It’s the stuff of sci-fi movies and novels: people harnessing the power of the atom to travel to other planets and explore space. But soon it will become reality. So, how safe is a nuclear-powered rocket?
When it was announced last month that NASA and the Defense Advanced Research Projects Agency (DARPA) would join forces to create and launch a nuclear thermal rocket engine by 2027, many people were excited to hear about such an innovation, a giant leap forward in space travel only dreamed of in the works of science fiction.
However, some wondered how safe such a vehicle will be. According to officials, the Demonstration for Rocket to Agile Cislunar Operations (DRACO) program is safe.
“The reactor will not explode,” Tabitha Dodson, DARPA program manager for DRACO, assured Spectrum News.
Understand the mechanics
For a more in-depth safety statement, it’s helpful to understand the reason for going nuclear.
Take Artemis I’s Orion spacecraft, for example. It used two propellants (fuel and an oxidizer) that combined to propel the craft to the moon and back.
NASA described that the propulsion will work in the DRACO nuclear-thermal rocket.
“In a nuclear thermal rocket engine, a fission reactor is used to generate extremely high temperatures. The engine transfers the heat produced by the reactor to a liquid propellant gas, which is expanded and vented through a nozzle to propel the spacecraft,” NASA said.
Dodson went on to explain that nuclear propulsion uses propulsion mass much more efficiently than chemical propulsion. And since this new engine does not use an oxidizer, that increases the speed of the vehicle.
“Nuclear propulsion systems can produce vehicle speeds 30 to 70% faster than chemical propulsion systems,” she stated.
For context, the Orion spacecraft flew past the moon at about 5,000 mph. With a nuclear-powered rocket engine, it could have flown as fast as 6,500 mph to 8,500 mph.
And speed is what NASA is looking for to reduce the travel time to Mars for manned missions.
Dodson explained that a spacecraft, such as Orion, will eventually be mounted on top of this new nuclear rocket engine, but the engine itself will not be used for launches. Lifting rockets — such as the Space Launch System rocket used to send Orion into space — will launch this new engine and its spacecraft into space.
As for what type of spacecraft will be used for the unmanned test flight of this nuclear-powered rocket in 2027, there will be none, admitted Anthony Calomino, space nuclear technologies portfolio leader in NASA’s Space Technology Mission Directorate.
“No capsule will be integrated into the DRACO demonstration vehicle. Plans for future human deep-space missions are still being planned and it is too early to give details about the number of astronauts or the size of the vehicle capsule,” he explained to Spectrum News.
He went on to say that during the DRACO demonstration in 2027, “there will be nuclear engineers on site to monitor the demo remotely.”
As soon as the nuclear-powered rocket engine is launched into space, it turns on.
“After launch, the plan is to leave the reactor off until the vehicle is far enough from Earth to turn the reactor on. Therefore, the reactor and its materials will remain radiologically inert during launch and during all stages of space operations,” said Dodson.
Calomino described how such a missile would be used in future missions.
“It is anticipated that for future crewed NASA spacecraft, nuclear propulsion systems, like any other space propulsion system, will be designed to operate autonomously and reliably throughout their lifetime without the need for human maintenance,” said Calomino.
This is an illustration gif of what a spacecraft will look like with a nuclear propulsion system. (NASA)
NASA’s history with nuclear engines
This isn’t the first time NASA has worked on this type of engine. The last nuclear thermal rocket engine tests were done in 1972, more than 50 years ago, under NASA’s Nuclear Engine for Rocket Vehicle Application (NERVA) and Rover projects.
The NERVA/Rover program conducted hundreds of nuclear thermal rocket experiments and delivered many important lessons, Dodson said, such as operational and startup techniques, thermal environments, and mechanical and structural requirements.
“We will build on the lessons learned for DRACO,” she said.
Since NERVA/Rover, there have been other designs from NASA, the US Department of Defense, the US Department of Energy and private industry, Dodson revealed. She said past work paved the way for the DRACO program to begin a demonstration test launch in 2027, just four years later.
“The US has been working on design and fuel for decades, and both agencies have a big head start on technology investment so far. Both DARPA and NASA believe that a rigorously executed project can be successfully accomplished,” she said.
How safe is a nuclear-powered rocket engine?
The NERVA/Rover engines contained a level of thermal power far greater than that of a nuclear power plant, Dodson said.
“(Nuclear power) plants can have the same amount of power, but terrestrial plants are physically much larger than a (nuclear thermal rocket), which is generally the size of a washing machine,” she stated.
With all that power, could something go wrong and cause an explosion? Not according to Dodson, who explained how the engine is supposed to work.
“The reactor will not explode. In addition, as long as the reactor is not turned on, it will not generate … fission products. If there is some defect in the first stage launch vehicle that causes the reactor to break and expose the core, the materials in the core will be safe for those around the launch site,” she said.
So people on the ground are safe and so are the astronauts, Dodson added.
“Since the reactor has not been used and will not contain any fission products, people can safely work around and close to it. When the reactor is used to propel a spacecraft used to carry astronauts, the reactor will be shielded, just as a submarine’s nuclear reactor is shielded to protect submarines,” she said.
Speaking of submarines, Calomino used the same analogy to describe how these particular nuclear missiles will be maintained in space.
“For future missions, crews could maintain and care for engines similar to how the Navy has crews to care for its nuclear propulsion engines,” he said.
The sense of urgency and excitement
There’s a mixture of emotions for both Dodson and Calomino to get the DRACGO program done and see how it changes how we travel through space.
“I feel a huge urgency. If we don’t finish the DRACO program now, we may never get the chance to realize nuclear missiles again,” she admitted.
“It’s very exciting, we’re developing future capabilities that could change human presence in space and open up huge opportunities for new planetary exploration missions,” Calomino said.