by Tom Clancy
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-111F 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 Inst
ruments 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 positional 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."
The other munitions program the Air Force has pinned its hopes to is the Joint Direct Attack Munition System, or JDAM. Trust me when I say this, JDAM is the program that must work if the Air Force is to be a viable force into the 21st century. There is that much riding on it. The JDAM family of munitions is designed to replace the old Paveway II-series weapons, which are starting to show their age. Like JSOW, the JDAM program began as a pair of Navy/Marine and Air Force programs that were combined into a single joint requirement. Currently, the program is being competed for by two contractor teams consisting of McDonnell Douglas and Rockwell International on one side with Lockheed Martin and Trimble Navigation on the other. Rockwell and Trimble are on the teams to supply GPS/inertial guidance system expertise, since that, as in JSOW, will be the primary guidance system for the JDAM family of munitions. Selection of a final winner is expected in 1996, with the weapons entering service in the late 1990s.
The idea is to produce a weapons family with the accuracy of the early LGBs, utilizing only a GPS/strapdown inertial-guidance system to find the target. This is the critical requirement. For the first time, aircraft without a laser-designator or data-link pod will be able to deliver precision weapons onto known targets. And it will do so without exposing the launching aircraft to direct fire by enemy defenses. Thus, stealth aircraft like the F-117A, F-22A, and B-2A will be able to use JDAM without generating telltale data link or laser designator emissions which might be detected by an enemy.
The basic features of the baseline JDAM family of weapons (called Phase I) include the following:
• 32.8 foot/10 meter three-dimensional accuracy at the point of impact.
• A common guidance kit for every version of the weapon, independent of the warhead used.
• Interfaces with the most popular bomb warheads (Mk 83, Mk 84, and BLU-109/B).
• In-flight targeting and delivery, independent of weather and/or lighting conditions.
• Good standoff range (more than 8.5nm./15.5km. downrange and 2 nm./3.7 km. cross-range) and the ability to target more than one target /weapon at a time.
While this may sound like quite a lot to ask of a munition which has yet to even undergo its first engineering drop tests, the principles behind the JDAM system are both sound and mature. GPS/inertial guidance systems proved their worth during Desert Storm, and are more than capable of doing the job with JDAM. And as we have mentioned earlier, JDAM may not even be the first GPS-aided bombs, if Northrop and Rockwell have their way.
As currently planned, there will be five separate versions of the Phase I JDAM family. They include:
Each JDAM kit will be composed of an aerodynamic nose cap which is bolted onto the nose fitting of the bomb warhead, and a guidance section/fin group which is bolted onto the rear. Contained in the fin group at the rear of the bomb will probably be a small GPS/receiver antenna system to pull in the signals from the satellites and feed navigational updates to the inertial guidance /steering system. Other than that, all mounting, fusing, and arming hardware will be identical to other PGMs.
A mockup of the Lockheed Martin entry in the Joint Direct Attack Munition (JDAM) competition. Built around a conventional bomb warhead, it is guided by an onboard GPS satellite receiver to its target. McDonnell Douglas is the other JDAM competititor.
John D. Gresham
As for their employment, all the pilot of an attacking aircraft will require is a known target location (preferably one with coordinates correlated with GPS accuracy), and a weapons delivery system capable of plotting a ballistic course to the target. While an onboard GPS receiver would be of great help, it is not necessary to the delivery of the JDAM munition. Once the bomb has been fed the target position and is launched, it will do its best, within the limits of the energy imparted by the launch aircraft, to head for the three-dimensional position of the target. Once there, it acts like any other bomb and explodes — in short, a very simple, yet very elegant solution to getting PGMs on target. Early tests of JDAM hardware on test benches are already showing accuracies in the 3.3-to-9.8 foot / 1-to-3 meter range, without any other added guidance systems. This is the future of PGMs, where the attacking aircraft only has to know the position of a target to kill it.
AIR-TO-GROUND MISSILES
Ever since young David used a stone projected by a sling to slay the giant warrior Goliath from a safe distance, warriors have dreamed of weapons that allow them to attack from a distance that makes counterattack impossible. Standoff. This has been the idea behind almost every weapon innovation — from the catapult, to the cannon, to the Intercontinental Ballistic Missile (ICBM). During the 1940s and 1950s, a generation of designers and engineers worked to create long-range weapons. For Nazi Germany, there was the Fi-103 flying bomb, known better as Vergeltungwaffe-1, or V-1. Called the "Doodlebug" or "Buzz Bomb" by its victims, it was the first practical example of what we now call a cruise missile. Later, in the 1950s, standoff cruise missiles were produced to extend the reach of nuclear bombers and maritime strike aircraft.
None of these early standoff weapons had any real precision; the mission was simple delivery of a large warhead to the general target area. True stand-off precision weapons had to wait for the development of electronic seeker technology in the 1960s. Earlier, we saw how the first precision seekers were developed for guided bombs like the Paveway-series LGBs, and the GBU-15, so that they could destroy point targets
like bridges and bunkers. A precision-guided missile combines seeker technology with a propulsion system to extend its range.
As we head towards the 21st century, the USAF has a growing array of standoff air-to-ground missiles (known by their AGM designator) for use against heavily defended targets. These weapons are highly specialized for the targets they are designed to destroy. They also tend to be expensive, with typical unit prices in the six-figure range. However, when compared to the cost of a lost aircraft ($20 million and up) and the human and political costs of lost or imprisoned aircrews, these weapons can be very cheap indeed.
AGM-65 Maverick
We'll start our look at what pilots like to call "gopher zappers" with the oldest air-to-ground missile in the USAF inventory, the AGM-65 Maverick. Maverick draws its roots from two different programs, the early electro-optical guided bomb projects and the Martin AGM-12 Bullpup (originally designated the ASM-N-7 Bullpup A by its first user, the U.S. Navy). Bullpup was an attempt to extend the range of the basic High Velocity Artillery Rocket (HVAR) used by U.S. aircraft since World War II. Bullpup provided a large warhead (250 lb./113.6 kg.), a rocket motor, and a guidance package to keep the whole thing on course. From a safe distance (8.8 nm./16.1 km.) one Bullpup could kill targets that previously required many aircraft with lots of bombs or unguided rockets. Guidance was provided by a command line-of-sight system, which sent the missile flying down a radio "pencil beam." All the operator had to do was keep the nose of his aircraft on the target, and the missile would fly down the beam and impact the target. When it came into service in 1959, it was a wonder to its operators, who saw it as something of a "silver bullet." The problem was that the AGM-12's guidance system compelled the combat aircrew to fly straight and level toward the target during the missile's entire time of flight.