@ Spiral 1 is a 250-pound bomb with the same GPS guidance as the Joint Direct Attack Munition.
@ Spiral 2 is the same 250-pound bomb and GPS guidance, but adds a low-cost terminal seeker to improve accuracy to three meters circular error probable. (Half of all bombs will land within three meters of the target.)
@ Spiral 3 (the Wide Area Search Autonomous Attack Miniature Munition) will add a rocket motor, allowing it to attack targets dozens of miles away.
Increases in accuracy could result in a weapon as small as 100 pounds. The Air Force is carefully studying ideas on the most critical aspect of the system, the permission to fire concept. It does no good to put a fighter over an enemy country with a dozen bombs if the pilot cannot get permission to drop one of them.--Stephen V Cole
The Air Force is moving development of its Small Diameter Bomb forward, evolving it into the Wide Area Search Autonomous Attack Miniature Munition. The general idea of the Small Diameter Bomb is that even a relatively small 250-pound weapon is enough to destroy many targets (such as moving trucks) if accurately delivered. If a fighter can replace the normal load of two huge 2,000-pound bombs with a dozen or more smaller weapons, it could attack many targets on a single mission. (Such a weapon could also be carried by unmanned recon drones such as Predator, and can be carried inside the stealthy closed weapons bays of the F-22 and F-35.) The Small Diameter bomb is being developed in a series of steps: