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Old 06-20-2014, 03:09 AM   #1
z0boson
 
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Default Explosions and cover

Hello,

this is probably a very stupid question, but to which extend does cover protect against the shockwave of an explosion? The effect against fragmentation is obvious, but will the shockwave travel around cover? Will someone in a trench or behind a corner or behind some sandbags get full damage, no damage or something in between?

Thanks for your help!
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Old 06-20-2014, 06:32 AM   #2
ed_209a
 
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Default Re: Explosions and cover

My understanding is that explosive shockwaves can bounce, but not bend.

I think the cover would give full protection from an explosion, up to the point that the explosion destroys the cover, then whatever is left affects whatever is behind it. (plus possibly extra frag from the debris of the cover.)
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Old 06-20-2014, 09:36 AM   #3
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Default Re: Explosions and cover

Thank you. That is certainly the best solution game-wise, I am glad if it also represent reality well!
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Old 06-20-2014, 10:20 AM   #4
Anthony
 
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Default Re: Explosions and cover

Quote:
Originally Posted by ed_209a View Post
My understanding is that explosive shockwaves can bounce, but not bend.
They're waves, they can do both, but generally not very well, and it will certainly protect from incidental fragments. I'd probably treat cover as flexible DR.
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Old 06-20-2014, 11:45 AM   #5
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Default Re: Explosions and cover

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Originally Posted by Anthony View Post
They're waves, they can do both, but generally not very well, and it will certainly protect from incidental fragments. I'd probably treat cover as flexible DR.
My reasoning was also that the part of the wavefront corresponding to low frequency waves should be able ignore cover (after all you will certainly hear the blast behind cover). However, I have no idea if this corresponds to a significant part of the energy.

Treating cover as flexible DR is a nice and uncomplicated solution, thank you. I think I will adopt that.
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Old 06-20-2014, 11:58 AM   #6
Nereidalbel
 
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Default Re: Explosions and cover

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Originally Posted by z0boson View Post
My reasoning was also that the part of the wavefront corresponding to low frequency waves should be able ignore cover (after all you will certainly hear the blast behind cover). However, I have no idea if this corresponds to a significant part of the energy.

Treating cover as flexible DR is a nice and uncomplicated solution, thank you. I think I will adopt that.
Mythbusters covered this with the "injury" and "death" sensitive sensors. Long story short? Anything durable enough to not be destroyed outright by the blast wave causes some injury, but, not death.
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Old 06-20-2014, 11:58 AM   #7
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Default Re: Explosions and cover

Spall can be an issue - High Tech has some rules, although these are generally limited to HESH warheads (which are designed specifically to generate spall) and to the Renault FT17 (which is particularly susceptible to the phenomenon) and typically only come into play on direct hits. With the way waves propagate, the most accurate way to model how the shockwave affects protected characters would be to draw a straight line from the center of the explosion to the outermost limits of the cover, and keep going. This will designate the area (an infinite cone) that is protected by the cover - for everything outside of this area, determine damage normally. For "protected" targets, determine how many hexes they are from the line and add this value to their effective range from the explosion. So, let's have a character 2 hexes away from the explosion, meaning he'd normally take 1/6th the explosion's rolled damage. Put a piece of impenetrable cover close to the explosion, and he's now in the protected area. Let's say the closest line is two hexes away from him, and the point of intersection is 3 hexes from the explosion. The character is now effectively 5 hexes away, and suffers 1/15th the explosion's damage.

The easier way, of course, is to just assume if the cover isn't penetrated, the characters aren't damaged.
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Old 06-20-2014, 12:02 PM   #8
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Default Re: Explosions and cover

The other problem is that the GURPS explosion rules are sort of non-physical to start with, in that overpressure is actually quite crappy at killing humans. If you assume the 'damage' score from an explosion includes incidental fragmentation, cover will stop fragments fine.
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