Small Diameter Bomb

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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
Wars War in Afghanistan, Iraq War, Gaza War
Production history
Manufacturer Boeing Integrated Defense Systems
Unit cost US$40,000 (SDB)[1]
US$250,000FY2014[2] (SDB II)
Produced 2005–present
Variants GBU-39 / GBU-40
Weight 285 lb (129 kg)
Length 70.8 in (1.80 m)[3]
Width 7.5 in (190 mm)

Warhead AFX-757 Dense Inert Metal Explosive[citation needed]
SDB: penetrating blast fragmentation[4]
SDB FLM: blast ultra low fragmentation[5]
Warhead weight 206 lb (93 kg)[4][5]

SDB I (GBU-39)
more than 60 nmi (110 km)[3]
45 miles (72km) against moving targets[6]
SDB I (GBU-39)
GPS/INS with coupled IMU/datalink, IIR and millimeter wave Active radar homing
Accuracy SDB I (GBU-39)
5–8 m CEP
1m CEP est.
GBU-39 Small Diameter Bomb

The GBU-39 Small Diameter Bomb (SDB) is a 250 lb (110 kg) precision-guided glide 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 lb (907 kg) bomb.[7]

The Small Diameter Bomb II (SDB-II) / GBU-53/B scheduled to enter production in January 2014 will add a tri-mode seeker (radar, infrared homing, and semiactive laser guidance) to the INS and GPS guidance of the original SDB.[8]


The original 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.[9]

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 pounds (17 kg) of AFX-757 high explosive.[citation needed] 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.[10]

  • Warhead penetration: 3 feet (0.91 m) of steel reinforced concrete [11]
  • Fuze: Electronic safe and fire (ESAF) cockpit selectable functions, including air burst and delayed options.

The GBU-39 has a circular error probable (CEP) of 5–8 meters,[10] which means it has a 50% probability of hitting within that distance of its intended target. 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.


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.[12][13]

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.[14] And on August 10, 2010 the U.S. Air Force awarded a $450 million contract for engineering and development.[15]

Although unit costs were somewhat uncertain as of 2006, the estimated cost for the INS/GPS version was around US$70,000. 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. US$317m was spent on R&D and spares for SDB II in FY13/14, with US$148.5m requested in these categories for FY15, the total budget split roughly 70:30 between USAF and USN.[2] SDB II production began in FY14 with 144 bombs for the USAF at a unit cost of US$250,000.[2] The FY15 budget requested 246 bombs at a cost of US$287,000 each.[2]


  • October 2001 – Boeing is awarded the SDB contract.[16]
  • September 2005 – Small Diameter Bomb certified for operational test, evaluation.[17]
  • September 2006 – SDB team deliver the first SDBs to the USAF.[18]
  • October 2006 – Initial Operational Capability declared for SDB on the F15E.[19]
  • October 2006 – First use in combat.[20]
  • February 2008 – 1,000th SDB I and first 50 FLM delivered.[21]
  • September 2008 – Israel receives approval from the US Congress to purchase 1,000 bombs.[22]
  • December 2008 – Reportedly used against Hamas facilities in the Gaza Strip, including underground rocket launchers.[22]
  • January 2009 – Unnamed Boeing official stated that they have yet to deliver any SDBs to Israel.[23]
  • August 2010 – U.S. Air Force selects Raytheon's GBU-53/B for Small Diameter Bomb II Program.[24]


The SDB is currently integrated on the F-15E Strike Eagle, Panavia Tornado, and AC-130W. 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.

Ground-launched SDB[edit]

Boeing is modifying the Small Diameter Bomb with a rocket motor to be launched from ground-based missile systems such as the M270 MLRS. With the Army demilitarizing cluster munitions from M26 rockets, the company says a special adapter case could reuse the rocket to launch the SDB. After the motor launches it to a high enough altitude and speed, the wings will deploy and glide the bomb to its target. The company believes it can fill a gap for long-range precision fires while using its smaller warhead to save larger rocket munitions for strategic targets. While typical MLRS systems follow a ballistic trajectory, the rocket-launched SDB can be launched to an altitude and glide on a selected trajectory.[25][26] Boeing and Saab Group conducted three successful GLSDB tests in February 2015. The system is cost-effective, utilizing an existing weapon paired with a stockpiled rocket motor, while maintaining the loadout on a rocket artillery system. Unlike other artillery weapons, the GLSDB offers 360-degree coverage for high and low angles of attack, flying around terrain to hit targets on the back of mountains, or circling back around to a target behind the launch vehicle. The GLSDB has a range of 150 km (93 mi), and can also hit targets 70 km (43 mi) behind it.[27]

Laser SDB[edit]

In mid-2012, the U.S. Senate recommended zeroing out funding for the SDB II due to fielding delays with the F-35 Lightning II. With the delay in SDB II fielding, Boeing recommended an upgrade to their SDB as a temporary gap-filler to get desired performance at a fraction of the cost. Called the Laser Small Diameter Bomb (LSDB), it integrates the laser used on the JDAM to enable the bomb to strike moving targets. Boeing began testing the LSDB in 2011 and successfully hit targets traveling 30–50 mph (48–80 km/h).[28] In June 2013, the Air Force announced it would award Boeing a contract to develop and test the LSDB; the contract is for phase one part two engineering, integration and test, and production support and an LSDB Weapon Simulator. Boeing says the LSDB can be built at a lower cost than the planned Raytheon SDB II, as it will use the same semi-active laser sensor as the JDAM to hit moving and maritime targets. However, Boeing admits that it does not have the capability to engage targets in zero-visibility weather, as it lacks the SDB II's millimeter wave radar.[29]

SDB Focused Lethality Munition (FLM)[edit]

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.[30]

On 28 February 2008, Boeing celebrated the delivery of the first 50 FLM weapons.[31]

The USAF intends to use the same FLM casing on a weapon of 500 pounds (227 kg).[32]

In December 2013, Boeing delivered the last of the 500 FLMs under contract.[33]


  1. ^
  2. ^ a b c d "United States Department Of Defense Fiscal Year 2015 Budget Request Program Acquisition Cost By Weapon System" (pdf). Office Of The Under Secretary Of Defense (Comptroller)/ Chief Financial Officer. March 2014. p. 59. 
  3. ^ a b Small Diameter Bomb (SDB) - Boeing IDS
  4. ^ a b Boeing Small Diameter Bomb Increment I (SDB I)
  5. ^ a b Boeing SDB Focused Lethality Munition
  6. ^
  7. ^ Boeing / Lockheed Martin SDB (Small Diameter Bomb) - Designation Systems
  8. ^ "GAO-13-294SP DEFENSE ACQUISITIONS Assessments of Selected Weapon Programs". US Government Accountability Office. March 2013. pp. 101–2. Retrieved 26 May 2013. 
  9. ^ Boeing Small Diameter Bomb II Successfully Engages Target in Flight Test
  10. ^ a b SDB - Global Security
  11. ^ Boeing: Small Diameter Bomb
  12. ^ GBU-40 Small Diameter Bomb II (SDB II)
  13. ^ Comptroller General of the United States on Lockheed Martin Corporation--Costs
  14. ^ Raytheon's GBU-53/B Small Diameter Bomb II Completes First Flight
  15. ^ Air Force picks small diameter bomb
  16. ^ Boeing Awarded Small Diameter Bomb Contract - Boeing press release
  17. ^ Small Diameter Bomb certified for operational test, evaluation, Air Force Print News
  18. ^ Small Diameter Bomb I delivered ahead of schedule, Air Force Print News
  19. ^ ACC declares IOC for Small Diameter Bomb - Air Combat Command
  20. ^ GBU-39/B Makes Combat Debut in Iraq - USAF press release
  21. ^ Boeing Celebrates Small Diameter Bomb Delivery Milestones
  22. ^ a b Katz, Yaakov (2008-12-29). "IAF uses new US-supplied smart bomb". Jerusalem Post. Retrieved 2008-12-29. 
  23. ^ Butler, Amy (2009-01-16). "Mystery SDB". Ares Blog. Aviation Week. Retrieved 23 December 2011. 
  24. ^
  25. ^ Boeing furthers Ground-Launched SDB -, May 24, 2013
  26. ^ Boeing Developing Ground-Launched Small Diameter Bomb -, 22 October 2013
  27. ^ Boeing, Saab Unveil Ground Launched SDB -, 10 March 2015
  28. ^ Boeing: Laser Small Diameter Bomb Could Fill Gap -, 9 August 2012
  29. ^ USAF to award Boeing Laser SDB contract -, 28 June 2013
  30. ^ "Small Diameter Bomb (SDB) - Defense Update". 
  31. ^ "Boeing Celebrates Small Diameter Bomb Delivery Milestones". 
  32. ^ USAF Eyes Low-Yield Munitions
  33. ^ Richardson, Doug (13 January 2014). "Boeing delivers final Focused Lethality Munition to USAF". IHS Jane's Missiles & Rockets. Retrieved 14 January 2014. 

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