NASA
How do you manage a nuclear propulsion system in space? The answer is: with extreme care. To address this, researchers at Oak Ridge National Laboratory (ORNL) have created a simulated nuclear reactor test platform designed to advance the development of engines capable of taking astronauts to Mars and beyond.
The Transportation Barrier in Space Exploration
One of the biggest barriers to human exploration of the Solar System—or even the deployment of advanced robotic missions—is the absence of efficient transportation between celestial bodies.
Traditionally, access to space and the transport of heavy payloads across the Solar System have depended on chemical rockets. While these engines have proven reliable, they’ve been operating close to their theoretical limits since the very first V2 rocket left Earth’s atmosphere in 1944. Advances since then have focused mostly on refining designs and reducing mass, but the fundamental limitations remain.
Why Chemical Propulsion Falls Short
Because of these constraints, chemical propulsion barely makes a crewed Mars mission possible. To put it into perspective: lifting one tonne of payload into orbit demands roughly 16 tonnes of fuel, and sending that same tonne to the Moon requires about 1,000 tonnes. This is why the Saturn V rocket towered like a skyscraper at launch, but returned to Earth carrying only a spacecraft the size of a shed.
To push further into space—or even to move quickly and affordably around the Earth-Moon system—something far more powerful is required: nuclear propulsion.
How a Nuclear Rocket Works
A nuclear rocket essentially functions as a reactor that superheats hydrogen propellant to about 3,000 K (2,727 °C / 4,940 °F). This process nearly doubles the efficiency of chemical propulsion in terms of thrust and specific impulse.
Still, nuclear engines face two major hurdles. The heat must be precisely managed to prevent the reactor from melting, and the compact, highly radioactive system must be controlled remotely in deep space, where technicians cannot intervene. On top of that, the engine needs the ability to start, shut down, and throttle on demand, making it far more complex than a stationary terrestrial reactor.
Although not widely known, nuclear rocket research has been ongoing for about 80 years—dating back to just after Einstein’s revelations about the immense energy stored in matter. Serious proposals emerged shortly after the first atomic bomb was detonated, and NASA has since explored several nuclear propulsion projects, establishing the foundations of viable designs.
Inside NASA’s Nuclear Engine Design
NASA’s nuclear rocket concept centers on a cylindrical core filled with uranium-235 fuel elements, through which hydrogen flows via multiple channels. Surrounding the core is a beryllium reflector to bounce neutrons back and sustain the reaction. A ring of rotating drums coated with beryllium on one side and boron on the other controls the reactor: turn toward beryllium to maintain fission, rotate toward boron to absorb neutrons and shut it down, or adjust partially to throttle the output.
Tests in the 1960s, such as the NERVA program, used rigid preprogrammed sequences—similar to the cycle of a bread machine—to regulate the engines. While sufficient for ground trials in Nevada, such systems lack the adaptability required for real missions.
ORNL
This is where ORNL steps in. Their test bed includes six control drums positioned around a mock reactor, equipped with resolvers, optical encoders, and torque meters to measure their behavior. A two-phase mix of water and air mimics liquid hydrogen propellant flowing through pumps, valves, and sensors that track pressure, flow, and temperature.
A NVIDIA Jetson single-board computer oversees the entire setup, running a message queuing telemetry transport (MQTT) broker to manage communication between physical components and reactor-simulation software. Using a non-nuclear test environment not only ensures safety but also accelerates design changes and troubleshooting.
Our test bed allows engineers to push autonomous control systems to the limit in a safe, repeatable way,” explained ORNL’s Brandon Wilson. “That means we can identify and fix issues here on Earth—before astronauts depend on these systems millions of miles away.
Read the original article on: New Atlas
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