A SMART bullet that can twist and turn in the air to follow its target's movements is being developed by the US air force.
Details of the previously secret project have been declassified by the US Department of Defence. Prototypes of the bullets, called Barrel Launched Adaptive Munitions, or Blams, are being tested by Ron Barrett, an aerospace engineer at Auburn University in Alabama. "This technology could change the nature of war," Dr Barrett said.
The Blams are guided by a laser beam and steer to their target by twitching their noses to change the angle they make with the airflow. "At supersonic speed, very small angles generate huge amounts of lift," Dr Barrett said.
Blams will initially be used for fighter aircraft munitions because they can follow the twists and turns of an enemy in a dogfight. Ultimately, miniaturisation is expected to lead to smart bullets for small arms, allowing snipers to hit targets several miles away with deadly accuracy by compensating for the effects of gravity and wind. The nose of the smart bullets swivels around a ball-and-socket joint and is directed by rods made of a piezoceramic material. These change length when an electric current is applied and can change length hundreds of times a second.
According to a report in today's New Scientist, tests have found that the rods can survive the enormous forces - up to 17,000 times greater than gravity - generated inside a fired bullet. In wind tunnel tests, Dr Barrett has already proved the rods can control the direction of bullets travelling at 2,250 mph - up to three times the speed of sound.
The bullet would contain a guidance system, like the smart bombs used in the Gulf war, that followed a laser beam to the target. According to Dr Barrett, small and accurate guidance systems have been available for 30 years. A quartz window at the tip of the Blam's nose would cover a sensor, allied to microelectronics costing about £60.
So far, the work has concentrated on large calibre Blams, with diameters of 20 millimetres or more, for aircraft cannon. These are notoriously inaccurate because the rounds can be blown off course by the wind and drop significantly over distances greater than two-thirds of a mile. Pilots guarantee a hit by filling the sky with bullets, but at a considerable cost - each one costs around £20.
Dr Barrett said pilots would need only one Blam bullet to get a hit because the steerable bullets could generate lift to counteract the effects of gravity and the wind. Although the steering system and microelectronics inside a blam will mean each round costs about £90, the steerable bullets are likely to lead to cost savings. "You'd fire only one Blam when otherwise you'd fire hundreds of bullets," Dr Barrett said.