Physics in Shadowrun, When Mad Magic Science erupts! Options

[nezumi]

I have a player who is really on fire about elemental effects, especially with spells and elementals. As such, he has asked about a few different interactions I'm not sure about, so I open them up to the DSF community to see if anyone has a better answer than I do...

How does fire interact with:
Bullets - how hot do they need to get to go off? How much damage does an exploding bullet do? What about 100 exploding bullets?
Grenades - as above. Do different types of grenades have different vulnerabilities to fire?
Plastic explosives - obviously won't go off when exposed to fire, but what about the Blast elemental effect? Electricity?
Neurostun & other chemicals - what happens when heated for a moment by a fireball? What about sustained heat?
Rockets and missiles - are these vulnerable to misfiring due to heat?
Electronics (now mostly optics) - are these especially vulnerable to lightning still? What about light/laser attacks? Water?

Would the heat of a fireball create enough of a change in air pressure to dissipate smoke from a smoke grenade?

Also a related question... Imagine a hallway so full of smoke that you can't see from one side to the other on the physical plane. There is a mundane at the far end of the hall. The PC turns to astral perception to be able to spot the person, even though he can't see him physically. Can the PC caster cast fireball? Manabolt? Does he suffer any visibility modifiers? I would assume yes, but for some reason that rubs me the wrong way.

[kigmatzomat]

Bullets tend to go off ~400F. (Thank you Myth Busters!) It's probably about 10-15 seconds after being dropped in a hot fire.

They tend to do very little damage when unrestrained and uncontained i.e. just sitting on the ground. Generally Light stun. It would be more if you were wearing them in a bandolier. I'd either use a long burst or supressive fire rules for 100 of them.

Not sure about grenades' flash temp. Odds are the temperature is about the same but the heavier casing means it would take longer, so figure 30seconds - 1 minute. And it'll do normal damage when it blows.

Plastique will burn when exposed to non-instantaneous fire. Lightning will make it go blooey.


Momentary heat will have little damage on contained gases & drugs. Vaporous chemicals will likely burn readily. Heck, cement dust and laser toner will explode when airborne.

Extended exposure to heat (multiple minutes) will probably denature the chemical. Odds are it is still toxic but with a slower adsorption rate and reduce lethality.

Rockets & missiles have a decent amount of heat shielding. It would take 30+ seconds of being in a fire to detonate. the fuel probably has more explosive energy than the warhead. I'd take the amount of plastique it would take to make the warhead and double the mass to find the blast damage.

Electronics won't be as vulnerable but there's still the chance of blowing out the battery or zotting the WiFi. (Lightning likes antennas the way fat kids like ice cream.) Lasers don't conduct the same way electricity does, so it's all direct damage to devices. Water can short batteries or the wifi portion of an optical device. Milspec and cyber is pretty much waterproof, at least to 10meters of depth.

Fireballs wouldn't really dissipate smoke but it might burn it up. The amount of air volume required to move smoke around is pretty high (think a leaf blower).

Physical barriers still block astral sight, be they projecting or just dual natured. See p.181 where it talks about "non living objects appear as a faded semblance of their selves, gray and lifeless." And astral person can't see through a wall or a cloud of smoke because they still see the "faded semblance" of the physical wall or smoke.

[mfb]

you need compression and heat to set of plastic explosives. a lightning bolt might set off the blasting cap you put into a wad of plastic explosive, which would set off the plastic explosive itself, but i think there are safeguards built into the caps that keep any old electrical charge from setting them off. i'm not sure what would happen if a bolt hit the plastic explosive itself--the resistance provided by the explosive would probably create a lot of heat, but i'm not sure if there'd be any source of blast.

[tisoz]

[mfb]

maybe. lightning bolt has always struck me as less Zeus and more Emperor Palpatine.

[tisoz]

Agreed.

I got caught up in the name.

[nezumi]

Wow, kigmatzomat. Good answers all. Thank you very much!

[BishopMcQ]

I'll need to go home to reference my books, but in the Combat section of SR3 there are secondary effects listed for fire, electricity, etc. MitS has the expanded effects. As I recall it was based off of Object Resistance, modifiers for compatability and the Damage Code. M was presumed to be the basis for secondary effects, so S or D would receive more dice.

SR4 has a nearly identical set of rules, using new mechanics--This time reference the Combat or Magic chapters of SR4, and Street magic

[nezumi]

The problem is that the rules make absolutely no sense. A piece of granite is more likely to burst into flame than rocket fuel (because Object Resistance is based on how 'natural' an object is).

[BishopMcQ]

That's where the compatabilty modifiers come in. A piece of granite would receive a bonus to resist being lit on fire, whereas rocket fuel would suffer a penalty.

[nezumi]

The recommended bonus or penalty is +/-2, if memory serves, which still isn't enough to raise granite from 3 or 4 up to infinity (since granite doesn't burn), or reduce rocket fuel from 12 or 14 to 2 or 3. And if it DOES allow for that degree of change, then the rules are pretty useless because ultimately it just comes back to me as the GM figuring out the TNs without any help from the rules.

[lorthazar]

[Angelone]

IIRC for plastique and blasting caps they won't go off when hit by any random shock. It takes a certain charge to set them off.

Not sure about rocket fuel but the fuel military vehicles uses is suprisingly stable and doesn't ignite/explode as often as regular gasoline.

[hyzmarca]

Electrical detonators for blasting caps actually use heat to set them off (electricity passing though a metal wire heats the wire depending on the amperage and the wire's resistance).

[nezumi]

So they require heat and pressure?

[Kagetenshi]

Secondary explosives (generally the explosive proper) generally require heat and pressure—either by itself won't do it, except insofar as extreme pressure will generate heat. Primary explosives will go off with a number of things, which is why they generally only serve as small detonators.

~J