Space nuclear power and propulsion technologies are poised for a breakthrough after decades of development, but will need consistent government investment to transition to operational systems, according to L3Harris executives.
“We are finally at the cusp for both nuclear electric propulsion and nuclear thermal propulsion,” said Kristin Houston, president of space propulsion and power systems at L3Harris Technologies. “These solutions can be matured and be ready for flight in the next five years.”
Houston leads the business unit absorbed from L3Harris’s acquisition of Aerojet Rocketdyne — a longtime supplier of space nuclear propulsion systems to NASA.
Several NASA programs are harnessing innovations in space nuclear technology, Houston noted.
L3Harris is supplying the Multi-Mission Radioisotope Thermoelectric Generator for NASA’s Dragonfly mission to Titan, the largest moon of Saturn. Scheduled for launch in July 2028 and arrival in 2034.
The industry is also closely monitoring NASA’s Fission Surface Power program, which aims to develop nuclear power systems for lunar and Mars surface operations. Currently in a three-way competition, the program features teams from Westinghouse with L3Harris, Lockheed Martin, and X-Energy.
A second phase is expected to start later this year, Houston said. The program targets systems capable of providing 40 kilowatts — enough to power about 30 households continuously for a decade — and represents a crucial milestone in understanding NASA’s long-term funding priorities for lunar and Mars infrastructure.
Power generation vs. propulsion
Space nuclear applications often fall into two primary categories: power generation and propulsion.
For power generation, radioisotope thermoelectric generators convert heat from radioactive decay into electricity. These systems are crucial for missions traveling to deep space where solar power becomes impractical.
On the propulsion side, two primary technologies are advancing:
Nuclear Thermal Propulsion (NTP): This uses a nuclear reactor to heat a propellant (typically liquid hydrogen) which is expelled through a nozzle to generate thrust. These systems offer high thrust levels similar to chemical rockets but with improved efficiency.
Nuclear Electric Propulsion (NEP): This process converts thermal energy from a nuclear reactor into electricity as a way to power electric thrusters. This approach provides lower thrust but exceptional efficiency, making it ideal for sustained acceleration on long-duration missions.
National security and scientific applications
These technologies have applications beyond science and exploration, Houston said. “It enhances strategic mobility by providing faster and more efficient transportation of spacecraft, enabling quicker development and repositioning of assets in space.”
Nuclear propulsion technologies offer significant advantages for future Mars missions, she added. Spacecraft powered by nuclear thermal propulsion could reach Mars in approximately half the time of chemical engines, while NEP systems could efficiently transport cargo vehicles.
NASA and the Defense Advanced Research Projects Agency (DARPA) are co-sponsoring the Demonstration Rocket for Agile Cislunar Operations (DRACO) program to test a nuclear thermal rocket engine in space.
William Sack, director of advanced space and power programs at L3Harris, said demonstrations such as DRACO are important to showcase the capabilities of nuclear thermal propulsion. He noted that L3Harris has developed its own NTP vehicle concept. “We would expect to be a player in the future if NASA is going to be going forward with something like this, for going to Mars or somewhere else,” Sack said.
Despite the promising outlook, Houston emphasized that consistent government investments and leadership are essential to deploy these technologies to help accelerate the space economy.
