This popped in my head when I saw this thread on the GURPS forum, and I decided to resurrect my long-dead blog for it (I originally planned to do so by hijacking it for things I’d worked out for the DF-ish setting I’ve been working on recently, but all that still needs some work and this was comparatively simple to make). As with the previous entries in this blog, this first part has all the calculations, justifications, and so forth - scroll down to Implementation for the final rules. This wouldn’t be a proper Overhaul if I didn’t overdo things, so these rules can also be used for designing cybernetic limbs or giant mecha. I feel I should preface this by stating I find it more appropriate to have power armor add to Basic Lift rather than directly to ST, with ST calculated from the new BL. If you prefer adding straight to ST, build the armor for someone with ST 10, then have the same bonus to ST apply to everyone. Under this system, the +25 lb BL power armor I’ll be using for examples here would instead just be a straight +5 ST.
When considering a system for building power armor statistics, it seems to me it would be appropriate to look at biology - or at least, biology as it works in GURPS. A standard GURPS human has ST 10 and is around 150 lb. A healthy human is typically around 30-40% skeletal muscle and 15% skeleton by weight - we’ll go with 30% for the muscle, for 45 lb and 22.5 lb, respectively. The reason we include the skeleton is because any muscle system needs some sort of scaffolding to work off of. Biotech suggests that the above skeleton could actually support up to ST 12. However, we’re working with an exoskeleton, which are typically less efficient than endoskeletons, so we’ll ignore that. ST scales with the cube root of weight, while BL scales with the square of ST, meaning our power armor’s BL is going to scale with the 2/3 power of muscle weight (as we would anticipate from the square-cube law).
From this, a theoretical suit of power armor made of living muscle and bone would be designed as follows. Take the BL bonus, cube it, take the square root, and finally divide by 2. This tells you how much muscle weight is needed - use half this value for the weight of the bone scaffolding. For +25 lb BL power armor made in this way, muscle weight would be 62.5 lb and bone weight would be 31.25 lb.
You may notice that the increase to BL is apparently insufficient to offset the weight of the exoskeleton. However, a properly designed suit of power armor supports its own weight, in the same way a human’s muscles and bone support his weight. Multiply the combined BL of character and power armor by 7.5 to determine the full weight - including that of the character, suit, and any carried gear - the combination can support. Any weight in excess of this counts as encumbrance; any weight less than this functionally gives the character something like an external payload. An otherwise-naked standard GURPS human (BL 20, weight 150 lb) wearing the above muscle suit would have a nominal comfortable weight of 337.5 lb, yet the combination would only weigh 243.75 lb, for a “free” payload of 93.75 lb.
Optionally, underweight character+armor combinations can actually make the character faster. Based on P=Fv (P=power, F=force, v=velocity), speed would scale linearly with the BL-to-weight ratio (BL should scale linearly with power). My Mass and Volume Overhaul had every +20% to Move correspond to a +1 to skills that are penalized based on encumbrance. I don’t feel this is appropriate for power armor, but a bonus to DX-based uses of Battlesuit skill wouldn’t be out of the question. Our naked man running around in a muscle suit would have a Move of 5*(45/243.75)/(20/150)=6.92, which I’d round up to Move 7. This is +40% to Move, so a bonus of +2 to Battlesuit skill could be justified. Optionally, if you feel the armor shouldn’t make the character absolutely faster, treat the boost as Enhanced Move (so it’s only available when sprinting) and Super Jump only.
Of course, an actual suit of power armor isn’t going to be made of meat. For such, you would divide the muscle weight from above by how much stronger the synthetic muscle is than human muscle. Looking up some current attempts at making synthetic muscle, I’m getting powers anywhere from 3x human muscle to 200x human muscle, meaning nearly any multiplier is justifiable. I’d go with 5x at TL9, 10x at TL10, 20x at TL 11, and 50x at TL 12. Our reference +25 lb BL power armor can thus reduce its muscle weight to a mere 6.25 lb at TL 10. As the muscles are ridiculously light, I suggest making them with fairly low density. For no appreciable size increase (so that armor is normal weight), an SM+0 battlesuit can give up to +35 lb BL at TL9, +60 lb BL at TL10, +90 lb BL at TL11, and +150 lb BL at TL12. Increasing volume allows this to improve - every +5% armor weight is +5% to MaxBL. Beyond BLx6 (x14.7 to muscle weight), you’re piloting a mecha rather than wearing a battlesuit!
(Realistically, BLx2 is probably the largest a “true” battlesuit can get, with a sort of transition between battlesuit and mecha from BLx2 to BLx6, but a hard cutoff works better for GURPS)
The scaffolding of an actual suit of power armor similarly isn’t going to be made of living bone. Steel seems likely, but is actually a fairly poor contender when it comes to weight, as living bone is roughly 5x stronger than steel. The strongest currently known material is graphene at around 200x stronger than steel (40x stronger than living bone). Diamondoid is essentially graphene, so that gives us our TL11 structural material. The most common titanium alloy, grade 5, is around 1.5x stronger than living bone, and is probably appropriate for what Spaceships calls Light Alloy (TL7). This doesn’t quite give us an SSR-linear progression, but it would probably work OK to use a divisor of 10 at TL9 (advanced metallic laminate), 20 at TL 10 (nanocomposite), 50 at TL 11 (diamondoid), and 100 at TL 12 (exotic metal laminate). Our reference +25 lb BL power armor can thus reduce its structural weight to a mere 1.5625 lb at TL10. This reduces the total weight of our reference power armor to a mere 7.8125 lb.
Not all power armor is created equal - many give different bonuses to Striking vs Lifting ST. You may designate extra pounds of BL that apply to only Striking or Lifting ST, at half normal weight for the muscles. For simplicity, assume the same volume as an equal weight of normal synthetic muscle. For the scaffolding, Striking ST needs more support than Lifting ST, for a 70/30 split there.
A suit of power armor consumes energy while powered up. Assume a suit of power armor outputs Watts equal to 5xBL. This is roughly what a human of comparable strength would output as useful energy if working at a rate that drained 1 FP every hour (say, rowing a boat at travel speed), which is probably a fair enough average for power armor in active use. How much energy input it requires is going to be a function of efficiency, which would scale by TL. lwcamp’s “Burninators” has such a scaling hidden in it - 30% at TL9, 50% at TL10, 70% at TL11, and 100% at TL12. That doesn’t sound too horrible, so we’ll go with it. To my knowledge, there’s no official energy content for UT power cells, so I’ll just pull the values from my rough Vehicles to Spaceships conversion. This means for E cells and larger (20+ lb), you’re looking at 2 kWh at TL9, 3 kWh at TL10, 5 kWh at TL11, and 7 kWh at TL12. D cells and smaller (5- lb) store half as much energy per pound; one assumes there’s some transitional effect in play with power cells between 5 and 20 lb. Sticking with E-cells and larger, and factoring in efficiencies (and scaling to SSR), that’s a net output of 700 Wh/lb at TL9, 1500 Wh/lb at TL10, 3000 Wh/lb at TL11, and finally 7000 Wh/lb at TL12. An E-cell lasts for 150/BL hours at TL9, 300/BL hours at TL10, 700/BL hours at TL11, and 1500/BL hours at TL12. Our +25 lb BL power armor would last 12 hours on an E-cell at TL10.
Once you’ve built the exoskeleton and determined what sort of power supply it needs, now you need to actually armor the thing. I suggest using the Armor Design articles from Pyramid to do so. Built-in accessories and similar modifications (Sealed, Waste Relief System, Air Tank, etc) are extremely common for battlesuits. Most battlesuits are designed so that the weight of the exoskeleton, armor, accessories, and the power supply work out to 7.5x the BL of the suit, so that it perfectly eliminates the encumbrance it creates.
The most common optional accessory for a battlesuit is likely biomedical sensors, in large part because the sensor system needed to detect and translate the user’s movements into those of the battlesuit can be easily modified to function as such. The price and weight of the default sensor system is included in the price of the muscles, modifying it to function as biomedical sensors is only $100.
All that’s left at this point is cost. The scaffold is probably around 5x the cost of the material (roughly something akin to Plate construction), and the armor and various accessories are already set from the books and articles. The problem is the synthetic muscle, which I have no good way of estimating an appropriate price for. I’m going to try a not-so-good way, however.
TL9 Powered Combat Armor gives +10 to Striking and Lifting ST, or +60 lb BL in my system. Its synthetic muscles therefore weigh 18.4 lb. It has DR 70 on the Chest and Skull, DR 50 elsewhere. Assuming +20% to weight due to increased bulk, and assuming titanium nanocomposite with plate construction, the armor portion should weigh around 138.3 lb and cost $172875. The suit also has biomedical sensors ($200, 0.2 lb), a waste-relief system ($500, 1 lb), tactical ESM ($1000, 2 lb), a filter mask ($150, 0.5 lb), GPS, hearing protection ($50), a small radio ($50, 0.05 lb), a small laser comm ($400, 0.5 lb), hyperspectral sensors ($2000, 0.6 lb), and a large air tank ($200, 10 lb). It is sealed ($128.10) with vacuum support and climate control (LSS; $1000, 2 lb) and IR cloaking ($1921.5, 76.86 lb). Altogether, that’s $180,294.60 and 250.41 lb, with only the weight of the synthetic muscles in play. Unfortunately, even without accounting for the price of the synthetic muscles, it’s over twice as expensive and around 85 lb heavier than the armor in UT. Of course, Powered Combat Armor isn’t made of titanium nanocomposite (the first armor design Pyramid article was years away when UT was written), but more likely whatever TL9 combat hardsuits are made of. Including a helmet scaled up to DR 50/30, those would be around $14050 and 41 lb without all the accessories. That’s around $350/lb and a W of 0.053 when already taking into account the effects of construction. Made of that wonder material, the armor portion of our battlesuit would be 76.35 lb and $26723.13, for a total of $34142.73 and 188.46 lb. Interestingly, not increasing surface area by 20% would give a result of around 163 lb, almost identical to the 165 lb in UT. If we leave out the surface area boost, we’re looking at $29368.625 and 163 lb. That means the synthetic muscles cost $60631.375, which we’ll round down to $3000/lb. That’s for TL9 synthetic muscle. TL10 synthetic muscle is $7000/lb, TL11 synthetic muscle is $15,000/lb, and TL12 synthetic muscle is $30,000/lb - but as each +1 to TL is around -2 SSR to weight, this means synthetic muscles of equal BL cost roughly the same at each TL. To allow lower TL materials to be competitive at higher TL, reduce price/lb by -1 SSR per TL after introduction. Because muscle weight will almost always be a small fraction of a battlesuit’s total weight, expect battlesuits to have the lowest TL muscles necessary to get the desired BL for their volume.
Effect of TL: Many of the equations below include a value, T, which is based on the TL of the material/device. Note a single battlesuit can have different parts with a different value for T - a TL12 battlesuit might use cheaper TL10 synthetic muscle, a titanium alloy scaffold, and a TL12 power supply. T is 1 for TL9, 0.5 for TL10, 0.2 for TL11, and 0.1 for TL12.
BL vs ST: The below designs battlesuits as having their own BL score. When worn, add the BL of the character and that of the battlesuit to determine actual BL. To calculate effective ST, multiply the combined BL by 5 and take the square root.
+ST: Optionally, if you prefer your battlesuits function like those in UT (simply adding to ST), design them as though they were for a character with ST 10. A +5 ST battlesuit is designed as +25 lb BL, as a character with ST 10 (BL 20 lb) would need +25 lb BL to increase to ST 15 (BL 45 lb).
Muscle: The first step for designing your battlesuit is to set how much it increases BL. Once you have done so, you can calculate muscle weight based on the TL of the battlesuit. To determine weight in lb, use the following equation: (T/10)*S^(3/2), where S is the suit’s BL.
Volume: A strong battlesuit may make a character functionally larger, making the suit more expensive to armor. The maximum bonus to BL is +35 lb BL at TL9, +60 lb BL at TL10, +90 lb BL at TL11, and +150 lb BL at TL12. Every +5% to BL beyond this is +5% to armor weight, to a maximum of +500%. Any larger than this, you are piloting a mecha rather than wearing a battlesuit.
Striking vs Lifting: Optionally, you may add additional muscle mass that only adds to Striking ST or Lifting ST. To do so, design a musculature with the desired total BL bonus. Subtract the weight of your base musculature, halve the remainder, and add it to the weight of your current musculature to determine the actual weight. For purposes of Volume, above, treat such specialized musculature as the same volume as an equal weight of general synthetic muscle.
Price: TL9 synthetic muscle is $3000/lb, TL10 is $7000/lb, TL11 is $15000/lb, and TL12 is $30000/lb. A given synthetic muscle material is -2 SSR per +1 TL after introduction (TL9 synthetic muscle costs $1500/lb at TL10, $700/lb at TL11, and $300/lb at TL12).
Scaffold: The scaffold represents the rigid bars the muscles attach to. To determine its weight in lb, use the following equation: (T/40)*S^(2/3). TL9 is for titanium nanocomposite, TL10 is for advanced polymer nanocomposite, TL11 is for diamondoid, and TL12 is for hyperdense.
Striking vs Lifting: If you add additional muscle mass that only adds to Striking ST or Lifting ST, it still needs support. Striking-only muscle requires 70% as much support as normal muscle, Lifting-only requires 30% as much support as normal muscle.
Lower Tech: Note you can use lower tech materials here if desired (or if you feel the above is too generous). To do so, divide tensile yield strength of the material (in MPA) by its density (in g/cc). Divide 1300 by this number to find T. For example, grade 5 titanium alloy has a yield strength of 880 MPA and a density of 4.43 g/cc, for a yield/density of around 200 and a T of 6.5.
Price: Titanium nanocomposite is $1250/lb ($300/lb at TL10+), advanced polymer nanocomposite is $250/lb ($125/lb at TL11+), diamondoid is $250/lb ($125/lb at TL12), and hyperdense is $250/lb. For other materials, assume the price is the same as plate armor of equal weight (so, 5x the nominal price per pound).
Power: A battlesuit requires a power supply to function. To determine how many hours an E cell will last, use the following equation: 150/(T*S).
Striking vs Lifting: For battlesuits with higher Striking or Lifting BL, count the bonus at half value.
Power Plant: Some battlesuit designs might have a built in power plant or connect to some other power-generating device rather than relying on energy cells. Such a power plant needs a usable energy output of 5*S Watts.
Control: Controlling a battlesuit requires a series of built-in sensors that detect how the user is attempting to move so the suit can move in the same fashion. These are included in the price of the synthetic muscles. However, battlesuits also require a Complexity 1 program to run diagnostics on the suit and prevent unsafe movements, so at a minimum the suit must have an integral Complexity 1 computer, typically imbedded in the Chest. Most have computers more advanced than this to run other programs as well.
Armor: Battlesuits other than exoskeletons are usually heavily armored. Such armor is typically built-in, but can be designed to be attached instead as a feature (no effect on cost/weight). Design battlesuit armor the same way you design armor for a person of the same height.
Scaffolding: Armored battlesuits may not require separate scaffolding, as the muscles can attach to the armor itself. If the armor weighs at least 4x as much as scaffolding of the same material would, you may ignore the need for scaffolding. If the armor has different DR values for the arms, legs, and torso, work out if it would be heavy enough if it were all the same DR as the lowest value.
Accessories: Any and all standard armor accessories are available for battlesuits, and in fact are more prevalent amongst them than amongst lesser armors. Biomedical scanners can be added for no increase in weight and only $100, replacing the normal sensors used for controlling the suit.
Yo Dawg, I Heard You Like Battlesuits…: Mathematically, it is more efficient by the above rules to design a weak battlesuit, put a weak battlesuit on top of that, and a weak battlesuit on top of that, rather than simply designing a single strong battlesuit. This is a limitation of the model, not a legitimate way to do the design process! If you find this limitation problematic, build a suit that has the same BL as the character, then build a suit that has the desired total BL. The actual weight of the suit is the difference between the two.
Battlesuit Weight: Battlesuits typically weigh far less than they could support. A character in a battlesuit can support weight equal to 7.5xBL before encumbrance can start to come into play. Subtract this number from the character’s full weight (that is, weight of character, battlesuit, and anything carried) before calculating encumbrance.
Underweight: If the above is a negative number, the battlesuit has power to spare, making it faster. Divide the current BL-to-weight ratio by that of the character when he is naked. Multiply Land Move by the result. Every +20% to Move also gives a +1 to DX-based Battlesuit skill (including for purposes of determining maximum skill level for other skills). The maximum boost is x2 Move and +5 Battlesuit, but use the full calculated multiplier when jumping.
Partial Battlesuit: Instead of a full battlesuit, you can design one that only covers one limb. Determine the needed weight for musculature and scaffolding for a full battlesuit of the desired BL. If this is no more than 50% of the character’s BL, each full arm+hand is 15% of this weight, each full leg+foot is 20%. If it is more than 50% of the character’s BL, each limb is 25% of this weight, with power arms covering part of the chest, power legs covering part of the abdomen.
Arm ST vs Leg ST: A battlesuit can be designed to have boosted Arm or Leg ST, rather than (or in addition to) general boosted Striking/Lifting ST. Designing this basically follows the rules for the Partial Battlesuit, above. Arms don’t have to be boosted symmetrically, but legs do. Arm ST determines damage from hand weapons and how much you can lift at a time, Leg ST determines damage from kicks and encumbrance (which can influence movement and jumping).
Scaffolding as Armor: It is possible - sometimes probable - to strike the scaffold in combat. Most crushing and cutting attacks will always strike the scaffold, and it gives 1/6 protection against impaling, piercing, and tight-beam burning. More diffuse attack types (like burning and corrosion) ignore the scaffold. When struck, treat the scaffold as giving DR equivalent to plate armor of 4x the weight. Optionally, if the scaffold is struck and its DR is penetrated, roll against HT, or HT-5 if the penetrating attack dealt damage of at least twice the scaffold’s DR. On a Failure, that section of scaffolding is damaged, halving the BL of the affected limb until Minor Repairs have been performed. On a Failure by 5 or more, or any Critical Failure, that section of scaffolding is broken, crippling the affected limb until Major Repairs have been performed. Damaged/destroyed Chest scaffolding affects one arm, while damaged/destroyed Abdomen scaffolding affects one leg (in either case, decide randomly). Note the scaffold doesn’t extend to the head.
Armor as Scaffolding: As a corollary to the above, armor of sufficient strength can replace scaffolding, as the synthetic muscles simply attach to the armor rather than a dedicated scaffold. Armor must be 4x the weight of the necessary scaffolding of the same material to qualify. If also using Scaffolding as Armor and allowing for damage to the scaffold, crushing and cutting attacks that penetrate the armor’s DR can break the scaffolding as normal, and impaling/piercing/tight-beam burning attacks have a 1/6 chance of being able to have such an effect.
Endoskeleton: A battlesuit can be designed to have the scaffolding on the inside, typically right up against the wearer. This is more efficient - the scaffolding is only 20% normal weight. This is actually a bit more difficult to design - scaffolding is a net 50% normal cost. For balance, assume this option isn’t available unless Armor as Scaffolding is available. If allowing for damage to the scaffold, an endoskeleton’s musculature is susceptible to damage - while it is too diffuse to be affected by impaling, piercing, and tight-beam burning, other attacks will damage it normally. The musculature has total HP equal to 6 times the cube root of weight in lb, and limbs are crippled as normal for a character (damage to the Torso can be ignored). Endoskeleton battlesuits are easier to conceal than exoskeleton ones, so a lower LC may be appropriate.
Cybernetics: Instead of a worn suit, the same design process can be used to replace missing limbs. Use an endoskeleton scaffold (see above) even if such are unavailable for battlesuits. Determine the needed weight for musculature and scaffolding for a full battlesuit of the desired BL. If this is no more than 1.5x the BL of the character, each full arm+hand is 15% of this weight, each full leg+foot is 20%. If endoskeleton battlesuits are available, you may combine a cybernetic limb with a partial battlesuit to exceed the 1.5x BL limit. In all cases, the cybernetic limb uses only its own BL to determine ST. Each cybernetic arm requires a C2 program to control, while one or two cybernetic legs require a single C1 program to control.
Mecha: Instead of a worn suit, the same design process can be used to design a piloted mecha. Minimum size for a mecha is x6 armor weight, which corresponds to x2.45 to height (between +2 and +3 to SM). Use an endoskeleton scaffold (see above) even if such are unavailable for battlesuits. A mecha uses only its own BL, as the pilot is unable to contribute. A single C3 program can fully control a mecha, run diagnostics, and so forth.
Sight: While battlesuits can get away with a visored helmet (or, technically, no helmet at all), mecha typically require a video camera wired to an internal screen (or the HUD of the character’s helmet). Any of the cameras from UT will work, but note unless the system is capable of 3D recording and displays, the character will function as though he had the One Eye disadvantage.
Speed: For mecha lighter than 7.5xBL, divide weight by BL and multiply by 1.25 to determine Move. Optionally, apply +(Move-5) to Hnd. For mecha heavier than 7.5xBL, treat as having Move 5 and count weight above 7.5xBL as encumbrance.
Controls: A standard control station for a mecha is a cramped seat with hand (and possibly head and foot) controls, and costs $1000. Some mecha instead have a special supported bodysuit that allows the character to move around, his movements replicated by the mecha (and with safe force-feedback from the mecha). This allows the character to control the mecha with Battlesuit skill, and reduces the Complexity of the controlling program to C1. Such bodysuits cost $3000. A mecha can also be designed to use a neural interface instead of normal controls. Such a setup requires some means of interface (such as a neural interface implant in the pilot), but reduces the cost of the needed seating to only $100.
Optionally, a character controlling a mecha with Battlesuit skill suffers a penalty equal to the difference in SM between the character and the mecha, which can be negated with a per-SM Perk. Without the Perk, simply raising Complexity of the controlling program back to C3 will negate the penalty.
Hydraulics: A mecha that is controlled using a supported bodysuit can be designed to integrate that character’s strength, allowing him to contribute to BL. The additional musculature that allows this is at 1/10th normal weight. Note this usually isn’t worthwhile unless the character is abnormally strong or the mecha is particularly weak.
Example: Let’s say we want to design a battlesuit at TL10 that will give an ST 10 character a net Striking ST 15, Lifting ST 20. That means general BL is going from 20 to 45, while Lifting BL is going from 20 to 80. The +25 lb BL general suit has (0.5/10)*25^(3/2)=6.25 lb of TL10 synthetic muscle and (0.5/40)*25^(3/2)=1.56 lb of advanced polymer nanocomposite scaffolding. A +60 lb BL general suit would instead have 23.24 lb of TL10 synthetic muscle and 5.81 lb of advanced polymer nanocomposite scaffolding. That would be +16.99 lb muscle and +4.25 lb scaffolding, but as this is Lifting BL only, the additional muscle weight is halved to 8.5 lb, and the additional scaffolding weight is reduced to 30%, or 1.275 lb. Total weight is therefore 14.75 lb TL10 synthetic muscle ($22125) and 2.835 lb advanced polymer nanocomposite scaffolding ($708.75). With a 150 lb pilot, that’s a total of 167.59 lb, leaving us with up to 432.41 lb of additional payload before we need to even worry about encumbrance.
A standard 20 lb E-cell will power such a battlesuit for (150/(0.5*42.5))=7.06 hours. If we instead wanted a dedicated power plant, it would need an output of (5*42.5)=212.5 W. We’ll want to include some sort of computer - we’ll go with a Hardened Tiny Computer (C5, 2A/20 hr, $100, 0.1 lb). For armor, typical threats are going to be piercing (bullets) or burning (lasers), so we’ll cover it in bioplas. That’s MaxDR 138/46 for the Skull/Chest, 92/30 for everywhere else. We’ll go with an optimized fabric bioplas suit of 135/90 (45/30 against everything but pi/burn), which is 10.773 lb for the Skull/Chest, 15.876 lb for everywhere else, and thus 26.65 lb total. Cost would be $31980, but we’ll have 1/6 protection on the Face be transparent (so the wearer isn’t blind), which boosts cost by $75.60, to $32055.60.
As for accessories, we’ll want Sealed ($106.75), a waste relief system ($500, 1 lb), biomedical sensors ($100), a personal radar/ladar detector ($50, 0.5 lb), trauma maintenance ($2000), a large air tank ($200, 10 lb), an extended life support system ($2000, 1 lb, 1C/18 hours), a tiny radio ($50, 0.05 lb), a filter ($100), a provisions dispenser ($50, 1 lb), hearing protection ($50), and a hyperspectral HUD ($2000, 0.6 lb). None of the accessories burn through energy quickly enough to make a real impact on endurance, so it will stay at 7 hours per E cell.
All told, after rounding to 2 significant figures, we’re looking at $62,000 and 59 lb. Counting our 150 lb wearer, that’s a total weight of 208 lb out of an expected 600 lb. Assuming less than 92 lb of gear (including the power cell and any backups), the character will have Movex2 while within the suit, and +5 to DX-based Battlesuit skill. His chest and skull have DR 135 against pi/burn (protecting from a point defense laser, anti material rifles firing APHC, or sniper railguns) and DR 45 against everything else (protecting from a gatling pulse laser). Everywhere else is DR 45 against pi/burn (protecting from a laser rifle, assault carbine firing APHC, or a gauss PDW) and DR 15 against everything else (protecting from a survival pulse laser).