A nuclear-powered rocket may sound like something from science fiction, but it might be the key to future commercial, military, and research missions to space. Some believe it will be essential for a successful mission to Mars. Recently, NASA and the Defense Advanced Research Projects Agency (DARPA) have taken several major steps toward making this happen.
NASA and DARPA Form Partnership on New Rocket Propulsion System
In January 2023, NASA and DARPA agreed to establish a partnership to develop and demonstrate that a nuclear-powered rocket could potentially take astronauts to Mars. The two agencies split the initial $499 million cost for the program.
The project’s goal is to design and demonstrate the world’s first in-orbit nuclear thermal rocket (NTR) under DARPA’s Demonstration Rocket for Agile Cislunar Operations (DRACO) program. Cislunar refers to an object between the Earth and the moon.
“With the help of this new technology, astronauts could journey to and from deep space faster than ever – a major capability to prepare for crewed missions to Mars,” said NASA Administrator Bill Nelson.
U.S. Space Force to Provide Initial Lift for Nuclear Rocket System
NASA, DARPA, and The U.S. Space Force will head the U.S. Government portions of the program. NASA’s Space Technology Mission Directorate will oversee the technical development of the nuclear thermal engine. DARPA is the contracting authority for the rocket stage and engine, including the nuclear reactor. The Space Force will provide the launch vehicle for the mission.
Safety is one of the project’s most critical aspects, leading to the need for the Space Force launch vehicle. As a safety measure, initial plans are to launch the NTR into orbit on a conventional, chemical-powered rocket and then start its nuclear rocket engine once it is a safe distance from the surface.
Lockheed Martin and BWX Technologies Collaborating on Launch Vehicle and Engine
DARPA and NASA have chosen Lockheed Martin and BWX Technologies to participate in the project. Lockheed Martin is working on the experimental NTR vehicle (X-NTRV) that will ride on the Space Command rocket. BWX Technologies (BWXT) will develop the nuclear reactor and produce the high-assay, low-enriched (HALEU) fuel it will use. HALEU powers modern reactor designs that are smaller, more flexible, and less expensive than earlier designs.
Fission-Based, Nuclear-Powered Rocket Offers Advantages
The DRACO project calls for a fission reactor to provide the NTR with power.
According to a DARPA study, NTRs “use a nuclear reactor to heat propellant to extreme temperatures before exhausting the hot propellant through a nozzle to produce thrust.”
Some advantages of this type of system are that it is lighter and more efficient than the chemical-based engines NASA currently uses. The NTR will use hydrogen gas because of its light weight. Chemical rockets make water vapor, which is heavier than hydrogen. This results in a rocket that can travel farther into space on less fuel.
Another advantage of using nuclear-powered rockets is that they will produce more power than current engines. The U.S. Department of Energy states that these engines will give rockets more speed, possibly reducing the travel time to Mars by 25%. Another expected advantage is that these faster rockets will be safer for astronauts as they will limit the time they are exposed to radiation during missions.
Work on Nuclear-Powered Rocket Began in 1955
The idea of developing a nuclear-powered rocket is not new. In 1955, the United States began research at the Los Alamos Scientific Laboratory on just such a concept with Project Rover. From 1959 to 1962, they began testing reactor designs and fuels. Then, in 1965, NASA joined with the Atomic Energy Commission to develop a nuclear-powered rocket for both long-range missions to Mars and to possibly use it as an upper stage for Apollo rockets.
They called this the Nuclear Engine for Rocket Vehicle Applications (NERVA) project. Over the next several years, they successfully tested engine designs, cooling components, and pumps. Eventually, however, the U.S. government decided in 1971 to abandon plans for a manned mission to Mars following the Moon landings. Despite this, some of the design concepts and technologies that emerged from Rover and NERVA are still valid today and may help continued development.
Safety Concerns Put DRACO Plans on Potentially Long Hold
The initial goal for the DRACO program was to conduct a test launch in 2027, and plans seemed to be moving forward. However, in Jan. 2025, the DARPA-NASA management team in charge of the project announced they were placing it on “on indefinite hold.”
The announcement mentioned that Lockheed Martin and BWXT had run into problems designing an engine that they could safely test on the ground. DARPA explained the decision.
“We’re bringing two things together—space mission assurance and nuclear safety—and there’s a fair amount of complexity,” said Matthew Sambora, one of two DRACO program managers in DARPA’s Tactical Technology Office. “2027 is not a date that we’re shooting for at this point.”
Sambora added that one of the program’s goals is still to conduct an in-orbit demonstration of the design, and that the problems they face are not “undoable” but rather “difficult.”
Safety Criteria Were Less Strict in the 1950s and 1960s
Jim Shoemaker, DARPA’s second DRACO program manager, referred to the early work on projects Rover and NERVA as “the time before safety was invented.”
He also said that scientists working on Rover and NERVA performed six open air ground tests of radioactive reactors between 1964 and 1969, “which we could never get approved to do today.”
Along with problems with testing safety, DRACO faces other challenges, such as storing hydrogen for the system once it reaches space. It does not appear that will happen in the next several years.
“Once a DRACO demonstration proves successful, it could take another 10-15 years before the technology is used on an operational basis,” said Shoemaker.
