Posted on 04/18/2002 6:07:21 AM PDT by Stand Watch Listen
Guided air-launched munitions are the way forward following the success of the low-cost JDAM weapons, writes Bill Sweetman
This is a bad time to visit the Joint Direct Attack Munition (JDAM) production line, apologizes the Boeing plant manager. "All the employees are in a meeting," he explains, gesturing to the door of a small conference room. Surely we must have misheard, because this factory is producing 600 guide-bomb tail-kits per month and is headed for 1,000 by mid-year. But he is right. The building that houses the assembly line is empty. The first-shift workers are in a meeting - all 11 of them. Together with six people on another half-shift, they constitute the entire JDAM assembly workforce.The JDAM plant, located in St Charles on the Missouri river flood-plain, is at the center of a revolution in air-to-surface munitions. When the JDAM project started in 1992, US Air Force (USAF) program managers set what was then considered a very challenging unit cost goal: US$40,000 in 1992 values for a complete kit to modify an existing 900kg Mk84 bomb into a guided weapon. Today's price is around US$20,000 in 2002 dollars, or well under half the goal. It is also a small fraction of the price of any previous guided weapon.
The success of the JDAM project in beating its cost target is immensely important, because it makes it reasonable to project a future in which all air-launched weapons will be guided. The current 'Enduring Freedom' operation in Afghanistan is halfway to that point. US Army General Tommy Franks, commander of the operation, told an Air Force Association symposium in February that 10,000 out of 18,000 air-launched munitions used in the operation were precision-guided. According to General Ed Eberhardt, commander of USAF Space Command, half those precision weapons - 5,000 in all - were JDAMs.
Gen Franks contrasts the 'Enduring Freedom' strikes with 'Desert Storm' (in 1990-91), in which some 9% of the weapons used were guided. "In 'Desert Storm', we had 3,000 sorties per day. In 'Enduring Freedom', we had 200 sorties, but they hit the same number of targets that we hit with 3,000 a day in 'Desert Storm'. Then, we used 10 airframes to a target; now, we assign two targets to an aircraft." While there are other factors in play - for example, Afghanistan's air defenses are almost entirely destroyed - the difference is nevertheless dramatic.
Moreover, the current JDAM is only the first of a line of low-cost weapons which will bring the same benefits to attacks on small, mobile targets and further increase the number of weapons which can be carried by either manned or unmanned aircraft.
These weapons will be particularly important to unmanned combat air vehicles (UCAVs). On current plans, even the operational version of the USAF/Defense Advanced Research Projects Agency (DARPA) X-45 UCAV will be able to carry 12 individually guided, hard-target-capable glide bombs. Development work is continuing on low-cost weapons which will be able to seek out mobile targets.
US exports of JDAM have already started, and newer weapons are also likely to be offered to allied nations, particularly alongside the F-35 Joint Strike Fighter (JSF) - the first manned combat aircraft, apart from the specialized F-117, to be designed to carry guided weapons as its primary armament. While other nations have similar weapons under study, the US has the only low-cost system in production and several more under firmly funded development programs.
JDAM itself is evolving into a family of weapons. The initial GBU-31 weapon kit converts either the Mk84 iron bomb or the BLU-109/B hard-target penetrator to a guided weapon. This 900kg version of the bomb was cleared into full-rate production in March 2001. It is operational on the B-2, B-52 and F-16, and is currently being cleared on the F-14 and F-15E. Boeing has also delivered 484 tail-kits to Israel.
The next version of the JDAM is the GBU-32, based on the 450kg Mk83 bomb or the BLU-110, which is similar but has a less sensitive explosive fill. This weapon is undergoing final operational tests on the F/A-18. Because it permits the F/A-18 to carry more weapons and return to the carrier with unused ordnance, the GBU-32 will be the US Navy's (USN's) principal version of JDAM. It is also the initial air-to-surface armament for the F-22.
Also under test is a 225kg version of the JDAM, to be fielded on the B-2 in 2004-05. This has a number of purposes. It has a smaller damage radius than the 900kg bomb, which may be important when collateral damage has to be avoided - such as in urban areas or in close proximity to friendly forces. For a bomber, it provides a very high load-out - as many as 80 weapons on the B-2, using the Smart Bomb Rack Assembly which is now under development.
Basic requirements
The JDAM's low cost reflects a number of important lessons for other weapon programs. The program was launched with a minimum of basic requirements: a 13m circular error probable (CEP), compatibility with aircraft targeting systems, a guaranteed 20-year storage lifetime and the US$40,000 maximum cost. Most standard military specifications (Mil Specs) for components and materials were avoided.
The assembly line reflects the principles of 'lean production'. Sub-assemblies such as fins, tailcones and guidance systems are delivered to the Boeing plant in containers which are placed directly on roller racks beside the assembly stations. Each assembly worker has a signal light to indicate when the supply of parts is running low; when the light is yellow, more parts are delivered to the roller racks and empty containers are removed. Assisted lift devices are used for components weighing more than 18kg: the hydraulic devices respond to the operator's hand movements.
Handling and processing are minimized: for example, the JDAM ship and store containers are first delivered to the company that produces the weapon's body strakes. The company loads the strakes into the containers before they reach Boeing, and they are not touched again until the complete weapon is ready to be assembled and used in the field. The tail-kits themselves are packed in foam-plastic blocks which are wrapped in a plastic film and vacuum-sealed.
The actual assembly work, however, is performed by hand. This makes the line very flexible, and able to switch almost instantly between different versions of the bomb, which have differently sized fins and tailcones but are assembled in the same way.
The basic JDAM is being steadily improved to reduce costs and to avoid problems caused by obsolescent components. Changes are grouped in annual blocks. One important alteration is the replacement of the Honeywell ring-laser gyro (RLG) IMU with a new IMU based on micro-electromechanical systems (MEMS) technology, due to take place in the 2003-04 production block.
The JDAM concept has worked better than expected. The initial specification called for a CEP of 13m, but tests have demonstrated an average CEP of 4.9m. This has had a number of effects on the program. Development of a high-precision version of JDAM has been affected, because the user will require fewer weapons (harder targets can be attacked with the basic weapon) and the Global Positioning System/inertial navigation system (GPS/INS) can place the seeker closer to the target. For the user, the small CEP has also meant it has been more worthwhile to work on reducing target location error (TLE), which accounts for the greater part of miss distances in operational use, than to reduce weapon CEP itself.
Reducing TLE depends on the targeting approach being used. The aircraft itself can provide target data to JDAM with the aid of synthetic aperture radar (SAR) or a laser range-finder. The B-2, with a GPS-aided targeting system (GATS) which combines GPS with two SAR shots, remains one of the most accurate JDAM platforms.
In close air support (CAS) applications, the forward air controller (FAC) is likely to use a portable targeting system, such as the Rockwell Collins PLGR connected to the Leica Viper laser range-finding binocular. Currently, the FAC has to use voice radio to communicate with a JDAM-armed aircraft, but the US services are working towards the use of datalinks to convey information automatically to the bomber. Offboard targeting can also be performed with an unmanned aerial vehicle (UAV) which has a laser range-finder integrated into its payload.
The USN is supporting development of a precision-guided version of JDAM; the USAF has no current requirement for such a weapon, and regards the forthcoming Small Diameter Bomb (SDB) as a higher priority. Under current plans, the USN will award a contract to Boeing later this year to develop a higher-precision JDAM. Boeing itself will conduct a competition to select a seeker.
DAMASK option
A strong candidate technology for a more accurate JDAM is the navy-developed DAMASK (Direct Attack Munition Affordable Seeker). As tested by the navy at China Lake and Edwards Air Force Base (AFB), DAMASK is based on a Raytheon thermal imaging camera. The camera stems from research that started when Hughes - now part of Raytheon - was owned by General Motors, and is the same as that offered on the Cadillac DeVille automobile. The seeker uses a target template which is created on a PC or a mission-planning system, and which can be based on visual, SAR, thermal or overhead imagery.
In tests in 2000, a DAMASK-equipped JDAM was tested without GPS updating, to evaluate the system's usefulness as a back-up in case an adversary succeeded in jamming GPS. The seeker was activated 1.8km from the target, detected it and generated a correction signal that guided the weapon to impact.
Other potential seeker technologies include SAR. This was demonstrated in the Hammerhead program, completed by the USAF Research Laboratory's Munitions Directorate in 1999. Hammerhead showed that a low-cost SAR - which unlike DAMASK would be unaffected by clouds or smoke - could guide a weapon to impact in a steep dive.
USAF JDAM program director Mike Hatcher calls DAMASK a "low-end solution" to the requirement, and says there are other solutions on the table. "It depends on performance, cost and concerns of collateral damage," says Hatcher. Potential solutions include millimetre-wave (MMW) radar, SAR and both fixed infrared (IR - as in DAMASK) and a gimballed IR seeker.
There are no currently funded plans to put a wing kit on JDAM, says Hatcher. "There is interest at the operator level, but the customer at the senior level has not funded it." However, Australia has apparently expressed some interest in a winged JDAM, perhaps based on the BAE Systems Australia Awadi wing kit tested in the late 1980s.
The USAF program office has also looked at adapting a wing-kit and the J-1000 warhead - an advanced penetrator warhead used on the Lockheed Martin Joint Air-to-Surface Stand-off Missile (JASSM) to the JDAM. "We supplied cost and schedule data to Air Combat Command," remarked Hatcher. "It's very effective on the F-22."
Small Diameter Bomb
The USAF's principal focus for the F-22, however, is the Small Diameter Bomb (SDB). This program is being pushed along at a rapid pace. The award of two pre-development contracts for the SDB was originally due in late 2001, in the first quarter of Fiscal Year 2002 (FY02), but was moved up to the last quarter of FY01 and took place last September. According to USAF program manager Colonel Jim McClendon, the plan is to "deliver an 80% solution quickly", with the first weapons entering service in 2006 on the F-15. The next aircraft to receive the SDB will be the F-22.
The SDB is the outgrowth of the Miniature Munitions Technology Demonstration (MMTD) and Small Smart Bomb (SSB) projects of the mid-1990s. The goal of these programs was to show that a combination of GPS-inertial guidance and new warhead and fuzing technology would make it possible to destroy a wide range of targets with a weapon half the size of a Mk82. It could therefore be carried in much larger numbers (particularly by fighter-sized stealth aircraft, with limited weapon bay volume) and would be easier to transport, store and handle on the airfield.
The overarching goal of the SDB is to double the number of kills per sortie against 85% of the existing targets, according to the USAF. The USAF wants to carry at least four weapons on a rack which is compatible with the internal bays on the F-22, F-35 and UCAV. A Boeing model of the operational UCAV variant shows the company is aiming at six weapons per rack, or a total of 12 per aircraft, so it would not be surprising if Lockheed Martin was doing the same.
Another important requirement is that the SDB must be capable of being released from the F-22 at its M1.7 supercruise speed. Under those conditions, the USAF expects a 90km stand-off range. Since the USAF now expects the F-22 to spearhead the attack on long-range surface-to-air missile (SAM) systems, this is a very useful capability; it allows the F-22 to release weapons at several aimpoints in the SAM site while remaining outside the missile's effective range.
The USAF is looking at a weapon in the 100-110kg class. SDB is a unitary weapon (not a combination of warhead and tailkit) with folding wings for increased range. A smart bomb rack is an integral part of the SDB system, because the current MIL-STD-1760 databus that connects the aircraft to the weapon is too slow to handle multiple SDBs. Instead, basic targeting data will be sent to the rack, which will then generate detailed data for each weapon.
As in the case of JDAM, the SDB program is breaking new ground in acquisition reform. The USAF, says Col McClendon, has set out simple criteria that will determine its choice between the Boeing and Lockheed Martin designs at the end of the current competition. These include load-out - the number of weapons per station - and range. The weapon must be compatible with a variety of USAF aircraft and mission-planning systems. Weapon effectiveness is assessed according to the number of weapons required to kill a prescribed set of targets, as was done in the JASSM program.
The USAF is planning 'spiral development' of the SDB. This term describes a process in which a basic version of the weapon is designed and fielded quickly, with as little risk as possible. At the same time, a version of the weapon which meets more of the user's ultimate requirements is being designed, and will go into full-scale development once the first version is ready. Throughout the process, lessons and user inputs are allowed to influence requirements.
The first SDB spiral, Col McClendon explains, is "a mini-JDAM with anti-jam GPS". The current competition will proceed as a "rolling downselect", he says, in which the customer will periodically give the contractors feedback on their performance and the contractors will be able to question the customer to clarify the requirement.
During the competition, the contractors are expected to define their approach to the 'Spiral 2' requirement, which calls for an SDB that can find and attack relocatable targets, such as SAM or surface-to-surface missile launchers. The USAF will consider the risks of each company's Spiral 2 approach in its final decision.
The USAF expects to pick an SDB contractor at the end of FY03. Low-rate initial production (LRIP) will start in mid-2005, with an initial batch of 140 racks and associated weapons. The winner will proceed with system development and demonstration (SDD) of the Spiral 1 weapon, while starting 'component advanced development' for the Spiral 2. The first Spiral 2 weapons are expected to be available in FY10. The contractors are entirely free in their choice of a seeker technology: again, the concepts will be assessed according to their effectiveness against a set of targets.
The USAF is also funding an SDB-related laboratory-level program called Precision Direct Attack Munition (PDAM), which involves a flight demonstration of candidate SDB sensors. Boeing and Lockheed Martin are both engaged in PDAM work, which should lead to flight testing.
Boeing has conducted most of the public SDB-related demonstrations to date. The most recent was the Small Smart Bomb Range Extension (SSBREX) test, which successfully concluded, in December 2001, with two guided weapon releases from an F-16 at White Sands Missile Range in New Mexico.
The SSBREX vehicles were fitted with the Alenia Marconi Systems (AMS) DiamondBack wing, which uses a modified diamond platform with four lifting surfaces. Advantages of the AMS design include high aspect ratio, for low drag and long glides, combined with light weight and stiffness. (In some respects, it can be regarded as a transonic biplane.)
The SSBREX weapons were also equipped with the lattice tail surfaces first used on Russian missiles (such as the R-77 air-to-air missile). One of the most ingenious innovations in missile design since the AIM-9 Sidewinder's 'rollerons', the lattice tails generate very strong control forces but are aerodynamically balanced, so they do not require a great deal of power to move them. Moreover, they can be folded forwards for internal carriage, on a robust hinge, and snap into the open position under pressure from the airflow around the missile. The lattice tails were adopted for the SSBREX because they are reliable at supersonic launch speeds.
No cost target for the SDB has been published, but the unit price will be a composite of the weapon and its 'smart rack'. For the purposes of the competition, the USAF is estimating costs on the basis of buying 24,000 weapons - an equal number of Spiral 1 and Spiral 2 bombs - and 2,000 racks.
There is some discussion of a Spiral 3 SDB, which would be able to search a wider area, and locate and attack targets autonomously, but Col McClendon says it is not yet defined. However, some industry sources suggest that it could meet the USAF's requirement for a Wide Area Search and Autonomous Attack Munition (WASAAM). In this case, it would be an alternative to Lockheed Martin's Low-Cost Autonomous Attack System (LOCAAS).
LOCAAS approach
A miniature cruise missile with a laser radar and a multipurpose warhead, LOCAAS was demonstrated as a glider in 1996 and was then developed into a powered vehicle with a 0.13kN turbojet engine. LOCAAS integrates a number of new technologies: it is a very small, air-delivered vehicle with a turbine engine; the laser detection and ranging (ladar) sensor is intended to acquire and classify mobile targets; and the warhead is designed to detonate in different modes according to the type of target. Finally, LOCAAS vehicles are expected to communicate with one another in order to prevent one LOCAAS from attacking a target that another has already killed. It is a complex mission and the weapon has taken time to develop.
Challenges have included reliable engine operation (alternatives to the Hamilton Sundstrand engine currently being used are under consideration) and the automatic target recognition software. "We are improving our ability to find targets in the middle of nowhere," comments USAF program manager Fred Davis. Automatic Target Recognition (ATR) algorithms compare the high-resolution, three-dimensional map of the object produced by the ladar with a stored library of targets: improvements have addressed such issues as articulation (rotating antennas or turrets) or a target that is parked on an inclined surface.
A flight test in February demonstrated the flight qualities and guidance system of the air vehicle. The vehicle navigated through a series of waypoints and demonstrated some in-flight maneuvers in a 10min flight. In June, a LOCAAS vehicle will perform a similar test, but with the ladar active. The test range will include both typical targets and 'confuser' vehicles to evaluate the weapon's ATR.
In October 2002, the USAF and Lockheed Martin plan to test a LOCAAS with a live warhead, evaluating the lethality of the warhead and the system's ability to select a detonation mode according to the target. (The self-forging warhead is designed to form an aerostable slug for maximum stand-off range, a long-rod penetrator for anti-armor use, or fragments for soft targets.) The last currently programmed test, in April 2003, will demonstrate the ability to start the engine and deploy the wings after release.
According to program officials, LOCAAS is attracting increasing USAF interest as a potential weapon for the armed version of the turboprop-powered Predator B UAV. The Hellfire missile used on the current armed version of the RQ-1 Predator is unsuitable for the turbine version, which cruises above the Hellfire's maximum launch altitude. The USAF, apparently, may fund a pre-SDD demonstration of an operational LOCAAS. This would include the production of sufficient missiles to arm USAF Predator Bs. Full-scale SDD could start as early as 2005, followed by LRIP in 2008.
Advocates of an improved SDB, rather than LOCAAS, have suggested that the loitering, armed vehicle with its autonomous attack system could present a danger to non-combatant vehicles and other targets. LOCAAS supporters counter that a LOCAAS can be launched against a mobile target and instructed to search only the area defined by the TLE of that target - that is, the area within which the target may have moved since it was detected. If there is no target in the area, the LOCAAS will pitch or roll through 90º and detonate its warhead in fragment mode, limiting any damage on the ground. (An SDB or similar weapon will eventually hit the ground and detonate.) The high-resolution ladar is also claimed to have a false-target rate that is two to three times better than any other seeker.
On the move
There are still other potential solutions to the problems of attacking mobile and moving targets. DARPA's Affordable Moving Surface Target Engagement (AMSTE) program envisages the use of a datalink to guide a missile to a moving target. This approach potentially reduces the cost of the missile by eliminating the onboard seeker. In August 2001, a Northrop Grumman team used a Joint STARS radar, a JSF radar on a testbed aircraft, and a Lockheed Martin PDAM test vehicle with a datalink to hit a moving target at Eglin AFB under overcast conditions. There was no seeker on the missile. In September, DARPA selected Northrop Grumman to proceed with the next phase of AMSTE, involving more intense testing under more realistic operational conditions, including faster-moving targets and more clutter.
The early involvement of the prototype JSF radar in AMSTE indicates that the datalink-based approach is a potential solution to the problem of hitting moving ground targets from the JSF. The use of the PDAM in the test also shows that the moving-target attack weapon could be related to SDB, and would be compatible with the same internal rack on the aircraft.
The rapid progress of GPS-INS weapons, however, indicates that these autonomous guided bombs will remain crucial for the majority of targets. They will also endow aircraft like the F-22 and JSF with the ability to attack several small, hardened targets with a single load of weapons - vastly increasing their offensive firepower. If SDB lives up to its billing, it will truly represent a revolution in airpower.
Given the current level of production of 7,200 kits per year, this relatively small, 3-4-month engagement consumed excatly 18 months worth of production. This if Boeing is the sole manufacturer. I guess Saddam needs not to worry for the next couple of years, unless we're getting at him with dumb bombs.
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