For example: Let's say after disarming a bomb that was going to take out the presidents personal shuttle one of your players decides they're going to remove its explosive filler so they can repurpose it later.
Great! Smart lil bugger.... Now you just gotta figure out how much boom-boom is in this dang thing. Sure you can just pull a number out of your butt buuuut then you gotta hope you remember why you picked this number later if you have to do this again and hope no of your players are an "expert" on explosives and go, "Actually!"
Well good thing there is a way to figure how much explosives are in the warheads listed in Ultra-Tech!
First you just have to figure out how much a given warhead weighs and if you have read this blog post you should already know how to do this but to make your life easier I'll just give your the formula again.
Warhead weight = Warhead diameter (in mm)3 × 0.000002.
See Warheads R' Us for how I came up with this, my more observant readers might notice that this will give you same results as stating up a small warhead in GURPS Vehicles 3rd ed which in turn is the standard that Transhuman Space used for it's warheads (which in turn was a major influence on the 4th ed version of Ultra-Tech).
Now that you have how much the whole warhead weighs, we can now separate the explosive filler from the casing, fuse and other necessary components.
To do that just take the warheads weight and multiply if by 0.78 annnnd boom! The product is the weight of the actual boomy part of the thing. Of course in real life this would vary based on what kind of warhead it was, how it was fused and so on this does at lest give you a good rule of thumb that is consistent and lines up with GURPS RAW.
Oh right.... you want to know how I came up with this, silly me.
Well, if you open up your Basic Set to pg. 415 you'll see there's handy little formula to figure how much damage a given amount of explosives do. You just needed to know the weight and the explosives REF (relative effectiveness factor, or how powerful it is compared to the same amount of TNT).
Now let's look at a 100mm warhead which weighs 2lbs and a TL 9 HE warhead does 6d×5 cr ex.
To give a base line let's look at what 2lbs of TL 9 HE would do (I'll save you the crunch on this one but it's safe to say that TL 9 military explosives in Ultra-Tech are Plastex B/ Octanitrocubane) with a REF of 4).
Using the listed formula 2lbs of HE would do 6d × square Root of (2lbs × 4 × REF(4)) or 6d×5.56, which would normally be rounded to 6 but that would throw off the results.
Now if we compare how much damage a 100mm warhead does compared to 2lbs of just HE that the warhead does only about 88% of the damage. Now since damage is based on the square root of the weight of the explosives, just convert that 88% to a decimal and square it which gives us a weight modifier of about 0.78.
So this means that a 2lbs warhead should have 2lbs × 0.78 or 1.56lbs worth of explosives. So if I'm wright, if we plug 1.56lbs into the explosives damage formula we should get 6×5 and look at that, the formula gives us 6d×4.99 dice worth of damage. Bam!
Oh, and another use for this knowledge is now you can swap out the plastex B and try out different types of explosives. For example, if we decided that we wanted that 100mm warhead filled with Nanoscale Thermite (Ultra-Tech, Too Pyramid 3/51 Tech and Toys III) we now knows that it can hold 1.6lbs worth which will burn for eight seconds and cost $320.
I know this wasn't too big of a post, especially with how long I've been out of the game but rest assure I do have some more post in the works, two that give you more warheads to play should be done soon, with as well doing some major research into Robotech: The Next Generation/The Sentinels mecha and weapons so I should have more Ultra-Tech fun for you guys soonish.