Function: Bomb with guidance control system.







Description: The Guided Bomb Unit-28 (GBU-28) is a special weapon developed for penetrating hardened Iraqi command centers located deep underground. The GBU-28 is a 5,000-pound laser-guided conventional munition that uses a 4,400-pound penetrating warhead. The bombs are modified Army artillery tubes, weigh 4,637 pounds, and contain 630 pounds of high explosives. They are fitted with GBU-27 LGB kits, 14.5 inches in diameter and almost 19 feet long. The operator illuminates a target with a laser designator and then the munition guides to a spot of laser energy reflected from the target.



The GBU-28 "Bunker Buster" was developed specifically to destroy Iraqi underground hardened command bunkers during the Gulf War. Scratch built from a section of surplus 8" howitzer barrel filled with 600 pounds of explosives, the 5,000 pound GBU-28 is capable of penetrating more than 20 feet of reinforced concrete and deeper than 100 feet underground. Equipped with essentially the same guidance hardware as the GBU-10 Paveway II, the GBU-28 is capable of hitting discrete, hardened targets deep underground. The GBU-28 was successfully used twice during the Gulf War, with each of the weapons being released by FB-111F Aardvarks for use against buried command bunkers.







Background: Precision-guided munitions (PGM) can trace their origins back to World War Two. These early weapons, such as the QB-17G "Aphrodite" were essentially airframes packed with explosives and guided via radio direction signals to their target, where they would crash and explode. While guidance was extremely crude by today's standards, these weapons were more accurate than conventional dropped munitions, and did not expose aircrews to deadly enemy anti-aircraft fire. Unfortunately, such weapons were unwieldy, unsuitable for small targets, and were themselves subject to defensive fire. The first truly precision-guided munitions did not appear until the Vietnam War. Serving as a major supply conduit for North Vietnam, the mile long Paul Doumer Bridge over the Red River was the most important ground target of the war. Unfortunately, it was also one of the most heavily defended, its approaches ringed with anti-aircraft guns and surface to air missile emplacements. While American pilots were able to attack the bridge using conventional munitions, such missions were extremely hazardous and casualties were high. In 1967 the Rockwell International Corporation was tasked with producing a precision munition using electro-optical guidance technology. The end result was the GBU (Guided Bomb Unit) 8 or Homing Bomb System (HOBOS), a conventional Mk. 84 2,000 pound bomb with a TV like electro-optical guidance package in the nose to provide direction and a modified tail fin assembly in the rear to provide lift. To launch the GBU-8 the pilot aligned the TV camera sight in the bomb with the target and the weapons officer locked the bomb's seeker onto the target. Once aligned, the bomb could be released well away from the target area and it would guide itself into the target with a high degree of accuracy.







History: The GBU 28 "Bunker Buster" was put together in record time to support targeting of the Iraqi hardened command bunker by adapting existing materiel. The GBU-28 was not even in the early stages of research when Kuwait was invaded. The USAF asked industry for ideas in the week after combat operations started. The bomb was fabricated starting on 1 February, using surplus 8-inch artillery tubes. The official go-ahead for the project was issued on 14 February, and explosives for the initial units were hand-loaded by laboratory personnel into a bomb body that was partially buried upright in the ground outside the laboratory in New York. The first two units were delivered to the USAF on 16 and 17 February, and the first flight to test the guidance software and fin configuration was conducted on 20 February. These tests were successful and the program proceeded, with a contract let on 22 February. A sled test on 26 February proved that the bomb could penetrate over 20 feet of concrete, while an earlier flight test had demonstrated the bomb's ability to penetrate more than 100 feet of earth. The first two operational bombs were delivered to the theater on 27 February.



The Air Force produced a limited quantity of the GBU-28 during Operation Desert Storm to attack multi-layered, hardened underground targets. Only two of these weapons were dropped in Desert Storm, both by F-111Fs. One weapon hit its precise aimpoint, and the onboard aircraft video recorder displayed an outpouring of smoke from an entrance way approximately 6 seconds after impact. After Operation Desert Storm, the Air Force incorporated some modifications, and further tested the munition. The Fy1997 budget request contained $18.4 million to procure 161 GBU-28 hard target penetrator bombs.