Researchers from Sandia National Laboratories in New Mexico have invented a dart-like, self-guided bullet for small-caliber, smooth-bore firearms that could hit laser-designated targets at distances of more than a mile (about 2,000 meters). Sandia is seeking a private company partner to complete testing of the prototype and bring a guided bullet to the marketplace.
Researchers have had initial success testing the design in computer simulations and in field tests of prototypes, built from commercially available parts. Sandia’s 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.
Most bullets shot from rifles -- which have grooves, or rifling -- that cause them to spin so they fly straight, like a long football pass. To enable a bullet to turn in flight toward a target and to simplify the design, the spin had to go. The 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, just as a dart does.
Computer aerodynamic modeling shows the design would result in dramatic improvements in accuracy. Computer simulations showed an unguided bullet under real-world conditions could miss a target more than a half-mile away by 9.8 yards, but a guided bullet would get within 8 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.
As the bullet 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. But the natural body frequency of this bullet is about 30 Hz, so corrections can be made 30 times per second.
Testing has shown the electromagnetic actuator performs well, and the bullet can reach speeds of 2,400 feet per second, or Mach 2.1, using commercially available gunpowder. The researchers are confident it could reach standard military speeds using customized gunpowder.