You may have heard the term rocket-propelled grenade, and you've probably seen news images of their use and the destruction they can cause, particularly if you've kept up with current world events in the Middle East. Rocket-propelled grenades are a commonly used explosive projectile weapon, used by many armies across the world. They play a major part in contemporary warfare, and are also highly used among insurgent and terrorist groups.
How Rocket Propelled Grenades Work
Parts contrinuted by Shane Speck & wikipedia.org
Description
A rocket propelled grenade (RPG) is a loose term describing hand-held, shoulder-launched anti-tank weapons capable of firing an unguided rocket equipped with an explosive warhead. RPG is the Russian abbreviation of "Ruchnoy Protivotankovy Granatomyot" (Ручной противотанковый гранатомёт, РПГ) and is translated into English as "handheld anti-tank grenade-launcher". The commonly used term "rocket-propelled grenade" is a mistranslation, is technically incorrect to use, backformed from the acronym RPG, and does not follow correct naming conventions used by English speaking militaries to describe these weapons.[citation needed]
Most modern main battle tanks (MBTs) are largely immune to hand-held unguided anti-tank weapons due to advances in armor design requiring more precise aiming to hit vulnerable weak spots. RPGs, however, are still used very effectively against lightly-armoured vehicles such as armored personnel carriers (APCs) or unarmored wheeled vehicles, as well as against buildings and bunkers. They can still be a threat to an MBT under certain tactical conditions. One exception is the RPG-29, the most advanced model, which uses a tandem-charge HEAT warhead to penetrate explosive reactive armor. It is apparently capable of destroying even highly advanced MBTs such as the T-90.
An RPG comprises two main parts: the launcher and the rocket, which is equipped with a warhead. The most common types of warheads are high explosive (HE) or high explosive anti-tank (HEAT) rounds. These warheads are affixed to a rocket motor and stabilized in flight with fins. Some types of RPGs are single-use disposable units similar to the U.S. M72 LAW; others are reloadable, such as the Soviet RPG-7.
The RPG launcher is a hollow tube that concentrates the rocket exhaust to create an over-pressure within the tube. This over-pressure propels the warhead at a higher speed than from the specific impulse of the rocket alone. This higher speed is necessary for the rocket to be stable in flight. The launcher is also designed so that the rocket burns completely within the tube and exits the launcher without discharging an exhaust that would be dangerous to the operator. The high-temperature rocket exhaust is hazardous 15 to 20 meters to the rear of an RPG launcher. The launcher must be cleaned periodically, as built-up residue will result in an excess of over-pressure, causing the sighting mechanism to be driven into the operator's eye when the rocket is fired. Blindness in one eye often results.
All RPGs are similar in concept, however, there are significant differences in their operation.
An RPG is an inexpensive way to deliver an explosive payload a distance of 100 yards with moderate accuracy. Substantially more expensive, wire-guided rockets are used when accuracy is important. These rockets trail a thin wire behind them during firing and can be steered by the operator while in flight. In 1982, British troops were sent to the Falklands War armed with a number of wire-guided MILAN anti-tank missiles even though there were no Argentine tanks in the Falklands Islands. The British used these expensive weapons to destroy Argentine bunkers because they did not have any cheap unguided rockets available. This prompted the U.S. military to field the SMAW, the U.S. equivalent of the RPG.
RPG History
The most widely distributed and used RPG in the world is the Soviet Union-developed RPG-7. The Soviets developed the basic design of the RPG during WW II, combining important design features of the US Bazooka and the German Panzerfaust.
RPG Basics
At its core, a rocket-propelled grenade can be thought of as something like a rocket and mortar hybrid. It's an explosive projectile weapon with two separate parts; the grenade and a device for launching it. In many cases the launcher can be reloaded, reducing the overall cost at the expense of increased weight. Weight is, of course, important if you have to carry the weapon to your target, but cost can also be important if your army is small and low on resources.
Photo courtesy Department of Defense Defense Visual Information Center
An Ecuadoran commando checks the back blast area before firing an M-72 light anti-armor weapon (LAW) during small unit training conducted as part of the joint Ecuadoran/U.S. exercise Blue Horizon '86.
The launcher is basically a tube that rests on the operator's shoulder. It is open at both ends, and a projectile with a small rocket engine is affixed to the front end of the tube. Firing is usually accomplished through a trigger mechanism, at which point the grenade's rocket engine is activated and a short, high-powered burst of ignited gases launches the grenade for a short distance - maybe between 500 to 1,000 feet (150 to 300 meters) depending on the target and the skill of the operator. An RPG operator should be aware of what's immediately behind him; the exhaust gases will flare out behind the device in a cloud of searing hot smoke.
Photo courtesy Department of Defense Defense Visual Information Center
An Opposition Forces Marine fires an AT-4 light anti-tank weapon during a skirmish.
The projectile itself travels toward the target, usually exploding upon impact. However, some modern grenades use an electronic fuze system instead of a mechanical or chemical fuze so that the projectile will detonate after a particular time-span has elapsed.
Most RPGs follow this basic operational design, although different models feature various refinements and modifications. Some are designed to be most effective against troops; some are designed to work well against armored vehicles and tanks, launching high explosive anti-tank projectiles. The M-72 Light Anti-tank Weapon (M-72 LAW) is popular with American forces, and features a pre-packaged rocket which is fired and then discarded. The M136 AT-4 also features a disposable launch device, and its 820 feet (250 meter) range and re-usable night-sight bracket has led to it becoming the U.S. Army's principal light anti-tank weapon.
M136 AT-4 Light Anti-armor Weapon
Launcher:
Length - 40 inches (1,020 mm)
Weight (entire system) - 14.8 pounds (6.7 kg) Rocket:
Caliber - 3.3 inches (84 mm)
Muzzle Velocity - 950 feet per second (290 mps)
Length - 18 inches (460 mm)
Weight - 4 pounds (1.8 kg)
Maximum Effective Range - 985 feet (300 meters)
Penetration - 15.8 inches (400 mm) of rolled homogenous armor
Source: GlobalSecurity.org
Although not favored by the U.S. Army, by far the most common rocket-propelled grenade in use today is the RPG-7, a Russian designed weapon closely related to the German Panzerfaust anti-tank weapon, dating from World War II. Like missiles, these grenades have a built-in rocket propulsion system. Let's take a closer look at the RPG-7.
The RPG-7
The RPG-7 anti-tank grenade launcher is robust, simple and lethal. It is also extremely popular. As it exists today, the RPG-7 is the result of many years of revisions and modifications. The "original" RPG -- based on the German Panzerfaust anti-tank weapon - was eventually followed by the RPG-2, the RPG-3 and so on. In fact, although the RPG-4 had passed field trials in 1961, test findings of a newer model, the RPG-7, were released that same year, but with much improved firing range and armor piercing capabilities. So in 1961 it was the RPG-7, not the RPG-4, which the Soviet Armed forces adopted for actual use. Today, the RPG-7 is used by the armies of over forty different countries and is also used, reportedly, by a range of terrorist organizations in the Middle East and Latin Americas.
Now that we know what an RPG-7 is, let's take a look at how one operates.
Firing an RPG-7
The RPG operator or an artillary assistant takes a propelling charge (booster, in image below) and screws it onto the end of a warhead. Basically, this is a stabilizing pipe
that has four stabilizing fins that are folded around it with two additional fins at its rear end. A cardboard container encases the back end of the stabilizing pipe. Inside the cardboard container, a squib of nitroglycerin powder is wrapped around the stabilizing pipe and a primer or charge of gunpowder is stuffed into the end of the stabilizing pipe.
The RPG operator or artillary person then takes this assembled artillery and loads it into the front end of the RPG launcher so that it lines up with the trigger mechanism.
After the RPG operator pulls the trigger, this is what happens:
- A percussion cap ignites the primer, gases build up inside the launcher’s chamber, thereby breaking apart the cardboard container and propelling the grenade forward through the barrel of the launcher. In this way, the cardboard container is a lot like the casing containing the gunpowder on a bullet.
- The force of the built-up gases throws the grenade out of the tube at approximately 384 feet per second (117 meters per second). The abrupt acceleration of the grenade leaving the launcher triggers a piezoelectric fuze that ignites the primer (pyro-retarding gunpowder mixture). This then ignites the squib of nitro, thereby activating the rocket propulsion system (sustainer motor) to carry the grenade the rest of its trajectory.
- As the grenade leaves the launcher, the fins along the stabilizing pipe spread out, which, along with the rocket motor, allow the grenade to travel a long distance at a potential speed of about 965 feet per second (294 meters per second). The grenade moves like a football, rotating through the air; the fins stabilize its flight.
- A socket in the breach block alleviates recoil during firing. The exhaust gases exit to the rear of the launcher unit and the operator is free to immediately reload the weapon. In practice, however, no RPG operator would ever remain stationary and spend the time to reload; the launching flash and whitish blue-gray smoke provides a clear indication to the enemy of the RPG launcher's location. An effective, surviving RPG operator is one who quickly changes position and gets under cover.
There are several types of grenades that can be used in the RPG-7. Some have a point initiating, base-detonating (PIBD) piezoelectric fuze: meaning that they are impact grenades. And, many others have back-up time delay systems, so that if they have not reached a target in a certain amount of time (something like four and a half seconds) the grenade will self destruct. The most commonly launched grenades are a High Explosive(HE) or High Explosive Anti Tank (HEAT) rounds.
Impact grenades must be unarmed until they are actually fired because any accidental contact might set them off. Since they are usually shot from a launcher, they must have an automatic arming system. In some designs, like the one we describe above, the arming system is triggered by the propellant explosion that drives the grenade out of the launcher. In other designs, the grenade's acceleration or rotation during its flight arms the detonator.
As for the back-up timed delay, the same fuze mechanism that sets off the the rocket would set this off. The spark ignites a slow-burning material in the fuze. In about four seconds, the delay material burns all the way through. The end of the delay element is connected to the detonator. The burning material at the end of the delay ignites the material in the detonator, thereby exploding the warhead.
