Our Words Are Backed By…

[lugaid]

Nuclear Weapons!

I was looking through the tech books, and I noticed that High-Tech and Ultra-Tech differ on the matter of nukes. In HT, p. 195, it says that a nuke's burning damage (and associated radiation and surge) is divided by 2×distance in yards from the detonation. Okay, good. Unfortunately, UT differs on this issue, stating on p. 156 that the burning, etc. damage is divided by just the distance from the blast center. Now, I can see an argument, not a good one mind, that UT nukes are just that much more efficient, but this seems like a matter for errata to me. Which of these makes more sense? I am leaning toward dividing by double the distance, but that wave of heat and radiation could very well be more extensive. Since it's an erratum either way, should we call in an editor on this one?

[Rupert]

You'll note they also give different damages for a 0.1KT nuke, too. UT assumes the total dice of damage is split between the types (so does Spaceships, errors aside), while HT assumes it's referring only to the blast damage, with the flash damage as a 'bonus'.

As for your question, damage dropping off at a rate of 1xrange as in UT makes sense if damage is assumed to be proportional to the square of energy. However, for energy weapons the assumption in GURPS is that damage is assumed to be proportional to the cube, which better fits 3xrange, though that isn't really correct either.

The funny thing is, what changing the multiplier really does is alter the amount of burn damage compared to blast damage. In either case the effect is still 'double the range, halve the damage'.

Here's the really messy part - both books bundle radiation damage into the flash, and radiation in GURPS is measured linearly (as it is in real life), which means it drops off with the square of range (actually a bit faster, due to atmospheric absorption and scattering).

I'd go with 3xrange for both effects and call it a day, unless being nuked is a major part of the game, in which case I'd do some research and go with descriptive effects rather than simple damage rolls, because the way people get hurt by nukes compared to the way buildings and cars do is different, how much flash damage you take is affected by the colour of your clothes and how clear the air is that day, and so on.

[Varyon]

Originally Posted by Rupert

You'll note they also give different damages for a 0.1KT nuke, too. UT assumes the total dice of damage is split between the types (so does Spaceships, errors aside), while HT assumes it's referring only to the blast damage, with the flash damage as a 'bonus'.

I think the HT method is the way nukes are rated IRL - that is, their rating is based on explosive power, not simply "all energy that is released." I could be mistaken, however.

Due to UT having... issues, whenever there are disagreements between it and a later book, I usually favor the later book. In this case, I'd go with HT's rules - explosive power equal to nominal yield, radiation damage of 70% of explosive damage, and divide radiation damage by 2x(distance in yards). UT may have access to cleaner pure-fusion nukes; I'd put the radiation damage of such at 30% or 50% of explosive damage, but that's mostly just pulling numbers out of the air.

[The Colonel]

Did anyone ever stat unconventional atomics like the neutron bomb?

[Varyon]

Originally Posted by The Colonel

Did anyone ever stat unconventional atomics like the neutron bomb?

Hmmm... looking it up on Wikipedia, a typical Fission bomb is 50% blast, 35% thermal, 5% immediate radiation, and 10% residual radiation. The GURPS stats probably concern themselves mostly with the first three, but we'll assume immediate and residual are rolled together for radiation.

Neutron bombs, on the other hand, are 30-40% blast, 20-25% thermal, 30-45% immediate radiation, 5% residual radiation. Let's assume minimal blast/thermal and thus maximum radiation. This sets us to 30% blast, 20% thermal, and 50% radiation.

For a 0.1 kiloton "tactical" warhead, HT gives 6dx900 cr ex + 6dx650 burn ex rad sur. Considering the above actually releases 0.2 kilotons (the rating is specifically for the blast), with the Wikipedia proportions we'd expect 6dx900 for the blast, 6dx750 for the burn, and... some amount of radiation damage (hard to say exactly how that scales). The burning damage is lower than anticipated, corresponding to something more like 25% thermal rather than 35%. That would leave 25% of the energy as radiation, and as burn rad means the target takes rads equal to the burning damage, that tells us rad scales the same way as blast and thermal, which is useful.

With that in mind, a 0.1 kiloton-equivalent neutron bomb would deal 6dx700 from the 60-ton blast, 6dx550 from the 40-ton thermal output, and 6dx900 from the 100-ton radiation. That works out to 6dx700 cr ex + 6dx550 burn ex rad sur + 6dx350 tox ex rad (the 6dx900 is split between burn and tox).

An easy way to do the adjustment may be to take the stats of a comparable "traditional" nuclear warhead, switch the cr and burn damage, cut the resulting burn damage in half, and note the radiation damage is actually twice the burning damage (rather than equal to it). The above becomes 6dx650 cr ex + 6dx450 burn ex2 rad2 sur. Note ex2 means the second level of the Explosive Enhancement (divide by 2 per yard rather than by 3 per yard), rad2 means you take double the burn damage in rads. Compared to the above, it loses 7% of its blast damage and nearly 20% of its burn damage, but it retains its radiation damage (the primary point of a neutron bomb anyway) and is simpler to use in-game. Provided you're in a game where neutron bombs are a common enough occurrence to worry about simplicity, anyway (GURPS Rick and Morty?).

Optionally, because the surge effect is due to the radiation, treat surge-susceptible targets as though they took twice the burn damage to determine if surge comes into play. This is a bit of an edge case, however - you'd have to take between a point over 1/6th and exactly 1/3rd HP in burn damage for it to make a difference. Assuming average damage (9450 burn ex2 rad2 sur2) and nothing in the way, and an HP 30 machine, you'd take 10 HP damage at 430 yards, and 6 HP damage out to 787 yards, so between these two ranges, the sur2 nature will require the character to roll against HT to avoid shorting out. Any closer, damage is above 1/3rd HP anyway and have to roll; any further, and the doubling doesn't put damage over 1/3rd HP.