Researchers at Sandia National Laboratory have developed a bullet for small-caliber, smooth-bore firearms that can guide itself to a laser-designated target up to a mile away. The 4-in.-long bullet carries an optical sensor that detects the laser beam reflecting off a target. The sensor sends that data to onboard electronics that use an 8-bit processor to generate control signals about 30 times per second for electromagnetic actuators. These actuators control the four fins on the tail of the bullet.
The bullet is initially encased in plastic sabots that create a gastight seal between the round and barrel and protect the fins as the bullet travels through the barrel. The sabots drop off when the round leaves the barrel. The bullet must be used in smooth-bore weapons because rifling or spiral grooves in some barrels makes the bullet spin. This guided bullet will not work if it is spun out of the barrel.
So far, test have shown the bullet is accurate when fired at 2,400 fps, about Mach 2.1. Researchers are confident it will remain accurate when fired at standard military speeds, which are about two to three times higher.