From: Neil Asato <[n--sa--o] at [wiliki.eng.hawaii.edu]> Subject: BTRC: armor To: jerry (Jerry Stratton) Date: Wed, 7 Apr 1993 14:48:41 -1000 (HST) Subject: armor and armor-piercing for BTRC copyright 1992 by Neil Asato This post is generally for those who are using 3G3 or Timelords and want to make use of megaforce type equipment. Note that most comparisons of armor and penetration will be compared to homogeneous steel armor (4 AV per millimeter of thickness), and DV to penetrate is equal to that number divided by 0.55. Megaforce Anti-Armor Designs The APFSDS rounds are normally designed to penetrate up to 4 times their bore diameter in homogeneous steel armor. This generally comes up to having a maximum DV of 29.1 times the bore diameter, for TL12. The HEAT round are generally designed to penetrate from 3 to 6 times their bore diameter. This generally means having a maximum DV (at TL12) of 43.6 times the bore diameter. The HESH round generally penetrates about equal to its bore diameter. HESH rounds should be designed like high explosive rounds, with an armor piercing bonus against what it impacts against. This generally means having a DV of 7.27 DV times their bore diameter in millimeters, for TL12. The "bee-hive" round. This is designed to kill large amounts of infantry protected by light armor or less. True bee-hive rounds is basically a high-explosive fragmentation round that is designed to fire flechettes (steel darts) through a cone-shaped volume, killing/maiming anything that is has light armor or less. (Note that sometimes flechette rounds, which fire the flechettes from the barrel of the gun itself like a shotgun, is sometimes confused with the bee-hive rounds, which fires the flechettes as the main shell is travelling to the target). Strangely, there does not seem to be a 120mm bee-hive round currently in existance, though there was a 105mm round for the M60 tank (it was called XM494E3 APERS-T, anti- personnel with tracer). The bee-hive round is designed like a high explosive round with a special fragmentation effect, with only 50 % of its volume can be filled with explosive, and 75 % of the bore AREA allowed for the flechettes. The standard design will have 5,000 flechettes per round, with the flechettes having a damage RC of 2, and a design projected cone of 400 meters long and 130 meters in diameter. While it is not needed to know this, they generally had a min. range for the main shell of 3 m, and a max range of 4400 m for the main shell, with the fuse set at the time of firing. The historic M60 beehive round performed below expectations, though this was true of its HEAT and APFSDS rounds also for some reason, getting the equivalent of damage RC 2 and a DV of 25 (about 1/10 of the expected energy), and it had a projected cone of 300 meters long and 119 meters wide. For those who want to see what a M1A1 bee-hive round might be like (once the designers realize that the tank has to be able to fight infantry and and helicopters on a mass scale), it comes up to be damage RC 3, and DV 110 at TL12; the DV drops to 92 if 10,000 flechettes per round are used, and a lower damage RC. This is enough to handle nearly any powered armor(AV50), APC(AV57), and armored helicopter (AV30). As an extra note, the following HEAT weapons are of the following bore diamters: M151E2 TOW (147mm), Maverick (305mm), and RPG-7 (85mm ?). The M72A2 LAW can penetrate up to 280mm homogeneous steel, though some new models supposedly can get up to 300 mm of steel. The ARBRUST can penetrate up to 300 mm of steel.. The M47 Dragon can penetrate up to 580 mm of steel. The three previous weapons have a range up to 1 km. The M151E2 TOW can penetrate up to 580 mm of steel, and it has a range of up to 3.75 km. The disadvantage for infantry lauched missles is that it can take longer that 10 seconds for the missile to reach its target and (in the case of the TOW) you might have to keep your launcher aimed at the target the whole time, whereas the tank round only takes a second or so to hit distant targets (pray that the tank does not use a bee-hive round to get rid of the launcher). Armor Designs Spaced armor involves having at least 10mm of steel plate set at least 12 inches (up to 18 inches) from the main armor. The idea is to have the weapon use up part of its energy on the outer layer and be knocked off balance, spread out the molten jet, etc of the weapon. For armor purposes, multiply any weapon that penetrates the outer plate by 0.75 for the DV (decrease in energy by 25 %). Note that this is not really much on a thickness basis, but it is reasonably cheap to do. Its main disadvantage is that it does take up a lot of room, making the tank a bigger target, wich usually is not worth the relatively small amount of extra protection. If the spacing is less than 12 inches, just treat it as layered armor. Sloping armor generally improves the effectiveness of the armor by increasing the AV to 1.5 the normal AV. Basically it helps deflect the attack and increases the effective thickness that the weapon must go through. GMs might rule on whether or not it will apply in situations where the attack might come in at right-angles to the armor, negating the sloping effect. Reactive armor uses a explosive disruption to disrupt an explosive attack. It basically involves an explosive layer sandwiched between two steel layers, with the explosive triggered by the attack. It only affects explosive based attacks and only works once. They have an effective AV of 3 to 5 (5 is for experimental TL12 ones today) times the same thickness in steel. They have the advantage of being relatively light-weight and easily replaceable. Composite armor is very difficult to quantify. It basically involves using different materials to complement one another to achieve a desired effect. For tanks, this generally means getting 5 (for the weakest modern tank) to 10+ (for the most heavily armored modern battle tank) times the effective thickness of steel armor for the same thickness (generally 120mm or more). For large structures where large volume and low weight is a concern, buildings and possibly "giant robots", 1 to 3 times the effective thickness in steel, with lower density will probably be used. For powered armor, small volume, will probably limit the armor to 1 to 3 times the effective thickness in steel for the same thickness. Note that composite armor tends to be easier to crack, though very much much harder to penetrate (you could hit a tank composite armor with a sufficiently powerful machine gun and get a lot of surface cracks and small dents without really affecting the resistance of the armor, though the tanker would be upset with the surface damage) than steel armor. One way is to have alternating layers of strong (but brittle) material and tough (but soft) material. The strong material serves to spread out the kinetic energy, while the tough material absorbs it and holds the strong material in place. In some other variants the strong layer is actually a bunch of chips in the tough layer, to help diffuse the energy more efficiently (it gives the armor or more spring-like ablility). Another method is to use fibers in a matrix, generally with the fibers in a mesh to hold the matrix together even when the matrix is cracking. In general, the possible combinations of materials and manufacturing techniques is quite diverse. Residual stresses and pre-stressed materials can also be used. For composite armor, the resistance to attacks can vary with the type of attack. Generally, the armor is designed to be somewhat general purposed. Unless the GM has advanced knowledge of armor design or materials science, it is probably easier to just stick with one AV against all attacks. Composite armor could suffer from an attrition type of degradation before the armor is actually pierced. If the GM really wishes to go through the computations, take the material with the highest AV and compute the AV as if the entire armor was made of that material, then compute the BP of the armor by taking the BP as if the entire armor was made of the material with the highest BP (perhaps multiplied by the ratio of the effective thickness of the armor versus steel armor). Note that the computed values are for the armor itself, not the protection it gives. Now anytime an attack occurs, if the AV for the armor itself is exceeded take the damage to its BP. The loss of BP affects the AV protection it gives, but not the AV for the armor itself. This is just an option, as it adds considerably to paperwork and would slow the game down. When designing powered armor or "giant robots" keep in mind the amount of power being consumed. Generators for the "back-packs" of powered armor will generate up to 200 Watts for 2 to 8 hours, with batteries to act as energy reserves and storage. "Giant robots" will generally have a maximum weight of 40 tons and 10 meter length or height (at least until TL12 or 13) and their engines would have an output from 670 kW to 1.2 MW (roughly the same as modern tanks). In general, powered armor (and to a lesser extent, the "giant robot") has to be designed around the limitations of the power source, since you do not have much power to play with (those with matrix level technology excepted). Always base the design on the amount of weight supported to give you an idea of how rapidly you use up your fuel/energy reserves. Do the weight in Joules (mass multiplied by acceleration due to gravity). At 10% of the weight, the power source supports walking/ slow movement. At 50% of the weight, the power source supports rapid movement/movement across very rough terrain. At 80% of the weight, the power source supports melee combat/evasive actions. At 100+ %, the power source supports those super-powered/anime type actions. For those who want to use a technomagic campaign, enchanted diamonds in the "back pack" of the powered armor could supply the armor with enough energy to allow super-powered actions on a constant basis. Powered armor is generally going to be oriented toward "door-to-door" fighting. This generally anti-terrorist and "anti-dictator" (basically, where you want to get one target without destroying the entire building around it.) Limitations of volume, would generally limit the AV to around 50, which is good enough against nearly all hand-held, non-anti-armor weapons. As a rule, a powered armor that can't fit in the doorway is a badly designed powered armor. The role of "giant robots" is not really known, as the optimum design is not really known. If it was just an automated vehicle (whether a tank or not), it will probably be used mainly as "cannon fodder" (going in and wreaking havoc as long as it remains functional, and probably self- destructing once it ceases, to weaken the opposition or as a distraction). It will not compete with a tank, as a tank will probably kill it. It will generally be used in terrain that a tank cannot maneuver well, and serve as a mobile support base for powered armor infantry (recharging batteries, fuel storage, ammo and weapons storage, performing construction work (again, this is for situations where it is difficult to get the proper construction equipment into the area.) Most likely the second type will have a small nuclear reactor as a source of power to give it a long use in the field (General Electric has been testing nuclear reactors the size of home water heaters, including the radiation shielding, though I have not heard much about what their output is supposed to be beyond being above 10 kW). The armor is likely to be replaceable, and relatively cheap and light, probably using a variant of spaced armor with composite armor. An example might be to have moist clay packed into the space, to absorb the attack, perhaps with two layers of spaced armor. In terms of firepower, it will probably be somewhere between a heavy machine gun nest to a tank, as I doubt there would be any point in letting support equipment be placed in any more danger than necessary (mainly for situations where enemy forces attempt to overrun your base). Bee-hive rounds and machine gun ammo will probably make up most of the ammunition for the "giant robot", with some HEAT rounds just in case a tank surprises the robot. As with any other equipment, the smart strategist and tactician would use all equipment to provide the best overall result, and not rely on one equipment to do everything, though there might be situations that dictate otherwise due to logistics.