In WWII there was a strange balance between tank armour and guns. Sides were examining what thickness of armour the opponent uses and install a gun just right to penetrate it but without excess. The idea was that if 70mm cannon could penetrate enemy armour the 85m cannon would be a waste (too heavy, too expensive for no additional/marginal gain).

I'm thinking of using such system. The premise here is that the player observes (spys, combat reports) the enemy ships design (armour) and try to install guns able to counter these armours (just right guns, not the most powerfull possible). In addition it would encourage the player to have different forces vs different enemies (vs enemy that tend to build ships with high armour a high penetration gun fleet would be used, while a cheaper/faster fleet would be used vs enemies that have low armour).

Post anything related, I just want to talk about it :)

How it could be done:

The assumption here is that combat is automated & abstracted, AI captains fire at each other following just general orders of the player.

Variables:

* ships have Armour rating, it's two numbers like "Armour:5-3" (since armour can be of different thickness in front/sides/rear)

* weapons have Penetration rating, it's one number like "Penetration:4"

* weapons have Damage rating, it's independent from Penetration (but usualy high damage guns would also have high penetration)

* weapons have FireRate rating, basicly smaller guns with low penetration & damage can fire more often (these don't necessarily have to be cheaper)

Mechanic:

* each turn/battle phase there is a roll on current Armour of the target (between max/min), it's affected by maneuverability (more maneuverable ships can position themselves better than heavy one and assure they face them front, where their armour is the thickest), tactical skills of the captain (can outsmart enemy captain and position the ship better), level of targetting computers (able to target more vulnerable parts of enemy armour)

* if the Penetration is higher or equal to Armour of the target the hit deals full damage, if it's lower it deals half damage, if it's less than 1/2 of the Armour it deals no damage at all

Ships composition:

* this system dictates that each ships should have at least two gun types, the main gun useful for at least scratching high armour targets and smaller/point defence guns that fire fast but are effective against low armour targets only

Other idea:

Quite similar, but ther Armour has three numbers (front/sides/back) like "Armour:8-3-2" or "Armour:5-2-2". It's less intuitive but more in the mood (everyone understands that whatever vehicle it is it's more armoured on front, less on sides and the least on the rear). Althrough, maybe it's not so intuitive for space ships?

With space ships you could also throw energy usage into the mix, giving a sci fi twist to the tank armor mechanic. So if you need a little extra fire power or extra shields, you send extra reactor power to one or the other. Maybe even to your engines if you need more speed. The idea is that the energy would be more versatile, but costly and temporary. Maybe kind of like will power in The Banner Saga.

Hardly related perhaps, but this reminds me how I've implemented shields in my space combat prototype.

Shields would not have bullets collide with them, but they would alter bullets in several ways:

- Shields would deal recurring damage to bullets in their area. Though this did not mitigate any damage per se, bullets which either didn't have much resilience, or were slow to start with, would risk being eliminated before hitting the hull.

- Shields could slow down bullets. Since the damage dealt to a ship was also based on its kinetic energy (speed), slowing down a projectile would also limit damage (and increase the amount of time the projectile would be stuck within the shield's field).

- 'Refraction' Effect: Shields could somehow slowly shift the angle of movement of bullets that would come in their path so as to deviate some shots. Light bullets would be more easy to shift that way.

So, depending on the weaponry you are expecting to face, you can invest in shields that do any of the above well to mitigate the risks (Refraction shields being ideal against chain-gun-like weapons, slow effects ideal against buckshots and mitigation shields perfect to detonate missiles further from the hull and minimize the shock damage).

I tend to prefer systems where projectiles' efficiency is governed by a global set of rules, as opposed to a global set of variables. I find it more appealing as a player as well.

I tend to prefer systems where projectiles' efficiency is governed by a global set of rules, as opposed to a global set of variables. I find it more appealing as a player as well.

Could you expand on this further, I'm not sure I follow. If I am parsing it correctly, using your example above, those shield types would all be the same across all ships, ie there would not be a RefractiveShield strength X, but just RefractiveShield.

The WWII example is interesting, it sort of has a nice dynamic, as you end up with straight armor piercing rounds, armor piercing high explosive, high explosive and high explosive anti-tank. The first three tend to have a sort of rock-paper-scissor effect. The first round is great at penetrating, but doesn't hurt internals all that much, just pokes nice holes. APHE has less penetration, but if it does penetrate, does a good deal of system/crew damage. And then HE has terrible pen, but is good for unarmored targets, and is area of effect, and it also doesn't lose penetration over range and can be used for damaging external systems. HEAT is an odd duck of the bunch, and tends to mostly fall in the realm of being a better APHE, except not as good against certain armor types, in WarThunder it also tends to have terrible velocity.

For space, it'd be kind of weird to lose penetration over range, but I don't think that's a critical component to gameplay. The danger with penetration is that you can have battles that are completely unwinnable by one side. And it can be no fun being that person. (w40k Tabletop suffers from this) You can mitigate this somewhat by having some form of randomness to the pen, perhaps critical hits, but one has to be careful, or the risk goes the other way, and no one bothers to buy heavy armor, as lots of cheap rapid fire can take down anything via volume of fire. I've thought about limiting non-penetrating critical hits to only doing enough damage to incapacitate a target's offensive capability (Like knocking out sensors, turning thrusters, locking turret mounts in place) Just something that would have the heavily armored juggernaut that is completely swarmed to become less effective and/or be forced to withdraw from the battle, but not going to be killed outright by a lucky shot. One could also make it so that those debilitating effects are temporary, so a swarm would have to continue to hammer at the juggernaut, creating more of a stalemate. You might also be able to get around it with a secondary mechanic, boarding parties, teleporter bombs, etc.

You may want to play with firing angles as well, certain ships might be able to mount a really big gun, but it's only forward facing, and the ship is kind of slow to turn, which naturally leads it to being not so great against nimble ships.

EDIT: For armor, I personally like front/sides/rear. With just two ratings, a unit can go from invulnerable to dead a little too fast when only flanked slightly.

EDIT: Also another idea to avoid the unstoppable high armor unit is to have armor degradation. Reactive armor on modern tanks is something that can basically run out, leaving it down to just the non-reactive portion.

Actually the relation is 3 way between armor protection, gun size and movement speed/maneuverability (as it also is for ships)

The bigger the gun the more volume/bigger-structure needs to be covered by armor, as well as to contain the engine/mechanics needed to move the bulk at some speed. Within the same relations is the containment of fuel/ammo which increase in size themselves by the sizing of the gun/engine (so a duration kind of factor).

Increase a factor (effectiveness) and its at the cost of the others

There also are practical limits to how big you could make something before it becomes too unwieldy/complicated

The WWII example is interesting, it sort of has a nice dynamic, as you end up with straight armor piercing rounds, armor piercing high explosive, high explosive and high explosive anti-tank. The first three tend to have a sort of rock-paper-scissor effect. The first round is great at penetrating, but doesn't hurt internals all that much, just pokes nice holes. APHE has less penetration, but if it does penetrate, does a good deal of system/crew damage. And then HE has terrible pen, but is good for unarmored targets, and is area of effect, and it also doesn't lose penetration over range and can be used for damaging external systems. HEAT is an odd duck of the bunch, and tends to mostly fall in the realm of being a better APHE, except not as good against certain armor types, in WarThunder it also tends to have terrible velocity.

No, there is no rock-paper-scissor relationship between different shell types because they have the exact same role: hurting what they hit, despite armour. With a single armour type (thick and tough steel) and no significant difference between the vulnerability of people and internal tank subsystems, the relationship between shell types and armour types cannot be more complex than the one-dimensional tradeoff that against better armour, shell designs that penetrate more at the expense of damage are more effective.

Such a choice of shell types isn't even necessarily relevant in the game, because:

• Some shell types could be better in all respects than obsolete ones.
• Some shell types could be preferable because they are cheap and plentiful. For example, if on average an enemy tanks is disabled after taking 4 AP rounds or 5 HE rounds and you can choose between going into battle with 15 AP rounds or 35 HE rounds, HE is likely better if getting shot at a bit more is acceptable.
• Tanks don't necessarily carry different shell types.
• Any available shell type could be too ineffective at a given size, requiring the adoption of bigger guns (as discussed in the OP), or conversely they could all be overkill.
• Instead of switching to optimal shell types, tanks can switch to optimal targets. For example, if enemy tanks are very tough the tanks could usefully employ their mediocre guns against buildings and fixed defenses, leaving enemy tanks to infantry or artillery specialists with rocket launchers.

There can be rock-paper-scissor relationships beyond the narrow scope of armour penetration, in particular:

• Focusing on a fixed budget, armour quality vs weapon quality vs number of vehicles. With the right realistic cost structure, swarming tends to beat weapon quality (the larger army shoots more against less targets), armour quality tends to beat numbers (as it virtually reduces enemy firepower and works better if one gets shot more), weapon quality can easily beat armour if good enough (taking advantage of armour effectiveness nonlinearities).
• Focusing on the tactical level, armour weight vs gun weight vs being light and fast. The tank can expect to get hit and survive if slow and tough, to get hit less than normal because the enemy dies first if slow and well equipped, or to be missed if very fast.

I think you're missing the point, in that what happens after a shell penetrates the armor? A solid core round continues to go straight through, which is great if it was aimed directly at something important, not so great if it was aimed at something non-critical, like just empty space or more armor. A round that penetrates and then explodes is going to hit a large area, and send shrapnel or hot copper all over the compartment. Also, WWII had more than just a single armor type, spaced armor made it onto plenty of tanks.

Historically, tanks also always tended to carry different ammunition. That said, for a space game, and to keep things simple for both UI and player, swapping ammo types might be something that should be avoided.

No, there is no rock-paper-scissor relationship between different shell types because they have the exact same role: hurting what they hit, despite armour.

I think he meant that there were 2 types of shells with completelly different purpose, penetrating one to kill tanks and explosive one to kill infantry & destroy bunkers. Same for cannon length (short cannons to kill infantry - low range big shell; long cannons to kill tanks - high range, high starting speed small shell).

Not that it has anything to do with armour :D Also I need it for space ships so there won't be "soft targets" anyway (unless you try to hit a space monster I suppose :D)

No, there is no rock-paper-scissor relationship between different shell types because they have the exact same role: hurting what they hit, despite armour.

Totally wrong. While there where exceptions (like very heavy HE Shells, like the russian 152mm, that did a fine job even against tanks), most round where designed to do one thing well, and ended up doing everything else rather poorly:

- High Explosive: for use against fortifications, guns and dug in infantry. Not too great against infantry in the open (because they could spread out), and not too great against tanks (except well aimed hits at periscopes, weakspots, using spalling effects to damage the interior (fixed with spall liners later on), or very heavy shells that could deform the tanks armour with the blast alone, and even just stun or kill the crew if the tank didn't take critical damage).

It seems the HE shells might have worked brilliantly against lightly armoured targets when it penetrated the armour and exploded inside. Also vehicles like armoured cars where highly vulnerable to getting its wheels blown to bits by a HE shell it seems.

- Armour Pirercing: Rounds created to pierce armour... worked fine at the beginning of the war, while stopping being too effective except for very high caliber guns, or against older tanks at the end of the war.

- HEAT: Rounds created to pierce extreme thick armour. Worked quite well for that, to this day. Of course pretty useless against anything but armoured targets (apart from some dual mode ammunition that can be set upt to detonate on impact like some kind of HE shell instead)... the less well known disadvantage of HEAT shells is that actually for the newer types created in the 50s, that have like an insane penetrative power, the actual damage they do to the interior is very little.

There are interesting stories about the Korean war, where 2 different types of russian RPGs where used, one older with a wider jet which didn't penetrate as much armour, and a newer one with a more narrow jet and more penetrative power.

If used against the US Walker Bulldogs (which had pretty much zero armour), the US tanks tended to be out of order about 2 or so hits from the older type, but some could take more than 5 hits from the newer type of RPG and still kept going. The metal jet basically penetrated the tank, but the narrow stream either completly missed anything vital inside, or there was just not enough mass left inside the tank to do any critical damage.

- APCR, Sabot: first one is an AP round with a core made from a harder material (tungsten, usually, nowadays depleted uranium), second one is a narrow penetrator made from a very hard material enclosed by a discardable sabot breaking up when leaving the barrel. Pretty much useless against anything other than tanks, and very expensive to manufacture, so usually only used if needed.

- HESH: stick to the armour, then explodes, using a spalling effect to damage the interior of tanks. Might also be useful against guns, maybe fortifications, though I have my doubts if it will do anything against dug in infantery.

There are other types like APHE, but they all are just modifications to the existing types trying to increase the effectiveness in their one, single application.

Oh, and then there is the story with different armour types. For WW2 era, that is not so interesting, still there are some notable differences:

- Steel quailty: At the beginning of the war, germany seemed to have a very good armour quality... at the end of the war, because germany lost access to important sources for some metal alloys, there armour tended to be very low quality and brittle, breaking up on impact.

- Hardening: Some countries used special treatments to "face harden" their armour. AFAIK the idea was that against softer AP shells, the shell would break up on impact, loosing almost all of its penetrative power just because of that. Don't know how well that worked though.

- Rolled vs cast armour: some countries used to cast large sections of armour, which allowed them to create rounded armour. Others mainly used straight rolled plates of armour, welded or rivetted together.

- Rivetting vs welding: Welding just became more wide spread just before WW2 for tanks. Rivets tended to make the tank heavier, and posed a great danger for the crew if hit by enemy fire (they could loosen and ricochet into the interior even if the armour hold up against the hit). Welds on the other hand could prove a weakspots, if improperly done.

If we move on some years, we are entering the wonderful world of composite and reactive armour:

- The composite armour used today by western army tends to be extremly effective against Sabot and HEAT ammo. HE and AP ammo would quickly destroy the composite armour plates hit, and would create a weakspots for the next round of HEAT or Sabot ammo to hit the same spot. Lucky for western armies HE tends to only be used against tanks in emergencies, and AP fell out of favour for tank gun use.

- Reactive armour used by the russian / ex-sovjet countries seems to be just as effective as composite armour against the first hit on a certain spot... of course, as soon as a part of the armour has been detonated, that certain spot has no reactive armour anymore and becomes a weakspot. Also, the age old tactic of using infantry in close support of tanks no longer works, as your grunts now have to keep a safe distance from the explosives on the tanks.