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Rocket propelled grenade
A rocket propelled grenade (RPG) is a man-portable, shoulder-launched weapon capable of firing an explosive device longer distances than an otherwise unassisted soldier could throw. Its design purpose is broader than that of the Antitank Rocket Launcher , and it is somewhat less effective in that role than more specialized weapons.
An RPG is composed of two major parts, the launcher and the grenade. Some types of RPGs are single-use disposable units (the U.S. M72 LAW, for example), others reuse the launcher by reloading it after each grenade is fired (the Soviet RPG-7, for example). The most common grenades are a High Explosive (HE) or High Explosive Anti Tank (HEAT) round. This warhead is affixed to a rocket motor, to which fins are affixed.
The weapon is usually made inexpensively from stamped sheet metal or die-cast aluminium, fiberglass, or zinc. This reduces cost and weight, allowing the weapon to be distributed in even the poorest countries to infantrymen who usually must march to their objectives. In all common man-portable RPG systems the launcher rests on the user's shoulder, with the user aiming through a reticule. The rear of the launcher is open to allow the rocket exhaust to vent. Firing is accomplished with a trigger mechanism.
In an RPG, the launcher does pressurize to an extent. This overpressure allows the warhead to obtain enough speed (greater than that which could be obtained from the specific impulse of the rocket motor). This high speed is necessary to allow the rocket to have enough momentum to be stable in flight, without continuing to burn past the forward lip of the launcher. The RPG-7 is heavier and more robust than a M-72 LAW. This is due to the fact that the RPG-7 is reusable, and must be more rugged to withstand the stress of repeated firing. This is not meant to imply that an RPG is a cannon, the smaller overpressure (compared to a cannon or a rifle) being used to boost the speed of the warhead, not completely contain and create the thrust. The high temperature rocket exhaust is hazardous 15 to 20 m to the rear of an RPG launcher. The launcher must be cleaned periodically. Failure to clean the launcher results in an excess of overpressure, which causes the reticule to be driven into the eye of the user, when the rocket does release. Blindness in one eye often results.
All RPGs are similar in basic operation, however there are significant differences in specific operation.
In the common RPG-7, the warhead is loaded into the front of the launcher. Pulling the trigger strikes a percussion cap. The cap ignites a solid-fuel rocket. The rocket propels the 85 mm warhead forward without significant recoil. As the warhead emerges from the launcher, fins spring out from the base of the rocket tube, stabilizing the warhead's flight.
In the M-72 LAW (also reproduced as the Soviet RPG-18) the launcher consists of two tubes, one inside the other. The outer assembly acts as a watertight container for the rocket and the percussion cap-type firing mechanism that activates the rocket. The outer tube contains the trigger, the arming handle, front and rear sights, and the rear cover. The inner tube telescopes outward toward the rear, and houses the firing pin assembly and detent lever. The detent lever moves under the trigger assembly in the outer tube, both locking the inner tube in the extended position and cocking the weapon. When fired, the propellant in the rocket motor completely combusts, producing gases around 1,400 °F (760 °C). The rocket propels the 66 mm warhead forward without significant recoil. As the warhead emerges from the launcher, fins spring out from the base of the rocket tube, stabilizing the warhead's flight.
The HE (grenade) warhead is designed for use against exposed troops, light armor (including APCs), bunkers and other 'soft' targets of opportunity. In Afghanistan and Somalia it was effective against helicopters. The HE warhead is impact fused, and detonates with a large explosion in the direction of travel. The case and charge generate moderate amounts of shrapnel and blast.
The HEAT (anti-tank) round is a standard shaped charge penetrator, similar in concept to those used in Main battle tanks. In this sort of warhead, the shape of the explosive material within the grenade focuses the explosive energy on a copper (or other similar metal) lining. This melts the metal and propels it forward at a high speed. This speed, along with the high temperatures and pressures involved, converts the metal into a narrow, solid jet. The jet's high speed and narrow impact zone allows it to punch through Rolled Homogenous Armour (RHA) used in armoured vehicles including some types of main battle tanks.
Specialty grenades are available for illumination, smoke, CN (tear gas), and white phosphorus. Russia, many former Warsaw Pact nations, and China have developed a fuel-air explosive warhead. Another recent development is a tandem HEAT warhead capable of penetrating composite armor, as well as RPG screens and reactive armor().
Accuracy limits the standard RPG-7 to a practical range of 50 m, although it can reach 150 or even 300 m in skilled hands. It has an indirect fire (bombardment) range to 920 m, limited by the 4.5 second self-destruct timer.
There are persistent rumours of laser-guided Israeli RPG-7s accurate to the self-destruct radius.
RPGs are a favorite counter-technology weapon for insurgents.
The basic scheme is to get close, and make the shot count. To counter this, well-equipped armies prefer to maintain some distance and destroy the RPG shooters with artillery, antipersonnel gunfire or bombardment with submunitions, fuel-air bombs or napalm. Less-well-equipped armies use infantry screens to destroy RPG teams. Obviously, laser-guided RPGs would completely change these tactics.
In Afghanistan, Mujahideen insurgents used RPG-7s to destroy invading Soviet vehicles. To assure a kill, two to four RPG shooters would be assigned to each vehicle. In areas where vehicles are confined to a single path, (road in mountains, swamps, snow, urban areas) RPG teams trapped convoys by destroying the first and last vehicles of the convoy. This was especially effective in cities. Convoys learned to avoid approaches with overhangs, and to use a screen of infantry in hazardous areas.
Multiple shooters were also effective against heavy tanks with reactive armor: The first shot would be against the driver's viewing prisms. After that, shots would be in pairs, one to set-off the reactive armor, and the second to penetrate the tank. The favored parts of the tank were the top and the back of the turret. Chechen rebels attacked Russian tanks from basements. This was effective because the tanks' guns could not depress far enough to allow return fire. Both artillery suppression and infantry screens prevented antitank attacks by RPG teams. Russian tank columns were eventually protected by including antiaircraft artillery that were able to depress and destroy Chechen ambushes.
South African and Soviet APCs would be shot as soon as they stopped to let off troops. The South Africans developed a doctrine of driving the APC in widening circles, using automatic gunfire from one side to destroy the RPG teams. This prevented the APCs from becoming stationary targets as they would if they stopped to let off troops.
Helicopters would typically be ambushed as they landed or hovered. Again, multiple shooters were most effective. Both of the Blackhawk helicopters lost by the U.S. in Mogadishu, Somalia, were downed by RPG-7s. In Afghanistan, Soviet helicopters countered by clearing landing zones (LZs) with antipersonnel saturation fire. They also began arriving with unpredictable numbers of wingmen (two or three), to upset Afghan force estimations and preparation. The Afghans countered by digging prepared firing points with overhangs. The Soviets countered by using fuel-air bombs to clear LZs. The Afghans countered by changing to longer-ranged weapons (Stinger missiles) and prevailed.
Afghans sometimes used RPG-7s at extreme long range, exploded by their 4.5 second self-destructs. This performed expedient indirect antipersonnel bombardment, and sometimes was used to discourage reconnaissance by aircraft.
During the U.S invasion of Iraq and the subsequent occupation, the rocket-propelled grenade became a favored weapon of the Iraqi guerillas fighting U.S troops. Since RPG-7 rounds cannot penetrate M-1 Abrams tank armor — although there is believed to be evidence of a tandem warhead RPG penetrating and disabling an M1A1 tank () — it was primarily used to attack soft-skinned Humvees in supply convoys and as an anti-personnel weapon to target patrols.
In Iraq, U.S. anti-insurgent operations developed another effective tactic. In misty, dusty or night-time situations, advanced optics, such as infrared telescopes, permit helicopter gunships to surveil convoys from beyond human-visible range, and still attack insurgents with inexpensive anti-personnel fire. This approach is more economical than area-denial. Protecting as little as 20% of the convoys rapidly depletes an area of active insurgents.
The most widely distributed and used RPG in the world is the RPG-7, developed by the Soviet Union. The Soviets developed the basic design of the RPG during WW II, imitating and combining important design features of the US Bazooka and the German Panzerfaust.
The abbreviation RPG is an interesting example of a cross-cultural designation, since it translates to both English Rocket-Propelled Grenade and Russian as Ruchnoy Protivotankoviy Granatomet, "a handheld anti-tank grenade launcher". It was also sometimes used by the Vietcong to destroy most notably American or ARVN APCs traversing through the highways of Vietnam.
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