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Old 12-06-2022, 05:09 AM   #21
The Colonel
 
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Default Re: Explosive Arrows and Ancient Rockets

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Originally Posted by stranger38 View Post
Isn't the hale rocktet high explosive? something like dynamite?
Well then, didn't GURPS Napoleon have stats for the Congreve rocket ... which definitely was black powder?
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Old 12-06-2022, 09:49 AM   #22
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Default Re: Explosive Arrows and Ancient Rockets

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Isn't the hale rocktet high explosive? something like dynamite?
No. Nobody had high explosives that were stable enough for the purpose until pretty much the 20th century. Hale rockets were black powder.
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Old 12-06-2022, 10:44 AM   #23
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Default Re: Explosive Arrows and Ancient Rockets

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No. Nobody had high explosives that were stable enough for the purpose until pretty much the 20th century. Hale rockets were black powder.
A significant part of Jack Parson's / John Parson's / Marvel Parson's research before and during WW II was finding substitutes for black powder as a solid rocket fuel. (As a teenager, he was making better black powder rockets).
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Old 12-06-2022, 10:54 AM   #24
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No way black powder sunk a WW2 ship!!

It's the formula that don't get through my thick skull
Per page B415, multiply the concussion damage by the square root of (this rocket's REF / REF for serpentine powder). I think any fragmentation damage will be unaffected.

Eg. if the original rocket does 1d-1 concussion, and you change the warhead from serpentine powder (REF 0.3) to TL 5 Black Powder (REF 0.5) damage is 2.5 points x sqrt (5/3) = 3.2 points, so about 1d concussion
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Old 12-06-2022, 11:37 AM   #25
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I think any fragmentation damage will be unaffected.
You could probably just apply the same multiplier to it, so x1.15 to go from Serpentine to Corned, x1.3 to go from Serpentine to Improved Corned.

Of course, now that I work it out, the damage value given for the fire arrow (1d-1, I assume cr ex, or maybe cr ex inc) doesn't match the 1 oz charge. 1 oz is 0.0625 lb; 0.0625 lb of REF 0.3 explosive should deal 1.64d, or around 1d+2 (incidentally, with Corned and Improved Corned this would be 1.9d and 2.12d, or around 1d+3 and 1d+4, respectively). I'm away from most of my books; if the fire arrow has fragmentation, that could explain it... although losing over half of your explosive damage to producing fragments is fairly extreme*.

*EDIT: Actually, more than just "fairly" extreme. I dug up my old explosive-designing houserule (or at least found the last time I mentioned it on the forums) that generally matches the performance of most published fragmenting explosives, and found that it calls for every point of "sacrificed" explosive damage to be worth 2 point of fragmentation damage; thus, that would put that 1 oz charge as doing 1d-1 [2d-1] cr ex... and I'm pretty certain you can't generally have explosives that deal more fragmentation damage than explosive damage. So the arrow's charge probably contains less than 1 oz of serpentine powder...
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Old 12-06-2022, 04:40 PM   #26
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Default Re: Explosive Arrows and Ancient Rockets

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Originally Posted by Polydamas View Post
Per page B415, multiply the concussion damage by the square root of (this rocket's REF / REF for serpentine powder). I think any fragmentation damage will be unaffected.

Eg. if the original rocket does 1d-1 concussion, and you change the warhead from serpentine powder (REF 0.3) to TL 5 Black Powder (REF 0.5) damage is 2.5 points x sqrt (5/3) = 3.2 points, so about 1d concussion
Think i get it now.
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Old 12-06-2022, 06:29 PM   #27
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Of course, now that I work it out, the damage value given for the fire arrow (1d-1, I assume cr ex, or maybe cr ex inc) doesn't match the 1 oz charge.
Back at my books, I've found that none of the explosives in LT appear to use REF 0.3 for serpentine. The fire arrow - which doesn't produce shrapnel - as I already noted has less than half the explosive damage it should for an ounce of serpentine. The paper bomb - which is stated to contain 3-4 pounds of serpentine - similarly deals less than half the explosive damage it should. The iron bomb - which uses 14 pounds of serpentine - actually does have the correct explosive damage (6dx4)... but then gets a free 2d of fragmentation.

1d-1 cr ex calls for 0.0035 lb of TNT, while 5d cr ex calls for 0.174 lb of TNT. If we assume the latter contains 3 lb of serpentine, that gives both an REF of only 0.056 or 0.058... which seem too close to be coincidence. I guess those two used a really low-grade form of serpentine (fire arrows specifically state they use low-grade powder, at least) with something like an REF of only 0.06. Meanwhile, the iron bomb would deal 25d cr ex if it didn't produce shrapnel, which calls for an REF of 0.31... which is close enough to 0.3 we can assume that it is in fact using serpentine, and there's just a rounding issue involved (technically it should be 23d [2d] rather than 24d [2d], but the latter can be expressed as 6dx4 [2d], hence the books going with that).

So for your fire arrows, before upgrading to corned powder you kind of need to upgrade from the utter-crap quality black powder it's normally using to serpentine. Serpentine is $10/lb in LT, making an ounce of it cost only $0.625; having fire arrows making the arrow cost $6 more than normal (rather than the default +$5) would be more than sufficient to cover the difference. I'd say it may be appropriate to have serpentine fire arrows be +$6 and +1d+2 cr ex, corned fire arrows be +$7 and +1d+3 cr ex, and improved corned fire arrows be +$8 and +1d+4 cr ex.

Of course, it's also possible that, considering black powder isn't a true explosive (it's just something that burns quickly rather than something that detonates), the REF values are only appropriate if you keep it contained while it burns (as is the case in an iron bomb or a firearm). The fire arrow and paper bombs, however, can't properly contain the burning powder, hence a markedly weaker "explosion." If that's the case, then my previous suggestion - no bonus for corned, boost to 1d cr ex for improved - is probably appropriate. Sure, the weapons use a full ounce or even 3+ pounds of black powder, but only ~20% of it properly explodes, the rest just gets spread out and burns up without accomplishing much beyond producing smoke (and maybe igniting highly-flammable objects in the area).
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Old 12-06-2022, 08:37 PM   #28
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Default Re: Explosive Arrows and Ancient Rockets

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Back at my books, I've found that none of the explosives in LT appear to use REF 0.3 for serpentine. The fire arrow - which doesn't produce shrapnel - as I already noted has less than half the explosive damage it should for an ounce of serpentine. The paper bomb - which is stated to contain 3-4 pounds of serpentine - similarly deals less than half the explosive damage it should. The iron bomb - which uses 14 pounds of serpentine - actually does have the correct explosive damage (6dx4)... but then gets a free 2d of fragmentation.

1d-1 cr ex calls for 0.0035 lb of TNT, while 5d cr ex calls for 0.174 lb of TNT. If we assume the latter contains 3 lb of serpentine, that gives both an REF of only 0.056 or 0.058... which seem too close to be coincidence. I guess those two used a really low-grade form of serpentine (fire arrows specifically state they use low-grade powder, at least) with something like an REF of only 0.06. Meanwhile, the iron bomb would deal 25d cr ex if it didn't produce shrapnel, which calls for an REF of 0.31... which is close enough to 0.3 we can assume that it is in fact using serpentine, and there's just a rounding issue involved (technically it should be 23d [2d] rather than 24d [2d], but the latter can be expressed as 6dx4 [2d], hence the books going with that).

So for your fire arrows, before upgrading to corned powder you kind of need to upgrade from the utter-crap quality black powder it's normally using to serpentine. Serpentine is $10/lb in LT, making an ounce of it cost only $0.625; having fire arrows making the arrow cost $6 more than normal (rather than the default +$5) would be more than sufficient to cover the difference. I'd say it may be appropriate to have serpentine fire arrows be +$6 and +1d+2 cr ex, corned fire arrows be +$7 and +1d+3 cr ex, and improved corned fire arrows be +$8 and +1d+4 cr ex.

Of course, it's also possible that, considering black powder isn't a true explosive (it's just something that burns quickly rather than something that detonates), the REF values are only appropriate if you keep it contained while it burns (as is the case in an iron bomb or a firearm). The fire arrow and paper bombs, however, can't properly contain the burning powder, hence a markedly weaker "explosion." If that's the case, then my previous suggestion - no bonus for corned, boost to 1d cr ex for improved - is probably appropriate. Sure, the weapons use a full ounce or even 3+ pounds of black powder, but only ~20% of it properly explodes, the rest just gets spread out and burns up without accomplishing much beyond producing smoke (and maybe igniting highly-flammable objects in the area).
wow! 1d+4 with TL5 powder?
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Old 12-07-2022, 01:04 AM   #29
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Default Re: Explosive Arrows and Ancient Rockets

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B(technically it should be 23d [2d] rather than 24d [2d], but the latter can be expressed as 6dx4 [2d], hence the books going with that).
You seem to be assuming that dice of blast damage are converted directly into fragment damage on a one-to-one basis, which is questionable.
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Old 12-07-2022, 02:56 AM   #30
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Default Re: Explosive Arrows and Ancient Rockets

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You seem to be assuming that dice of blast damage are converted directly into fragment damage on a one-to-one basis, which is questionable.
It certainly doesn't match with real world munitions.
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