Plasma Guns, Re-Energized!

Sup everybody! It's GURPS Day so it's time to roll out some tasty GURPS flavored content for ya! 

I've always been a rules tweaker and have had countless ideas brewing in my noggin for a while and seeing the endless waves of new content that GURPS fans have pumped out every Thursday has long since inspired me to publish them. But despite this I've just sat on the idea. I just procrastinated, made up excuses to be lazy and sat on it....

But not anymore!

About a year and a half ago I made a post where I broke down how to use David's Blaster and laser design article to stat up custom plasma weapons. Today what I bring you what pretty much amounts to an vastly updated and improved  version (though this version leaves off Plasma Flamers). This version builds on that old post, fixes a few mistakes I made and throw in a whole slue of extra options to maximize your customization options!   
Well with that, I bring you.....

Plasma Guns, Re-Energized!

While GURPS Ultra-Tech gave us a good range of futuristic weapons to play with, each type of weapons generally only got a handful of examples to represent them and only a few had examples of a higher tech level versions. This, along with the fact that no info was given on how to stat custom weapons meant that GURPS players who wanted to do scifi campaigns had to make the most of a what little options they had to play with or just stick to conventional guns and try and up tech level the load of guns listed in High-Tech. 

Then came November of 2011 and the great and powerful GURPS gods delivered us Pyramid 3/37 Tech and Toys 2 and it was good and the players and GM's did sing its praises. Key among its positive respounce was David L. Pulver article, Eidetic Memoery: Blaster and Laser Design which was the first time that the general GURPS playing public got to see how GURPS stated its energy weapons... 

Well almost all of them.  Among the energy weapon types left off were the plasma weapons, flamers and plasma guns. This saddened me a tad since plasma gun type weapons are some of my favorite scifi weapons to have in my campaigns. 

So, given my tendencies to take apart and rebuild rules for tech I endeavored to see if I could figure out how plasma guns were stated and after much crunching and headaches... I finally figured it out!

Below is how to amend the Blaster and Laser Design article (which you will need to make full use of these options) to let you design high-energy ionized goodness. Also along the yeah I throw in a few optional rules that I use that I think add a little more character to a weapon. I also give an example how to build a plasma pistol to show you how it works. 

Tech Level 
Plasma guns are available starting at TL10^. At TL11^+ plasma guns become more powerful and become know as fusion guns.

Example: Lets build a TL10 plasma gun. Let's make it a pistol since even in the future most people are going to be carrying them over other types of guns in most circumstances. This plasma pistol will be used as a base line example of what a plasma pistol should be in the setting, much like a Beretta M9 or 1911 does today. Lets call it the Macrotech PG-108, a 5.4kJ weapon with a 1.3mm aperture that while doesn't do anything revolutionary, is well established as a proven and reliable weapon that has been adopted by many nations and colonies military. Outside of being a plasma weapon, this will not incorporate any superscience  and to maintain compatibility with the guns listed in Ultra-Tech I will not be using any of my house rules (save two very minor ones) in its design though here and there I will show hypothetical examples using my optional rules to demonstrative them better.

Beam 
Plasma guns fire a toroid bolt of super heated, ionized matter at super sonic velocity dumping so much energy onto the target that the matter located at the point of incident violently explodes! It inflicts burning damage with a (2) armor divisor and has the explosive and surge damage modifiers.  

Example: And of course it will be a plasma gun.  

Focal Array 
 Realistically this should always be medium (×1), anything that would boost the plasma bolts range would also increase its damage and the energy needed to fire it (particle beam weapons also should follow this). Of course plasma weapons are already boarder line "rubber science" so there's no harm in going full on rubber.

Example: I'm going to follow my above suggestion and  give the PG-108 a medium focal array. 

Generator 
I always felt that the options listed in the article to be a little too limiting and the fact that both semi and light automatic both had the same weight modifier just strike me as weird. To amend this, I came up with two potential fixes, one that stays close to RAW but just expands the options  a bit (and is somewhat based on numbers that seemed to have used to stat at lest some of the weapons in Ultra-Tech) and another that replaces RAW completely but gives more granularity.

Option 1: Near RAW

• 1 for single shot.
• 1.25 for semi-automatic.
• 1.5 for light automatic. 
• 2 for heavy automatic.
• 4 for Gatling.
  

Option 2: There be house rules here
Realistically the weapons power supply and cooling systems should scale directly with the weapons ROF. This option gives a little more detail and while it wont give results that are a 100% match to RAW, they do get pretty close. 

• Figure G as 1+(ROF/20). If you want a weapon with a ROF less then 1 G becomes 0.5 if the weapon can only fire once every 2 turns or lower. 
• If you use this option and want to make a Gatling plasma weapon then the extra barrels should add extra weight. Multiply the weapons weight by 1.3+(0.3×number of barrels).

Example: Since we're building a pistol a ROF of 3 is fine so we choose a semi automatic generator.

Damage Dice
Plasma guns, like pulsars are more energy efficient then other beam weapons, weighing half as much for a given amount of damage.  

Example: Since the PG-108 is just as efficient as a pulsar, 7d worth of damage works about right since a 8d pistol would be pretty heavy for a base line pistol at TL10^ and 6d would make the pistol a little to light as well. 

Empty Weight
E is 6.

Note: Plasma gun weight are divided by 2 at TL11^ (Ultra-Tech calls TL11^ plasma weapons "fusion weapons"). Note while not official yet, based on forum posts by David it seems that a TL12^ plasma guns weight would be divided by 4.

Optional Rules

Heavier or lighter barrels
This optional rule let you give the weapon either a heavier, more heat resistant barrel along with more robust cooling systems increasing the weapons sustained fire rate but making it heavier or giving it a lighter barrel and reduced cooling to reduce weight but at the cost of its ability to sustain fire.

• If you use this optional rule, amend the empty weight formula to read (D×S/E)^3×F×G×B
• If you use a heavy barrel B is 1.5.
• If you use a light Barrel B is 0.75.
  

Example: The PG-108 does 7d of damage, is non-superscience, has a semi automatic generator and medium barrel giving it a empty weight of (7×1/6)^3×1.25×1 or 1.98lbs which we round up to 2lbs.

 For added detail, if you were going to use optional rule number 2 for figuring G, this gives a G of  1+(3/20) or 1.15. The empty weight for our weapon would then be (8×1/6)^3×1.15×1 which gives us 1.8lbs.

Or if you wanted to make a light machine plasma gun  with these optional rules with say 12d worth of damage, ROF of 16 (giving a G of 1.8), a medium length heavy barrel it wound weigh (12×1/6)^3×1.8×1×1.5 or 21.6lbs which we would round up to 22lbs. 

Configuration 
Nothing new here outside of the fact that plasma gun probably wouldn't work good as "beamers" do to their recoil.

Example: Our PG-108 plasma pistol is, big surprise, a pistol!

Damage
Plasma gun have an armor divisor of (2) and do burning (NOT tight-beam burning damage) explosive damage with the surge modifier.  

Example: The PG-108 is a plasma gun with 7d worth of damage. This is recorded as 7d(2) burn ex sur.

Accuracy

• Pistols have an Acc of 4.
• Rifles have an Acc of 8.
• Cannons  have an Acc of 12. 
  

Optional Rules
If you want a little more variation in Acc between plasma weapons of the same class but different sizes like with modern guns  (such as making a difference between a plasma carbine and full on rifle) try 4× cubed root of the weapons empty weight (before any weight modifiers from options such as making the weapons Rugged) to figure its Acc.

Example: Since our example weapon is a pistol, by RAW it has a Acc of 4. Using my optional rule it still has an Acc of 4 (4×1.4^(1/3) is 4.47 which rounds down to 4).

Range
1/2D Range (Yards) = D×50×Rf
Max Range (Yards)= 1/2D Range×3

Optional Rules
While the technobabble used to describe how plasma guns work in Ultra-Tech might not be practical (a laser powerful enough to burn a hole in the atmosphere is powerful enough to be used as a weapon its self)  it may be possible to get some range out of a "realistic" plasma weapon by using a powerful Z-pinch to create the plasma then form it into a torrid (think something like a smoke ring), siphon off some of the plasma to create a sacrificial "trail head" pulse that is launch ahead of the main bolt to blast some of the air out of the way and then launch the bolt a super high velocity. However, even if this works, the range is probably not going to be so great. For some  harsh realism, at TL10^ 1/2D range should be D×6 and a max range 1.15 that, at TL11^ 1/2D range should be D×12 and max range is 1.15 that and at TL12^ 1/2D range becomes D×36 and max range being 1.5 times that.

Example: With a damage of 7d and a Rf of 1 our example pistol has a 1/2D Range of 7×50×1 or 350yards and a max Range of 350×3 or 1,050 yards. If using the optional harsh realism rules, as a TL10^ weapon its 1/2D Range becomes 7×6 or 42 yards and a Max Range of  42×1.15 or 48.3, rounded down to 48 yards.

Rate of Fire
If using my optional rules for figuring a plasma guns beam generator weight modifier  the semi-RAW option a Gatling  generator has a ROF between 21 and 40. If using my more detailed house rule option then a Gatling can have any ROF you choose but a ROF of between 10 and 12 times the number of barrels is reasonable.

Example: We already choose a ROF of 3, so our example pistol has a ROF of 3. Logic! 

Shots
While plasma gun don't use power cells per se, instead using self contained "power cartridges" that hold a non-rechargeable power cell and a bit of hydrogen, they are effectively just "reskinned " power cells and weigh and cost the same amount. I would imagine that the magazine the power cartridges are in is a sealed, disposable package. 

• A TL10^ cell holds 6,750.
• A TL11^ cell holds 16,875
• By this logic a TL12^ cell should hold 42,187.5.
  

Optional Rules
The way number of shots increase as TL increases for plasma guns are... weird. For a given amount of damage, TL11^ plasma weapons only hold  2.5× more shots then a TL10^ version. This a problem since most energy weapons power cells quadruple their energy destiny every TL increase and the weapons themselves double in efficiency the TL after their introduction. This leads to a 8× increase in number shots for given level of damage the first TL after a weapons introduction and a 4× every TL after. So why do plasma weapons seem to get shafted here? 

Well, I got a theory. 

It seems that plasma gun were stated up before the standard of having a 4× increase in power cell energy density was established. If you look at page 285 of the Basic Set it shows how much longer higher TL energy systems would power any electronics a suit of armor has and its a much more modest increase. A TL11 system only lasts 1.25× longer then a TL10 one. If you take into account the doubling of efficiency energy weapons gets when it advances a TL that leaves you with... you guess it... a 2.5× increase. This isn't the only place in Ultra-Tech that used that earlier progression either. Just take a look at the TL 9 and 10 power armor (which also leads to the Murphy where despite having the same type of power cells, the much larger TL9 combat walker actually has a longer operating duration then the TL9 power armor!). 

So now that I got that long winded explanation out of the way, this optional rule just updates how many extra shots you get at TL11^ and 12^ to better match the progression the other energy weapons. 

• A TL10^ cell holds 6,750.
• A TL11^ cell holds 54,000.
  A TL12^ cell holds 216,00. 

 Example: We want out pistol to have a good number of shots but don't want it to be encumbered by an oversized magazine. We choose a single C cell sized magazine and with the gun being TL10^ and having 7d worth damage gives 6,750/7^3 or 19.7 shots with we round up to 20 shots. 


Reloading Time
While this might be a borderline house territory here but since the power cells that plasma guns use are actually suppose to be magazines that basically hold plasma bullets then I'd rule that no matter how many cells you use to power a plasma gun they count as a single magazine for the purposes of determining how long it takes to reload (basically so long as the total weight of the cells are less then a D cell then it should take no more then 3 seconds to change them out). Hell, for the matter it should be the same for all energy weapons! All the power cells a weapons use should be packed together like a laptops battery pack since who'd buy a laser pistol if you had to pop out all the cells individual in the middle of a battle like you were changing Duracell's in a friggin' TV remote?! 

Example: Since the PG-108 only uses 1 C cell magazine its reload time is (3).  

Weight

Example: The PG-108's empty weight was 2lbs. Its "power cells" are built in; with a single C cell magazine that weights 0.5lbs so its loaded weight is 2.5lbs. Its weight is recorded as 2.5/1C.

Strength Requirement
The formula used in the original article is a problem for us on two levels. On one, unlike most energy weapons plasma guns have felt recoil which the articles formula doesn't take into account. Also, the formula in general is... odd. It does not look anything like the actual formula to figure a weapons Strength Requirement and while it gets decent results when building small arms.... it gives very wrong results when trying to stat large scale energy weapons (a 250lbs auto cannon with recoil has a ST of 28 while a 250lbs recoiless laser cannon ends up with a ST of 38!).

Now, after a dangerous and bold infiltration of Warehouse 23 where many bothan spies lost their lives I was able to gleam a look at the actual formula used to figure a weapons Strength Requirement. However... since there has been absolutely no hints of how the formula works that I've found hidden away on the forums or anyway of really reverse engineering the formula without using a good deal of luck or a ridiculously high Mathematics (Applied) skill so it's unfortunately against my policy to release said formula so I gotta get clever here to have a complete rules break down. 

• If building a mounted plasma gun look up your weapons empty weight on the chart below, if its weight falls between two values use the higher one. From there look across to the P-Pistol column, that is your  mounted weapons ST. Note a M next to it on the weapons stat line.
  

• If building a plasma pistol look up your weapons loaded weight on the chart below, if its weight falls between two values use the higher one. From there look across to the P-Pistol column, that is your pistols ST.

• If building a plasma rifle look up your weapons loaded weight on the chart below, if its weight falls between two values use the higher one. From there look across to the P-Rifle column, that is your  mounted weapons ST. Note a † next to it on the weapons stat line.

 

Weapons Weight	P-Pistol	P-Rifle
0.1	4	3
0.2	5	3
0.5	6	4
1	7	5
2	8	6
3	9	7
5	10	7
6	11	8
7	11	8
8	12	8
10	12	9
13	13	9
14	14	10
17	14	10
18	14	10
20	15	10
24	15	11
27	16	11
29	16	11
30	16	12
36	17	12
39	17	12
40	18	12
48	18	13
55	19	13
58	19	14
60	19	14

Annnd, since I'm feeling generous, here's a corrected chart for recoiless energy weapons like laser or particle beams.

• If building a mounted energy weapon you can ignore the required strength stat! So long as whatever its mounted to is strong enough to hold it, it require no more ST to brace then a radar mast of the same mass.

• If building a energy pistol look up your weapons loaded weight on the chart below, if its weight falls between two values use the higher one. From there look across to the L-Pistol column, that is your pistols ST.

• If building a energy rifle look up your weapons loaded weight on the chart below, if its weight falls between two values use the higher one. From there look across to the L-Rifle column, that is your  mounted weapons ST. Note a † next to it on the weapons stat line.





Weapons Weight	L-Pistol	L-Rifle
0.1	3	2
0.2	4	3
0.5	5	3
1	6	5
2	7	5
3	8	6
5	9	6
6	9	7
7	10	7
8	10	7
10	10	7
13	11	8
14	11	8
17	12	8
18	12	9
20	12	9
24	13	9
27	13	9
29	14	10
30	14	10
36	14	10
39	15	10
40	15	10
48	15	11
55	16	11
58	16	11
60	16	12

 

 

Sorry about the crappy looking tables >.> I'm really new to HTML and I probably warrant the skill incompetence quirk when it comes to coding... This hot mess took me two days to get even looking this legible!

Example: Our pistol has an loaded weight of2.5lbs Looking at the weight column we find 2.5lbs is between 2 and 3lbs so we round up to 3lb. We then look across to the P-Pistol column and see that it has a Required ST of  9.

Bulk
As with Required Strength, the formula used for determining Bulk given in the article is wrong. While I do not know the exact formula used by Hans and David I do know its logarithmic in scale and is based on the weapons weight, length and then a "eyeballed" modifier based on the weapons type and form factors. That being said, unlike the Required Strength formula this one, in so far as I can tell, gets close enough to the actual rules that it for the most part works. 
 

Example: The PG-108 has a pistol form factor and weights 2.5lbs giving it a bulk of square root (2.5)×1.25 or 1.98 which we round up to -2. 
 

Recoil
Plasma guns have a Rcl of 2.   
 

Cost 
Bc is $2,000. 
 

Optional Rules 
If using my more detailed rules for figuring G under empty weight then use the same value as G for Gc.
 

Also to bring up Ultra-Tech weapons to High-Tech's standards (and the closer we can get Ultra-Tech to High-Tech's standards the better heh) the cost of the weapons power cell should follow after the weapons empty cost. This is the one of  the two only house rules I will use on the PG-108's final stat line.

Example: With an empty weight of  2lbs and a ROF of 3 our plasma pistol costs $2,000×2×1 (for being semi automatic) giving a cost of $4,000. If using my optional rules then cost is figured as $2,000×1.8×1.15 (for a ROF of 3) which gives a cost of $4,140.  

Legality Class
A plasma guns base LC is 3. 
 

Example: The PG-108 is a plasma gun that weights under 5lbs so its LC is 3.  
 

Accessories 
 

Example: As a baseline gun example the PG-108 won't be coming with an bells or whistles.

Skill Required

Example: As a pistol the PG-108 uses the Beam Weapon (Pistol) skill. 
   
Ok, and with that we've covered all of the tweaks we need to update the Blaster And Laser Design article to handle plasma weapons.! Yaaaayyyy! 
 

Before we finish wrapping up the stats for our example pistol, here's a few additional rules and ideas that I tend to use when I design weapons to feel give them a little more character. 

Equipment Modifiers
I like to use equipment modifiers such as rugged and compact to flesh out variants of the same model or the tendencies of some companies to make weapons that focus on a particular characteristic. 
 

Variants

Don't be afraid to  stat up different versions of the same type of gun to fill out the world. In the real world many makes of weapons out there ares just variants of a common model often just chambers with a different round. To emulate this with plasma guns use equipment modifiers like rugged to make durable military models, up the damage a little to make a "long barrel" version or lighten the damage a bit to make a snub nosed one.

Scaling Weapon DR and HT with TL
As a general rule, firearms gets DR 4, HT 10 and HP based on their weight (treated as unliving). At higher TLs however, advances in material technology and better understanding of how to design a given piece of technology means that DR and HT should go up with TL.

• At TL9: DR6, HT stays at 10.
• At TL10: DR9; HT 11.
• At TL11: DR14; HT 11.
• At TL12: DR20; HT 12. 

Sustained Fire
According to Ultra-Tech a energy weapon can safely fire for ROF×10 seconds before needing to cool down. To bring this in line with the more detailed rules published in High-Tech, this should go up with TL. I used this options when designing the example plasma guns below.

• At the energy weapons introductory TL its rate of sustained fire is ROF×10. 
• At introductory TL+1 its rate of sustained fire is ROF×30.
• At introductory TL+2 its rate of sustained fire is ROF×45.
• At introductory TL+3 and higher its rate of sustained fire is ROF×60.
• If going by RAW and weapon uses the Gatling option then a weapons rate of sustained fire is ∞ 
• If using my optional rules and the weapon uses a heavy barrel then its rate of sustained fire is its base rate of sustained fire×1.5
•  f using my optional rules and the weapon uses a light barrel then its rate of sustained fire is its base rate of sustained fire×0.5
• f using my optional rules and the weapon uses the Gatling option then its rate of sustained fire is its base rate of sustained fire×how many barrels it has (This stacks with having a heavy and light barrel) .

Hot shots

Since plasma guns have recoil I feel that hot shotted plasma rounds should follow the example of +P rounds from High-Tech and a plasma guns ST should be also by multiplied by 1.3 when using them. This is the only other house rule  I use in my write up for the PG-108. 

Optional Fluff 

Here's some optional stuff that has no in game effects but let you flesh out the guns back ground a little bit more.

Plasma bolts output
To figure out a plasma weapons "muzzle energy take (Dice of damage/4)^3 in  kilojoules. This is actually the  RAW way of figuring out how much energy a plasma guns shots have! Pulsars have same output.

For lasers and particle beam weapons muzzle energy is (Dice of damage/2)^3 in  kilojoules. For force weapons its ~(Dice of damage/2.7(Its actually 2 and 2/3rds))^3 in  kilojoules and for graviton  weapons its (Dice of damage)^3 in  kilojoules.

Plasma Guns Aperture
To get an idea of a plasma guns "caliber" multiply its dice of damage by 0.188 millimeters. This is here for pure fluff reason alone and unlike with the output formula this is 100% house rule and can be completely skipped. If you're interested were I got this number, its based on how wide an electron beam of the same output would be (its beam waist) since an charge particle beam is the closest thing I could find in the real world that's like a plasma gun. Looking into electron beams is also were I got the harsh realism figure for a plasma guns range. I would also like to thank Luke Campbell who's immense knowledge in real world energy weapons is the reason I got those figures in the first place.

Macrotech PG-108 5.4kJ Plasma Pistol  (TL10^)

Designed by Macrotech's Advanced Energy Designs Intersolar division, the Plasma Gun model ten, version eight has become the intergalactic standard for reliable and out of the box accurate plasma weapons. The baseline model has become common place for both private, police, security forces and even some military units has adopted it as standard side arm. It fires a 5.4 kilojoule plasma bolt from a 1.3mm aperture.

The Macrotech HEP-12 is a ruggedized (Counts as Rugged. Multiply weight by 1.2, double cost. Double weapons DR and add +2 to HT) version meant for military sales, Wt. 2.9/1C, Cost $4,000/$10, DR8,  HT12.

The Cynllunio Infinite Ldt M-2198 is a locally produced variant used the Seren Ddisglair home guard that's designed to only fire hotshotted  11.4kJ rounds. It has the same basic frame with custom receiver with a 1.7mm aperture and made to be Fine (Reliable) to counter act the tendency for hotshotted weapons to malfunction.  Dmg. 9d(2) burn ex sur, Rng. 450/1,350, shots 10, ST12, Cost $5,000/$10. Does not have malf. 14.

BEAM WEAPONS (PISTOL) (DX-4, Most other Beam Weapons-4 or Guns (Pistol)-4) 

TL    Weapon                    Damage              Acc    Range        Weight   ROF  Shots   ST   Bulk   Rcl    Cost         LC 

10^  Macrotech PG-108   7(2) burn ex sur   4       350/1,050    2.5/1C    3         20(3)   9     -2        2     $4,000/$10   3