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Old 08-09-2008, 08:37 PM   #1
Jonas
 
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Default Nukes 4ed

I've been browsing the archives lately, and came upon this post regarding figuring out nuclear effects in 4ed. However when I ran it against the listed value for Little Boy in High Tech my values were off by an order of magnitude. Now I know the official stats have been tweaked for playability, but this was far beyond that.

So my question is, do these still give fairly realistic yet playable results or should I keep looking elsewhere?
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Old 08-09-2008, 10:37 PM   #2
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Default Re: Nukes 4ed

Quote:
Originally Posted by Jonas
I've been browsing the archives lately, and came upon this post regarding figuring out nuclear effects in 4ed. However when I ran it against the listed value for Little Boy in High Tech my values were off by an order of magnitude. Now I know the official stats have been tweaked for playability, but this was far beyond that.

So my question is, do these still give fairly realistic yet playable results or should I keep looking elsewhere?
GURPS High-Tech has some official stats for nuclear weapons.

Enjoy.

Mark
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Old 08-10-2008, 09:54 AM   #3
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Default Re: Nukes 4ed

Yes, for Little Boy (12.5 KT) and for a Generic 0.1 KT ADM "Suitcase" warhead. I own High Tech, have looked it over, and while I can get the generic weapon effects I was hoping for something a bit more detailed. Hence the reason I posted the link above, asking if the formula listed within it was at least close enough for gaming purposes partly due to the posts age.
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Old 08-10-2008, 04:00 PM   #4
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Default Re: Nukes 4ed

Quote:
Originally Posted by Jonas
I've been browsing the archives lately, and came upon this post regarding figuring out nuclear effects in 4ed. However when I ran it against the listed value for Little Boy in High Tech my values were off by an order of magnitude. Now I know the official stats have been tweaked for playability, but this was far beyond that.

So my question is, do these still give fairly realistic yet playable results or should I keep looking elsewhere?
Let's see, shall we?

Little boy was about 12 kT. Using the figures in the post in the above quote gives a thermal pulse of 6d x 1,400. Richard Rhodes' book The Making of the Atomic Bomb shows a radius of destruction of about 1 to 1.5 miles for the devastation that was Hiroshima. The bomb exploded at an altitude of 1900 feet, or 633 hexes. 1 mile is about 1600 hexes. At 1 mile from ground zero the distance to the bomb would be SQRT(1600^2+633^2)=1720 hexes, so at 1 mile the damage would be about 5d-1. At 1.5 miles, it would be about 3d+1.

Basic set says that a single hit that does more than 10 points of basic damage will ignite clothing and catch wooden shields on fire. You would thus get pretty much total ignition within 1 mile and significant ignition within 1.5 miles, about what happened historically.

The rules for explosives in GURPS scale badly with the quantity of explosives. For large blasts, choose whether you want to have the damage scale with the cube root of the explosive yield, but have the damage fall off as described for standard GURPS explosions, or to fall off as the square of the yield (as described) but have the damage fall off as the distance to the 1.5 power (this is easily calculated by looking up the distance on the Speed/Range table, finding the hit modifier, multiplying by 1.5, finding what range has that Speed/Range modifier, and dividing by that range. Let's say for our purposes we choose taking the cube root of the explosive yield and having the damage fall off linearly with distance.

In this case, we would get Little Boy delivering 6d x 450 cr damage for the blast. Again, the blast caused destruction out to about 1 to 1.5 miles. At 1 mile from ground zero, Little Boy would deliver 1d+2 cr damage. This is enough to shatter windows and smash through drywall, although framing lumber would probably still be standing.

Note that the most significant injury to people was due to the burns - the blast wave caused little actual injury but was much more effective at smashing structures.

The values in High Tech would have Little Boy igniting significant fires (10 points of basic damage) at 13,000 hexes, or 8 miles - this is much farther that what is observed in actual nuclear detonations. Likewise, the blast would cause 3d damage at more than 12 miles, well more that what is observed.

Here's a useful source to find your own scaling of blast damage
http://nuclearweaponarchive.org/Nwfaq/Nfaq5.html
It suggests Little Boy would have collapsed residential buildings at 2.3 km, or 1.5 miles, and would have caused 3rd degree burns at 1.2 miles. Third degree burns over much of the body are immediately incapacitating and very often eventually fatal (although they don't kill immediately), ignition of clothing usually occurs at about the distance at which the heat pulse would cause third degree burns (so 10 points of GURPS burn damage would be about right for this threshold). I'll let you decide what damage is typically necessary to collapse residential structures for setting blast damage (but keep in mind that unprotected people will survive those overpressures).

Luke
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Old 08-10-2008, 04:32 PM   #5
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Rember boys and girls that the only way to be certain is to nuke them from orbit.
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Old 08-10-2008, 05:52 PM   #6
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Default Re: Nukes 4ed

I appreciate the response, though I do have one question. Any idea why the damage in HT was so far off?

*Edit*

Thanks.
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Old 08-10-2008, 05:54 PM   #7
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Default Re: Nukes 4ed

Quote:
Originally Posted by Jonas
I appreciate the response, though I do have one question. Any idea why the value in HT was to far off?
Because the explosives scaling in Basic is incorrect.
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Old 01-31-2023, 02:04 PM   #8
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Default Re: Nukes 4ed

Hello, lwcamp (eh, asking after 12 years), thanks for your calculations, they helped me a lot with supers.
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so at 1 mile the damage would be about 5d-1. At 1.5 miles, it would be about 3d+1.
I tried calculating with your formulas, and for thermal radiation I was getting 5 points of damage at 1700 hex distance. Maybe am I missing something?
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Old 01-31-2023, 02:22 PM   #9
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Default Re: Nukes 4ed

Quote:
Originally Posted by KeplerMine View Post
Hello, lwcamp (eh, asking after 12 years), thanks for your calculations, they helped me a lot with supers.

I tried calculating with your formulas, and for thermal radiation I was getting 5 points of damage at 1700 hex distance. Maybe am I missing something?
It looks like the calculations probably divided by the distance in yards instead of by 3x the distance as per Campaigns???
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Old 01-31-2023, 08:54 PM   #10
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Quote:
Originally Posted by KeplerMine View Post
I tried calculating with your formulas, and for thermal radiation I was getting 5 points of damage at 1700 hex distance. Maybe am I missing something?
The tricky thing with explosions is that thermal radiation and blast overpressure don't fall off at the same rate. GURPS mostly ignores thermal radiation, which is OK for most conventional explosions, but it's a huge factor in nuclear blasts.

I'd start with a base of 10 HP of burn damage at the maximum listed historical distance for 3rd Degree ("full thickness") burns, then scale from there.
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