Therefore, my house rule is that the ground-zero damage done by an explosion (at 1 meter range or less) is proportional to the square root of the energy released. I have selected a damage of 6d*8 for 1 kg of TNT; this is somewhat more than the standard amount in GURPS, but I think it matches reality better. To find the damage done by an explosion, first find out how many kg of TNT it's equivalent to (this is the mass of the explosive, multiplied by its REF). Take the square root of that number, then multiply by 48d and round off as convenience dictates.
Note: Most explosive warheads are not 100% explosive by mass. Of the
ammunition types in GURPS Vehicles (table on p. 112), only HEC warheads
should get their entire mass counted as explosives. Ordinary HE warheads
and others that do the same amount of damage (C*X/16,000 in that table)
should be counted as 75% explosive by mass; the rest is fragmented casing
or similar auxiliary stuff. APEX ammo is only 50% explosive by mass.
Formula: GZD = sqrt(mass*REF),
where GZD stands for "Ground-Zero Damage",
mass is in kg, and REF is the Relative Explosion Force (see High-Tech or
MA Lloyd's Vehicles addenda in the GURPSnet ftp site).
In atmosphere, the "lethal range" of an explosion seems to scale as the
cube root of the energy in the explosion. This fits well with a simple
physical consideration: If an explosion goes off in a homogenous medium,
the total volume subjected to at least some given level of "damage" should
be a sphere whose volume is directly proportional to the energy involved.
Since damage scales as the square root of the energy, this means that
damage should be inversely proportional to the 3/2 power of range. Yeah,
you'll need a calculator with a "power" button to compute this; who doesn't
have such a calculator in this day and age?
Formula: DAM = (GZD)/(range)^1.5
In space, the damage done by an explosion is pretty much entirely
transmitted by the flash of heat and light; there is no intervening
medium to absorb damage along the way, so the energy density is
inversely proportional to the square of the range. Damage should
then be inversely proportional to range.
Formula: DAM = (GZD)/(range).
Surface area (sf) Damage multiplier Below 5 x0.5 5-50 x1 51-125 x2 126-250 x3 251-400 x4 401-600 x5 601-850 x6 851-1100 x7 1101-1450 x8 1451-1800 x9 1801-2200 x10And so on, the progression should be fairly obvious. This should be precomputed for every vehicle and large critter. Back to GURPS page.