Precision-guided munition
"Smart bombs", used to strike targets precisely From Wikipedia, the free encyclopedia
"Smart bombs", used to strike targets precisely From Wikipedia, the free encyclopedia
A precision-guided munition (PGM), also called a smart weapon, smart munition, or smart bomb, is a guided munition intended to hit a specific target, to minimize collateral damage and increase lethality against intended targets.[1] During the Persian Gulf War guided munitions accounted for only 9% of weapons fired, but accounted for 75% of all successful hits. Despite guided weapons generally being used on more difficult targets, they were still 35 times more likely to destroy their targets per weapon dropped.[2]
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Because the damage effects of explosive weapons decrease with distance due to an inverse cube law, even modest improvements in accuracy (hence reduction in miss distance) enable a target to be attacked with fewer or smaller bombs. Thus, even if some guided bombs miss, fewer air crews are put at risk and the harm to civilians and the amount of collateral damage may be reduced.[lower-alpha 1][lower-alpha 2]
The advent of precision-guided munitions resulted in the renaming of older, low-technology bombs as "unguided bombs", "dumb bombs", or "iron bombs".
Recognizing the difficulty of hitting moving ships during the Spanish Civil War,[9] the Germans were first to develop steerable munitions, using radio control or wire guidance. The U.S. tested TV-guided (GB-4),[10] semi-active radar-guided (Bat), and infrared-guided (Felix) weapons.
The CBU-107 Passive Attack Weapon is an air-dropped guided bomb containing metal penetrator rods of various sizes. It was designed to attack targets where an explosive effect may be undesirable, such as fuel storage tanks or chemical weapon stockpiles[11] in civilian areas.[12]
The Germans were first to introduce PGMs in combat, with KG 100 deploying the 3,100 lb (1,400 kg) MCLOS-guidance Fritz X armored glide bomb, guided by the Kehl-Straßburg radio guidance system, to successfully attack the Italian battleship Roma in 1943,[13] and the similarly Kehl-Straßburg MCLOS-guided Henschel Hs 293 rocket-boosted glide bomb (also in use since 1943, but only against lightly armored or unarmored ship targets).
The closest Allied equivalents, both unpowered designs, were the 1,000 lb (450 kg) VB-1 AZON (from "AZimuth ONly" control), used in both Europe and the CBI theater, and the US Navy's Bat, primarily used in the Pacific Theater of World War II — the Navy's Bat was more advanced than either German PGM ordnance design or the USAAF's VB-1 AZON, in that it had its own on board, autonomous radar seeker system to direct it to a target. In addition, the U.S. tested the rocket-propelled Gargoyle, which never entered service.[14] Japanese PGMs—with the exception of the anti-ship air-launched, rocket-powered, human-piloted Yokosuka MXY-7 Ohka, "Kamikaze" flying bomb did not see combat in World War II.[15]
Prior to the war, the British experimented with radio-controlled remotely guided planes laden with explosives, such as Larynx. The United States Army Air Forces used similar techniques with Operation Aphrodite, but had few successes; the German Mistel (Mistletoe) "parasite aircraft" was no more effective, guided by the human pilot flying the single-engined fighter mounted above the unmanned, explosive-laden twin-engined "flying bomb" below it, released in the Mistel's attack dive from the fighter.
The U.S. programs restarted in the Korean War. In the 1960s, the electro-optical bomb (or camera bomb) was reintroduced. They were equipped with television cameras and flare sights, by which the bomb would be steered until the flare superimposed the target. The camera bombs transmitted a "bomb's eye view" of the target back to a controlling aircraft. An operator in this aircraft then transmitted control signals to steerable fins fitted to the bomb. Such weapons were used increasingly by the USAF in the last few years of the Vietnam War because the political climate was increasingly intolerant of civilian casualties, and because it was possible to strike difficult targets (such as bridges) effectively with a single mission; the Thanh Hoa Bridge, for instance, was attacked repeatedly with iron bombs, to no effect, only to be dropped in one mission with PGMs.
Although not as popular as the newer JDAM and JSOW weapons, or even the older laser-guided bomb systems, weapons like the AGM-62 Walleye TV guided bomb are still being used, in conjunction with the AAW-144 Data Link Pod, on US Navy F/A-18 Hornets.
In World War II, the U.S. National Defense Research Committee developed the VB-6 Felix, which used infrared to home on ships. While it entered production in 1945, it was never employed operationally.[16] The first successful electro optical guided munition was the AGM-62 Walleye during the Vietnam war. It was a family of large glide bombs which could automatically track targets using contrast differences in the video feed. The original concept was created by engineer Norman Kay while tinkering with televisions as a hobby. It was based on a device which could track objects on a television screen and place a "blip" on them to indicate where it was aiming. The first test of the weapon on 29 January 1963 was a success, with the weapon making a direct hit on the target. It served successfully for three decades until the 1990s.[17][18]
The Raytheon Maverick is the most common electro optical guided missile. As a heavy anti-tank missile it has among its various marks guidance systems such as electro-optical (AGM-65A), imaging infrared (AGM-65D), and laser homing (AGM-65E).[19] The first two, by guiding themselves based on the visual or IR scene of the target, are fire-and-forget in that the pilot can release the weapon and it will guide itself to the target without further input, which allows the delivery aircraft to manoeuvre to escape return fire. The Pakistani NESCOM H-2 MUPSOW and H-4 MUPSOW is an electro-optical (IR imaging and television guided) is a drop and forget precision-guided glide bomb. The Israeli Elbit Opher is also an IR imaging "drop and forget" guided bomb that has been reported to be considerably cheaper than laser-homing bombs and can be used by any aircraft, not requiring specialized wiring for a laser designator or for another aircraft to illuminate the target. During NATO's air campaign in 1999 in Kosovo the new Italian AF AMX employed the Opher.[20]
In 1962, the US Army began research into laser guidance systems and by 1967 the USAF had conducted a competitive evaluation leading to full development of the world's first laser-guided bomb, the BOLT-117, in 1968. All such bombs work in much the same way, relying on the target being illuminated, or "painted," by a laser target designator on the ground or on an aircraft. They have the significant disadvantage of not being usable in poor weather where the target illumination cannot be seen, or where a target designator cannot get near the target. The laser designator sends its beam in a coded series of pulses so the bomb cannot be confused by an ordinary laser, and also so multiple designators can operate in reasonable proximity.
Originally the project began as a surface to air missile seeker developed by Texas Instruments. When Texas Instruments executive Glenn E. Penisten attempted to sell the new technology to the Air Force they inquired if it could instead be used as a ground attack system to overcome problems they were having with accuracy of bombing in Vietnam. After 6 attempts the weapon improved accuracy from 148 to 10 ft (50 to 3 m) and greatly exceeded the design requirements. The system was sent to Vietnam and performed well. Without the existence of targeting pods they had to be aimed using a hand held laser from the back seat of an F-4 Phantom aircraft, but still performed well. Eventually over 28,000 were dropped during the war.[2]
Laser-guided weapons did not become commonplace until the advent of the microchip. They made their practical debut in Vietnam, where on 13 May 1972 they were used in the second successful attack on the Thanh Hóa Bridge ("Dragon's Jaw"). This structure had previously been the target of 800 American sorties[21] (using unguided weapons) and was partially destroyed in each of two successful attacks, the other being on 27 April 1972 using AGM-62 Walleyes.
They were used, though not on a large scale, by the British forces during the 1982 Falklands War.[22] The first large-scale use of smart weapons came in the early 1990s during Operation Desert Storm when they were used by coalition forces against Iraq. Even so, most of the air-dropped ordnance used in that war was "dumb," although the percentages are biased by the large use of various (unguided) cluster bombs. Laser-guided weapons were used in large numbers during the 1999 Kosovo War, but their effectiveness was often reduced by the poor weather conditions prevalent in the southern Balkans.
The Lockheed-Martin Hellfire II light-weight anti-tank weapon in one mark uses the radar on the Boeing AH-64D Apache Longbow to provide fire-and-forget guidance for that weapon.
Lessons learned during the first Gulf War showed the value of precision munitions, yet they also highlighted the difficulties in employing them—specifically when visibility of the ground or target from the air was degraded.[37] The problem of poor visibility does not affect satellite-guided weapons such as Joint Direct Attack Munition (JDAM) and Joint Stand-Off Weapon (JSOW), which make use of the United States' GPS system for guidance. This weapon can be employed in all weather conditions, without any need for ground support. Because it is possible to jam GPS, the guidance package reverts to inertial navigation in the event of GPS signal loss. Inertial navigation is significantly less accurate; the JDAM achieves a published Circular Error Probable (CEP) of 43 ft (13 m) under GPS guidance, but typically only 98 ft (30 m) under inertial guidance (with free fall times of 100 seconds or less).[38][39]
The precision of these weapons is dependent both on the precision of the measurement system used for location determination and the precision in setting the coordinates of the target. The latter critically depends on intelligence information, not all of which is accurate. According to a CIA report, the accidental United States bombing of the Chinese embassy in Belgrade during Operation Allied Force by NATO aircraft was attributed to faulty target information.[44] However, if the targeting information is accurate, satellite-guided weapons are significantly more likely to achieve a successful strike in any given weather conditions than any other type of precision-guided munition.
Responding to after-action reports from pilots who employed laser or satellite guided weapons, Boeing developed a Laser JDAM (LJDAM) to provide both types of guidance in a single kit. Based on the existing Joint Direct Attack Munition configurations, a laser guidance package is added to a GPS/INS-guided weapon to increase its overall accuracy.[45] Raytheon has developed the Enhanced Paveway family, which adds GPS/INS guidance to their Paveway family of laser-guidance packages.[46] These "hybrid" laser and GPS guided weapons permit the carriage of fewer weapons types, while retaining mission flexibility, because these weapons can be employed equally against moving and fixed targets, or targets of opportunity. For instance, a typical weapons load on an F-16 flying in the Iraq War included a single 2,000-pound (910 kg) JDAM and two 1,000-pound (450 kg) LGBs. With LJDAM, and the new GBU-39 Small Diameter Bomb (SDB), these same aircraft can carry more bombs if necessary, and have the option of satellite or laser guidance for each weapon release.
A cannon-launched guided projectile (CLGP), is fired from artillery, ship's cannon, or armored vehicles. Several agencies and organizations sponsored the CLGP programs. The United States Navy sponsored the Deadeye program, a laser-guided shell for its 5 in (127 mm) guns[56] and a program to mate a Paveway guidance system to an 8 in (203 mm) shell[57] for the 8"/55 caliber Mark 71 gun in the 1970s (Photo). Other Navy efforts include the BTERM, ERGM, and LRLAP shells.
Precision-guided small arms prototypes have been developed which use a laser designator to guide an electronically actuated bullet to a target.[74] Another system in development uses a laser range finder to trigger an explosive small arms shell in proximity to a target. The U.S. Army plans to use such devices in the future.[75]
In 2008 the EXACTO program began under DARPA to develop a "fire and forget" smart sniper rifle system including a guided smart bullet and improved scope. The exact technologies of this smart bullet have not been released. EXACTO was test fired in 2014 and 2015 and results showing the bullet altered course to correct its path to its target were released.[76]
In 2012 Sandia National Laboratories announced a self-guided bullet prototype that could track a target illuminated with a laser designator. The bullet is capable of updating its position 30 times a second and hitting targets over a mile away.[77]
In mid-2016, Russia revealed it was developing a similar "smart bullet" weapon designed to hit targets at a distance of up to 6 mi (10 km).[78][79]
Pike[80] is a precision-guided mini-missile fired from an underslung grenade launcher.
Air burst grenade launchers are a type of precision-guided weapons. Such grenade launchers can preprogram their grenades using a fire-control system to explode in the air above or beside the enemy.[81][82][83]
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