Sandia National Laboratories engineers have invented a dart-like, self-guided bullet for small-calibre, smooth-bore firearms that could hit laser-designated targets at distances of more than a mile.
‘We have a very promising technology to guide small projectiles that could be fully developed inexpensively and rapidly,’ said Sandia’s Red Jones.
Sandia’s design for the 4in (10cm)-long bullet is said to include 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 8-bit central processing unit to command electromagnetic actuators. These actuators then steer tiny fins that guide the bullet to the target.
Most bullets are shot from rifles with rifling cut into the barrel, which causes them to spin in order to fly straight. Jones said that, to enable a bullet to turn in flight towards a target and to simplify the design, the spin had to be removed.
The bullet flies straight thanks to its aerodynamically stable design, which consists of a centre of gravity that sits forward in the projectile and tiny fins that enable it to fly without spin, just as a dart does, he explained.
Computer aerodynamic modelling shows that the design would result in dramatic improvements in accuracy, according to Jones. Computer simulations showed that an unguided bullet under real-world conditions could miss a target more than half a mile away (1,000m) by 9.8 yards (9m), but a guided bullet would get within 8in (20cm), according to the patent on the design.
Plastic sabots provide a gas seal in the cartridge and protect the 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 (which usually contain a relatively heavy inertial measuring unit), 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 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,’ said Jones.
Testing has shown that the electromagnetic actuator performs well and the bullet can reach speeds of 2,400ft (732m) per second — or Mach 2.1 — using commercially available gunpowder. The researchers are confident it could reach standard military speeds using customised gunpowder.
Potential customers for the bullet include the military, law enforcement and recreational firearms users.
Sandia is now seeking a private company partner to complete the testing of the prototype and bring a guided bullet to the marketplace.