Enhanced Guided Bomb Unit (EGBU)-28
The new EGBU-28 (the "E" being for enhanced) replaces the GBU-37. This latest version of the "bunker buster" uses the Global Positioning System for guidance so that it can be dropped with accuracy at higher altitudes in foul weather. The amount of rock and concrete that the EGBU-28 can penetrate is classified, but Major Dick Wright, who was the weapon's test manager in 1991, said that the older version "went through 20 feet of concrete like butter" and when dropped onto hard ground, penetrated down to 100 feet.
On September 22, 1999 Raytheon Systems Company, Tucson, Ariz., was awarded a $13,695,026 modification to a firm-fixed-price contract, F42630-98-C-0149-P00003, to provide for the following in support of the GBU28 Enhanced Paveway III Laser Guided Bomb: 173 Guidance Control Units, 173 Bomb Stabilization Unit Air Foil Groups, 173 Conduit Assemblies, and associated data. There was one firm solicited and one proposal received. Expected contract completion date was Dec. 31, 2000. Negotiation completion date was July 14, 1999.
In October 2001 the Precision Strike Systems Program Office, Air Armament Center, Eglin AFB Florida, awarded a sole source Phase II contract to Raytheon Missile Systems to integrate the GBU-28B/B weapon system into the B-2A aircraft. Raytheon was on contract to produce a quantity of GBU-28B/B weapons under Contract F42630-98-C-0149. This sole source contract is a follow-on to a Phase I effort under Contract F42630-01-C-0004, performed by Raytheon. Required improvements include an inertial measurement unit (IMU) with sufficient accuracy to guide the weapon close enough to the desired target basket that the Global Positioning System (GPS)/IMU/Kalman Filter and Laser designation modes may be used to achieve desired weapon system accuracy. Weapon development is necessary to decrease weapon circular error probability equivalent to the GBU-31 weapon system accuracy, provide full interface for the B-2A aircraft and incorporate an IMU-only mode. The GBU-28B/B upgrade provides a power-only mode for the F-15E aircraft, GPS/IMU/Kalman Filter guidance/navigation capability, and laser designation, while retaining the GBU-28A/B performance. The Phase II contract effort provides the full interface capability to the B-2A aircraft, GPS/IMU/Kalman Filter mode, an IMU/Kalman Filter mode for GPS jamming capability, battery qualification testing, weapon simulation upgrade, Paveway field test set (TTU-373) software update, Common Munitions BIT/Reprogramming Equipment programmable circuit cards, and training.
The New York Times reported on 10 October 2001 that the GBU-28 had been used in combat in Afghanistan as part of Operation Enduring Freedom. Strikes conducted on 09 October, the third day of air operations, reportedly included the first use of the 5,000-pound bomb. Prior to this time the only operational aircraft known to be certified to carry the GBU-28 was the land-based F-15E fighter/bomber. However, there were no reports that the F-15E was participating in the air campaign, and it was reported by CNN beginning on 11 October that the GBU-28 was being delivered from the B-2 stealth bomber.
New production would be for about 350 weapons. Development is slated to begin this fiscal year with a single contractor team. Production is expected to start in 2005. The B-2 and F-15E will remain the only launch platforms for the weapon. The Air Force has developed a new steel that is available for bidders to use. Called Eglin Steel (ES-1), it is a collaboration between the Air Force and National Forge, which builds the casing for the BLU-113. The largest ingots that can be made, current producer are 69 inch diameter. Current size ingots being made, current producer are 39 inch diameter. ES-1 alloy is weldable, as it is a "low carbon alloy" Penetrator wall thickness of 2 inches has been heat treated. Test Sections 4 inches thick have been evaluated, with excellent and consistent hardenability through wall. Among the candidate explosive fills is the AFX-757 used in the warhead of the Joint Air-to-Surface Standoff Missile. The Air Force-developed fill produces more blast energy and is less likely to be set off in a fire than Tritonal. The current BLU-113/B contains about 600 lb. of Tritonal.
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