The GBU-39/B Small Diameter Bomb (SDB) is a

precision-guided A precision-guided munition (PGM, smart weapon, smart munition, smart bomb) is a guided munition intended to precisely hit a specific target, to minimize collateral damage and increase lethality against intended targets. During the First Gu ...

glide bomb that is intended to provide aircraft with the ability to carry a higher number of more accurate 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 bomb. The Small Diameter Bomb II (SDB II) / GBU-53/B, adds a tri-mode seeker (

radar Radar is a detection system that uses radio waves to determine the distance ('' ranging''), angle, and radial velocity of objects relative to the site. It can be used to detect aircraft, ships, spacecraft, guided missiles, motor vehicles, w ...

, infrared homing, and semiactive laser guidance) to the

INS INS or Ins or ''variant'', may refer to: Places * Ins, Switzerland, a municipality * Creech Air Force Base (IATA airport code INS) * Indonesia, ITF and UNDP code INS Biology *''Ins'', a New World genus of bee flies * INS, the gene for the insulin ...

and GPS guidance of the original SDB.

Description

The original SDB is equipped with a GPS-aided inertial navigation system to attack fixed/stationary targets such as

fuel A fuel is any material that can be made to react with other substances so that it releases energy as thermal energy or to be used for work. The concept was originally applied solely to those materials capable of releasing chemical energy bu ...

depots, bunkers, etc. The second variant (Raytheon's GBU-53/B SDB II) will include a

thermal seeker Infrared homing is a passive weapon guidance system which uses the infrared (IR) light emission from a target to track and follow it seamlessly. Missiles which use infrared seeking are often referred to as "heat-seekers" since infrared is radi ...

and radar with automatic target recognition features for striking mobile targets such as tanks,

vehicle A vehicle (from la, vehiculum) is a machine that transports people or cargo. Vehicles include wagons, bicycles, motor vehicles ( motorcycles, cars, trucks, buses, mobility scooters for disabled people), railed vehicles ( trains, trams ...

s, and mobile command posts. The small size of the bomb allows a single strike aircraft to carry more of the munitions than is possible using currently available bomb units. The SDB carries approximately of AFX-757

high explosive An explosive (or explosive material) is a reactive substance that contains a great amount of potential energy that can produce an explosion if released suddenly, usually accompanied by the production of light, heat, sound, and pressure. An e ...

. 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. Warhead penetration is of

steel reinforced concrete Reinforced concrete (RC), also called reinforced cement concrete (RCC) and ferroconcrete, is a composite material in which concrete's relatively low tensile strength and ductility are compensated for by the inclusion of reinforcement having hig ...

under 3 ft of earth and the fuze has electronic safe and fire (ESAF) cockpit selectable functions, including air burst and delayed options. The SDB I has a circular error probable (CEP) of . 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 An Air Operations Center (AOC) is a type of command center used by the United States Air Force (USAF). It is the senior agency of the Air Force component commander to provide command and control of air operations.Link 16 to SDB-equipped aircraft.

Alternative guidance and warheads

In November 2014, the U.S. Air Force began development of a version of the SDB I intended to track and attack sources of

electronic warfare Electronic warfare (EW) is any action involving the use of the electromagnetic spectrum (EM spectrum) or directed energy to control the spectrum, attack an enemy, or impede enemy assaults. The purpose of electronic warfare is to deny the opponen ...

jamming directed to disrupt the munitions' guidance. The home-on-GPS jam (HOG-J) seeker works similar to the AGM-88 HARM to follow the source of a radio-frequency jammer to destroy it.Guided-Bomb Makers Anticipate GPS Jammers
- Defensenews.com, 1 June 2015 In January 2016, the Air Force awarded a contract to Scientific Systems Co. Inc. to demonstrate the company's ImageNav technology, a vision-based navigation and precision targeting system that compares a terrain database with the host platform's sensor to make course corrections. ImageNav technology has demonstrated target geo-location and navigation precision within three meters. In January 2016, Orbital ATK revealed that the Alternative Warhead (AW), designed for the M270's GMLRS to achieve area effects without leaving behind unexploded ordnance, had been successfully tested on the SDB.

Development

In 2002, while

Boeing The Boeing Company () is an American multinational corporation that designs, manufactures, and sells airplanes, rotorcraft, rockets, satellites, telecommunications equipment, and missiles worldwide. The company also provides leasing and ...

and Lockheed Martin were competing to develop the Small Diameter Bomb,

Darleen A. Druyun Darleen A. Druyun (born November 7, 1947) is a former United States Department of the Air Force civilian official, Boeing executive, and convicted felon. In 2004, Druyun pleaded guilty to a felony in relation to her role in the United States Air ...

– 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. 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. And on August 10, 2010 the U.S. Air Force awarded a $450 million contract for engineering and development. 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-39/B (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. SDB II production began in FY14 with 144 bombs for the USAF at a unit cost of US$250,000. The FY15 budget requested 246 bombs at a cost of US$287,000 each. When the Pentagon approved the SDB II for production and deployment in May 2015, it had a unit cost of .

Timeline

* October 2001 – Boeing is awarded the SDB contract. * September 2005 – Small Diameter Bomb certified for operational test, evaluation. * September 2006 – SDB team deliver the first SDBs to the USAF. * October 2006 – Initial Operational Capability declared for SDB on the F-15E Strike Eagle. * October 2006 – First use in combat. * February 2008 – 1,000th SDB I and first 50 FLM delivered. * September 2008 – Israel received approval from the

US Congress The United States Congress is the legislature of the federal government of the United States. It is bicameral, composed of a lower body, the House of Representatives, and an upper body, the Senate. It meets in the U.S. Capitol in Washi ...

to purchase 1,000 bombs. * December 2008 – Reportedly used against

Hamas Hamas (, ; , ; an acronym of , "Islamic Resistance Movement") is a Palestinian Sunni-Islamic fundamentalist, militant, and nationalist organization. It has a social service wing, Dawah, and a military wing, the Izz ad-Din al-Qassam Bri ...

facilities in the

Gaza Strip The Gaza Strip (;The New Oxford Dictionary of English (1998) – p.761 "Gaza Strip /'gɑːzə/ a strip of territory under the control of the Palestinian National Authority and Hamas, on the SE Mediterranean coast including the town of Gaza. ...

, including underground rocket launchers. * January 2009 – Unnamed Boeing official stated that they have yet to deliver any SDBs to Israel. * June 2010 – FMS request by the Netherlands for 603 units and support equipment valued at US$44 million. * August 2010 – U.S. Air Force selects Raytheon's GBU-53/B for Small Diameter Bomb II Program. * 2014 – Work begins on home-on-GPS jam. * May 2015 – SDB II approved by Pentagon for production and deployment on the F-15E. * April 2016 – FMS request by Australia for 2,950 units and support equipment valued at US$386 million.

Aircraft

The GBU-39/B began separation tests on the F-22 Raptor 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. The SDB is currently integrated on the F-15E Strike Eagle, Panavia Tornado, JAS-39 Gripen,

F-16 Fighting Falcon The General Dynamics F-16 Fighting Falcon is a single-engine multirole fighter aircraft originally developed by General Dynamics for the United States Air Force (USAF). Designed as an air superiority day fighter, it evolved into a successful ...

, F-22 Raptor and AC-130W. Future integration is planned for the F-35 Lightning II,

A-10 Thunderbolt II The Fairchild Republic A-10 Thunderbolt II is a single-seat, twinjet, twin-turbofan, straight wing, straight-wing, Subsonic aircraft, subsonic attack aircraft developed by Fairchild Aircraft, Fairchild Republic for the United States Air Force ...

B-1 Lancer The Rockwell B-1 Lancer is a supersonic variable-sweep wing, heavy bomber used by the United States Air Force. It is commonly called the "Bone" (from "B-One"). It is one of three strategic bombers serving in the U.S. Air Force fleet along w ...

B-2 Spirit The Northrop (later Northrop Grumman) B-2 Spirit, also known as the Stealth Bomber, is an American Heavy bomber, heavy strategic bomber, featuring low-observable stealth aircraft, stealth technology designed to penetrator (aircraft), penetrat ...

B-52 Stratofortress The Boeing B-52 Stratofortress is an American long-range, subsonic, jet-powered strategic bomber. The B-52 was designed and built by Boeing, which has continued to provide support and upgrades. It has been operated by the United States Air F ...

and

AC-130J The Lockheed AC-130 gunship is a heavily armed, long-endurance, ground-attack variant of the C-130 Hercules transport, fixed-wing aircraft. It carries a wide array of ground-attack weapons that are integrated with sophisticated sensors, naviga ...

. Other aircraft, including UCAVs, may also receive the necessary upgrades. The General Atomics Predator C is also planned to carry this weapon.

Variants

GBU-39A/B – SDB Focused Lethality Munition (FLM)

Under a contract awarded in September 2006, Boeing developed 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. On 28 February 2008, Boeing celebrated the delivery of the first 50 FLM weapons. The USAF intends to use the same FLM casing on a weapon of . In December 2013, Boeing delivered the last of the 500 FLMs under contract.

GBU-39B/B – Laser SDB

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 . 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. The Laser SDB began fielding with the

U.S. Special Operations Command The United States Special Operations Command (USSOCOM or SOCOM) is the unified combatant command charged with overseeing the various special operations component commands of the Army, Marine Corps, Navy, and Air Force of the United States Arm ...

in 2014.

SDB II (GBU-53/B)

The GBU-53/B is designed with sensors to be able to recognize and hit moving targets. In late September 2020, the SDB II (GBU-53/B) was cleared for operational service by

USAF Air Combat Command Air Combat Command (ACC) is one of nine Major Commands (MAJCOMs) in the United States Air Force, reporting to Headquarters, United States Air Force (HAF) at the Pentagon. It is the primary provider of air combat forces for the Air Force, and i ...

on the F-15E Strike Eagle, after testing at Eglin Air Force Base. About a year of delay was caused by a clip restraint for the fins, with an early version suffering vibration fatigue. Testing with the F-35 is the next phase of the introduction into service.After yearlong delay, the US Air Force is ready to field Raytheon’s new smart bomb
Valerie Insinna, DefenseNews.com, 2020-10-14

Ground Launched Small Diameter Bomb (GLSDB)

Boeing and Saab Group have modified 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 altitude and glide on a selected trajectory. Boeing and Saab Group conducted three successful GLSDB tests in February 2015. The system utilizes an existing weapon paired with a stockpiled rocket motor, while maintaining the loadout on a rocket artillery system. Unlike traditional 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 , and can also hit targets behind it. In a 2017 demonstration, the GLSDB engaged a moving target at a distance of . The SDB and rocket motor separated at altitude and the bomb used an SAL seeker to track and engage the target. A 2019 test extended this range to against a target at sea. It is also being considered for use in Ukraine with the HIMARS system. Ukraine has long wanted the ATACMS missiles for their long range. The GLSDB would be a compromise giving them a range of some 150 kilometres (94 miles) using a M26 rocket engine and an SDB. Both the SDB and the M26 are common in the US arsenal. It could be delivered by early 2023 using surplus bombs from the conflict in Afghanistan. Each would cost $40,000 USD.

References

External links

GBU-39 Small Diameter Bomb / Small Smart Bomb - Global Security
* ttp://www.ausairpower.net/APA-SDB.html GBU-39/40/42/B Small Diameter Bomb I/II {{USAF Weapons Guided bombs of the United States Boeing Military equipment introduced in the 2000s