collaborate on plans to launch and test DARPA’s Demonstration Rocket for Agile Cislunar Operations (DRACO). DARPA has already worked with private companies on the baseline design for a fission reactor and rocket engine—and the spacecraft that will serve as an in-orbit test stand—and has solicited proposals for the next phase of work. Now NASA is climbing on board, deepening its existing ties to DRACO’s work in nuclear thermal propulsion (NTP) technology—an “enabling capability” required for NASA to meet its Moon to Mars Objectives and send crewed missions to Mars. NASA and DARPA representatives announced the development at the American Institute of Aeronautics and Astronautics SciTech Forum in National Harbor, Md., on January 24.

A “resurgence of interest” in nuclear propulsion for space missions is described in a new article authored by science writer Jon Kelvey for the American Institute of Aeronautics and Astronautics’ (AIAA’s) Aerospace America website. The focus of Kelvey’s article is nuclear thermal propulsion (NTP), which, according to the Department of Energy, “could significantly reduce travel times and carry greater payloads than today’s top chemical rockets­—giving humans a great chance of exploring deep space.”

General Atomics Electromagnetic Systems (GA-EMS) has completed the baseline design of a reactor and engine for a nuclear thermal propulsion (NTP) rocket and has successfully tested key reactor components under contract from the Defense Advanced Research Projects Agency (DARPA), the company announced on November 7. The work was performed under a Track A, Phase 1 contract for the Demonstration Rocket for Agile Cislunar Operations (DRACO) program; Phases 2 and 3 of DRACO could culminate in a demonstration of the nuclear-propelled spacecraft in cislunar space (the region between the Earth and the Moon) during fiscal year 2026.

ANS’s August 4 online event “The New Space Race is Going Nuclear” featured several expert panelists who discussed the growing importance of nuclear technologies in space commercialization and exploration. Although nuclear energy has long played a role in space missions, participants discussed the latest exciting developments in the space nuclear field and presented their views on how increased application of nuclear technologies could fundamentally transform the ways in which both crewed and uncrewed space missions are carried out.

The Defense Innovation Unit (DIU), a Department of Defense organization focused on swiftly putting commercial technology to use in the U.S. military, has awarded contracts for two nuclear technologies—compact fusion and radioisotope heat—for spacecraft that could carry a high-power payload and freely maneuver in cislunar space. The objective is to accelerate ground and flight testing and launch a successful orbital prototype demonstration of each approach in 2027.

The Department of Defense wants to deploy spacecraft in cislunar space—the area between Earth and the moon’s orbit—with thrust and agility that only nuclear thermal propulsion (NTP) can provide. The Defense Advanced Research Projects Agency (DARPA), through its Demonstration Rocket for Agile Cislunar Operations (DRACO) program, is looking to private industry for the design, development, fabrication, assembly, and testing of a nuclear thermal rocket engine fueled with high-assay low-enriched uranium fuel to heat a liquid hydrogen propellant.

With three commercial teams under contract to produce reactor designs for nuclear thermal propulsion rockets that would use solid high-assay low-enriched uranium fuel to heat hydrogen propellant, NASA’s investment in nuclear thermal propulsion (NTP) has increased in recent years. But just as there is more than one way to fuel a terrestrial reactor, other fuels are under consideration for future NTP rocket engines.

Nuclear thermal propulsion (NTP) is one technology that could propel a spacecraft to Mars and back, using thermal energy from a reactor to heat an onboard hydrogen propellant. While NTP is not a new concept, fuels and reactor concepts that can withstand the extremely high temperatures and corrosive conditions experienced in the engine during spaceflight are being designed now.

BWX Technologies announced on December 13 that it has delivered coated reactor fuels to NASA for testing in support of the Space Technology Mission Directorate’s NTP project. BWXT is developing two fuel forms that could support a reactor ground demonstration by the late 2020s, as well as a third, more advanced and energy-dense fuel for potential future evaluation. BWXT has produced a videoof workers processing fuel kernels in a glovebox.

The U.S. Department of Defense is aiming to demonstrate a novel nuclear thermal propulsion (NTP) system above low Earth orbit by 2025. The Defense Advanced Research Projects Agency (DARPA) announced on April 12 that following a competitive solicitation process, it has awarded a contract to General Atomics Electromagnetic Systems (GA-EMS) for the design of the nuclear reactor that will power the Demonstration Rocket for Agile Cislunar Operations (DRACO). Blue Origin and Lockheed Martin will work on a parallel track to design a spacecraft tailor-made to demonstrate the NTP system.

An artist's concept of a fission power system on the lunar surface. Image: NASA

A national strategy for the responsible and effective use of space nuclear power and propulsion (SNPP)—Space Policy Directive-6 (SPD-6)—was released by the White House on December 16 as a presidential memorandum.

Space nuclear systems include radioisotope power systems and nuclear reactors used for power, heating, or propulsion. Nuclear energy can produce more power at lower mass and volume compared to other energy sources and can shorten transit times for crewed and robotic spacecraft, thereby reducing radiation exposure in harsh space environments. SPD-6 establishes a road map for getting space nuclear systems into service and sets up high-level goals, principles, and federal agencies’ roles and responsibilities.

Illustration of a Mars transit habitat and nuclear electric propulsion system. Image: NASA

NASA aims to develop nuclear technologies for two space applications: propulsion and surface power. Both can make planned NASA missions to the moon more agile and more ambitious, and both are being developed with future crewed missions to Mars in mind. Like advanced reactors here on Earth, space nuclear technologies have an accelerated timeline for deployment in this decade.

Space nuclear propulsion and extraterrestrial surface power are getting funding and attention. New industry solicitations are expected this month, and a range of proposed reactor technologies could meet NASA’s specifications for nuclear thermal propulsion (NTP). Nuclear electric propulsion could increase the feasibility of crewed missions to Mars with a shorter transit time, a broader launch window and more flexibility to abort missions, reduced astronaut exposure to space radiation and other hazards, expanded payload mass capabilities, and reduced cost.

The United States is pursuing the objective to land humans more than 100 million miles away on Mars, and nuclear power has the potential to be a key technology in getting to the Red Planet and providing power while there. Specifically, nuclear thermal propulsion (NTP) is a promising approach that could enable astronauts to travel from Earth’s orbit to Mars and back in a fraction of the time, and with greater safety, than is available with other options.