The fourth variant of the Paveway III family is a unique version for the F-117A Nighthawk Stealth Fighter, the GBU-27/B. The reason for this is that the F-117A design was frozen before the new bomb was even in design, and the Lockheed designers had originally assumed that they would only have the older Paveway II-series weapons with their relatively small airfoil groups to fit into the weapons bays of the F-117s. With the coming of the Paveway III- series weapons, though, the USAF wanted to get the new bombs, especially ones equipped with the BLU-109/B, onto the new stealth birds. The problem was that the BSU-84/B airfoil group was too large to fit into the Nighthawk’s weapons bays. This problem was overcome when the TI and Lockheed designers realized that the F-117A was almost never going to fly the kind of low-level delivery profiles that the F-111Fs and F-15Es were going to. In fact, the Nighthawk normally flies its weapons delivery profiles straight and level at various altitudes, dropping its precision weapons under the control of the pilot. Thus, the TI designers came up with a slightly different version of the fin group used on the Paveway II family, which fits nicely inside the limited volume of the F-117A weapons bay. The normal warhead of the GBU-27/B is the BLU-109/B, though the Hardback adapter is deleted because of the unique “trapeze” weapons handling gear of the Nighthawk.
A drawing of the GBU-24/B Paveway III Laser-Guided Bomb.
Jack Ryan Enterprises, Ltd., by Laura Alpher
The final version of the Paveway III family deserves special attention. It is the famous “Deep Throat” super penetrator bomb that was used on the last night of Desert Storm. Officially designated as the GBU-28/B. Its origins date back to August 1990, when the first planning for an offensive air campaign against Iraq began. As the planners in what was known as the Black Hole began to look at strategic targets around Baghdad, they noted a series of super-hard command and control (C2) bunkers, so heavily built that there were doubts about the ability of the BLU-109/B warhead to penetrate and destroy them. With this in mind, a request was made to study the problem at the USAF Air Armament Division at Eglin AFB, Florida. Down at Eglin AFB, a quiet study was started to look over the problems associated with an improved penetrating bomb. In the study group, headed by Major Richard Wright, there was an engineer named Al Weimorts, who began to make some early sketches of a concept bomb that might just do the job. And that was where the idea stayed until the early BDA results from Desert Storm began to come in. By January 21st, 1991, it was clear that the BLU-109/ B-equipped LGBs were just not getting the job done. All they had done to the big bunkers was scab the surface, and not much else. Worse, with more and more of the other Iraqi C2 bunkers being destroyed, a greater percentage of the top Iraqi leadership was taking refuge in the big command bunkers and continuing operations. This made the destruction of those bunkers a top priority, and the word went out to the team down at Eglin to find a way to do so quickly.
Given their marching orders, TI, as well as the BLU-109/B team at Lockheed, got to work on a number of different problems at once. First there was the problem of the warhead. While the basic design of the BLU-109/B was sound, what was needed was something larger—longer and heavier, with a larger explosive payload. Also, because they had to bolt a modified Paveway III kit onto it, and because they had to maintain the necessary clearance to fly and drop it from either an F-111F or F-15E, it would not have a larger diameter than the BLU-109/B. This made for a long, skinny warhead section, with a long interior cavity, or “throat,” for the explosive filler. Thus the bomb got the nickname “Deep Throat.”
The two GBU-28/B “Deep Throat” super penetrating bombs at the Royal Saudi Air Force Base at Taif just before being loaded onto F-111F fighter bombers of the 48th Tactical Fighter Wing (Provisional). The BLU-113/B warheads have already had their fin groups mounted, and the guidance sections will be mounted once loaded. Captain Ron Evans
Next, to machine and finish a forged-steel blank would take months, and the Eglin team had days. Luckily, an engineer at the Lockheed plant where the BLU-109/Bs were made was a retired U.S. Army trooper who remembered a stock of old 8-inch/203mm howitzer gun barrels lying around (literally) at the Letterkenny Arsenal in Pennsylvania. Made of the same kind of hardened steel as the BLU-109/B, they had been happily rusting away for some time. By February 1st, 1991, a number of the old gun barrels were shipped to the Watervliet Army Arsenal in upstate New York and machined into the shape of what would become known as the BLU-113/B Super Penetrator. Eventually, around thirty-two of the BLU-113/Bs would be built for integration into what was going to be known as the GBU-28/B. Several inert (non-explosive) tests indicated that the new bomb was capable of doing the job. This included one test on a rocket sled at Holloman AFB, New Mexico, where it penetrated 22 feet/6.7 meters of reinforced structural concrete, and then continued on to careen downrange for another mile or so without any damage whatsoever to the BLU-113/B. Each of the new warheads eventually weighed in at 4,700 lb./2,136.4 kg., and had to be hand-loaded with some 1,200 lb./545.45 kg. of explosive, and then integrated with the guidance kits from TI.
Those guidance kits were a whole story on their own. Meanwhile, the original Paveway III development team had long since moved onto other jobs within TI, and had to be reconstituted as quickly as possible. Murl Culp from Lockheed contacted TI and discussed the feasibility of guiding the new penetrator with a derivative Paveway III GCU. Luckily, Bob Peterson, an original Paveway III engineer, was still with the company, and was able to reassemble enough of the original team to get the ball rolling. And other members of the team were pulled off of other important TI programs to staff the effort. By February 12th, the TI/Lockheed team was down at Eglin AFB briefing guidance concepts to the Air Force.
Once the new guidance software was completed, the major testing normally associated with development of a new Paveway GCU would have to be accomplished in days rather than years. A key problem was access to the only wind tunnel in the Dallas/Fort Worth area capable of doing the testing required to develop and validate the new LGB’s software. Owned then by LTV/Vought, it was heavily booked with projects, and the security around the GBU-28/B precluded doing anything special to “force” the owners to provide access for TI. Thus, TI would have to use the only open “window” on the tunnel’s calendar, on the weekend of February 16/17, just four days away. Now, it should be remembered that at the time all of this was going on, TI, Lockheed, and the Air Force did not have any sort of contract for this project. What they did was done on a handshake and good faith, and TI decided to trust in that when they scheduled the tunnel time. They constructed a 1/4 subscale model to establish the ballistics of the new BLU-113/B/Paveway III combination, which was designated the GBU-28/B.
The tunnel testing was completed by the early hours of Monday, February 18th, and the effort now fell completely on the shoulders of the TI team. Over the next week or so, they worked around the clock to produce the software that would allow the bomb to guide successfully to a target. Almost as an afterthought, the Air Force called with an order for the first two guidance kits on the 19th, and the GBU-28/B was finally an official project, financially and contractually. Two days later, on the 21st, a TI-chartered aircraft loaded with four large airfoil groups took off from Love Field in Dallas, bound for Eglin AFB. These would be part of the actual kits that would be shipped to the Taif RSAFB, where the 48th TFW was based. The decision had been made that the F-111F would deliver the new bombs, mainly because the airframe was more mature than that of the F-15E.
On February 22nd, TI was asked to produce two more of the GBU-28/B guidance kits and ship them ASAP out to Nellis AFB, Nevada. The Air Force wanted to do a full-up test of the new bomb being dropped from an F-111F before it went to combat over Iraq. The ground war into Iraq and Kuwait was only hours from starting, and the Air Force wanted to be sure the system worked.
On the morning of February 24th, the final test of the new bomb took place. A fully integrated bomb (with an inert warhead; the explosive charge was not loaded) was dropped by an F-1
11F at a target on the Nellis AFB range. The results were stunning. Not only did the GBU-28/B hit the target as advertised, but it dug a hole over 100 feet/30.5 meters deep in desert caliche (hard clay soil with roughly the same consistency as concrete!). The BLU- 113/B-equipped LGB was buried so deep, it could not be retrieved. It remains there to this day.
After the single “event” (as tests are sometimes called), TI programmed two GBU-28 GCUs (designated WSU-36A/B), and flew them out to Eglin AFB on Monday, February 25th. These were mated with two of the previously shipped airfoil groups, strapped to a pallet along with a pair of BLU- 113/B warheads, loaded aboard a USAF C-141B StarLifter, and flown to Taif RSAFB on February 27th. Since the normal BSU-84/B planar wing section was too big to allow the proper ground clearance and separation from the F-111F, and a gliding bomb was not really required (the GBU-28/B was to be dropped from high altitude), a modified version of the GBU-27/B tail fin assembly was developed for attachment to the new bomb. Covered with signatures and messages from everyone who had handled them during the program, they were two of the oddest-looking weapons ever built.
Within five hours of landing at Taif, the two bombs were loaded aboard a pair of 48th TFW F-111Fs, and their crews were briefed to hit a very special target that very night. For some time, a bunker known as Taji #2 had been monitored closely by elements of the U.S. intelligence community. Located at the al-Taji Airbase, approximately 15 nm./27.4 km. northwest of Baghdad, it had been hit no less than three times by F-117As with GBU-27/Bs early in the war. In the words of General Horner, they only “dug up the rose garden.” Since that time, various estimates had suggested that the top national command authorities of Iraq, including possibly Saddam Hussein himself, were running the war from this bunker. With less than twelve hours left before the planned cease-fire, scheduled for 0800 Local Time (0500 Zulu) the next morning (February 28th), CENTAF was ordered to hit the bunker with the bombs. Each F-111F was loaded with a GBU-28/B under one wing and a single 2,000 lb./909.1 kg. GBU-24A/B under the other, for balance. Even so, while they taxied to takeoff position, the F-111s “leaned” to one side because of the weight imbalance.
On the night of February 27th/28th, 1991, the two F-111Fs took off and headed north towards the airfield northwest of Baghdad. The aircraft made their runs and dropped their bombs. They aimed for an air shaft on the top of the bunker, and at least one of the bombs hit its target. Penetrating the thick, reinforced concrete, it detonated in the heart of the bunker. The results were horrific. All six of the bunker’s armored blast doors were blown off their hinges; then a huge glut of flame and debris swelled up. Anyone inside was clearly dead, though to this day we do not know who was there. Though they have never been confirmed, postwar rumors claim that a number of senior Iraqi civilian and military personnel perished in the destruction of Taji #2. But it’s certain that the GBU-28/B did the job exactly as designed; it was an unqualified success.
With the war won, the quick-reaction program transitioned to a more normal type of USAF procurement. Approximately twenty-eight additional sets of BLU-113/Bs and GBU-28/B kits were produced so that a proper test program could be conducted. And some additional units were kept in reserve for combat use, should the need arise. In addition, the Air Force has contracted with TI for an additional one hundred GBU-28/B guidance kits; and a firm up in Pennsylvania is forging one hundred new production BLU- 113/B warheads to go along. The idea is to provide U.S. national command authorities with a non-nuclear option to hit hardened targets like command bunkers and missile silos with precision munitions that do not generate a lot of collateral damage.
It’s a staggering idea, and it is all due to the original vision of folks like Weldon Word, and his idea for a bomb with a beam of light for its guide. As for the future of the Paveway-series weapons, they may finally be coming to the end of the line. While new Paveway III kits are being manufactured by TI for U.S. and overseas customers, there are no new versions planned. The tactical limitations of LGBs, along with the rapid maturing of GPS technology, is making satellite navigation the guidance system of choice for the next generation of U.S. precision munitions. Nevertheless, Paveway LGBs will be the backbone of the USAF PGM capability well into the next century.
The Future: JSOW and JDAM
By now your head may be hurting slightly from the array of air-to-ground munitions in the previous pages. For what it is worth, USAF strike planners have similar problems when they consider the targets that need to be struck, the damage required to negate those targets, and the weapons required to do the job.
The folks down at Eglin AFB, Florida, who run the conventional munitions programs for the Air Force, are attacking the problem of what kinds of bombs to develop and buy. In particular, they’re trying to buy fewer kinds of weapons that do more kinds of things. That was the basis for the TMD series of CBUs like the CBU-87/B, as well as the Paveway III-series guidance kits; and it’s at the core of the development of new weapons.
Several new and exciting kinds of air-to-ground weapons are being prepared for service with the Air Force. As might be expected in these days of limited budget dollars, weapons are usually joint-service ventures like the AIM-9X. In addition, they have been designed with many of the following criteria in mind: • The use wherever possible of available, off-the-shelf components and technologies to lower risks and costs.
• Safe carriage and employment on the widest possible range of aircraft from all services, including fighters, bombers, and even attack helicopters.
• Improved accuracy over existing types of weapons, without the requirement of designation or data link guidance equipment.
• Enhanced weapons-delivery options, including greater standoff range and less exposure of the delivery aircraft to enemy air defenses.
With these requirements in mind, let’s explore two new programs that the Air Force is getting ready to put into service in the next few years.
A Texas Instruments AGM-154 Joint Standoff Weapon (JSOW) munitions dispenser. Guided by an onboard GPS satellite receiver, it will provide the ability to hit area-type targets from long standoff ranges. Rockwell International
The first of these is the ultimate answer to the problem of delivering cluster munitions into an impossibly heavy air defense environment, the AGM- 154 Joint Standoff Weapon (JSOW). JSOW is the result of a joint Air Force/Navy/Marine effort to produce a new munitions dispenser which can be launched at long range toward the target, completely outside the range of enemy defenses. It started life as a Navy/Marine program called the Advanced Interdiction Weapons System (AIWS), which had a requirement for a full man-in-the-loop data link control system like the GBU-15. Texas Instruments won the AIWS competition in 1991, and in 1992, the AIWS requirement and program was merged with the Air Force’s own standoff cluster munitions program to become JSOW. Like the TMD, it is designed to function as a submunition “truck,” capable of carrying a wide variety of payloads; it can also be used from almost any tactical or bomber aircraft of any service. The key to JSOW is a technology I have often praised, the NAVSTAR Global Positioning System (GPS), which will be the primary baseline guidance system for every variant of the AGM-154. For the first time in history, a satellite navigation system will guide a weapon throughout its entire flight, from launch to weapons impact.
The AGM-154 is composed of a nose section containing the GPS-based guidance and flight control system, a weapons carriage bay topped by a folding planar wing system to provide lift during flight, and an aft guidance fin section. The 13.3 foot/4.1 meter-long JSOW, while not exactly stealthy, is definitely of a low-observable design. As designed, the JSOW is capable of gliding unpowered for up to 40 nm./73.1 km. before delivering its load of submunitions on target. Guidance accuracy for the GPS-based system is expected to be within 32.8 feet/10 meters in three dimensions, more than good enough for delivery of cluster weapons. The GPS-based guidance systems used on the new generation of precision munitions are actually hybrid systems, with a GPS receiver feeding positi
onal updates to a small strapdown inertial guidance system which actually controls the flight-control system. In this way, the weapon can continue to the target with acceptable accuracy should the GPS system fail or be jammed.
Currently, two versions of the AGM-154 have been approved for production, one loaded with 145 BLU-97/B CEMs and the other with six of the BLU-108/B SFWs. These are expected to enter service late in the 1990s. There are also plans to produce versions with large (1,000 lb./454.5 kg.) unitary warhead and terminal guidance systems. Given the recent cancellation of the AGM-137 Tri-Service Standoff Attack Missile (TSSAM), this idea has to be considered a possibility. The new Northrop Brilliant Anti-Tank (BAT) weapon, which homes in on the sounds of enemy vehicles, and the Gator mine have also been considered for use on JSOW. And there are growth provisions for the addition of rocket and turbojet motors to extend range, as well as the possibility of enlarging the weapons carriage bay. There have even been proposals to produce “non-lethal” versions of JSOW, to provide logistical support for forward deployed troops such as special operations forces. Before you laugh too hard, consider how many Meals, Ready-to-Eat would fit into the 5.7 foot/1.7 meter-long bay of an AGM-154. It may be the ultimate expression of the statement that “every bomb is a political bomb.”