< PREV | NEXT > | INDEX | SITEMAP | GOOGLE | LINKS | UPDATES | BLOG | EMAIL | DONATE | HOME

[6.0] Modern Glide Munitions (2)

v3.0.0 / chapter 6 of 10 / 01 apr 12 / greg goebel / public domain

* The development of smart bombs and missiles has taken a jump forward in the last decade. This chapter outlines leading-edge developments in smart air-to-surface munitions.

Small Tactical Munition


[6.1] CBU-97 / CBU-105 SFW
[6.2] MINIATURE GUIDED BOMBS
[6.3] AGM-154 JSOW
[6.4] MJOELNIR
[6.5] PGM / MSOV
[6.6] FOOTNOTE: TARGETING PODS

[6.1] CBU-97 / CBU-105 SFW

* The current generation of CBUs feature "smart" submunitions that provide enhanced lethality. One prominent example is the "CBU-97/B Sensor Fuzed Weapon (SFW)" cluster bomb. The SFW carries a smart antiarmor submunition, designated the "BLU-108/B", that allows a single CBU to engage and destroy multiple armored targets simultaneously.

The SFW is an outgrowth of work on smart weapons by Textron Defense Systems beginning in the mid-1980s under the ASSAULT BREAKER effort. Development of such systems was accelerated by the defense cutbacks in the 1990s that have required the military to obtain "force multipliers" to make the best use of limited resources. Tests of the SFW began in the early 1990s and demonstrated the lethality of the weapon. In a test conducted in late 1991, for example, an F-16 dropped four SFW canisters from low altitude, which then dispersed a total of 40 BLU-108/B submunitions over a column of 24 vehicles. 17 hits were scored on 11 of the vehicles.

The CBU-97/B SFW is based on the standard TMD canister, and has a loaded weight of 450 kilograms (1,000 pounds). The SFW can attack armored vehicles over a wide footprint. The munition can be delivered at altitudes from 60 meters to 6 kilometers (200 to 20,000 feet). An F-16 can carry 4 SFWs, with each canister carrying ten BLU-108/B submunitions in two rows of 5, and each submunition containing four smart hockey-puck shaped "Skeet" warheads each. An F-15E can carry 10 SFWs.

BLU-108/B SFW submunition

Once a dispenser is released, a pyrotechnic charge pops open the TMD's three panels to release the ten submunitions. Each submunition is a cylinder that is decelerated by a small parachute. The parachute also orients the submunition vertically over the target area. Chute deployment timing is staggered to allow the submunitions to disperse, and the actual area covered is a function of aircraft speed and the timing interval selected.

As the cylinder descends, the four Skeet warheads flip out from the body of the submunition. Each Skeet consists of a 13.3 centimeter (5.25 inch) diameter disk of flat copper backed by an explosive charge that is boresighted to a protruding infrared sensor. Once the cylinder is aligned properly over the target area, the parachute is cut loose as a rocket motor fires through two nozzles, which are canted so that they stop the cylinder's fall and start it spinning. Once the cylinder is spinning rapidly, the Skeets are released in pairs to spin away from the cylinder. They wobble in flight to allow the infrared sensor to scan over the ground below in a spiral pattern.

When a Skeet flies over a vehicle, the warhead's infrared sensor identifies it as a target and fires the explosive charge. This slams the wadded-up copper plate into the target at about 1,500 KPH (930 MPH), punching through armor and sending splinters through the interior. Explosive reactive armor is ineffective against such a "kinetic kill" projectile. If the Skeets don't find a target after a certain length of flight, they explode into fragments as a harassment measure and to prevent "pollution" of the landscape by hazardous dud submunitions. The infrared sensor is capable of working through fog, since it is close to the target, and works at night and through electronic countermeasures. Not all the warheads are expected to find targets, but the dispersal pattern of the 40 Skeets carried by an SFW is expected to be effective against concentrated targets such as an armor column.

Sensor-Fuzed Weapon in test

Although SFW development proved more troublesome than expected, baseline SFWs are now in the US military's inventory, and tests have demonstrated they are more lethal than required by specification. The US Air Force plans to obtain 5,000. They were introduced to combat during air strikes during the Kosovo campaign in 1999, with SFW-loaded CBUs acquiring the nickname of "cans of whup-ass".

Further development of the basic CBU-97 SFW has focused on adding the WCMD inertial guidance tailkit, resulting in the CBU-105/B SFW. The latest SFW configuration includes seeker improvements to permit attacks on naval vessels and even parked, cool aircraft and ground vehicles. The explosively-formed projectile scheme is being modified and enhanced, and a highly reliable self-destruct system is being considered to reduce collateral damage. The new projectile includes a ring of 16 explosively formed penetrators around the central main penetrator, providing an additional shotgun effect. In addition, a more insensitive explosive is used to meet Navy requirements for shipboard storage and handling.

* The Russians have fielded an SFW-class submunition, designated "SPBE-D" when used with a cluster-bomb unit and "MOTIV-3M" when used with the Smerch multiple-launch rocket system. A Smerch rocket can carry five MOTIV-3M submunitions. Each MOTIV-3M submunition measures 284 x 255 x 186 millimeters (6.2 x 10 x 7.3 inches) and weighs 15 kilograms (33.1 pounds). When the missile arrives in the target area, the five submunitions are dispensed, with each popping out a parachute and then hunting for a target with a dual-band infrared seeker with a field of view of 30 degrees. At about 150 meters (500 feet) above the target, the submunition fires on its target, using an explosively-formed penetrator that can punch through 7 centimeters (2.75 inches) of armor.

BACK_TO_TOP

[6.2] MINIATURE GUIDED BOMBS

* There has been work on new, even smarter submunitions. The US Air Force worked with Lockheed Martin to conduct a lengthy investigation of a submunition designated the "Low Cost Autonomous Attack System (LOCAAS)", which was effectively a small cruise missile, loaded up four to a TMD dispenser, that would conduct a search pattern around a target area, recognizing targets with a laser radar system and then attacking them with an explosively-formed projectile warhead.

While LOCAAS got as far as tests, there was no commitment to production and the program seems to have gone quiet. The Air Force does seem to be pursuing a number of loitering submunitions along the lines of LOCAAS with a confusing variety of designations -- the Boeing "Air Dominator" and the Lockheed-Martin "Surveilling Miniature Attack Cruise Missile (SMACM)" -- but it wise to take them with a grain of salt. The concept of "vaporware", invented by the computer industry, also applies to the arms industry.

Such a comment should not be interpreted as a slam. Investigation programs are just that, investigations, and there's no particular reason to assume that most weapon concepts being investigated will advance to operational status. The investigation may prove that the weapon isn't practical -- ineffective, too expensive, too unreliable, beyond the limits of current technology -- or even if it is, military requirements or funding may change, shoving the weapon off the bottom of the priority queue. Even weapons that do reach operational status may follow a confusing evolution through various programs, sometimes with changes in definition and configuration, before they reach the front lines.

* As a good case in point, the US Army and Northrop Grumman developed another smart submunition, the "Brilliant Antiarmor Munition (BAT)". This 20 kilogram (44 pound) weapon looked like a cylinder about 1.5 meters (5 feet) long with a bulbous head when stored in its dispensing system. When released, the BAT popped out four wraparound tailfins and four long, straight cruciform gliding wings around the midbody. The bulbous nose was fitted with an infrared sensor, and the wingtips were fitted with long spikes fitted with acoustic sensors.

Once deployed, the BAT glided to a preprogrammed target location, with a cluster of BATs dispersing to ensure that they didn't attack the same targets, and used the acoustic sensors to identify the general location of a tank. Once a target was boxed by the acoustic sensors, the infrared sensor took over, directing the BAT to hit the target directly from the top, destroying it with a two-stage penetrating warhead. An Improved BAT (IBAT), with a combined millimeter-wave radar / infrared imager seeker, was also developed.

The plan was to deploy the BAT on the Block II version of the Army Tactical Missile System (ATACMS or "Attack 'Ems"), updated to carry a warload of 13 BATs. However, the Block II ATACMS was canceled in 2003 and BAT went into limbo. A smart weapon that could smash enemy armor concentrations was no longer a particularly relevant weapon for the "dirty little wars" the Army was suffering through by that time. It might have been a nice thing to have, but other weapons were needed at the time.

The irony was that a simplified BAT ended up being a perfectly useful weapon. It was straightforward to mate a laser seeker to the BAT airframe, and in the spring of 2003, the Army performed a demonstration of a laser-guided BAT named "Viper Strike". The weapons were test-dropped from a US Army Hunter drone at the end of March 2003 and scored seven hits out of nine drops.

The lightweight, accurate Viper Strike seemed like an ideal weapon for drones, themselves good weapons for dirty little wars, and quickly went into service as the "GBU-44/B", with the Hunter apparently the initial carriage platform. The munition was handled and carried in a bomblike canister with tailfins that ejected the Viper Strike after drop.

Viper Strike small smart bomb

The BAT smart submunition didn't turn out to be what was needed at the time, but the Viper Strike proved a handy little glide bomb. Viper Strike is intended for high-precision "top down" attacks on targets, particularly in urban or other built-up areas where collateral damage is a concern. Some Viper Strikes have been modified from such stockpiles of BATs as were accumulated before that program went on hold, with these weapons retaining the wingtip probes for the BAT acoustic sensors, but the probes have been deleted from new-build GBU-44/Bs.

The military is very enthusiastic about Viper Strike. The munition is being integrated with other drone platforms, and the US Special Operations Command (SOCOM) is obtaining a ten-round dispenser under the "Gunslinger" program for C-130 Hercules special operations aircraft. The ability to carry and dispense large numbers of such small munitions provides a great deal of mission flexibility, for example allowing an intensive attack on one floor of a building with little damage to innocent bystanders on other floors. The reach of the Viper Strike also enhances its capability: it has a glide ratio of 10:1, meaning that it only falls one meter for every ten meters of horizontal flight, and so a drop from a mere kilometer of altitude gives the munition an attack "footprint" with a radius of up to ten kilometers. A backup GPS-INS navigation system has been developed to permit midcourse guidance for long-range drops, laser guidance being troublesome when the target is very far away; improved software has also made the munition more effective against moving targets.

A range of Viper Strike enhancements is in the works or in planning, including a datalink; a fragmentation belt for the shaped-charged warhead to add anti-personnel effects; replacement of the current fixed "staring" laser seeker to a gimbal-mounted unit with a wider field of view; and a mode to disable the warhead, turning the munition into a "smart rock" -- 20 kilograms moving at hundreds of kilometers an hour can make a strong but selective impression on an unarmored target. Whatever the mix of actual options implemented, the next variant of Viper Strike will be designated the "Special Operations Precision Guided Munition (SOPGM)".

It will not, however, be made by Northrop Grumman. In late 2011, the firm sold rights to the Viper Strike and the production facility to the European MBDA firm.

* Lockheed Martin did not fail to notice the interest expressed in the Viper Strike and has developed their own little smart bomb, the "Scorpion". It has a weight of about 10 kilograms (33 pounds), four popout tailfins, and a straight pivoting wing. The default seeker system is semi-active laser, but the Scorpion is designed to support swap-in seeker modules based on other technology, such as millimeter wave.

Lockheed Martin Scorpion small smart bomb

Lockheed Martin has designed a carrier that can accommodate three Scorpions on a Hellfire missile launch rail, with the interface protocols emulating the Hellfire's. The Scorpion's form-factor is similar to that of the LUU-series parachute flares, and so the little bombs can be carried in a four-tube SUU-25 pylon-mounted flare dispenser, with two bombs per tube for a total warload of eight bombs.

Lockheed Martin has also introduced a 5 kilogram (11 pound) laser-guided glide bomb named the "Shadow Hawk" -- possibly derived from technology developed for the Lockheed Martin DAGR laser guidance system for the 70 millimeter (2.75 inch) rocket, discussed later, Shadow Hawk also having a diameter of 70 millimeters; length of the bomb is 68.6 centimeters (27 inches). It is intended for carriage on small UAVs.

Matra BAE Dynamics has developed a small glide bomb, the "Small Air Bomb With Extended Range (SABER)", featuring a switchblade-type wing system; GPS-INS midcourse guidance; a laser terminal seeker, with other seeker options possible down the road; and a rocket-boost capability for standoff range. It is available in configurations from 4.5 kilograms (10 pounds) to 13.6 kilograms (30 pounds).

MBDA SABER

Raytheon has developed their own small smart bomb, the "Small Tactical Munition", with a weight of 6 kilograms (13.5 pounds), with a GPS-INS midcourse navigation system and laser seeker. ATK developed an "ultralight" glide bomb named the "Hatchet", with a weight of 1.8 kilograms (4 pounds), but it doesn't appear to have been any more than an experimental effort.

BACK_TO_TOP

[6.3] AGM-154 JSOW

* While the JDAM and WCMD projects have provided the US military with a degree of short range standoff attack capability, other programs have worked on weapons to attack targets at greater ranges. One of the most important of these, the US Navy and Air Force "Joint Stand Off Weapon (JSOW)" is now in operation and has been used in combat.

The JSOW project was initiated in 1986 under the initial name of "Advanced Interdiction Weapon System (AIWS)", the goals being a lightweight, low cost, fire and forget weapon with medium range and the capability to carry different types of warloads. A development contract was awarded to Texas Instruments in 1992. Texas Instruments was later acquired by Raytheon. Initial tests of JSOW began in 1994.

AGM-154 JSOW

JSOW is an unpowered glide bomb with popout switchblade wings and a GPS-INS navigation system. The weapon is smart enough to fly a preplanned path to its target, making turns and hiding behind mountains. If the proper preplanned launch point cannot be reached, the pilot can release it and, as long as the target is within a pie-slice wedge on the cockpit display, let the weapon determine its own flight plan. JSOW is light enough to be carried by smaller attack aircraft such as the F/A-18, the F-16, or AV-8B Harrier.

   AGM-154A JSOW:
   _____________________   _________________   _______________________
 
   spec                    metric              english
   _____________________   _________________   _______________________

   wingspan                2.7 meters          8 feet 11 inches
   length                  4 meters            13 feet
   total weight            475 kilograms       1,050 pounds
   speed                   subsonic glide weapon
   range at altitude       75 kilometers       47 MI / 40 NMI
   _____________________   _________________   _______________________

The first version of JSOW to be developed was the "AGM-154A" or "JSOW-A", which entered full-scale production in 1999. The AGM-154A carries 145 BLU-97A/B CEMs for use on "soft" targets. When the weapon makes its final attack dive on a target, it blows off covers on either side of its boxy fuselage, and a gas-inflated aluminum bladder scatters the submunitions out the sides. The CEM submunitions produce armor-piercing, fragmentation, and incendiary effects.

JSOW was introduced to combat in January 1999, during air strikes by US Navy aircraft on Iraqi air-defense sites, and was used in later combat actions. The results of these strikes exceeded expectations, and the US Air Force accelerated its efforts to get JSOW into full service. Some of the strikes demonstrated that JSOW wasn't able to correct for wind drift as well as desired, but Raytheon implemented software fixes to correct the problem. A new multiple ejector rack has been developed to allow carriage of two JSOWs, or other weapons of similar size, on a single stores pylon. This will allow a small attack aircraft to carry four JSOWs instead of two.

* Both the US Air Force and the Navy considered an antiarmor version of the JSOW, the "AGM-154B" or "JSOW-B", with six BLU-108/B SFW submunitions, but it was canceled. The Air Force decided that the WCMD-ER, described previously, was a better standoff antiarmor solution. The WCMD-ER could carry 10 SFW submunitions instead of six, could be developed quickly, and could leverage off the huge stockpile of 100,000 Tactical Munitions Dispensers built. The Navy decided they couldn't afford the AGM-154B on their own.

The US Navy has acquired a variant with a unitary warhead, the "AGM-154C", or "JSOW-C" featuring a British-developed two-stage "Broach" penetrating warhead. It also features an imaging infrared seeker and datalink, compatible with the existing pylon-mounted control pod for the Navy Walleye glide bomb, to allow precision strikes on a target. The seeker, inherited from the SLAM-ER cruise missile, is capable of autonomous operation for "fire and forget" attacks.

Low-rate production of the AGM-154C began in the summer of 2003, with operational introduction in 2005 on the F/A-18. Improvements have been phased into production, such as a simplified and refined airframe and a new antijam GPS unit. A "JSOW-C1" subvariant with an infrared seeker capable of attacking mobile maritime targets, and a two-way Link 16 datalink performed its first free flight test in 2011, with introduction to service scheduled for 2013.

Turkey and Poland ordered JSOW for their F-16s, with Singapore also ordering the JSOW for their new F-15s and Australia obtaining the weapon for their F/A-18s. Several other nations have expressed interest. Raytheon has developed a low-cost JSOW with using a Mark 82 225 kilogram (500 pound) unitary warhead, with this variant designated the "AGM-154A-1" and intended for the export market.

A version of JSOW powered by a Williams International WJ-24 turbojet and named the "Griffin-36" was offered for the British Conventionally Armed Standoff Missile (CASOM) competition in 1996, but was not selected. Raytheon flight-tested an extended range "JSOW-ER" in 2009, fitted with a Hamilton Sundstrand TJ150 small turbojet, with the weapon achieving a range of 480 kilometers (300 miles / 260 NMI). The baseline JSOW design actually included space for an engine.

BACK_TO_TOP

[6.4] MJOELNIR

* A European standoff weapon system, developed by DASA of Germany, is available in both glide and powered forms. The best developed of this family of weapons is the "BombKapsel 90 (BK-90)" gliding cluster munition dispenser, developed primarily for the Swedish Air Force's JAS-39 Gripen fighter. It has been named "Mjoelnir", after the thunder god Thor's mighty hammer.

The Mjoelnir is a descendant of an MBB (ancestor of DASA) concept for a "Container Weapons System (CWS)" proposed in the 1980s. The idea behind CWS was to essentially take the core of the MW-1 cluster munitions dispenser, used by Luftwaffe Tornadoes, and fit it out with various modular nose, tail, and fin kits to allow it to be used as a short-range glide weapon, a long-range glide weapon with popout wings, or a rocket-propelled standoff weapon.

Mjoelnirs & Mavericks on Gripen

This scheme was apparently a bit too complicated, since the Mjoelnir follows the same basic design configuration as the CWS but abandoned the modular approach. The weapon is something like a "flying MW-1". The BK-90 contains 12 submunitions launch tubes on each side, with multiple submunitions contained in each tube. It has a boxy fuselage with very stubby wings, as well as tail fins on each corner of the fuselage box.

   BK-90 MJOELNIR:
   _____________________   _________________   _______________________
 
   spec                    metric              english
   _____________________   _________________   _______________________

   wingspan                1 meters            3 feet 4 inches
   length                  3.5 meters          11 feet 6 inches
   total weight            600 kilograms       1,320 pounds
   speed                   unpowered glide weapon
   range at altitude       22 kilometers       14 MI / 12 NMI
   _____________________   _________________   _______________________

The BK-90 is intended to be released at high speed and low altitude. Essentially it allows a strike aircraft to "toss" the weapon onto a target, with the weapon using INS navigation and terrain-following radar to navigate into the target area. It can be also released from high altitude for more standoff range, and has an optional GPS-INS capability for such long range attacks. Toss range at low altitude is up to about 8 kilometers (5 miles), while the range at high altitude is up to 22 kilometers (14 miles).

Once over the target, the BK-90 blasts its submunitions out of the ejector tubes, with the submunitions deploying small chutes to stabilize their descent. The dispersal pattern is up to about 250 by 400 meters (800 by 1,300 feet). There are two types of submunitions:

The BK-90 is being built and marketed in the US as the "Autonomous Free-Flight Dispenser System (AFDS)" by an American subsidiary of DASA named CMD. The AFDS has been evaluated by the USAF.

DASA also refers to the BK-90 as the "Dispenser Weapon System 39 (DWS-39)" because of its association with the JAS-39 Gripen, as well as "DWS-24", with the "24" designating the number of dispenser tubes. DASA offers other variants of the BK-90 of different sizes and weights: the 400 kilogram (880 pound) "DWS-16" with 16 tubes; the 1,000 kilogram (2,200 pound) "DWS-40" with 40 tubes; and the 1,400 kilogram (3,100 pound) "DWS-60" with 60 tubes.

BACK_TO_TOP

[6.5] PGM / MSOV

* Alenia-Marconi of Italy has developed a new family of "Precision Guided Munitions (PGM)" conceptually similar to the US AGM-130, consisting of a rocket-boosted bomb with glide fins, midcourse guidance system with a command update capability, and a terminal seeker system giving a CEP of two meters (less than 7 feet). Cruciform fins are fitted to the tail, while a pair of small winglets are fitted to the nose.

PGM-500

The company offers two versions of the PGM, including the "PGM-500", which is unsurprisingly a 500 kilogram (1,100 pound) weapon sized for smaller fighters, and the "PGM-2000", which is a 2,000 kilogram (4,400 pound) weapon. Laser-homing, TV, and imaging infrared seekers are offered. The PGMs are intended for platforms such as the Dassault Mirage 2000, F-16, Northrop F-5, and BAE Hawk. The United Arab Emirates apparently obtained PGMs in the mid-1990s, naming the weapon the "Hakim".

MSOV

* Israeli Military Industries (IMI) has developed a switchblade-wing glide dispenser named the "Modular Stand-Off Vehicle (MSOV)" that is similar to JSOW, and apparently based on the "Tactical Air Launched Decoy (TALD)" glider manufactured by the company. MSOV weighs 1,050 kilograms (2,300 pounds) and can carry a 675 kilogram (1,490 pound) warload, including a unitary penetrator warhead or submunitions such as antiarmor mines, runway penetrators, combined effects bomblets, and so on. It uses GPS-INS guidance. First trials were performed in 1998.

BACK_TO_TOP

[6.6] FOOTNOTE: TARGETING PODS

* With the introduction of laser guided bombs in the early 1970s, some means were also required to guide them, and that need led to development of targeting pods. They have since been improved considerably.

A typical targeting pod features a motion-stabilized turret in the nose containing a camera boresighted with a laser system that illuminates a target, with the laser system also providing rangefinder capabilities. The camera may be a daylight or low-light-level TV (LLLTV) camera; or a forward-looking infrared (FLIR) imager; or both. The camera or cameras will have multiple levels of zoom to provide either a wide field of view or a close-up on a target.

Sniper targeting pod on F-16

The pod is typically carried by a two-seat strike aircraft, with the weapons system officer (WSO) in the back seat viewing the target image provided by the pod, and using a joystick or similar hand controller to keep the target lined up in the display crosshairs. The pod may have "smarts" that allow it to keep the crosshairs on the target automatically.

As mentioned earlier, the USAF used the ALD targeting system early on, later fielding the Pave Knife pod. It left something to be desired and was quickly followed by better technology:

The first generation of targeting pods was followed by still better systems, most significantly the Martin-Marietta (now Lockheed Martin) "Low Altitude Navigation and Targeting, Infrared, for Night (LANTIRN)". LANTIRN actually includes a pair of pods, one for targeting and one for navigation -- the navigation pod provides a wide-angle FLIR and a radar coupled to a terrain-following flight direction system. It was carried by F-15s and F-16s, and has been manufactured in improved variants, some of them consolidating targeting and navigation elements in one pod.

In the 21st century, air forces can choose from a number of different targeting pod offerings:

Some aircraft built specifically for the strike role may actually have a built-in targeting system, eliminating the need to carry a pod. As a prominent example, from the late 1970s the US Navy's Grumman A-6E Intruder strike aircraft were fitted with an undernose turret with a FLIR and laser designator / rangefinder, designated the "AN/AAS-33 Target Recognition and Attack Multisensor (TRAM)".

Another example of a built-in targeting system is the Soviet-Russian "Klyon PS" carried by some variants of the Sukhoi Su-22 Fitter, Su-25 Frog, and Mikoyan MiG-27. This is a very unusual target designator by Western standards, since the laser isn't mounted in a turret and the pilot doesn't have either a TV display or a hand controller. The laser shines through a forward window and has a limited range of travel. The pilot lines up the target initially in his sight, and once the target is locked the laser tracks the target automatically on the target under control of the aircraft's flight navigation systems.

Most modern multirole combat aircraft actually do not have to carry a pod to perform ground attack, since they are fitted with multimode radars that include a "synthetic aperture radar / moving target indicator (SAR/MTI)" mode that can not only provide a radar image of a target area but also identify targets that are moving on the ground faster than a specified velocity. Traditionally, SAR/MTI could be used to pinpoint a target but not actually guide a weapon to it, as does a targeting pod. The development of GPS-guided weapons now gives the capability of pinpointing a target, obtaining its GPS coordinates, and downloading the coordinates into a GPS-guided weapon just before weapons drop. Targeting pods remain useful, however, to provide the maximum precision for strikes.

BACK_TO_TOP
< PREV | NEXT > | INDEX | SITEMAP | GOOGLE | LINKS | UPDATES | BLOG | EMAIL | DONATE | HOME