If you’re writing a scene that involves firepower of any kind and you need expert advice, Adam Firestone is your man. He returns this week to share his technical knowledge about some weapons whose looks might be a tad deceptive.
In June 1942, a strange looking weapon system was issued to the US Army. It looked like nothing so much as a four and half foot long piece of olive drab stovepipe with vertical hand grips. This weapon, the “Rocket Launcher, M1,” came to be better known as the “Bazooka.” It was to inspire several generations of shoulder-launched anti-armor rockets. Perhaps the best known of the Bazooka’s descendants is the ubiquitous RPG-7 anti-tank rocket propelled grenade launcher, still being produced by Russian factories. Almost twenty years after the Bazooka was unveiled, the US Army began trials of another tube launched shoulder fired rocket weapon. Instead of tanks, however this rocket was intended to destroy airplanes and helicopters. The FIM-43 “Redeye,” like the Bazooka, was to inspire generations of successors around the world, including what is arguably the most successful short range air defense system ever fielded, the FIM-92 Stinger missile.
For writers, the visual similarities, and resulting confusion and misconception, between these types of weapons create a very real risk of misemployment within a story. (One simply doesn’t use an RPG-7 to shoot down an airliner on final approach!) For the rest of this post, we’ll explore the similarities and critical differences between shoulder fired, rocket propelled anti-armor grenade launchers (“RPGs”) and Man-Portable Air Defense Systems (MANPADS).
RPG and MANPADS launchers have the same basic set of requirements: They have to contain a rocket during transit, act as a platform for mounting a sighting system, fit reasonably comfortably on the operator’s shoulder and provide a launch tube for the rocket at the moment of firing. As a result, they share a number of external similarities: They tend to be tubular, of three to five feet in length, have centrally located vertical handgrips with triggering mechanisms and dorsally located sighting systems. As a result, the uninformed are tempted to assume that they are intended to perform similar operational tasks. Looks, however, can be deceiving. A closer look at a typical example of each weapon system can shed some useful light on the matter.
The RPG launcher is reloadable. It is essentially a steel tube with an inside diameter of 40 millimeters (about 1.6”) and a length of about 38”. It weighs about fifteen pounds. The center section of the tube is wrapped with a lacquered wood heat shield to protect the operator. The rear end is flared to assist in blast shielding and recoil reduction. Typically, magnifying optical sights are provided (usually a variant of the PGO-7 2.7x scope), but the launcher comes with back-up iron sights as well.
The grenade protrudes from the launch tube. There are a number of grenades available for the RPG-7, including High Explosive Anti-Tank (HEAT; more on that below), tandem HEAT, fragmentation and thermobaric. Warhead diameters vary from 40mm for the fragmentation variant to 105mm for the thermobaric and tandem HEAT variants. The most common versions are the single stage HEAT variants, with warhead diameters of 85mm and 93mm. These weigh between five and six pounds for a total system weight of about twenty pounds.
The grenade has three sections, a head which contains the warhead and fusing mechanism, the rocket motor itself and the booster which expels the grenade from the launch tube. Upon firing, the booster, which contains a small powder charge, ignites, and the expanding gases push the grenade out of the launcher at approximately 380 feet per second. Spring loaded stabilizing fins pop out as the grenade leaves the launcher. After the grenade has traveled approximately 33 feet, the sustainer rocket motor ignites, boosting the grenade’s speed to about 965 feet per second out to a maximum range of about 1,000 yards. This two stage ignition process protects the operator from being burned by the rocket exhaust. If the grenade has not impacted a target by the time it reaches 1,000 yards, it self-destructs.
The grenade itself, once launched, is unguided. As a result, accuracy is directly proportional to distance. US Army studies indicated that at about 220 yards, the probability of a hit was approximately 50%, with the likelihood dropping significantly as the distance increased past that point.
The most common warhead found on the RPG-7 is HEAT. HEAT warheads use an explosive shaped charge to create a very high-velocity particle stream of metal that can punch through solid armor, building materials or other solid material. The stream material is formed by a carefully shaped cone of metal foil lining (copper in the RPG-7).
The stream moves at hypersonic speeds (up to 25 times the speed of sound) in solid material. For the warhead to be effective, the detonation point must be precisely controlled. If the warhead is detonated too close to the target’s surface there is not enough time for the particle stream to fully develop. As a result, most modern HEAT warheads have what is called a “standoff”, in the form of an extended nose cap or probe in front of the warhead.
The key to the effectiveness of a HEAT warhead is the diameter of the cone about which the explosive is wrapped. Early HEAT rounds penetrated armor to a depth of 150% to 250% of their diameter. Since the Second World War, the penetration of HEAT rounds relative to projectile diameters has steadily increased as a result of improved liner material and metal jet performance. The RPG-7’s 93mm PG-7VL warhead can penetrate some 22” of rolled homogenous armor, an impressive 600% penetration to diameter ratio.
The killing effect of an RPG-7’s HEAT warhead (euphemistically known as “behind armor damage” or BAD) is caused by a combination of blast and interior fragmentation. Once the armor or building is penetrated by the warhead, a significant overpressure event takes place. Blast overpressure can result in severe tissue and materiel damage. Additionally, high velocity armor fragments are injected into and bounce around the interior space, slashing and tearing at anything in their path. The results are, however, generally NOT spectacular. No grand explosions, no resulting fireballs (other than those from secondary explosions). A vehicle killed by a HEAT warhead will typically have only a single finger sized hole to indicate the cause of damage.
It’s worth a quick look at the visual and structural similarities that give rise to the confusion between RPGs and MANPADS, especially as an understanding of what appears to be the same will allow us to focus on the critical differences. For our comparison, we’ll focus on the Stinger.
Both the Stinger and the RPG use a long, tubular launcher which sits on the operator’s shoulder, and onto which fit the firing grip as well as the sighting mechanism. This, however, is where the similarities end. The Stinger is both longer (about 60”) and heavier (about 35 pounds). The missile’s performance is significantly different as well. For one thing, it has an internal passive infrared guidance system that allows it to detect and home in on the heat produced by an aircraft in flight relative to the surrounding environment. For another, the Stinger’s maximum speed is in excess of mach 2.2, or about 2,460 feet per second with a maximum range of three miles (as opposed to the RPG’s 965 feet per second and 0.57 mile range). And finally, the Stinger’s blast-fragmentation warhead, which is optimized for use against thin skinned targets like airplanes and helicopters, is radically different in design and operation than the RPG’s HEAT warhead.
As noted earlier, the tactical employment of an RPG is not much different than using a large single-shot firearm; a grenade is fitted into the launcher, the launcher shouldered, sighted and fired. The choreography of MANPADS employment is significantly more complex. Again, we’ll use the Stinger as our exemplar:
The Stinger missile comprises three discrete sections comprising guidance, warhead and propulsion components. The guidance section consists of a guidance assembly, a control assembly, a missile battery, and four control surfaces. The guidance assembly identifies target infrared /ultraviolet (IR/UV) sources and provides guidance commands to steer the missile toward these sources during flight. The seeker tracks the IR /UV source automatically after the gyro mechanism is unlocked (the technical term is “uncaged”). This is a key distinction between the Stinger and the RPG; the RPG, like a rifle bullet, has no in-flight guidance mechanism.
The warhead section consists of a fuse assembly and approximately 6.6 pounds of high explosive material within a cylindrical titanium case. The warhead can be detonated in three ways: by means of a low impact switch, by a proximity sensor, or by self-destructing. In any case, if no target is intercepted 17 seconds after launch, the warhead will detonate, destroying the missile.
As with the RPG, propulsion for the missile is provided in two stages. First, a booster provides initial thrust that ejects the missile about 28 feet from the launch tube. In the process, the booster is separated from the missile. At 28 feet, the flight motor starts and provides thrust for the missile during flight. Thrust for the flight motor is provided in two phases: boost and sustain. Initially, both phases take place simultaneously. The boost phase rapidly accelerates the missile to its top speed. The boost phase ends, but the sustain phase, maintaining missile speed for a time sufficient to complete the mission.
To ready a Stinger for firing, the operator retrieves the sealed launch tube containing a ready missile and attaches a reusable gripstock assembly. On the gripstock assembly are the safety and actuator device, uncaging switch, firing trigger, automated Identification Friend or Foe (IFF) antenna assembly, IFF interrogation switch, IFF interrogator connector, and Battery Coolant Unit (BCU) receptacle. The operator inserts a BCU into the gripstock. The BCU provides argon gas which is used to cool down the infrared seeker and electrical power for the missile systems.
The IFF system helps to ensure that the operator doesn’t unintentionally engage friendly aircraft. When the gunner starts the IFF sequence, a coded signal is sent to the target aircraft. A transponder on the target sends a coded reply. If the aircraft provides the correct code, the system alerts the operator with a tone indicating a friendly aircraft. If the aircraft sends an incorrect reply, the system sends the gunner a tone indicating that the aircraft’s status is unknown.
Once the decision to engage has been made, the operator continues tracking and ranging the target. When the target is within range, the operator switches a safety and actuation device. When the target acquisition tone is heard, the operator selects switch that uncages the seeker’s gyros. The aiming reticle is placed on the target, and if the acquisition tone is still distinct, the firing trigger is pressed, and the missile is sent on its way.
The Stinger achieves target effect in a manner distinctly different than the RPG’s HEAT warhead. Specifically, the Stinger uses a blast-fragmentation warhead that is designed to defeat thin skinned targets such as airplanes and helicopters by both damaging external components and sending many high-velocity metal fragments into sensitive and vulnerable portions of the aircraft. While this sort of warhead would be effective against thin skinned ground vehicles such as trucks and automobiles, it would be generally ineffective against armored vehicles such as tanks or personnel in bunkers or strongly constructed buildings. (Blast and fragmentation are the types of attack that armored vehicles are specifically designed to withstand.)
Despite external similarities, shoulder fired anti-armor rockets, like the RPG are very different, tactically and technologically from MANPADS such as the Redeye or Stinger. To recap:
• RPGs kill tanks, ground vehicles, buildings and bunkers; MANPADS kill aircraft;
• RPGs are unguided; MANPADS have sophisticated guidance systems;
• MANPADS tend to be significantly larger and heavier;
• MANPADS are significantly more expensive ($2,000 – $3,000 will get you an RPG, for a Stinger you’ll need to put out at least $40,000); and
• RPGs typically use HEAT warheads to defeat many inches of armor; MANPADS usually use a variant of the blast-fragmentation warhead.
What does this mean for you, the writer? It means that your protagonist simply cannot use an RPG to take down that 747 flying overhead (one sitting on the tarmac, 100 yards away, is another thing entirely), nor is she going to use a MANPADS to eliminate the threat posed by a charging T-72 tank. Technological realism is both expected by readers and a testament to the author’s craft.
Have you encountered any difficulties achieving technological realism in your writing? Let us know if you’d like Adam to tackle a particular problem in a future post.
Join us Wednesday when author LAURA MOORE discusses writing trilogies.
Bio: Adam Firestone brings more than 25 years of experience with weapon systems including small arms, artillery, armor, area denial systems and precision guided munitions to Romance University. Additionally, Adam is an accomplished small arms instructor, editor, literary consultant and co-author of a recently published work on the production of rifles in the United States for Allied forces during the First World War.
Adam has been providing general and technical editing services to authors and publishing houses specializing in firearms books since the early 2000s. Additionally, Adam provides literary consulting services to fiction authors including action scene choreography, technical vetting and technical editing. In this line of experience, Adam has had the fortune to work with well known authors including Shannon McKenna and Elizabeth Jennings.
Check out Adam’s blog here: http://adamfirestoneconsultant.blogspot.com/
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