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Old 05-09-2015, 04:10 AM   #1
johndallman
 
Join Date: Oct 2010
Location: Cambridge, UK
Default [Basic] Skill of the week: Explosives

Explosives is the IQ/A skill of working with explosive and incendiary materials. It has several specialisations: (Demolition), for blowing stuff up; (Explosive Ordnance Disposal), for making explosives safe; (Fireworks), for making pyrotechnic devices; (Nuclear Ordnance Disposal), for making nuclear devices safe, and (Underwater Demolition), for doing (Demolition) underwater. All of these were separate skills under 3e, and drawing them together is a good example of the ways that skills changed at 4e. Most of the skills default to each other at -4, but the two kinds of Disposal default to each other at -2, and (Demolitions) and (Underwater Demolitions) do the same. (Demolition) defaults to Engineer (Mining) or (Combat) at -3, with reverse defaults at -6 and (Fireworks) defaults to Chemistry -3.

Explosives skills are not something you want to do hurriedly or carelessly: modifiers include -1 to -5 for distractions, Time Spent (B346), and equipment modifiers. Some disadvantages also seem contra-indicated to me, notably Klutz and Overconfidence. The prerequisite of DX12 or better for (EOD) (and presumably (NOD)) is a bit strange as a hard requirement, and seems to the only case of a skill with a basic attribute prerequisite in Basic. Saying that the military and police forces that do most (EOD) training normally demand above-average DX in candidates might make more sense, in much the same way as the description of (Underwater Demolition) says that you usually need Swimming or Scuba skill to make use of UD. The Flexibility advantage is also useful for getting into places where explosives need to go, or be removed. And Luck is valuable when dealing with things that Are Not Your Friend.

If you have Explosives skill, it's wise to have it at a decent level, and to try to get all the bonuses you can manage. Failures are always risky, and (EOD) is downright dangerous, given that you need to win a QC against the maker of the device you're trying to disarm.

Explosives is (mostly) a Use skill in the Design/Repair/Use triad scheme. Quite a few Engineer specialisations include designing applications of explosives, but there doesn't seem to be a Repair skill: fixing damaged explosive systems may well be considered too dangerous. Creating new kinds of explosive is Chemistry, and manufacturing them is chemical-plant operation.

Explosive traps are set with (Demolitions) at -2, rather than Traps skill, and that penalty can be bought off with the Set Trap technique. Basic also points out that the Work by Touch technique can be bought for Explosives specialisations.

Rules for explosions and blowing stuff up are on B414-415, and are expanded on P181-189 of High-Tech. Low-Tech covers TL3-4 explosives and incendiaries, which demand care and respect, on P84-87. Tactical Shooting adds improvised explosive devices, and Ultra-Tech covers science-fictional explosives and supporting equipment, although I'm terrified by the low price of antimatter at TL12, even if it is LC0. Underground Adventures has non-combat explosives applications, in tunnelling and seismology.

Explosives skills are fairly common on templates for high-tech characters, with (Demolition) being the most common. Action naturally has a lot about Explosives, too much to summarise. High-Tech has more details of equipment, throughout the book. Monster Hunters has less explosive detail than Action, but it should be easy to apply the Action rules if required. Surprisingly, there are no Talents in PU3 that include Explosives, although there are several applicable wildcards in PU7. PU1, Powers and Chinese Elemental Powers cover using powers with Explosives skills. Space adds (Nuclear Demolition) specialisation, and Zombies warns of the drawbacks of blowing up contagious enemies.

I've seen (Demolition) used a lot, by the Demolition Woman in our Action/Reign of Steel game, and done a bit myself, feeding ten pounds of time-fused RDX to the Great Worm of Bethnal Green in a WWII campaign. EOD has so far been left to NPC specialists, and my Elizabethan character with (Fireworks) never got to use it.

How have you exploded a scenario, or defused one?
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Old 05-09-2015, 10:19 AM   #2
Ulzgoroth
 
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Default Re: [Basic] Skill of the week: Explosives

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Originally Posted by johndallman View Post
Explosives is (mostly) a Use skill in the Design/Repair/Use triad scheme. Quite a few Engineer specialisations include designing applications of explosives, but there doesn't seem to be a Repair skill: fixing damaged explosive systems may well be considered too dangerous. Creating new kinds of explosive is Chemistry, and manufacturing them is chemical-plant operation.
Explosives somewhat grabs the full trinity. It (specifically the Demolitions specialization) is the skill to use to design and assemble charges for a specific purpose, as well as to place them. It's as good as Chemistry and better than any other skill for most cases of cooking explosive compounds in the first place.

I'd say that repairing explosives as such is mostly impossible...you could attach a new detonator to a charge that no longer detonates normally, and you can certainly disassemble an unsatisfactory explosive (using EOD) and re-use the materials in a new charge, but what would it even mean to repair one?

Repairing, designing, and building nuclear weapons is another, much more complex matter. High Tech pretty much dismisses the topic, outside a cinematic special case (which it allocates to Engineer (Nuclear)), and I don't know if any other sources really address that. It does seem that there should be a viable technician skill for maintaining nuclear warheads, which are rather sophisticated objects and do have potentially user-serviceable parts inside.
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Old 05-09-2015, 11:07 AM   #3
malloyd
 
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Default Re: [Basic] Skill of the week: Explosives

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Originally Posted by Ulzgoroth View Post
Repairing, designing, and building nuclear weapons is another, much more complex matter. High Tech pretty much dismisses the topic, outside a cinematic special case (which it allocates to Engineer (Nuclear)), and I don't know if any other sources really address that. It does seem that there should be a viable technician skill for maintaining nuclear warheads, which are rather sophisticated objects and do have potentially user-serviceable parts inside.
That would be Armoury (Heavy Weapons). Though demanding a unique new specialization wouldn't be ridiculous either.

And it's not unreasonable to allow somebody with Engineer (Nuclear) and Explosives (Demolitions) to design a nuclear weapon even in a realistic setting. It's the *building* part that's hard, between the difficulty of obtaining fissionables, their toxicity, and getting the necessary high precision out of something as inherently inexact as *explosions* to drive the parts together hard enough they'll go bomb critical rather than melt or release just enough energy to blow the pieces back apart.

Hm, now that I consider it, if you didn't care about the nuclear weapon being *portable*, I wonder if it might be easier to build a mechanical system of assembling the parts really fast? There may be a mad genius super-villain plot in there involving somebody "redeveloping" a old city center rail yard with apparently purposeless catapults and giant rotary slings.....
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Old 05-09-2015, 11:11 AM   #4
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Default Re: [Basic] Skill of the week: Explosives

Back in the day, in a Caribbean pirates campaign, I played the ship's master gunner, Fornication Jones ("Me da named me 'Fly-Fornication Jones,' him being a Puritan, but while I was in the army the 'Fly' dropped off"). There was an episode when we were being pursued by a rival pirate ship whose captain was notoriously ruthless. Jones combined his Explosives (Pyrotechnics) and Mechanic (Clockwork) skill to prepare two casks full of powder timed to go off at a set interval after we dropped them over the stern. Thanks to a critical success on one of the rolls, they set off the other ship's magazine. . . .
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Old 05-09-2015, 11:57 AM   #5
johndallman
 
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Default Re: [Basic] Skill of the week: Explosives

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Originally Posted by malloyd View Post
Hm, now that I consider it, if you didn't care about the nuclear weapon being *portable*, I wonder if it might be easier to build a mechanical system of assembling the parts really fast? There may be a mad genius super-villain plot in there involving somebody "redeveloping" a old city center rail yard with apparently purposeless catapults and giant rotary slings.....
You don't have to be all that mad. It has to be a gun-assembly device, with no compression. That means using U235 rather than plutonium, and U235's low spontaneous fission rate means the assembly doesn't have to be terribly fast. Big springs will do. Some LARPers once asked me to work up a concept for a nuclear device to work in a world where explosives didn't work. Steam did, though: heat up a boiler to a nice high pressure and have it rupture a diaphragm.
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Old 05-09-2015, 12:10 PM   #6
Ulzgoroth
 
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Default Re: [Basic] Skill of the week: Explosives

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That would be Armoury (Heavy Weapons). Though demanding a unique new specialization wouldn't be ridiculous either.
Yeah, you're clearly right there. And I would be strongly inclined to rapidly complicate the Armory landscape if I were left to my own devices and ignoring the little reminder that nearly nobody cares about realistic divisions in technical skills.
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Old 05-09-2015, 02:29 PM   #7
Kale
 
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Default Re: [Basic] Skill of the week: Explosives

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Originally Posted by johndallman View Post
You don't have to be all that mad. It has to be a gun-assembly device, with no compression. That means using U235 rather than plutonium, and U235's low spontaneous fission rate means the assembly doesn't have to be terribly fast. Big springs will do. Some LARPers once asked me to work up a concept for a nuclear device to work in a world where explosives didn't work. Steam did, though: heat up a boiler to a nice high pressure and have it rupture a diaphragm.
Well that's terrifying. I had no idea you could generate the necessary compression without resorting to explosives. I suppose a boiler could do it not that you say it: I've heard of cold seawater hitting a boiler destroying a steamship from the reaction.
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Old 05-09-2015, 03:07 PM   #8
johndallman
 
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Default Re: [Basic] Skill of the week: Explosives

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Well that's terrifying. I had no idea you could generate the necessary compression without resorting to explosives.
Compression is not actually necessary. Critical mass depends on density, so compression is a good idea, and economises on the expensive fissionable material, but it's not required.

The tricky bit with assembling a critical mass is doing it fast enough. You want to achieve rather more than a critical mass, or the reaction stops very quickly as it expands (at the relevant pressures and temperatures, the physical strength of the materials is utterly irrelevant, and the only thing limiting expansion is inertia).

Plutonium has a fairly high rate of spontaneous fission, so if it is assembled slowly, the reaction tends to start before assembly is complete, and you get a "fizzle". The only practical way to assemble it is at the very high speeds of an implosion.

U235 has a much lower spontaneous fission rate, and taking a few hundredths of a second to assemble it is no problem.

There's no real need to worry about this. Building a practical implosion system is much easier than making plutonium or U235. Every nation-state that has carried through a nuclear weapons program seems to have succeeded on their first attempt. Controlling the manufacture and storage of those materials is the main thing done to limit access to nuclear weapons.

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I suppose a boiler could do it not that you say it: I've heard of cold seawater hitting a boiler destroying a steamship from the reaction.
That seems to be because cold water hitting a boiler will cool the metal of the boiler rapidly, which is likely to cause it to crack. At which point it bursts, releasing all its steam.
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Old 05-09-2015, 03:18 PM   #9
RogerBW
 
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Default Re: [Basic] Skill of the week: Explosives

As anyone who's played games with me will know, I tend to use this skill quite a bit as a player and expect it of PCs when I'm GMing, so it shows up a great deal in my character archive. I have at least once dropped Nuclear Ordnance Disposal on a pre-gen character sheet purely to see the player's face when he realises what he might be expected to do. (And yes, there is an opportunity for him to use it in the scenario.)
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Old 05-09-2015, 05:17 PM   #10
Ulzgoroth
 
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Default Re: [Basic] Skill of the week: Explosives

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Well that's terrifying. I had no idea you could generate the necessary compression without resorting to explosives. I suppose a boiler could do it not that you say it: I've heard of cold seawater hitting a boiler destroying a steamship from the reaction.
You could literally make a nuclear explosion by hand, by taking two large subcritical masses and fitting them together. (EDIT: Or would that be an underpowered (but catastrophic nonetheless) fizzle because the fissionables of the core would burn out over a slightly longer time than if it was slammed together mechanically?)

Obviously not a survivable exercise.
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