Thursday, March 2, 2017

Warheads R Us

For this weeks GURPSday I tackle the most pressing issue faced by GURPS Ultra-Tech users....

How much the diffrent warheads weigh and cost!

Aaaanddd... a maybe a few other things but baahhhh, they're not that important. 

Would you like to know more?

While I think most players could agree that Ultra-Tech could of used a bit more variety in it's weapon allotment, I also think that it at lest gave players a lot of options for upgrading missile and projectile launchers (Rocket lawnchair!) with tons of different warhead options. 

 But once again, in typical Ultra-Tech fashion, it gives you some options it fails to give you all the details you could use with said options. Namely how much each warhead weights and how the base cost of a warhead scales.

Now while  this is not critical it can be useful knowing the weight of a given warhead in cases, for example, where a PC is removing the warheads from missiles or bombs to rig up an IDE, using GURPS Spaceships to stat up more detailed missiles for a setting and want to know how many spaces a warhead would take up or, I don't know, if someone had a missile design system in works...

So how did we figure how much an Ultra-Tech warhead weighs?

Well, hidden deep within Ultra- Tech its self was the answer all along!

Under Combat Robots on pg. 168 of Ultra-Tech we find the stats for the "genius" versions of the 64mm (Hunter) and 100mm (Striker) missiles from pg. 145. The Hunter has ST 3 and the Striker has twice the ST with 6 (a 4× increase which is about right for a 1.6× increase in diameter) and both have Payload 3 which gives in turn gives us a warhead weight of about 0.5 lbs for the Hunter and 2 lbs for the Striker.

Figuring out the base cost of the other warhead sizes is a lot easier. The cost for the 100 mm warhead is $40 while the 64 mm one is $10. Since the 64 mm warhead weighs 1/4th as much and costs 1/4th as much it's pretty safe to say that the base cost of warheads in Ultra-Tech is $20/lbs.

So with this knowledge we can extrapolate the weight and cost for all the other warhead sizes:

Warhead Diameter    Warhead Weight  Warhead Base Cost
10 mm                              0.002 lbs                 $0.04
15 mm                              0.007 lbs                 $0.14
18.5 mm                             0.01 lbs                 $0.25
25 mm                                0.03 lbs                 $0.63
40 mm                              0.125 lbs                  $2.50
64 mm                                  0.5 lbs                  $10
100 mm                                   2 lbs                  $40

Of course knowing the weights and costs of all the warhead sizes in Ultra-Tech is good an all but what if you want to stat up your own unique warhead size?

I gotcha covered!

Warhead weight: (Diameter in mm)3×0.000002 lbs.

If you want a heavier warhead then this formula spits out but you don't want to make it any wider then just multiply the base warhead weight by whatever factor you want. Note that some warhead type effects are based on the warheads diameter and so they will not be increased by making the warhead heavier. Shaped-Charge, HEMP and SEFOP rounds cannot use this option.

Base Warhead Cost: Warhead weight ×$20.

Ok, and with that, go forth and stat up your own personal arsenal of mass destruction!


What's that?

Being able to make warheads of any size is good and all but is kinda pointless unless you have some kind of boomy goodness to stuff into them? 

What do I look like? Some kind of crunchmesiter who would go through the trouble of looking over all of the warhead options and reverse engineering each and every one listed so you stuff your customs warheads with whatever kind of ultra-death you want?

Oh right, silly me. I am!

Below you will each of the warhead options from Ultra-Tech reverse engineered so you can apply them to a warhead of any size you come up with. For most you will only need the weight of your warhead but a few will need the warheads diameter or both. 

All these assume TL9 or the TL they first appear. See the relevant entry in Ultra-Tech under Warheads and Ammunition (pg. 152-159) for details on how to upgrade them do to higher Tech Levels.

Also note that that some of damage figures in the book were rounded off to make the figures look neater at the expense of them following a logical pattern (as well as possible cases of editing mess up, this is Ultra-Tech after all heh). This in turn means that if you try to match up my formula with the figures listed in the book, a couple will not  line up 100% but usually you will be see where David choose to round off the numbers and they will be in the same ball park.

If a warhead does fragmentation damage, the dice of damage done by the fragments can be figured as warhead diameter in mm/20.

Blast effect goes up by square root (warhead weight)×19.8. Divide the product by 3.5 to get dice of damage.

Biochemical Aerosol
Radii of effects goes up  by warhead diameter in mm/10.

Note that the chart listed in Ultra-Tech won't line up exactly with this formula but this is as close as a progression that I could fine. Huge thanks to Nemoricus from the GURPS Discord channel for decoding it, I was seriously overthinking it.

Doses goes up by (warhead diameter/15)5/2

The results of this new formula still doesn't line up 100% with what's listed but that's only for the 40 mm and 64 mm warheads, for everything else it's lines up pretty well.

Biochemical Liquid 
Note: According to the Ultra-Tech Errata the amount of doses a 64 mm warhead has is 65, and the number of doses that a 100 mm warhead has is 250.

Radii of effects goes up  by square root(warhead weight)×12.7yards. Round product off.

Doses goes up by (warhead diameter/15)3 × 0.85. Round off.

Radii of effect goes by warhead weight×10yards

Blast effect goes up by square root (warhead weight)×74.2. Divide the product by 3.5 to get dice of damage.

Shaped Charge
The penetration effect  is figured as 2.2×warheads diameter in mm. Divide product by 3.5 to get dice of damage.

The linked secondary blast effect goes up by square root (warhead weight)×39.6. Divide product by 3.5 to get dice of damage.

The penetration effect  is figured as 2.2×warheads diameter in mm. Divide product by 3.5 to get dice of damage.

Tanger ST is figured as cube root( warhead weight)×47.6. Round product off.

ST added per layer is figured as (Tanger ST×1.05)-Tangler ST.

Tanger radii of effect is figured as cube root(warhead weight)×0.7yrds.

Blast effect goes up by square root (warhead weight)×148.5. Divide the product by 3.5 to get dice of damage.

The penetration effect  is figured as 2.5×warheads diameter in mm. Divide product by 3.5 to get dice of damage.
The linked secondary blast effect goes up by square root (warhead weight)×39.6. Divide product by 3.5 to get dice of damage.

Stingray Round
Damage dice is figured as 0.05×warheads diameter in mm.

Will release a swarm that will fill a warhead weight×8yrd area. 

Note that the thermal pulse damage listed on pg. 156 is actually incorrect. The formula used here is the corrected version.

First figure out how many kilotons your mininuke has (of course, it being a mini one is optional heh). Your warheads kiloton yield is based on its weight and is equal to warheads weight×0.5 at TL9, warheads weight×2 at TL10, warheads weight×8 at TL11 and warheads weight×32 at TL12.

Blast damage is figured as 6d×(2,000×square root(yield in kilotons)).

Thermal damage is figured as 6d×(1,860×square root(yield in kilotons)).

First figure out how many micrograms of antimatter your warhead is going to have. The amount of micrograms of antimatter it can hold is equal to warhead weight×0.5 at TL10, warhead weight×8 at TL11 and warhead weight×500 at TL12.

Blast damage effect is based on 6d×(12×square root(micrograms of antimatter)).

Radiation pulse is based on 6d×(100,000×(micrograms of antimatter)).

Radii of effect is based on square root(warhead weight)×11.3yrds.

Blast effect is based on square root(warhead weight)×9.9. Divide the product by 3.5 to get dice of damage.

Expendable Jammer
Radii of effect in yards is equal to the warheads diameter in mm.

The affliction effect is equal to HT-(warhead diameter in mm/10). Round the difference off.

Radii of effect in yards is equal to warhead diameter in mm/10. Round the difference off.

Blast effect is based on square root(warhead weight)×79.2. Divide the product by 3.5 to get dice of damage.

Blast effect is based on square root(warhead weight)×148.5. Divide the product by 3.5 to get dice of damage.

Blast effect is based on square root(warhead weight)×1484.9. Divide the product by 3.5 to get dice of damage.

Radiation pulse effect is equal to 6d×(warheads diameter in mm).

Radii of effect is based on square root(warhead weight)×11.3yrds.

Radii of effect in yards is based on warhead diameter in mm×0.05.

Let's see this in action.

Let's say we wanted a really big anti-ship plasma warhead for our space navy to use while cursing around the expanse of space. 

I also want it to scale it with a GURPS Spaceships SM+4 hull so I want a warhead that weighs half a ton per system for maximum ship busting potential  but I don't want it anymore then 800mm wide.

A 800mm warhead will give us 8003×0.000002 or 1,024lbs which is a little over the 1,000lbs budget but is with in the normal "good enough" margin for Spaceships. Each warhead will cost $200,000.

Damage wise our half ton plasma warhead will do square root(1,024)×148.5 or 4,696 points of damage. Dividing that by 3.5 gives us 1,342 dice which we can convert to 7d×192 burn ex sur. Two warhead systems would increase this damage to square root(2)×1,342 or 1,872 or 7d×271 burn ex sur.  

Now that we have an anti-ship warhead, how about a space torpedo to use it in?

SIM-1449 Starfire 80cm Plasma Torpedo (TL10^)

 The Space Interceptor Missile 1449 Starfire is a heavy anti-shipping missile that uses an advanced limited super-science high-thrust fusion torch to give it both incredible acceleration and high specific impulse. This gives it 6G of thrust and 60mps of Delta-V giving it the legs to chase down any target. This does come at the expense of making it impossible to hide.

The torpedo's two 1,000lbs  plasma warheads do a total of 7d×271 brun ex sur and costs $400,000.

The Torpedo is 10 yards (30ft) long with a 10-ton (SM +4) unstreamlined hull.

If using this torpedo in your game I suggest modeling its torpedo bay by using an optimized hanger system rather then a missile battery. 

Front Hull     System
[1]                  Nanocomposite Armor (dDR 5).
[2]                  Tactical Array (comm/sensor 5).
[3-4]               Warheads (Two 80cm 1,000lbs plasma warheads).
[5-6]               Fuel Tanks (0.5tons of hydrogen with 7.5mps delta-V each).
[Core]            Control Room (C6 computer, comm/sensor 3, and no control stations).

Central Hull   System
[1]                  Nanocomposite Armor (dDR 5).
[2-6]               Fuel Tanks (0.5tons of hydrogen with 7.5mps delta-V each).

Rear Hull   System
[1-6]           Fusion Torch (High-Thrust, 6G acceleration).
[Core]         Fuel Tank (0.5tons of hydrogen with 7.5mps delta-V).

The torpedo is unmanned. 

TL  Spacecraft                       dST/HP  Hnd/SR    HT   Move         Lwt     Load    SM    Occ    dDR   Range   Cost

10^ Starfire Plasma Torpedo    15         0/4            12     6G/60 mps    10        1        +4       0         5        -            $1,844K

Found out I made a mistake with my stingray round damage formula! The correct formula is 0.05×warheads diameter in mm. Thanks to Mailanka for pointing it out! 


  1. Unless you've changed how Stingrays work, your math is definitely off. The book has an 18.5mm Stringray dealing 3.5 damage, while your math has it dealing 0.09 damage, and the book has a 64mm Stringray dealing 3d, and yours has it dealing 1d+1; only 100mm is correct (5d in both).

  2. Might of made a copy paste error, I'll check it out when I get home from work (assuming I don't just pass out heh).

  3. Just using your material like usual, and I double checked your warhead mass numbers and they line up perfectly with where Tech & Toys II expects them to be, and if I use your numbers, HEX grenades line up perfectly with plastex-B filling, and plasma grenades line up with plasma explosive filling. Just thought you should know how spot on your numbers were!

    1. Thanks for double checking!

      The more feed back I get like this, the more accurate my future posts will be.