| GBU-39 (Small Diameter Bomb) | |
|---|---|
4 SDBs (training/ground handling variant) loaded on an F-15E Strike Eagle |
|
| Type | Bomb |
| Place of origin | United States |
| Service history | |
| In service | 2006–present |
| Used by | United States Israel Italy |
| Wars | War in Afghanistan (2001-present), Iraq War, 2008–2009 Israel–Gaza conflict |
| Production history | |
| Manufacturer | Boeing Integrated Defense Systems |
| Produced | 2005–present |
| Variants | GBU-39 / GBU-40 |
| Specifications | |
| Weight | 285 lb (129 kg) |
| Length | 70.8 in (1.80 m)[1] |
| Width | 7.5 in (190 mm) |
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| Warhead | AFX-757 Dense Inert Metal Explosive |
| Warhead weight | 50 lb (23 kg)[2] |
|
|
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| Operational range |
more than 60 nautical miles (110 km) stand-off.[1] |
| Guidance system |
GPS / INS. |
| Accuracy | 5–8 m circular error probable |
The GBU-39 Small Diameter Bomb (SDB) is a 250 pound (113 kg) guided bomb that is intended to provide aircraft with the ability to carry a higher number of bombs. Most US Air Force aircraft will be able to carry (using the BRU-61/A rack) a pack of four SDBs in place of a single 2,000 pounds (910 kg) bomb.[3]
The initial SDB is expected to be replaced with the Small Diameter Bomb II (SDB-II) / GBU-53/B.
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In 2002, while Boeing and Lockheed Martin were competing to develop the Small Diameter Bomb, Darleen A. Druyun—at that time Principal Deputy Assistant Secretary of the Air Force for Acquisition and Management—deleted the requirement for moving target engagement, which favored Boeing. She was later convicted of violating a conflict of interest statute.[4][5]
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 (Boeing's GBU-40 or Raytheon's GBU-53 (SDB II)) will include a thermal seeker and radar with automatic target recognition features for striking mobile targets such as tanks, vehicles, and mobile command posts.[6]
The GBU-39 has a circular error probable (CEP) of only 5–8 meters,[7] which means it has a 50% probability of hitting its intended target within that distance. 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 theatre 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. It also has integrated "DiamondBack" type wings which deploy after release, increasing the glide time and therefore the maximum range. Its size and accuracy allow for an effective munition with less collateral damage.[7]
On May 1, 2009, Raytheon announced that it had completed its first test flight of the GBU-53/B Small Diameter Bomb II, which has a data link and a tri-mode seeker built with technology developed for the Precision Attack Missile.[8] And on August 10, 2010 the U.S. Air Force awarded a $450 million contract for engineering and development.[9]
The SDB is currently integrated on the F-15E Strike Eagle. Future integration is planned for the F-16 Fighting Falcon, F-22 Raptor, F-35 Lightning II, A-10 Thunderbolt II, B-1 Lancer, B-2 Spirit, and the B-52 Stratofortress. Other aircraft, including UCAVs, may also receive the necessary upgrades.
GBU-39 began separation tests on the F-22 in early September 2007 after more than a year of sometimes difficult work to integrate the weapon in the weapons bay and carry out airborne captive carry tests.
Although unit costs were somewhat uncertain as of 2006, the estimated cost for the INS/GPS version was around US$70,000. The cost of the second variant was more uncertain, but tentative estimates were $90,000 per unit or more. Boeing and the Italian firm Oto Melara have signed a contract covering the license production of 500 GBU-39s (INS/GPS) and 50 BRU-61/a racks for the Aeronautica Militare, at a cost of nearly US$34 million.
Under a contract awarded in September 2006, Boeing is developing a version of the SDB I which replaces the steel casing with a lightweight composite casing and the warhead with a focused blast explosive such as Dense Inert Metal Explosive (DIME). This should further reduce collateral damage when using the weapon for pin-point strikes in urban areas.[11]
On 28 February 2008, Boeing celebrated the delivery of the first 50 FLM weapons.[12]
The USAF intends to use the same FLM casing on a weapon of 500 pounds (230 kg).[13]