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Old 01-30-2014, 11:51 AM   #8
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Join Date: Jul 2004
Location: Montréal, Québec
Default Re: Explosive concussion damage: is GURPS not lethal enough?

Concussion isn't ideal for killing people. Fragments are more effective. That said, note a few things about real-world IEDs, converted to GURPS-speak:
  • The "average" IED (which might not exist, but the U.S. military does keep stats) is closer to 50 lbs. of ANFO, for a basic 6d×10 cr ex. Old artillery shells are also common; 6d×7 to 6d×11 cr ex is typical of the munitions used (100-125mm range). It would be sensible to use average damage for 6d×10, or 210 points, in discussions such as this one.

  • Thermobarics are turning up. Use the stats for the 93mm thermobaric RPG-7 or RPO-A warhead (High-Tech, pp. 148-149): 6d×9 cr ex, and divide damage by twice distance, not three times distance; see High-Tech, p. 170.

  • Many detonate under vehicles. This confines the blast. For a high-clearance vehicle, use Explosions in Enclosed Spaces (High-Tech, p. 181), which amounts to 1.5× damage because there are gaps between the wheels/tracks to relieve some of the pressure. For a low-clearance vehicle, the full 2× damage would apply (this is instead of Contact Explosions on p. B415, which amounts to ×1.7 damage).

  • Quite a few such devices use the rules for Explosively Formed Projectile (High-Tech, pp. 170), which instead apply the damage as pi++ with a (2) divisor at up to 200 yards.

  • A significant number of such devices have used Flat Charges (High-Tech, p. 183), which have special, somewhat complicated rules for failed DR penetration. Again, range is not relevant – in effect, this is a special kind of contact explosion.

  • If a vehicle sustains damage from any of the above, there will be fragments whizzing around inside. The Occupants and Vehicle Damage and Occupant Hit Table rules on p. B555 handle this. These are very likely to see people taking 4d cut, which averages 21 HP of injury.

  • Some IEDs are not intended for vehicles. These almost always include ball bearings, nails, or wound wire, and throw lethal fragments – anywhere from 4d (like a large antipersonnel mine) to 6d (like an artillery shell), most often cut or pi+ (×1.5 injury), or pi++ (×2 injury).
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