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

[Joseph Paul]

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.

[safisher]

Originally Posted by vicky_molokh

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

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.

[Joseph Paul]

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?

[Anthony]

Originally Posted by Joseph Paul

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?

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

[Joseph Paul]

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.

[safisher]

Originally Posted by Joseph Paul

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?

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.

[Varyon]

Originally Posted by Joseph Paul

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.

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.

Originally Posted by Joseph Paul

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?

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.

[GodBeastX]

Originally Posted by vicky_molokh

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!

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.