The Pentagon Wants a Particle Beam Weapon

The Pentagon wants a space-based directed energy weapon that would destroy enemy missiles shortly after takeoff. The weapon, called a neutral particle beam, would be tested from orbit in 2023.The Missile Defense Agency (MDA) wants a total of $380 million through the 2023 fiscal year to develop the directed energy weapon.

Neutral particle beam weapons work by accelerating particles without an electric charge—particularly neutrons—to speeds close to the speed of light and directing them against a target. The accelerated neutrons knock protons out of the nuclei of particles in their target, generating heat that would damage the target.

Particle beams can be more effective than lasers, which only burn the surface of their targets. Particle beams of sufficient power can penetrate beyond the surface of an enemy missile, igniting its fuel supply, melting its mechanical components and frying its electronics. Particle beams are also capable of bypassing laser-deflection measures like brightly polished, mirror-like surfaces.

Particle beams could be used to destroy ballistic missiles in the so-called “boost phase”—shooting them down seconds after launch, while they are still accelerating and before they release their warheads. During that stage—which only lasts about five minutes—the missiles are moving relatively slowly and are producing a massive heat signature that makes them easier to spot and track.

It gets more difficult. For the neutral particle beam to work, it will need to maintain a coherent beam over the 1,000 kilometers or so from low-earth orbit to the ground. Its power source needs to be able to hold that beam, but be light and small enough to be launched into orbit. And it will need to process real-time launch detection and tracking data from a constellation of moving satellites.

These are all issues Washington wrestled with in the 1980s—and which it couldn’t solve. It remains to be seen whether technology has advanced enough since then to make the project viable.

The Defense Department tested a particle beam weapon in 1989: the Beam Experiments Aboard Rocket (BEAR) project. But little has been done since then. The BEAR had a large accelerator and power supply, making it too heavy to launch into orbit.

The Pentagon is pursuing this technology in response to threats such as hypersonic weapons from adversarial countries like China and Russia. They seem well aware of the limitations of the technology, but are willing to at least seriously explore its possibilities. In five years, we should know if it’s doable.