: El interior de los tanques está completamente recreado al detalle, con escotillas utilizables, periscopios, ventanucos, etc. El conductor, el encargado de la MG y el comandante pueden asomarse por sus respectivas escotillas.
: Heroes of Stalingrad incorpora un sistema de daños mucho más complejo que Osfront. El daño a partes específicas como visores, motor, transmisión, mecanismo de rotación de la torreta, reserva de combustible, piñones, bandas de rodadura y más estan recreados y modelados. Los disparos que penetren el blindaje del carro de combate pueden matar a los ocupantes. Cada tripulante posee sus puntos de impacto individualmente dentro del tanque y son vulnerables a la munición perforante de un rifle AT.
: todos los tanques contarán con una dotación completa; cualquier posición jugable que no sea ocupada por un jugador, se rellenará con la IA. Pueden dársele órdenes a la IA como conducir o abrir fuego contra objetivos específicos según lo decida el comandante de carro.
: los comandantes de cada tanque pueden elegir entre bloquear sus vehículos o permitir que otros jugadores se unan a su tripulación.
: habrá un cargo de comandante de tanque por cada blindado; si los comandantes permiten que otros jugadores entren en sus tanques, las clases correspondientes se abrirán de manera dinámica. Esto hará que los jugadores no tengan que escoger entre utilizar más tanques operados por un sólo hombre o menos contando con tripulación completa.
: los tanques pueden verse afectados por explosiones secundarias, causadas por diferentes circunstancias, como incendio del combustible, explosión de la munición, etc.
1. Ballistics
Basically, the game uses the same form of ballistics calculations for large projectiles as for small arms. This means that we are tracking the actual flight-path downrange.
2. Armor locations
[Layouts now in the media section of the website]
T-34 consists of 21 plates, plus the driver hatch and gun mantlet. The mantlet and turret are cast steel, while the rest is RHA (rolled homogenous armor). The Soviets tended to use very high hardness steel, which is a good thing against lighter rounds, but lacks ductility and actually makes it more vulnerable against heavier rounds (such as the Panzer IV's 75mm). In addition, there are the turret vision slits as potential targets.
Panzer IV is a more complex shape, totaling 45 plates. The Germans used mostly RHA, with some of the key plates in the 30-50mm range being faced hardened (FHA) to a depth of about 5mm. The intention with FHA was to provide a harder outer face, to defeat smaller projectiles, while the remainder of the plate provided more ductility to defeat larger rounds. Also modeled are areas like the vision slits, with the armored glass behind them.
In game, each plate is modeled in its correct place and angle. Using the ballistics calcs, we can work out the actual velocity and angle the projectile hits the plate at.
3. Key hit locations
T-34:
http://www.heroesofstalingrad.com/wp-content/gallery/tank-pages/tank_t34_page_2.jpg Crew - Gunner/Commander, Loader, Driver, Hull gunner
Ammo - MG ammo in the back of the turret and beside the hull gunner, while the main gun rounds are stored in the hull floor, with a small number of rounds in clamps on the hull side
Fuel - tanks are in the hull sides; diesel fuel, so less prone to fires
Engine & transmission - the T-34 has the transmission/gearbox at the rear, as the drive sprocket is at the back of the tank
Gunnery & optics
Panzer IV:
http://www.heroesofstalingrad.com/wp-content/gallery/tank-pages/tank_pz24_page_2.jpg Crew - Commander, Gunner, Loader, Driver, Hull gunner
Ammo - MG ammo beside the hull gunner and in the hull behind the loader, main gun rounds stored in multiple bins around the hull, with the largest right behind the driver
Fuel - tank is in the hull floor; gasoline
Engine & transmission - rear engine, drive shaft down the center of the hull floor, with the transmission front and center, gearing front sides
Gunnery & optics
4. Penetration calculation
This gets complicated!
KEY POINT: here is a thing that most people don't realize about armor penetration... it is all probabilistic at core. People rush off and hunt down "penetration tables", but you need to go back to the actual data measurements to understand what is going on. For instance, the Germans look for the "limit velocity" at which 3 out of 5 (or 5 out of 7, depending on caliber) rounds penetrate a test plate. They then took that number and created all those nice penetration tables from them, not the other way around! They do that to give their gunners a ready-reference guide, but it is NOT absolute.
For simplicity, we generate a Penetration:Resistance ratio and plot the results as a bell curve. We take anything below a certain point as an "undermatch", which will never penetrate and any result above a certain point as an "overmatch" which will always penetrate. Anything in between will generate a PROBABILTY that the round will penetrate - and we compare to a random number for those cases. Probability theory at work. It is NOT absolute - even in German testing, they were looking for the point where the "majority" of rounds penetrate.
So, about how it works... we hold/calculate a whole bunch of data on the incoming round and the plate that is hit:
For the round/projectile:
Muzzle velocity
Hardness (BHN)
Caliber (actually "d", the size of the projectile - SUB-caliber projectile for APCR/HVAP)
Max RHA (take from the ever-friendly bollox tables on the internet)
Actual RHA (This one is tricky: it is basically the theoretical 50% probability thickness penetrated at point-blank)
Test plate hardness (BHN) (i.e. what was this round normally tested against?)
Slope effect modifier - largely dependent on the ogive shape/effect
Shatter number & Shatter T/d - dictates when a round is likely to shatter
Shatter penetration effectiveness - the effect that shattering has on penetration capability [a round that shatters is perfectly capable of penetrating - and the effects are messy]
For the armor plate:
Thickness
Angle to vertical
Type (FHA, RHA, Cast)
Face hardness
Depth hardness
Calculate overall hardness on 5mm of Face hardness, remainder at Depth hardness
Flaw multiplier (100% for "perfect", 90% for badly flawed armor)
High hardness plate (Y/N) (Usually "Y" for thin plate)
Plate strength (starts at 100% - may degrade with repeated hits)
And the calculations:
Calc T/d (Thickness of plate/diameter of projectile)
Resistance calculation for the plate: allows for high hardness plate effects, the difference between the target plate and the normal test plate and the angle of incidence with the armor (including the slope coefficient)
Possible projectile shatter - if T/d > the round's Shatter T/d, the round may shatter
Penetration calculation for the round: modify the Actual RHA figure for the impact velocity of the round
Pen:Res is Penetration:Resistance ratio
Final projectile shatter is dependent on Pen:Res, accounting for the impact velocity; if the round shatters, the Penetration is adjusted, also Pen:Res
Results:
- If the final Pen:Res < 0.89, then the round is under-matched and will FAIL to penetrate
- If the final Pen:Res > 1.12, then the round over-matches the plate and penetrates intact
- For anything in between, we generate a random number for comparison. If Pen:Res = 1.0, for example, there is a 50% chance the round will penetrate (see where "Actual RHA" comes from now?)
- If the round remains intact, but fails to penetrate, it has a chance of generating spalling
Deflection: if the round stays intact, but fails to penetrate, we degrade the velocity and track its progress, just in case it manages to hit a weak spot!
A couple of worked examples:
T-34 round impacting Panzer IV upper front hull plate (beside the driver's front view slit) at 300 meters: The round is a 76mm round, impacting at 603m/s, actual angle of impact 33 degrees (plate is at 5 degrees off the vertical, flat ground, tank angled at about 30 degrees). The plate is 50mm FHA, overall hardness BHN 357.
T/d = 0.66
Final resistance of the plate is 63.6mm - slight increase for the plate being harder than Russian test plate (BHN 300), plus the effects of the angle, against the Soviet BR-253A projectile
Penetration for the round is now 78.9mm, but the impact means that the round DOES shatter
Final penetration capability of the projectile, allowing for the shatter is 63.1mm, giving a final Pen:Res ratio of 0.9919
No overmatch or undermatch - and the bell curve gives us a 46.9% chance of penetration
On this occasion, random number generator says it fails to penetrate: the round deflects at 97 m/s - which doesn't matter anyway, as the round has shattered
Panzer IV impacting T-34, left side, between road-wheels 2 and 3, actual angle of impact 43 degrees (plate is vertical, tank moving at an angle across the Panzer's front). The plate is 45mm RHA, hardness BHN 400 - high hardness plate.
T/d = 0.60
Final plate resistance is 60.7mm - it would be higher if it wasn't high hardness plate
Penetration for the round is 104mm in this case and it doesn't shatter, leaving the penetration unchanged, giving a Pen:Res ratio of 1.7187
This is an immediate Overmatch - that side plate is no match for the incoming 75mm round, even when angled and at 500m range
The round penetrates - clipping through the forward left fuel tank and into the main ammo storage in the hull. Scratch one T-34.
5. Behind-armor effects
Any projectile that penetrates intact is tracked to see what it hits inside the tank, through the key hit locations. If a round shatters as it penetrates, then it will enter the tank as shrapnel. A round that almost penetrates may also spall pieces of steel off the inside face of the armor, which is also treated as shrapnel. Interior components can all be damaged or destroyed (depending on server settings). A level of "general damage" is also applied, which goes towards a general starting of fires - and usually guarantees that a tank can't take more than 3 or 4 penetrating hits without blowing up. Assuming that an earlier penetrating hit hasn't lit up the fuel or engine, or set off an explosion in the ammo stores...
6. Sources & References
Before all the "debates" start about what is "right" and "wrong", we'll just explain a little about some of the rationale and the sources.
First question: "Why not just use the equations given by DeMarre/Krupp/Nathan Okun/Someone else?" Because most of those people created equations (some around 140 years ago) to handle specific naval gunnery problems. There is actually only a relatively brief period of about 8-10 years when people were researching the effects of AP projectiles against RHA targets. There wasn't much research being done prior to about the mid-1930s - and after 1945 almost everything changes gear and starts to deal with APCR/HVAP projectiles, that become "long rod penetrators", and HEAT/SCW rounds impacting modern steel armors, then composites and reactives. Willi Odermatt largely owns that - and should we do a modern version, his equations will be at the top of my list!
So, given that we also need math that will cope with every single impact, varying angles, plate and round types, ogive shape and all the rest of it, we had to derive our own.
A lot of thanks go to people on our own forums, as well as on Tanknet, who's brains we have picked over the years. These include people like Paul Lakowski, Jeff Duquette and many others. It is a tortuous process, as we have to deal with all possible impacts, but keep the calcs to something manageable within a game. We think we have a decent compromise this time!
One of the key works is "World War II Ballistics: Armor and Gunnery", by Lorin Rexford Bird and Robert Livingston (private publication, long since out of print). But there are plenty of debates about flaws in that work - and pretty much any other, so you have to try and work it out for yourself a good chunk! Add in sometimes-defunct websites like Guns vs Armor and other sources of data - Jentz oft-quoted. The full list of sources used we can show separately - it is long! But some key pieces:
AT 285/4: 6 pdr, 17 pdr APCBC and APDS Shot Versus Stored Ammunition and Fuel Tanks, Fighting Vehicles Proving Establishment, ~1944, Classified “Secret”
Auler, H, Shape of Armor Piercing Projectiles [tr. From German], Rheinmetall-Borsig AG, Berlin, tr. March 1948 [Originally Classified “Restricted”, DoD and Contractors only]
Bethe, H A, Attempt of a Theory of Armor Penetration, Cornell University, May 1941 [Originally Classified “Confidential”, DoD and Contractors only]
Bird, Lorrin, ASL Armor Studies: Exceptions to the Rule, The General
Bird, Lorrin Rexford & Livingston, Robert D, World War II Ballistics: Armor and Gunnery [Second Edition, with Errata], Overmatch Press, 2001
German Steel Armour Piercing Projectiles and Theory of Penetration, British Intelligence Objectives Sub-Committee (BIOS), Final Report No. 1343, September 1945, Classified “Secret”
German Tank Armour, British Intelligence Objectives Sub-Committee (BIOS), Final Report No. 653, Undated – probably late 1945, Classified “Secret”
German Tank Armour, Final Report No. 653, Item No. 18, British Intelligence Objectives Sub-committee (BIOS), ~1946, Classified “Secret”
Lakowski, Paul, Notes on APFSDS, Private release, ~2007
Lakowski, Paul, Notes on effects of Hardness on penetration, Private release, ~2003
Penetration Figures for Ammunition at Various Angles of Armour, Unknown original source, RAC Tank Museum, 1947, Classified “Secret”
Rolled Armor, Ballistic Properties of Rolled Face Hardened Armor and Rolle Homogenous Armor of Various Hardnesses at Normal Incidence and at Various Obliquities, Watertown Arsenal Labs, Sep 1942, Classified “Restricted”
Stockdale, Maj D, The Perforation of Armour by AP Projectiles, Armour Section, School of Tank Technology, January 1944, Classified “Secret”
Unkovskiy, V A, Теория Стрельбы И Ее Приложение К Стрельбе Корабельной Артиллерии [The Theory of Ballistics and Appendix on Artillery Calculations], Voenizdat, 1939
7. My favorite target spots
Just for fun - where do I aim for?
If it is a front-on shot at either tank, I'll look for the ground angle to help me out. Catch either coming down a slope at you and the Pz IV's front hull roof armor is exposed, while the T-34's glacis is suddenly at a less acute angle. Alternative is lower hull plates if I can get at them. After that, the gunner's side of the mantlet on either tank, if the range is relatively close. Failing any of those, I'll be backing off!
If you get a shot at the T-34 from the side, I go low, between the second and third road-wheels, for the ammo storage in the hull floor. Pretty much the same for the Pz IV, aiming for the main fuel tank (gasoline, more likely to brew it).
