Engineers at Sandia National Labs in New Mexico have developed laser-guided bullets.
Red Jones and Brian Kast produced the dart-like 100mm-long projectile to hit laser-designated targets at 2,000m.
The design includes an optical sensor in the nose to detect the laser spot on a target.
Data from this goes to an on-board 8bit microcontroller which runs an algorithm to command the electromagnetic actuators which operate the fins.
The rifling that spins normal bullets in flight to stabilise them had to go.
Instead, the bullet is fired from a smooth-bore barrel and flies straight due to its aerodynamically stable design, with centre of gravity in front of the fins.
According to aerodynamic, said Jones, under conditions where an unguided bullet could miss a target at 1,000m by 9m, the guided bullet would get within 200mm.
Plastic sabots (shrouds to make the bullet fit the bore) provide a gas seal and protect the fins until they drop off as it leaves the barrel.
There is no inertial measuring unit - no gyros or accelerometers.
Instead, the researchers found that the bullet's relatively small size when compared to guided missiles "is helping us all around. It's kind of a fortuitous thing that none of us saw when we started," said Jones.
As the bullet flies, it pitches and yaws at a rate based on its mass and size, said Sandia. 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 30Hz, 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," Jones said.
The bullet can reach Mach 2.1 using commercial gunpowder and "the researchers are confident it could reach standard military speeds using customised gunpowder," said Sandia. While engineering issues remain, "we're confident in our science base and we're confident the engineering-technology base is there to solve the problems."