A U.S. document examined an engine concept that could propel spacecraft on long-distance journeys. Its fuel: hydrogen and boron, a chemical element found in nature.
When their atomic nuclei fuse, they produce three charged particles. Those particles could provide thrust and generate electricity, without much of the dangerous radiation associated with other types of fusion. But the reaction has to be started and sustained. No practical way to do that exists yet.
Particles That Create Thrust
Written in 2010 by the Defense Intelligence Agency, part of the U.S. Department of Defense, the document examined whether nuclear fusion could propel spacecraft. Fusion occurs when atomic nuclei join, releasing energy.
In the reaction under consideration, hydrogen and boron produce three charged particles. Because they are charged, they can be controlled with electricity. The document suggests they might be directed out the back of a spacecraft. As they move in one direction, the spacecraft is pushed in the opposite direction, like a rocket expelling gas behind it. Another possibility is to convert their energy into electricity.
Less Radiation for the Crew
The concept could also offer an advantage for a spacecraft’s crew. Some types of fusion produce neutrons, particles that can harm people. In this reaction, most of the energy comes out as charged particles rather than neutrons.
If that advantage bears out, the spacecraft might need less heavy material to shield the crew from radiation, leaving more room and weight for other things. But the document describes a possibility, not an engine that has been built and proven.
Promise Meets a Roadblock
The reaction requires extreme heat. The fusion also has to be started and sustained so that it produces more energy than it consumes. The document identifies this as the main obstacle. It also notes that energy could be lost in the form of X-rays.
The document reviewed existing ideas and knowledge. It did not present original research proving that the engine works. It described a possible route to long-distance spaceflight, along with the difficulty of turning that concept into a working engine.
What We Still Don’t Know
