Armor Damage in GURPS
by Peter V. Dell'Orto
GURPS fans have been blessed by a system that allows you to break shields, shatter weapons, cripple limbs, but even after you reduce your foe's weapons and shield to flinders and his body to -10xHT his armor is still fine.
Until now. The following rules are an extension of the rules for Armor Enchantment in GURPS Magic on p. M46. These rules expand upon those rules, and include further optional rules you can add on to bring this system to the level of grittiness you need for a campaign. This system does require some bookkeeping by GMs and players alike, but not really that much more than the Damage to Shields rules (p. B120) require. These rules add some extra realism to combat as well; armor wears out, requiring repairs and eventual replacement.
Armor Damage
Armor can only withstand a limited amount of destruction -- referred to as Maximum Penetrations -- before it is no longer capable of protection. Armor can take (DR+1)*5 penetrations before becoming useless as protection. For example, Reinforced Heavy Leather (DR 3) can take (3+1)*5=20 penetrations before becoming useless. For armor with split DR, such as chainmail, use the highest DR to calculate the Maximum Penetrations. A penetration is defined as any hit that does damage greater than DR. Blows that do less than or equal to DR do not count as penetrations. Armor divisors do lower the amount of damage needed to cause a penetration, but do not cause additional penetration to the armor. Penetrations are tracked on a per- location basis if using the Hit Location chart; if you use Basic Combat, calculate penetrations based on the torso and count all penetrations as being against the torso armor.
Note that some ultra-tech weapons (Flamers, sonic weapons, etc.) already do armor damage -- the effects should be combined if these rules are used as well. Magic can damage armor as well. As a rule, spells which cause damage reduced normally by armor DR (such as Fireball, Ice Dagger) will inflict penetrations like any other attack, while spells which bypass armor's protection (Dehydrate, Deathtouch) will inflict no penetrations. Some magic can be used to directly attack armor. For example, Shape Metal or Reshape can be used to shape armor completely off a location. Ruin inflicts PD and DR loss per p. M59, which will reduce the Maximum Penetrations by 5 per minute. Shatter and Disintegrate will succeed if the damage inflicted is greater than the Maximum Penetrations of the armor, and destroy that location's armor completely. If they fail, no damage is inflicted. The Weaken spell will inflict 1d6 penetrations per casting. And so on -- a GM's judgment is needed to cover the myriad of magic attacks that can damage armor.
As per GURPS Magic, Fortify and Deflect wear out as well and a little more rapidly. Regardless of any non- magical armor repair, magical armor will become non-magical after 5 times the base DR penetrations (0 base DR would get 5 penetrations). Chainmail would survive 15 penetrations before becoming non-magical, a leather jacket only 5. Both armors would need 5 more penetrations (At base DR, not DR + Fortify, which is gone when the spell is broken) before becoming useless as armor. While base DR is used to calculate the number of penetrations the enchantment can sustain, actual DR (including Fortify) is used to determine if armor has been penetrated. Fortify +5 Heavy Plate (DR 12) may take only 35 penetrations before becoming non- magical, and 40 penetrations before being ruined as armor, but it would take 35 attacks each doing at least 13 damage followed by 5 doing at least 8 each to do this! If the armor is destroyed as armor before an enchantment wears off (say, Light Leather with Deflect +5 cast on it), the enchantment is considered destroyed when the armor is destroyed. Magic such as the Repair spell will repair the enchantments on a damage suit of armor as well as fixing the mundane damages.
When calculating penetrations, only that individual layer of armor counts. If you are wearing a steel breastplate (DR 5) over Fortify +1 light leather (DR 2), you must take 8 points of damage for the light leather to be penetrated, but only 6 damage for the breastplate to be penetrated. Exception: Chainmail and its accompanying Cloth Armor should be treated as one layer for both simplicity and to prevent chainmail from rapidly losing the benefit of its cloth padding.
At no point in this process is PD or DR reduced (but see the various Optional Rules, below). Sealed armor is considered unsealed after it takes 10% of its Maximum Penetrations. Most high- tech sealed armor will have limited self-sealing capabilities; a single penetration is not enough to cause the armor to become unsealed. Note that this is cumulative with the unsealing effects of Flamers.
And yes, if an attack does Blow Through, excess damage is applied to the back of the armor piece. Truly destructive attacks can easily cause double penetrations. This is called an "exit wound."
Armor Repair
Damaged armor can be repaired. This requires appropriate skill (12+ in Armoury, or Leatherworking for leather armor) and materials (ranging from a needle, thread, and cloth patches to a full forge or machine shop). The cost to repair is 5% of the original cost plus the penetrations suffered vs. Maximum Penetrations, expressed as a percentage. After taking more than half of its possible penetrations, the cost is 20% of the original cost plus the percentage taken -- the armor is very badly damaged and needs a full rebuild. Cost assumes you are paying a professional to do the work -- if you do it yourself, cost of repair is halved (the cost is for materials expended). Note that after a certain point, armor can become so damage replacement is cheaper than repair. A Repair spell (p. M60) can be cast as well -- any armor having taken more than half of its Maximum Penetrations should be considered to have missing parts and give a penalty to skill. A penalty to cast the spell is a good justification for a hireling wizard to charge extra, if a GM so chooses. After all, the caster is taking an extra risk of failure or critical failure because of the damage taken.
Ultra Tech repair methods can also affect the cost of armor repair, at the GMs option. If armor is made from Living Metal (p. UT18) or Bioplas (p. UT17) it will slowly repair itself -- Living Metal at 1 penetration/hour and Bioplas at 1 penetration/6 hours. If the materials used in the armor are rare or the technology to repair it is expensive, the cost may increase. This applies to low tech and fantasy armor as well -- perhaps even higher skills (15+ or even 20+) are need to repair armors made from rare or magical materials. Cost will escalate as well -- but note that the base system already scales to make more expensive armor more expensive to fix. Armor that has been decorated (see optional rules, below), or armor of higher or lower quality, uses its increased (or for Cheap, reduced) cost to determine cost of repairs.
Example of armor repair: A heavy plate corselet costs $2300. It can suffer 40 penetrations and has taken 13. 13 is 32.5% of 40. The cost to repair the armor is $115 + $747.50 = $862.50. Plate is durable, but expensive! Had that same suit taken 21 penetrations, the cost would have been $460+$1207.50=$1667.50. Once the armor has taken more than 32 penetrations, it is actually cheaper to buy a new suit and scrap the old one for metal value (say, 5-10% of original cost). Of course, to get 32 penetration on this corselet requires 32 attacks doing 8 points of damage or more.
Wear, Tear, and Decoration
General wear and tear can damage armor. Armor that is not properly maintained (one hour a week by a skilled craftsman -- see Armor Repair, above) will suffer damage -- effectively, suffering the equivalent of penetrations. Armor that is being actively worn, or is just neglected, will suffer the equivalent of 1 penetration every two months unless it is being actively maintained. This represents accumulated wear on straps, minor breaks and tears, nicks, cuts, and scrapes of all kinds that eventually wear down the armor and require repairs. Penetrations suffered in this manner are treated normally for purposes of enchantment, repair, and optional rules such as DR reduction (see below).
GMs wishing to avoid the bookkeeping of penetrations but who wish to keep track of armor damage can use the wear and tear rule to keep PCs caring for their armor. After any battle in which a character was injured at least once, the armor can be assessed 1d6 penetrations. Modify this roll by -1 or -2 for a small skirmish or melee or by +1 (large battle) to +3 (desperate, huge battle). Penetrations can be assessed on a per-suit or per-location basis. After a Mass Combat, Armor Damage can be assessed normally (after determining the results on the Damage Table) or this simplified system can be used: apply any penalties to survival as a plus to the number of penetrations suffered.
Armor Decoration: Armor may be finely decorated, with precious metals, jewels, or just exceptionally fine construction. Well- decorated armor will cost more to purchase and to repair. Armor decoration is available in fine quality (4x cost) and Very Fine (20x cost, or more). These modifiers will multiply with those of armor quality. At a GM's option, fine decorations may give a +1 to reaction rolls and very fine decorations a +2. Naturally, decorated armor uses its decorated cost to determine cost of repairs . . .
Optional Rules
The following are optional rules that can be added onto the above system. Some of that add even more bookkeeping, and can change the dynamics of combat. All of them have been playtested, but a GM should exercise some caution before using them -- especially the PD reduction rules.
- Average Split DR: For armor types with different levels of protections against different attack types, average the DR and round down. For example, Chainmail with Cloth padding provides DR 4 against cutting or crushing attacks and DR 2 against impaling attacks 4 (cut) + 4 (crush) + 2 (imp)/3 = 3.33 rounded down to 3. Chainmail can therefore take (3+1)*5=20 penetrations. This tends to reduce the amount of damage it takes to destroy most "split DR" armors. GMs seeking more variation can multiply by the unrounded number, only rounding off the final number of penetrations -- for example, Chainmail could absorb up to 3.33 * 5 = 16.65 or 17 penetrations.
- Fragile Armor: While the armor damage systems works for most armor types, GMs may decide that certain armor types are especially fragile -- for example, Wood Slat or Cane Armor, or exotic types such as Antillian Glass Armor (see GURPS Conan p. 20). Armor determined to be so vulnerable will suffer double or triple penetrations from some or all attack types -- or, in the case of the glass armor, destroyed after a single penetration. Alternately, some armors can be damage normally but harder or easier to repair; simply double or half the cost to repair, respectively. Mail, for example, is fairly easy to repair -- replacing lost links is easier than replacing damaged scales or hammering gashes out of plate -- and can easily justify half repair cost. Some armors, such as the Straw Overcoat, can probably be repaired for free with access to appropriate materials.
- Multiple Penetrations: Under the base system, all weapons inflict penetrations equally well. GMs may feel that attacks from ultra-tech blasters or vicious axe swings should inflict more penetrations than a laser beam or arrow point.
Treat every full multiple of the DR that penetrates armor as an additional penetration. Damage Type multipliers other than Impaling are counted before determining total penetrations. For example, a suit of Reinforced Heavy Leather (DR 3) hit for 7 base cut (7-3 for DR, +50% for cut = 6) would suffer two penetrations. Had the blow only done 6 base cut (total damage 5) only one penetration would be inflicted. This allows large cutting or crushing attacks to tear large rents in armor, while focused impaling attacks still stave only small holes.
Another option is to rule that attacks that do more than 6d of damage do one penetration per 6d of base damage, if any penetrations are made. For example, a TL 9 Heavy Blaster (6dx3 damage) does 3 penetrations per hit, so long as 1 hit is done past DR. A GM can raise or lower the bar for certain weapons (say, Blasters or Flamers), all weapons (perhaps 3d?), or require that at least 1 hit get past DR for each penetration.
A further option is to make every 10 points of damage that exceeds DR count as a penetration, allowing for those high-damage attacks to fry armor as fast as it fries the wearer. Not that this option effectively makes all armor Ablative (GURPS Vehicles p.22).
- Cap Maximum Penetrations: Most TL 9+ armor have enough DR to make its destruction unlikely. A DR 80 Cybersuit will take 405 penetrations before becoming useless as armor. At that point, the wearer has taken at least 405 points of damage, making this (probably) irrelevant. A simple fix is to cap Maximum Penetrations -- any DR above 10 or 15 (for example) will not contribute to calculating Maximum Penetrations. This will lower the amount of penetrations needed to destroy a given piece of armor without making it any more vulnerable to penetration in the first place. The Maximum Penetrations Cap rule is recommended as the default for campaigns featuring TL6+ armor.
- Blunt Penetrations: Under the basic rules, blunt weapons can inflict penetrations -- minor tears, small punctures from spikes or flanges, deformation of the armor that does structural damage. However, some GMs may find this simplistic -- not all crushing attacks that injure the wearer will damage the armor -- or find the idea of a non-penetrating "penetration" unrealistic. Under this optional rule, non-bullet crushing attacks do not inflict penetrations. Instead, a penetration is inflicted for every "6" rolled on a crushing attack that penetrates DR. For example, DR 7 plate is hit for 3d of damage from a maul, with rolls of 6, 6, and 2. The wearer takes 7 points of damage, and the armor takes (1+1+0) 2 penetrations. This represents severe deformation of the armor that both does structural damage and requires repairs to keep the armor functional.
- DR Is Reduced By Damage: After a given piece of armor has suffered 10 penetrations, its DR is reduced by 1. Further penetrations do not reduce it any further. There is no minimum DR, since DR 1 armor will be destroyed after 10 penetrations, making this a non- issue.
Another option is to reduce DR by -1 for every 10 penetrations taken. Minimum DR is 1, although most armor will be destroyed before this point is reached.
A GM can also choose to base it as a flat percentage so DR declines as penetrations accumulate. Note that percentage systems mean that heavy armor rapidly loses DR while light armor stay fully functional until destroyed.
Ablative Armor, which loses 1 DR for every 10 hits that penetrates the armor, should suffer from both rules if a DR reducing optional rule is used, making it very vulnerable to repeated penetrations. Most Ablative Armor will reach 0 DR before it reaches its Maximum Penetrations, though, so the extra bookkeeping might not be worth it.
Armor that has had its DR reduced by damage is treated as "Cheap" (Editor's note: See "Chainmail . . . Why Bother?", coming next week) for purposes of sale value (but not for weight or repair cost) by the GM. This can lead to PCs "dumpster diving" in the hopes of purchasing high-quality armor on the cheap, or unscrupulous merchants selling cheap armor as good armor.
- PD Is Reduced By Damage: After a given piece of armor has suffered 10 penetrations, its PD is reduced by 1. Minimum PD is 0 -- armor can easily become unable to deflect blows effectively while still providing some DR. Torn and crumpled and holed armor can catch weapons that pristine armor would let glance off. Further penetrations do not reduce it any further. Armor that has had its PD reduced by damage is treated as "Cheap" (see above).
Percentage based PD reduction is also possible. Instead of reducing PD after a flat number of penetrations, PD is -1 for every 20% of Maximum Penetrations sustained. There is no minimum PD -- After 20% damage, even the heaviest armor can lose all PD while retaining some DR. On the downside, the lightest armors (light leather and cloth) lose all of their PD after two penetrations.
If DR reduction is also being used, PD can be reduced proportionally to DR per GURPS Vehicles, p. VE24.
- Penetrations Cause Permanent Damage: Once armor has been damage past a certain point it is often a write-off. The rules about already reflect this, but in some circumstances armor may be repaired anyway. Post-apocalypse survivors, stranded time travelers, adventures with unique and irreplaceable armor, may not have the option of buying new armor to replace old. Once armor has taken 80% or more of its Maximum Penetrations and been repaired, it loses 10% of its Maximum Penetrations. Heavy Plate (40 penetrations) would drop to 36 Maximum Penetrations after taking 32 or more penetrations and being repaired. This is applied only after repairs -- it would still take 40 penetrations to utterly ruin the plate in the example, but only 36 the next time. If the PD and or DR is reduced by damage due to other optional rules, use the original penetrations number to determine the actual PD. Note that accumulated damage can easily mean that the PD and/or DR of the armor is lowered permanently. This becomes a slippery slope -- the armor will be hit and penetrated more often, and less and less penetrations will be needed to cause further reductions.
Note that the Repair spell will eliminate such permanent damage; some high tech armors (especially those made of super- science materials like Living Metal) would be unlikely to suffer permanent damage.
- Critical Hits and Penetrations: GMs may wish to add armor damaging effects to the Critical Hit table -- or simply add such effects to existing rolls. For example, while Bypass All Armor criticals would inflict no penetrations (or inflict 1d6, representing a natural hit to a weak seam, sundering the armor -- GM's option), Double or Triple Normal Damage criticals could cause double or triple penetrations. Another option is to replace some Critical Hit Table entries with "Armor damage inflicted -- target's armor takes 1d6 penetrations."
- Field Repairs: PCs in a jam may need to fix their own armor, without access to the proper tools for the job. A lot of GM judgment is required on this -- without at least a hammer, never mind a forge and so on, you just are not going to be able to repair your steel breastplate. A good rule of thumb is that a skilled craftsperson (12+ in the appropriate skill - Armoury, or Leatherworking for leather armor) can repair 5% of the original Maximum Penetrations per point the skill roll is made by, to a maximum of 95% repaired. All penalties should be taken into account when determining the margin of success. Inadequate tools can make the difference between being able to do a passable job and doing a good job. GMs judgment is required to determine if a second attempt can be made. In some cases it should obvious that you can start over (rip out the stitches you put in the Cloth Armor and start over) and when you can't (You've hammered out the rent in the helm as best you could, but deforming it again to try again will hurt more than it helps). The amount of time for repairs can vary -- an armorer can repair Skill/2 penetrations per hour with the proper tools, minimum 1 hour.
* * *
Sources: GURPS Basic, GURPS Magic, GURPS Ultra Tech, GURPS Robots, GURPS Vehicles.
(Special thanks to Shawn A Fisher, Dan Howard, Bob Huss, and Sean Punch for numerous suggestions and to my players for testing these on their PC's armor.)
Article publication date: September 7, 2001
Copyright © 2001 by Steve Jackson Games. All rights reserved. Pyramid subscribers are permitted to read this article online, or download it and print out a single hardcopy for personal use. Copying this text to any other online system or BBS, or making more than one hardcopy, is strictly prohibited. So please don't. And if you encounter copies of this article elsewhere on the web, please report it to webmaster@sjgames.com.