GBU-39 Smart Bomb

boeing_gbu-39-smart-bombThe Small Diameter Bomb (SDB) transition program (formerly known as Miniaturized Munitions Capability) provides the warfighter with increased kills per sortie on current and future manned and unmanned aircraft. The Small Diameter Bomb system includes two variants of the Small Diameter Bomb, a bomb carriage system, a mission planning system and logistics support. The GBU-39 variant of the 250-pound class bomb is equipped with an INS/GPS guidance system suitable for fixed and stationary targets. The GBU-40 second variant adds a terminal seeker with automatic target recognition capabilities more suitable for mobile and relocatable targets.

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At just 5.9 feet long and 285 pounds, the bomb’s small size increases the number of weapons an aircraft can carry, therefore raising the amount of targets it can kill in one sortie. Because of its size and precision accuracy, it also reduces collateral, or unintended, damage in the target vicinity. In the urban conflict in Iraq, the warfighter struggles at times to find a weapon that gives them a desired effect on a target without an excessive effect, so the small diameter bomb will be a nice addition. Complementing the weapon is a smart miniature munitions carriage system. This system can carry four small diameter bombs, enabling an aircraft to quadruple its load out. The carriage system functions similar to an aircraft stores management system by communicating with and controlling up to four weapons.

A small diameter bomb can be used in adverse weather and has a standoff range of more than 60 nautical miles. Once released, the weapon uses its inertial navigation and an anti-jam Global Positioning System to fly to the target. Its guidance is further augmented by a differential GPS system, which provides corrections to enhance accuracy. As the Air Force chief of staff’s number one weapon priority, the small diameter bomb is the fastest major acquisition program in Eglin history.

The size and accuracy of small diameter bombs allows aircraft to carry more munitions to more targets and strike them more effectively with less collateral damage. Because of its capabilities, the Small Diameter Bomb system is an important element of the Air Force’s Global Strike Task Force. Under the official title of “Component Advanced Development for the Small Diameter Bomb,” the program is being conducted by the Air Armament Center and the Air Force Research Laboratory Flight Vehicles Integration Branch located at Eglin Air Force Base, Fla.

The weapon is scheduled to be in the hands of the warfighter for the first time in September 2006. Initial integration of the SDB is with the F-15E. Follow-on integration may occur with the F/A-22, F-35, UCAV, F-16 (Block 30/40/50), F-117, A-10, MQ-9, B-1, B-2, and the B-52. The F-22A is going to be the “day one” weapon system in the future. Right now it can only carry two, 1,000 pound Joint Direct Attack Munitions, but with small diameter bomb it will be able to carry eight. That’s a four-fold increase and will improve the effectiveness of the aircraft in the early hours of a conflict. The B-2 is set to carry between 64 and 192-216 SDBs on one mission.

The winner of the contract would develop the final SDB solution and produce a planned 24,000 or more SDBs. The Air Force is planning to acquire 12,000 fixed-target versions and a like number of the moving-target version. Other estimates suggest a program of 150,000 Small Diameter Bombs over 10 years. The Small Diameter Bomb (SDB) is a joint Air Force and Navy program. As of early 2005 the Navy had no plan to buy small diameter bomb SDB I, but was looking at the development efforts for SDB II. The Navy is likely to wait for SDB 2 until JSF enters service. The FY 2005 budget began production for the Air Force as well as follow-on development and beginning development for integration on Navy aircraft.

With the military construction and support costs, the total value of the Phase I program at $2.59 billion if the Air Force procures the 24,000 Phase I weapons and 2,000 carriages planned for the next 16 years. The cost estimates briefed to senior Air Force leadership for incorporation into the FY 2004 Program Objective Memorandum showed the total value of the program at about $4.27 billion when quantities originally identified for the program (12,000 Phase I and 12,000 Phase II) were included. The Air Force plans to purchase 24,000 small diameter bombs through 2017 at less than $30,000 a weapon. With the weapon on the verge of being handed over to the warfighter, it has set the bar high for other acquisition programs to follow.

The Small Diameter Bomb (SDB) is half the weight of the smallest bomb the Air Force uses today, the 500-pound Mark 82. It uses a 250 pound-class warhead that has demonstrated penetration of more than 6 feet of reinforced concrete. Utilizing a smaller weapon improves aircraft load-out and mission effectiveness. The size and accuracy of small diameter bombs allows aircraft to carry more munitions to more targets and strike them more effectively with less collateral damage. Because of its capabilities, the Small Diameter Bomb system is an important element of the Air Force’s Global Strike Task Force.

The Small Diameter Bomb range is extended to 60 nautical miles by pop-out wings and the speed and altitude of the aircraft using it. A Phase 3 version may have the ability to loiter or autonomously seek out targets. The Small Diameter Bomb is considered one of the most significant programs on the books because it will dramatically increase the strike capability of every combat aircraft in the inventory.

The Small Smart Bomb is a 250 pound weapon that has the same penetration capabilities as a 2000lb BLU-109, but with only 50 pounds of explosive. The 250 pound-class warhead that has demonstrated penetration of more than 6 feet of reinforced concrete. With the INS/GPS guidance in conjunction with differential GPS (using all 12 channel receivers, instead of only 5) corrections provided by GPS SPO Accuracy Improvement Initiative (AII) and improved Target Location Error (TLE), it can achieve a 5-8m CEP. The munition, with a smart fuze, has been extensively tested against multi-layered targets by Wright Laboratory under the Hard Target Ordnance Program and Miniature Munitions Technology Program. The length to diameter ratio and nose shape are designed to optimize penetration for a 50lb charge. This weapon is also a potential payload for standoff carrier vehicles such as Tomahawk, JSOW, JASSM, Conventional ICBM, etc.

A weapon like the small diameter bomb is not created overnight. It was born as the small smart bomb through an advanced technology demonstration at Eglin’s Air Force Research Laboratory Munitions Directorate. There, a team of engineers wanted to demonstrate weapon technologies that increased aircraft loadout and allowed multiple targets to be attacked in a single combat sortie. This was done by focusing on the delivery accuracy, controllability and penetration capability of a 250-pound class weapon with approximately 50 pounds of explosive. The success of the program emphasized the fact that accuracy and load out were sufficient to overcome the warhead size constraints. The group also wanted to explore increased standoff capability of the weapon. But they had to make sure they maintained the bomb’s effectiveness and penetration capability while doing this. The objectives were to develop a low-cost wing kit that could extend the range of this weapon to greater than 40 nautical miles. At the conclusion of this program, increased load out, supersonic carriage and release, standoff, and weapon effectiveness had all been demonstrated. Requirements set for the small smart bomb became small diameter bomb’s foundation. The program was transitioned over to the Air Armament Center for further development and fielding. Gen. John P. Jumper, Air Force chief of staff at the time, liked the new small diameter bomb so much that he wanted it fielded and ready for the warfighter by the fourth quarter of fiscal 2006. From their request for proposal, the new small diameter bomb program office picked two contractors to design and test their prototype weapon system. They would then select one of them to produce the bomb after completing the component advanced development phase. Schedule was number one from the beginning. Therefore, a lot of emphasis during the component advanced development phase was on design maturity so we could go right into a program with minimum changes. The small diameter bomb team accelerated the acquisition process for the component advanced development phase by using a lot of the same concepts as the Joint Direct Attack Munitions and Wind Corrected Munitions Dispenser program offices. The whole point of the competition was to have a higher probability of getting a weapons system that would perform to the requirements and have a price competition for the production options in out years. During the next two years the program office carefully graded and evaluated the two contractor’s different designs. In early ground testing, the weapon’s ability to penetrate six feet of reinforced concrete was demonstrated. In subsequent testing, a total of five weapons were dropped against targets with surveyed aim points (no target location error). The bombs’ accuracy was achieved through the use of a Differential Global Positioning System (GPS) guidance unit. A few tests demonstrated the abilityof the Munitions Directorate-developed Hard Target Smart Fuze to initiate bomb detonation at the optimum location duringpenetration. During the final flight test, a “live” MMTD warhead devastated an aircraft and its shelter. The slim orange weaponpierced through the top of the shelter and detonated precisely at the target’s center destroying the aircraft and equipment inside. While the technology has proven successful enough to be transitioned, the Munitions Directorate will continue to provide support to the concept though the MMTD Phase-II program. In this phase, program managers seek to integrate anti-jam GPS technologyand a terminal seeker into the baseline weapon, and extend its range.

Boeing was selected in 2003 to complete the system development and demonstration phase and produce the small diameter bomb. In 2005, 19 months after the weapon was awarded to Boeing, it was ready to enter operational testing. But the weapon had some GPS issues during operational testing. With their eyes still focused on staying on schedule, the small diameter bomb program office pulled together an independent team to review the bomb and find a fix. The review team included other program offices, staff organizations and members from industry. Within a month-and-a-half, they had identified the highly probable root causes and provided suggested fixes. Even though the weapon had suffered a setback, it never got off schedule and is now approximately halfway through operational testing. The Munitions Directorate’s successful completion of the Miniaturized Munition Technology Demonstration (MMTD) Program, provided an innovative weapon called the Small Smart Bomb. The miniaturized munition concept was a weapon that is six feet long, six inches in diameter, and weighs only 250 pounds with approximately fifty pounds of Tritonal explosive material. The weapon is effective against a majority of hardened targets previously vulnerable only to munitions in the 2,000 pound class. The Air Force Research Laboratory’s Munitions Directorate set the baseline for small bomb development by successfully demonstrating the technology that will be used to further the development of a 250-pound class munition. Small Smart Bomb’s size will allow future fighter and bomber aircraft to carry more weapons in their weapons bays.

During its developmental testing program, the small diameter bomb completed 35 out of 37 flight tests successfully. The program office attributed its success to having a good stable design early and keeping focused on the schedule.Since the program began in August 2001 it had never missed a major schedule event and remained on track to meet its Required Assets Available date of fourth quarter FY06. One of the keys to success was a very aggressive test program aimed at driving down risk before commencing with production. The flight test program had over a ninety per cent success rate spanning twenty-three guided flights and successfully demonstrated its capability to destroy realistic targets from ranges significantly greater than the required forty nautical miles with near precision accuracy.

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