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Old 09-04-2018, 04:34 PM   #1
JazzJedi
 
Join Date: Dec 2014
Default Realistic lightning damage

As I understand it, an average lightning strike carries 30,000 amps of current, 15 coulombs of electric charge and delivers 500 MJ of energy. Large bolts of lightning can have 120 kA of current. Ok, so GURPS uses the energy to determine damage, but this is probably not a good fit for lightning. A direct hit with a 500 MJ lightning bolt would deal about 3dx100 damage according to the formula from GURPS Space. That is WAY too much, or is it.

As I understand it, most lightning strikes are actually from splash strikes, so I put lightning damage as burn ex sur. Since splashes are known to occur out to 20 yards from the impact spot, this would divide the rolled damage by 60 would still be 16 damage on average! Is that excessive? 3dx100 damage would vaporize a person, and I don't think this is what happens. The current flows through the person (or creature) and does damage proportional to the amount of cooked flesh it does as it passes through. Elephants have been known to die from a direct hit from lightning, but most people survive even direct hits. It seems rather random.

Is there a way to model lightning damage more realistically? Should the damage be a random percentage of a creature's total HP, up to a maximum amount as determined by the energy? For example, you could say that a person hit by lightning takes damage equal to 4d-4 x 10% of the creature's total HP, to a maximum of 1,000 HP (average damage from a direct hit at 3dx100 damage)?
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Old 09-04-2018, 04:51 PM   #2
whswhs
 
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Default Re: Realistic lightning damage

There are a couple of things to consider about lightning. The first is that a bolt does have that huge amount of energy (subject to a lot of variation), but the energy is not all released at one point; it's released along an irregular curve thousands or tens of thousands of feet long. Only a small fraction is released within the six feet length of a human body. The second is that it may largely flow down the outside, rather than through the interior, and that makes a difference. The third is that it's all released in a fraction of a second. That is, it's mathematically similar to a nonlethal shock, which can have an incredibly high current during the spark but has a much lower average current. The current is still high enough to do real damage, but it's not comparable to putting your hand on a power line at the same voltage while you're grounded, where the power stays on (until it shorts out through your charred remains).

I would go with the figure in the Basic Set: 6d burning damage with a HT roll to see if you lose consciousness or your heart stops. With 6d damage, you'll roll HT-10, on the average, so getting a direct hit will stop your heart unless you get lucky. The burning damage also has a chance of being enough to kill you from cumulative injury. But as the GM, you're free to assume that there are mitigating factors that decrease the severity of the effect. And lightning is just so unpredictable that I wouldn't try to go beyond leaving it up to GM judgment.

(In your figures, for example, 15 C and 30,000 A implies that the charge is released in .0005 seconds, if you assume uniform flow, or maybe a few times that, if you assume a rise, peak, and fall. The average current flow over a full second is only 15 A, which is still lethal, but a lot less so.)
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Old 09-04-2018, 04:57 PM   #3
Anthony
 
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Default Re: Realistic lightning damage

That energy figure is for the entire length of the lightning bolt, and to figure the actual effect on a target you need to know the target's electrical conductivity, as well as the path the lightning takes.
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Old 09-04-2018, 05:37 PM   #4
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Default Re: Realistic lightning damage

Check out Powers:
Quote:
Originally Posted by Power page 117; Boxed section Benchmarking
Electricity (p. B432): Household current inflicts 3d burning damage, at worst. Industrial accidents and lightning bolts start at 6d and range up to 6dX3.
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Old 09-04-2018, 07:02 PM   #5
JazzJedi
 
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Default Re: Realistic lightning damage

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Originally Posted by whswhs View Post
There are a couple of things to consider about lightning. The first is that a bolt does have that huge amount of energy (subject to a lot of variation), but the energy is not all released at one point; it's released along an irregular curve thousands or tens of thousands of feet long. Only a small fraction is released within the six feet length of a human body. The second is that it may largely flow down the outside, rather than through the interior, and that makes a difference. The third is that it's all released in a fraction of a second. That is, it's mathematically similar to a nonlethal shock, which can have an incredibly high current during the spark but has a much lower average current. The current is still high enough to do real damage, but it's not comparable to putting your hand on a power line at the same voltage while you're grounded, where the power stays on (until it shorts out through your charred remains).

I would go with the figure in the Basic Set: 6d burning damage with a HT roll to see if you lose consciousness or your heart stops. With 6d damage, you'll roll HT-10, on the average, so getting a direct hit will stop your heart unless you get lucky. The burning damage also has a chance of being enough to kill you from cumulative injury. But as the GM, you're free to assume that there are mitigating factors that decrease the severity of the effect. And lightning is just so unpredictable that I wouldn't try to go beyond leaving it up to GM judgment.

(In your figures, for example, 15 C and 30,000 A implies that the charge is released in .0005 seconds, if you assume uniform flow, or maybe a few times that, if you assume a rise, peak, and fall. The average current flow over a full second is only 15 A, which is still lethal, but a lot less so.)
6d damage, even on a critical hit doing double damage will not come close to killing multiple elephants, or a herd of reindeer (from a single lightning strike), all of which have happened. The HT -1 per 2 points of damage, I assume would be scaled to total HP, so an elephant (with 43 HP) would only roll HT -1 per 8 points of damage.
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Old 09-04-2018, 08:16 PM   #6
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Default Re: Realistic lightning damage

Quote:
Originally Posted by JazzJedi View Post
6d damage, even on a critical hit doing double damage will not come close to killing multiple elephants, or a herd of reindeer (from a single lightning strike), all of which have happened. The HT -1 per 2 points of damage, I assume would be scaled to total HP, so an elephant (with 43 HP) would only roll HT -1 per 8 points of damage.
In the first place, I don't think there's any indication of the scaling you suggest. In the second place, the 6d is only the part of the electrical energy that is released over the 6 feet of a single human body. If it hit multiple people, each would experience a comparable energy release; after all, the total bolt is thousands of yards long, probably, and the energy isn't concentrated in one stretch. Treat it as an area attack doing X damage on each target in the area.
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Old 09-04-2018, 09:52 PM   #7
JazzJedi
 
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Default Re: Realistic lightning damage

Quote:
Originally Posted by whswhs View Post
In the first place, I don't think there's any indication of the scaling you suggest. In the second place, the 6d is only the part of the electrical energy that is released over the 6 feet of a single human body. If it hit multiple people, each would experience a comparable energy release; after all, the total bolt is thousands of yards long, probably, and the energy isn't concentrated in one stretch. Treat it as an area attack doing X damage on each target in the area.
That is a very good point about the 6d as an area attack. Thanks. Of course, as previously indicated in Powers, large bolts of lightning can do 6dx3 damage, so I think that actually solves my problem.
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Old 09-04-2018, 09:56 PM   #8
Anthony
 
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Default Re: Realistic lightning damage

Note that realistically, most area attacks should adjust their damage and/or wounding based on the size of the target.
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Old 09-04-2018, 09:56 PM   #9
whswhs
 
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Default Re: Realistic lightning damage

Quote:
Originally Posted by JazzJedi View Post
That is a very good point about the 6d as an area attack. Thanks. Of course, as previously indicated in Powers, large bolts of lightning can do 6dx3 damage, so I think that actually solves my problem.
Sure. Use 6d for normal lightning strikes, and multiples for extraordinary ones. I just thought you were mainly concerned with not having the damage so severe as to make death nearly inevitable for a normal person; for that, of course, you could decide to decrease the number of dice. In any case it's going to be a judgment call on your part; lightning is really unpredictable!
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Old 09-04-2018, 10:54 PM   #10
JazzJedi
 
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Default Re: Realistic lightning damage

Quote:
Originally Posted by whswhs View Post
Sure. Use 6d for normal lightning strikes, and multiples for extraordinary ones. I just thought you were mainly concerned with not having the damage so severe as to make death nearly inevitable for a normal person; for that, of course, you could decide to decrease the number of dice. In any case it's going to be a judgment call on your part; lightning is really unpredictable!
I think I'll roll 1d for the number of dice of damage of an "average" lightning strike. I'd roll 2d for a powerful strike, and 3d for an immense one. Maybe 1d-2(minimum 1) for a weak strike.
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