Nuclear thermal rocket to power NASA’s long-duration spaceflights
By Robert Doughtery
Nuclear thermal rocket engines could expand possibilities for the next generation of long-duration spaceflight missions, according to a partnership between NASA and DARPA.
The two government organisations are developing a Demonstration Rocket for Agile Cislunar Operations (DRACO) program to improve sending cargo to a new lunar base, humans to Mars, and robotic missions further.
A nuclear thermal rocket (NTR)-enabled spacecraft is planned to be tested for Earth orbit during the 2027 fiscal year, according to a DARPA announcement on 24 January.
Defence Advanced Research Projects Agency (DARPA) director Dr Stefanie Tompkins said, “DARPA and NASA have a long history of fruitful collaboration in advancing technologies for our respective goals, from the Saturn V rocket that took humans to the moon for the first time to robotic servicing and refuelling of satellites.
“The space domain is critical to modern commerce, scientific discovery, and national security.
“The ability to accomplish leap-ahead advances in space technology through the DRACO nuclear thermal rocket program will be essential for more efficiently and quickly transporting material to the moon and eventually, people to Mars.”
Nuclear thermal rockets have a thrust-to-weight ratio of around 10,000 times greater than electric propulsion and have two-to-five times greater efficiency than in-space chemical propulsion.
Highly enriched uranium was previously tested for NTR before the 1980s, however, the project will instead be using high-assay low-enriched uranium (HALEU) fuel.
The fission process will be like those used for nuclear power — heat will be created by splitting atoms, passed from the reactor along its rocket propellant and then used to turn rocket propellant such as hydrogen from liquid to gas.
Engineers will also configure the system to activate the engine’s fission reaction only once it reaches space, as a safety feature. Advanced materials will be used to tolerate the proposed solid core NTR temperatures of almost 5,000 degrees Fahrenheit.
NASA administrator Bill Nelson congratulated both teams on the exciting investment for the future.
“NASA will work with our long-term partner, DARPA, to develop and demonstrate advanced nuclear thermal propulsion technology as soon as 2027,” he said.
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.”
DRACO DARPA program manager Dr Tabitha Dodson said the project has also received support from the US Space Force, with the intent to provide the launch for the demonstration mission.
“NASA is uniquely positioned to provide guidance on the challenging rocket engine and cryogenic fluid management specifications with liquid hydrogen to meet specific mission needs,” Dr Dodson said.
“Since the NTR uses propellant more efficiently, it offers more aggressive trajectories and creative burn profiles to move heavy cargo more quickly in the cislunar domain as compared to today’s in-space propulsion methods.
“We will conduct several experiments with the reactor at various power levels while in space, sending results back to operators on Earth, before executing the full-power rocket engine test remotely.
“These tests will inform the approach for future operation of NTR engines in space.”