Self-guided bullet hits target a mile away

Posted by Kate Taylor

Two Sandia National Laboratories engineers - and hunters - have developed a dart-like, self-guided bullet accurate over a distance of a mile.

Red Jones and Brian Kast say their bullet is suitable for small-caliber, smooth-bore firearms, and are looking for a private partner to complete testing of the prototype and launch it commercially.

The design for the four-inch-long bullet includes an optical sensor in the nose to detect a laser beam on a target. The sensor sends information to guidance and control electronics that use an algorithm in an eight-bit central processing unit to command electromagnetic actuators. These actuators steer tiny fins that guide the bullet to the target.

While rifling keeps most bullets straight through spinning, the Sandia bullet flies straight due to its aerodynamically stable design, which consists of a center of gravity that sits forward in the projectile and tiny fins that enable it to fly without spin like a dart.

Computer aerodynamic modeling shows dramatic improvements in accuracy. Where an unguided bullet under real-world conditions could miss a target more than a half mile away by 9.8 yards, the guided bullet would get within eight inches.

Plastic sabots provide a gas seal in the cartridge and protect the delicate fins until they drop off after the bullet emerges from the firearm’s barrel.

Because of its small size, the prototype doesn't need the inertial measuring unit found in most guided missiles, and which would have added substantially to its cost.

As it flies through the air, it pitches and yaws at a set rate based on its mass and size. In larger guided missiles, the rate of flight-path corrections is relatively slow, so each correction needs to be very precise because fewer corrections are possible during flight.

"The natural body frequency of this bullet is about 30 hertz, so we can make corrections 30 times per second. That means we can overcorrect, so we don’t have to be as precise each time," says Jones.

Testing has shown the bullet can reach speeds of 2,400 feet per second, or Mach 2.1, using commercially available gunpowder. The researchers say they're confident it could reach standard military speeds using customized gunpowder.

And a nighttime field test, in which a tiny light-emitting diode, or LED, was attached to the bullet showed the battery and electronics can survive flight.

The bullet pitches less as it flies downrange, meaning accuracy improves at longer ranges.

The researchers hope to market the bullet to the military, law enforcement and recreational shooters.