GBU-39 Small Diameter Bomb SDB
Two variants are being developed. One version of the SDB is equipped with a GPS-aided inertial navigation system to attack fixed/stationary targets such as fuel depots, bunkers etc. The second variant (GBU-40) includes a thermal seeker with automatic target recognition features for striking mobile targets such as tanks, vehicles, and mobile command posts.
The GBU-39 has a circular error probable (CEP) of only 5-8 meters, which means it has a 50% probability of hitting within 5-8 meters its intended target, which should minimize collateral damage. CEP is reduced by updating differential GPS offsets prior to weapon release. These offsets are calculated using an SDB Accuracy Support Infrastructure, consisting of three or more GPS receivers at fixed locations transmitting calculated location to a correlation station at the Theater Combined Air Operations Center. The corrections are then transmitted by Link 16 to SDB-equipped aircraft.
The small size of the bomb allows a single strike aircraft to carry more of the munitions than is possible utilizing currently available bomb units. The SDB carries approximately 38 lb (17 kg) of AFX-757 high explosive, yet because of its design it has the same penetration capabilities as the 2000 lb BLU-109. During demonstrations, the SDB has successfully penetrated more than 8 ft (2.4 m) thick reinforced concrete[citation needed]. It also has integrated “DiamondBack” type wings which deploy after release, increasing the glide time and therefore the maximum range.
