[UT] Plasma Torch vs. big metal door on a spaceship?
 

Greetings, all!

I remember that drills and rotary hammers treat wooden, brick and stone obstacles as [semi-]ablative. However, I do not remember any similar notes about gradually cutting metal obstacles, even for things like the plasma torch (which does burning damage). So my questions are:

• Am I missing a rule about torches doing corrosion damage instead of burning when focusing on a single section of a hull/wall/door/etc.?
• If not, how does one cut down through metal armour and doors, since those tend to have non-ablative DR that increases with thickness.

Thanks in advance!

Re: [UT] Plasma Torch vs. big metal door on a spaceship?
 

Not that I'm aware of.

Cutting Cord?
Thermite?

(or UT-equivalents.)


ADDENDUM:

Found it. Pyramid #3/51: Tech and Toys III has REF values for ultra-tech explosives, and even Nanoscale Thermite in Ultra-Tech Too.

Re: [UT] Plasma Torch vs. big metal door on a spaceship?
 

Ablative or even perhaps semi-ablative is implied in some descriptive text attached to such devices but never made into a general rule. I would make such a general rule.

Re: [UT] Plasma Torch vs. big metal door on a spaceship?
 

Given that these are tools, not weapons, it seems reasonable for them to treat metal as semi-ablative outside of combat, otherwise they would be useless as tools.

Re: [UT] Plasma Torch vs. big metal door on a spaceship?
 

Watch some videos of plasma torches piercing and cutting shapes in thick steel. The following is obviously not RAW - but should work:

Assign an AD to the torch and let damage accumulate for every second it is on the start point until it over comes the DR. Assign a speed the torch can move while it cuts through that thickness of steel in inches per minute. Roll a successful Operation roll to continue to achieve that rate of progress. Once the metal is pierced the metal adjacent to the hole is hot and the plasma does not have to work on much surface area to bring it to melting point as it travels.

Re: [UT] Plasma Torch vs. big metal door on a spaceship?
 

Realistically, there should probably be a general rule for drilling (and sawing) that applies to any damage type in situations where the weapon can be held in a constant position against the target (or if you can continually hit the same point, which is probably comparable to targeting chinks in armor); there's a minimum threshold below which you can't drill at all, but as long as you can damage the surface at all you'll eventually get through.

Re: [UT] Plasma Torch vs. big metal door on a spaceship?
 

Basic Set p.559:
"Repeated impaling, piercing, and large
piercing attacks against the same small spot
(an area with SM 0 or less) lower DR at that
specific point as if it were semi-ablative;
repeated burning, corrosion, crushing, cutting,
or huge piercing attacks at that same spot
reduce DR at that point as if it were ablative."

Re: [UT] Plasma Torch vs. big metal door on a spaceship?
 

That's an effect that applies to wood, stone, brick and concrete. I'm looking for cutting through huge metal obstacles.

Re: [UT] Plasma Torch vs. big metal door on a spaceship?
 

Nothing in the text says that this only applies to wood and stone, only that wood and stone have a cap on how much DR can be ablated. The lack of a minimum DR for metals seems like an oversight, however.

Re: [UT] Plasma Torch vs. big metal door on a spaceship?
 

That * sign in the beginning of the paragraph on page 559 is a footnote from page 558. Notice that the DRs of wooden, concrete, stone and brick objects come with an *.

Re: [UT] Plasma Torch vs. big metal door on a spaceship?
 

Looking at the hvy plasma torch in UT - 4d+1(5) - I think the problem is that you need a real industrial torch or water jet cutter for anything over an inch in steel. And that should have an AD(10) and a much larger damage.

Also are you attacking the whole surface (112 DR/inch) or the Cover DR (~70DR)? I would rule that these tools are continuously piercing the Cover DR in a very small space. RAW doesn't seem to include metals in the semi-ablative/ablative note so move onto a better tool.

Re: [UT] Plasma Torch vs. big metal door on a spaceship?
 

Not over the course of a single GURPS combat turn.

Re: [UT] Plasma Torch vs. big metal door on a spaceship?
 

I am not sure I understand your objection. Care to expound?

Re: [UT] Plasma Torch vs. big metal door on a spaceship?
 

You appear to be looking for something that will penetrate very high DRs in a single round i.e. as in normal combat.

We can definitely say that HT torches don't work that way though they can penetrate very high DRs over a longer period of time. Possibly much longer. It took the Mythbusters many minutes to burn into a safe with a TL 8 "plasma" torch. It is to be hoped that UT torches will do at least a little better on that time/DR relationship.

So, modeling TL8 performance we need some kind of cumulative damage paradigm such as making metallic DR ablative or semi-ablative v. Burning damage or treating Burning as Corrosive and that's what has made up the bulk of discussion in this thread.

Re: [UT] Plasma Torch vs. big metal door on a spaceship?
 

Ultratech is calling Laser and Plasma Torches tools. Those are the combat stats, not how it affects objects during work. I think that if a GM has you measuring work load by combat damage then something fell apart.

Now if you are looking for how long a plasma torch would take to cut though a bulkhead then that's more math than I can offer =) Maybe someone wants to jump in with physics on this one.

Re: [UT] Plasma Torch vs. big metal door on a spaceship?
 

All plasma torches have thickness limits generally tied to the amperage they can put into the arc but the relevant industries seem to like plasma up to the 6 inch range. They find it more economical to use oxy-fuel cutting torches for really thick material – up to 40 inches. With a plasma cutter properly matched to the task at hand you will see very fast initial piercing and high cutting rates – because that makes it profitable to use. Last night I watched an industrial demonstration of cutting a part out of 2 inch thick material. The pierce took all of 2 seconds and the linear run was better than 20 inches in a minute. Every second that torch moved through a third of an inch or more of material completely annihilating it. That is several times the amount of material the initial pierce dealt with and I think that definitely shows that the torch is not only dishing out enough damage to overcome the DR but it is doing it several times a second. I can't speak to Jamie and Adam's experience because my googlefu is failing me (Got a URL?) but it seems we have seen very different examples of plasma torches. I know that hand held torches are designed to cut their max thickness at no slower than 10" per minute and the thinner stock goes much faster. CNC rigs can do 80 or more IPM.

I think the line of thought on having to treat the DR as semi or fully ablative is misguided and based on the relatively weak stats of tools that are light duty and meant to be highly portable. Neither the HT nor UT plasma torches detail how thick of a material they should be used for and that is what should be noted as well as the cutting speed in that thickness. Those stats answer the important story questions “Can we breach it?” and “How long will it take?”.

Re: [UT] Plasma Torch vs. big metal door on a spaceship?
 

In GURPS, Maximum Rof is 20. A cutting torch is a continues beam, so it should deal damage at least 20 times the listen damage in HT/UT. Probably you should consider over penetration rules if you don't move the torch, or move it to slow.

Re: [UT] Plasma Torch vs. big metal door on a spaceship?
 

I realize that, and I am saying that I would apply that rule to tools (cutting torches, etc.) against metal, armor, etc. The saws, torches, etc. in all the GURPS tech books work that way; it's how metal cutting tools work in the real world. That table you reference is referring to much larger areas (SM 0) rather than very small areas (SM -14 or so), and for non-tool attacks (such as super powers). If you are asking if there is a more canonical opinion, I don't know of one.

Re: [UT] Plasma Torch vs. big metal door on a spaceship?
 

https://en.wikipedia.org/wiki/MythBu...on)#Water_Safe

Episode "Crimes and Mythdemenors 2", segment "Water Safe. I see that they are referring to the tool used as a "thermal lance" rather than a "plasma torch".

There may be a YouTube video of at least part but I suspect it'd just be the climactic explosion.

Re: [UT] Plasma Torch vs. big metal door on a spaceship?
 

So could vicky_molokh and safisher do worked examples of figuring out how long it takes to cut a 1'x3' hole in a 2" thick airlock door?

Re: [UT] Plasma Torch vs. big metal door on a spaceship?
 

8' / cutting rate. Not much chance of getting realistic results from GURPS, though.

Re: [UT] Plasma Torch vs. big metal door on a spaceship?
 

Fred - here is the video I saw - https://www.youtube.com/watch?v=vsqFS7bbaMc

I would like to know how GURPS is supposed to stat something like this without it being a high damage paradigm.

Re: [UT] Plasma Torch vs. big metal door on a spaceship?
 

I don't know that there is an official answer. This is how I would do it.

The table in question says DR 112 and HP 75 for cutting a 10sqft hole in 2" steel. Also, I assume this works like for the bars and cables on the table -- that is, it's just an "attack" to achieve an effect. I'd reduce the HP, not the DR, for a proportionately smaller hole. I'd probably give the bonus for Forced Entry or an applicable tool operating skill, such as a repair skill.

As for how it works for a hot cutting tool, HT188 has thermite. It treats its attack as semi-ablative. According to Basic Set 415 you get max damage for contact explosions, so we will assume this max damage works for cutting tools not used in combat. Also, I'd treat a specifically designed cutting tool versus DR as ablative, not semi-ablative. It's not moving and you are specifically hitting a very specific point, i.e., all advantages go to the cutting tool.

A TL12 heavy graser torch is going to do 4d(10) per second. That's really DR11 versus Dmg 4d, max damage is 24, or 13 points per second. At 75 HP it'll take 6 seconds to cut the 10 square foot hole listed in the table, and less for a smaller hole.

A TL8 plasma torch does 3d+6(2), which means it's going to do 24 per second, facing DR 56. But it can't get through, so it will degrade that DR at -1 DR per second from 56 down to 0 in 56 seconds, after which point it can start doing damage of 24 per second, defeating the 75 HP in 3 seconds or so. And yes, you could start doing damage as soon as the DR is 23, so you'd save a few seconds if you figured it that way. Anyway, maybe a minute to cut through it. It's a lot slower than the TL12 torch above, but then, it should be.

That seems a decent WAG. Now, this assumes the GM would let the tool in question do it like this; I would not let a low-tech saw cut this material at all. I wouldn't allow this to work in combat where the target is moving, etc.

I'm not sure that answers the question in a canonical way, but maybe that's helpful.

Re: [UT] Plasma Torch vs. big metal door on a spaceship?
 

For a thing which is essentially unusable as a weapon I would not give it weapon stats. Its' "stats" would be ""makes cuts in common industrial metals of thickness x at rate y".

There isn't really a lot of reason to give it game stats or even describe its' workings in terms of combat Turns.

Re: [UT] Plasma Torch vs. big metal door on a spaceship?
 

The stats are in weaponized format because when you encounter a Wall etc. in GURPS, you have its stats in the format of HP, DR, perhaps but not necessarily material, and size. When someone makes a Binding or buys a Spaceship, you usually don't know the precise thickness of the targeted thing - you know the HP and DR. And so the cutting-tool stats need to be in a format that allows some sort of cutting-time calculation based on those stats.


Since when?

Re: [UT] Plasma Torch vs. big metal door on a spaceship?
 

Ultratech has many weapons over RoF 20, not sure where you got that.

Re: [UT] Plasma Torch vs. big metal door on a spaceship?
 

Then you're going to have to just make something up. You're not going to pass Reality Checks with a system created mostly to model projectile penetration at medium-high speeds when you're tying to handle what is only sort of "Burn" damage.

Re: [UT] Plasma Torch vs. big metal door on a spaceship?
 

We have stats for either destroying an object, or going through an object to hit someone else, but we don't have stats for "What if I want to cut a section out of an object?"

What I mean is for time/HP:

Cutting Point < Cutting Section < Cutting til Door is "Not Present"

Lowering DR makes no sense of the equation because you are lowering DR per location on the object. What I mean is, you cut a foot long slice in the door. If someone shows up with an assault rifle and shoots at it, the bullets are still going to bounce off.

Yet without lowering DR you will never be able to damage HP with a plasma torch. The only way to really make it work is if you can somehow treat cutting through the door as a series of cutting attempts through smaller increments of material. Like say, an inch. You figure DR/HP for that inch of area cut and figure out how many seconds of damage you have to do to that length. Then you determine the perimeter of the material you want to cut and apply inch by inch cuts.

... Which I think Safischer's suggesting.

Re: [UT] Plasma Torch vs. big metal door on a spaceship?
 

Err, we have rules for 'cut out a 10ft² section' rules, and they have been cited, but they're mostly calibrated to wood and stone. I'm looking to getting some of those clarified in contexts of metal and/or different-sized holes. Even HT drills are described in such a context, but some things aren't quite clear in it.

Re: [UT] Plasma Torch vs. big metal door on a spaceship?
 

Yeah, I spotted Safisher's post that this rule is somewhere after I wrote all that, so I figured everything is good. I don't know where that rule is written to figure it out, but I feel like if someone could just come up with some form of damage needed to cut an inch given DR/HP of material (I think DR is unchanging based on surface size but HP would change?) then you got your answer.

Re: [UT] Plasma Torch vs. big metal door on a spaceship?
 

For context on metals, I'd suggest ignoring DR entirely or effectively reducing it to no more than 1. This is based on layman's articles on real-life lasers and assuming that they would apply to both laser and plasma torches.

As I understand it, lasers initially heat up the surface of a material and as the surface heats, that heat penetrates more deeply as well as spreading laterally. Continuous beam lasers encountered a problem in that the surface continued absorbing heat even after it's transformation into the gaseous state because the laser beam effectively pressurized the gas preventing its escape and thereby degraded the efficiency of the laser. Pulse lasers were developed as a solution to the problem by briefly interrupting the beam to allow the heated surface gas an opportunity to "boil off" before resuming.

Assuming that laser and plasma torches have a pulsing interruption feature that allows the surface gas to boil off, it seems reasonable to say that the laser/plasma torch doesn't engage more than 1 mm of depth at any given instant, so it never has to deal with more than DR 1 due to thickness, so most of its burning damage is expended directly in attacking the HP of the wall.

Re: [UT] Plasma Torch vs. big metal door on a spaceship?
 

Exactly this. I am not following the logic of the 'must reduce DR' argument. The materials that this applies to are ones that generally lose material adjacent to the area being hit until a larger piece of it fails - block wall, stud wall, fracturing a rock etc. That doesn't really happen with a heavy plate of metal.

Unless I have missed something this is only true for some thickness of metal material. Take that TL 9 4D+1(5) torch to a half inch thick plate and you are doing avg dmg of 15 vs28DR/5-~6DR or 9 HP damage per second to it. [edited to correct DR of .5" steel]


As I stated earlier all plasma torches (and lasers, gas-axes, and water jet cutters) have a limit on how thick a material they will cut. Just letting it sit there and arc into the plate doesn't work once you've reached that limit. With plasma torches that limit seems to be closely associated with the amperage the rig can handle. It looks to me (still) like the examples given are pretty light weight ( the Heavy Plasma Torch is all of 40 pounds and works on Dp battery) and the real answer is get a bigger rig with more power. To me this is the equivalent of asking 'Why won't my 37mm AT penetrate the front of that Panther?"

As for cutting speeds we may have to do what we do for vehicles - look at actual stats and punt. There are graphs of cutting speed vs material thickness.

And yes it may very well be that on a damage per second basis that looks like the torch isn't doing as well as its damage would suggest it should. I would chock that up to the operation needing a certain amount of 'overkill' to maintain the arc or waste in needing to control the motion and not kill the arc etc. Remember what you are getting out of it is a hole right where you want it with out a lot of shrapnel flying around.

Re: [UT] Plasma Torch vs. big metal door on a spaceship?
 

Going off the YouTube timer, piercing starts at 0:13 (this is when the sparks start flying) and stops somewhere around 0:16 or 0:17 (when the sparks stop), for around 3-4 seconds there (not certain why the video says 2 seconds). The circle that gets cut out looks to have a diameter of approximately 2 inches (tough to say - the hole looks about as wide as the tool, which looks about as wide as the block is thick), and takes roughly 20 seconds (from around 0:18 to around 0:38 or 0:40) to cut all the way through. The second pierce is around 4 `seconds again (0:48-0:52), and that cut takes around 50 seconds (0:54-1:44). That shape is harder to quantify, but it looks like it could be approximated as a 3"x6" rectangle.

Assuming that chunk of steel were RHA (it probably isn't) or similar, that's 3-4 seconds to get through Cover DR 140, which the plasma torch from HT will do at maximum (or just consistently above-average for 4 seconds) damage if we just let things add up from round to round. Beyond that, we're looking at 20 seconds for a 2*pi in linear cut (the circumference of that circle), 50 seconds for 15 in. The first is 3.18 s/in, the second is 2.78 s/in. Considering the circle was done with two rotations - possibly just for added precision - I'd be tempted to go with 3 seconds per inch. That basically works out as something like piercing time per inch, which makes things a bit easier - work out pierce time, and multiply it by the length of the cut (or perimeter, if cutting out a section) +1 for the initial pierce. Realistically, torches have a maximum thickness - or perhaps just maximum DR - that they can reach. Looking at the specs for that particular model, that 2" pierce is actually around the best it can do, so something like a 3-second maximum may be appropriate. I don't know if the laser/plasma torches in UT work the same way, but it may not be horribly inappropriate to assume so.

For cutting into a thick metal door, then, a Fusion Torch (8d+2(5), or 50 damage vs 1/5th DR) has a piercing time of 0.2 seconds for a DR 50 door, 1 second for a DR 250 door, and at maximum can pierce through a 750 DR door in 3 seconds. Cutting a 2-yard by 1-yard "doorway" (to get through) takes P*217 seconds (perimeter of 216 inches, +1 for initial pierce), where P is Piercing Time - so around 45 seconds against DR 50, 217 seconds (~3.5 minutes) against DR 250, and 651 seconds (~11 minutes) for DR 750. Cutting a 1-yard diameter circle (to crawl/dive/fall through) takes P*114 seconds instead.

With the HPR400XD (the device from the video) and an airlock door made of steel, that's a 96" perimeter, for around 291 seconds. Using the Fusion Torch from UT, that 96" perimeter in a DR 150 or so airlock has a pierce time of 0.6 seconds, so you're looking at 58.2 seconds - about a minute to cut that hole.

These are all just rough estimates, but would probably work well enough for a game.

Re: [UT] Plasma Torch vs. big metal door on a spaceship?
 

It has been recently pointed out to me that Thermite (High-Tech 188) does turn metal armour semi-ablative for the purpose of cumulative damage (but only for a direct burn).
So what I'm thinking: should the two categories of TL9 torches be comparable to TL6 thermite for the purposes of cutting through metal? The question applies both to the 'normal' mode of functioning, and to some hypothetical higher-power mode of the devices.

Re: [UT] Plasma Torch vs. big metal door on a spaceship?
 

That sounds reasonable enough for both realism and playability.

Re: [UT] Plasma Torch vs. big metal door on a spaceship?
 

The question becomes how does it line up with the amount of energy spent by the torch when working from a power cell. E.g. a C-cell at TL9 seems to have an energy-per-unit-of-mass ratio that is slightly better than that of thermite; it would last about 20 seconds if it were to expend energy at the same rate as a stick of thermite from High-Tech, but a C-cell in a regular-sized torch lasts 15 minutes while doing ×2/3 the damage per second (counting by dice only) or ×3½ the DPS (counting dice multiplied by the armour divisor, since by Kromm ADs do affect the rate of armour ablation). How plausible is it for efficiency to be so much higher? How much higher can the efficiency be at TL9ish? I mean, it's 3 TLs of difference, but still.

(Other source of numbers: the regular Plasma Torch seems to require about ¼ the power compared to some modern plasma torches people tried bringing up.)

Re: [UT] Plasma Torch vs. big metal door on a spaceship?
 

Remember that thermite is radiating heat in all directions, while a torch is directing the majority of its energy into a very small area. That's what makes it more efficient than just putting thermite on what you want to cut through.

Re: [UT] Plasma Torch vs. big metal door on a spaceship?
 

It's a little bit more complicated than that. The "ash" from burning thermites is actually molten iron so the greatest damage from thermite is usually inflicted on the surface _below_ the burning mass.

Molten iron contains an enormous amount of energy by itself but when circumstances are right you get a layer of molten iron between the burning thermite and the surface below. That can transmit heat energy by conduction rather than radiation.

Your torch is having to work hard to be better at damaging materials than thermite.