A document prepared for the intelligence agency of the U.S. Department of Defense proposed an unusual way to propel a spacecraft: a series of tiny explosions that would repeatedly push it forward. The idea was intended to make it possible for humans to reach distant parts of the solar system.
The spacecraft wouldn’t rely on a conventional engine. With each explosion, hot material would shoot out in one direction, pushing the craft in the other. Rather than using a large plate to absorb the blasts, the proposal calls for a magnetic field to deflect the material. But how can an invisible force do that?
A Magnetic Field Instead of a Plate
The 2010 document proposes using deuterium, a form of hydrogen. Particles of the material would fuse, releasing energy in small explosions. Those repeated blasts would propel the spacecraft.
Earlier proposals for explosion-powered propulsion called for a large plate to absorb each blast and push the spacecraft forward. In this design, a magnetic field would take the plate’s place. It wouldn’t be a visible surface. Instead, it would act as a barrier, redirecting the hot material produced by each explosion. As the material shot one way, the spacecraft would move in the opposite direction.
A Beam to Trigger the Explosions
To set off the blasts, the document considers using a beam of charged particles. The beam would strike the material and trigger the process. An illustration in the document shows a massive facility designed to generate the beam, about a mile long.
The facility is part of a concept on paper, not a depiction of equipment that has been built. Both the beam and the magnetic field are meant to make the propulsion system work, but the design depends on engineering concepts that have yet to be proven.
What We Still Don’t Know
It’s unclear whether small fusion explosions can be triggered in the way the document proposes, or whether a facility capable of supporting them can be built. The document examines the idea in theory; it does not describe a technology close to being put to use.
On paper, one tiny explosion pushes the spacecraft, then the next follows.
