Nearly three years ago, the US Defense Advanced Research Projects Agency announced its intention to develop a flyable nuclear thermal propulsion system. The goal was to develop more responsive control of spacecraft orbiting the Earth, the Moon, and everything in between, giving the military greater operational freedom in these domains.
The military service called this program a Demonstration Rocket for Agile Cislunar Operations, or DRACO for short. The program consists of developing two things: a nuclear fission reactor and a spacecraft to fly it. In 2021, DARPA awarded $22 million to General Atomics for the reactor and made small grants of $2.9 million to Lockheed Martin and $2.5 million to Blue Origin for the spacecraft system.
At the same time, NASA was beginning to realize that if it was really serious about sending humans to Mars one day, it would be good to have a faster and more economical way to get there. An influential report published in 2021 concluded that the space agency’s only realistic path to putting humans on Mars in the coming decades was to use nuclear propulsion.
Nuclear thermal propulsion involves a rocket engine in which a nuclear reactor replaces the combustion chamber and burns liquid hydrogen as fuel. It requires significantly less fuel than chemical propulsion, often less than 500 tons, to reach Mars. That would be useful for a Mars mission that would include several advanced missions to prepare cargo for the red planet.
So this week, NASA said it’s working with the military agency and joining the DRACO project.
“NASA will work with our long-term partner DARPA to develop and demonstrate advanced nuclear thermal propulsion technology as early as 2027,” said NASA Administrator Bill Nelson. “Using this new technology, astronauts will be able to travel to and from deep space faster than ever before, an important capability in preparation for manned missions to Mars.”
The US space agency will not provide direct funding at this time. However, the Space Technology Mission Directorate will lead the technical development of the nuclear thermal engine, a key component of the spacecraft that will harness energy from the nuclear reactor. DARPA will continue to lead the overall development of the program, including the integration and procurement of missile systems.
Nuclear thermal propulsion has long been a goal of spaceflight proponents, dating back to the days of German rocket scientist Wernher von Braun and NASA’s Project NERVA. Those plans were never realized and the idea was put on the back burner for decades. This joint project is the most serious effort by the US to develop the technology since. It has the added benefit of interest from the US Congress, which pushed the space agency to get involved.
None of this will happen anytime soon. The technology is difficult and unproven, and of course there are regulatory issues with launching a nuclear reactor into space. The year 2027 seems optimistic for a demonstration, and the technology is unlikely to be used to send humans to Mars before the late 2030s.
But something is finally happening. That’s enough for now.