Help me stat a steam thrower weapon

[Green-Neck]

Hello fine folks,

My GM is going to run a post apocolyptic game and I'm trying to give my character an intersting weapon. The campaign is semi cinematic and set in nearish future australia.

I'm imagining a weapon that looks much like a ww2 flame thower, except it uses solid fuels like wood and coal to heat water to superheat steam.

I'm thinking of a 30 pound backpack with wand
A brazier that preheats a water tank, then fills a one quart steel tank that heats to about 250 C/480 f, thats about 40bar/600 psi.

The tank would have a temperature solinoid and thermo-electric-generator powered fan to moderate the fire.

My attempt at stating it so far:

Steam Projector,
0-1 yards, 4d cutting pi-
2-5 yards, 4d burn 1x1 cone.
6-8 yards, 2d burn 2x2 cone.

30 lbs, 10 shots, fire 1 per 3 rounds.
Reload 10 litres/quarts water, 2lbs/1kg coal or wood.
Bayonet, for inevitable complications between steam charges.
skill: liquid projector (steam), spear.


I'd welcome any thaughts on semi-realism and more refined stats.

Thanks.

[whswhs]

You're going to need a lot of insulation to carry around a tank whose contents are that hot. With a flamethrower that doesn't arise, because the heat isn't there until you use the weapon and the fuel starts burning.

[Green-Neck]

Thanks Bill.

Hopefully this post apocalyse senario has large ruined building with firedoors.
Such doors can contain high temp (1000 deg c) glass wool insulation, or some other source.

[Green-Neck]

The main reason for the steam weapon, I should point out, is a lack of high quality liquid fuels in the scenario.

[Anthony]

I am going to assume this is intended to be a cinematic weapon, because it's realistically nonsense -- any steam tank that isn't going to simply blow up and kill the operator won't produce a jet strong enough to be useful as a weapon at all. In which case, just invent numbers that sound cool.

[Green-Neck]

Well yes it probably does require some hand wavium, but pressure tanks to the specification above are common in our society, and pressure release valves should prevent an explosion.

I'll leave you with this quote:

In 1988, there was a steam line failure at the Mohave station in Nevada, USA. The hot reheater P11 pipe failed , at 31 bar,g and 593 C temp ( design temp was only 540 C, and it was overheated for 1 yr prior to failure). It failed outside of the plant cafeteria, and killed 11 operators who were eating lunch in the cafeteria.

[whswhs]

The cutting people in half part, at least, is not something you'd get with burning damage; it sounds like cutting damage, which is what I suggested the damage from high-pressure steam ought to be represented as for the greater part.

As for scalding people to death, that seems comparable to killing people with flame. But in GURPS, the damage from being immersed in flame is 1d-1 per second. That was what I suggested as an upper limit for the burning damage from steam, for rough consistency. That damage will add up—on the average, to 8 points every 3 seconds—but it won't kill you instantly; an average person will have to roll vs. HT to survive after 7.5 seconds. That's probably realistic, but in any case, it seems consistent with how GURPS handles burning damage. Maybe 1 point from ordinary steam, and 1d-1 from superheated steam, as burning damage, with added cutting damage in the latter case.

[Willy]

New to this thread, but I ask myself if anyone has thought about the fact that if you boil water regardless of the pressure, the steam ist not only denser than hot air of the same pressure aka more heat is delivered to the target, but there is a BIG catch for the victim. The steam will while hitting the target and delivering heat, become fluid once again, therefore stick to it ( like a molotov cocktail ) and therefore delivering more heat and damage than before.

I know a bit of what I speak in my youth I worked in a factory which powder coated surfaces, getting the stuff out of the walkable oven, still running full power, and therefore having at the skin near 150°C of hot air was in a short time no problem, no special protective gear needed, besides the shoes you could do it in shirts and short trousers. Normal steam at a kitchen has less °C, but I wouldn´t hold my hand in it.

[Turhan's Bey Company]

There does seem to be a questionable leap from "superheated steam is very dangerous," which is unquestionably true, to "superheated steam is very dangerous in this very specific way," which is, I think, what's tripping people up. And, again, if you want this weapon in your campaign, by all means do so. It doesn't have to be realistic, and if you think it is, you don't have to convince us. It's your game.

That said, if you're looking for something slightly less dubious (I mean, beyond problems with the backpack steam chamber), let me suggest something for which there's demonstrated proof of concept: a steam cannon. The basic idea is outlined and stated in Fantasy-Tech 1: A metal chamber is heated and a bit of water injected. The water flashes to steam, and the resulting explosive pressure propels a projectile. Modern experiments with the technique provide performance similar to a .50 caliber bullet. Fantasy-Tech has stats for a cannon-sized version, but if you're hand-waving the backpack unit, that concept could easily be applied to a portable version.

[Fred Brackin]

Originally Posted by Turhan's Bey Company

That said, if you're looking for something slightly less dubious (I mean, beyond problems with the backpack steam chamber), .

The steam chamber is probably the msot dangerous thing to the user (specifically the part whe it builds up and then holds the pressure) but the weak link in the superheated steam projection system is the flexible hose connecting the chamber to the wand part. There's no way that's going to withstand the same pressures as the chamber.