Going Nuclear (small question)

[FeiLin]

I can’t get the nukes from Spaceships p68 to line up with B414. So, a 25 kiloton nuke is 4d*10000 + 3d*10000 linked, so about 7d*10k. The formula on B414 says 6d*sqrt(lbs*4*REF), or 6d*sqrt(25000*2000*4*1) = 6d*14000+ = 7d*12k+. I seem to be ~20% off; have I missed something or is this a conscious rounding?

[Rupert]

It's probably rounding. But note that some of the Spaceships nuke damages are wrong. Also, though I might be wrong, I think I calculated that the SS nuke damage allowed for a small standoff distance.

[Anaraxes]

If a "megaton" is a million metric tons of TNT, then the value in the B414 formula should be 2200 pounds rather than 2000. So that's another 5% of difference.

Though even a 20% error is likely within the range for these formulae of gaming convenience, as opposed to textbook physics calculations.

[Fred Brackin]

Originally Posted by Anaraxes

Though even a 20% error is likely within the range for these formulae of gaming convenience, as opposed to textbook physics calculations.

Speaking of gaming convenience, there's already a simplifying assumption that nuclear bombs do a burning explosion and a crushing explosion in atmosphere but in vacuum the crushing explosion just goes away and you use only the burning explosion number.

Obviously nothing just goes away and the energy that was making the concussive blast wave in atmosphere is doing something else in vacuum. However, this is a case where even somewhat greater accuracy would bring disproportionately greater complexity.

My advice is to take the simplified answer and run with it. You can easily get into complexities that will not repay the effort that would have to be put into them.

[FeiLin]

Thanks!

Originally Posted by Anaraxes

Though even a 20% error is likely within the range for these formulae of gaming convenience, as opposed to textbook physics calculations.

Originally Posted by Fred Brackin

My advice is to take the simplified answer and run with it. You can easily get into complexities that will not repay the effort that would have to be put into them.

Sure, I dont have a problem with simplifying for the sake of gameplay. I was more trying to figure if I should go back to the formula or just fiat the numbers available for weapons.

[Fred Brackin]

Originally Posted by FeiLin

Sure, I dont have a problem with simplifying for the sake of gameplay. I was more trying to figure if I should go back to the formula or just fiat the numbers available for weapons.

I won't say that the exact numbers for nuclear explosions make"no" difference but you have to have a pretty estreme ship for them to really matter.

For example, a 10 megaton warhead in a proximity hit does 2800 dDam and that's a lot. A TL12^ SM+15 ship with a Heavy Force Screen does have dDR 3000 and can shrug off such a hit though it's best possible armor is only dDR 700 per layer. The TL11^ version can't shrug off such a hit and of course a direct hit does 100x more.

So most of the time a hit from a nuclear warhead (even proximity) is going to mean an effective kill for most ships. In universe navies are probably goign to worry more about point defense and as GM I might too.

[FeiLin]

Originally Posted by Fred Brackin

I won't say that the exact numbers for nuclear explosions make"no" difference but you have to have a pretty estreme ship for them to really matter.

For example, a 10 megaton warhead in a proximity hit does 2800 dDam and that's a lot. A TL12^ SM+15 ship with a Heavy Force Screen does have dDR 3000 and can shrug off such a hit though it's best possible armor is only dDR 700 per layer. The TL11^ version can't shrug off such a hit and of course a direct hit does 100x more.

So most of the time a hit from a nuclear warhead (even proximity) is going to mean an effective kill for most ships. In universe navies are probably goign to worry more about point defense and as GM I might too.

I’ve made similar observations, and I’d like to remedy that (doesn’t make for cool enough space battles for my taste). My first instinct was to check if it’s according to B-RAW or not.

The reason I’m a bit picky with the solution is that it would be neat if the damage was consistent with “character scale”, so that perhaps an nuclear arsenal storage facility could be turned into improvised bombs, etc. Of course, actual damage might matter even less on that scale. Still, it’s aesthetically pleasing and in the spirit of GURPS.

Point defence is a good idea, though, so if nothing else, perhaps that’s the solution. Thanks for the tip!

[Fred Brackin]

Originally Posted by FeiLin

perhaps an nuclear arsenal storage facility could be turned into improvised bombs,

I can't say whether or not the neutrons from one bomb might set off another bomb is they were touching outer casing to outer casing. It's probablyt an extremely technical (and specialized) question but it is somehting like what happens in a modern multi-stage nuclear device (though both nuclear cores are inside the same casing then).

Spaceships hypothetical fusion-only devices are even harder to say anything about as you need temperature and pressure rather than neutrons to set those off. Making large fusion-only nuclear devices explode might be very difficult.

[AlexanderHowl]

Nuclear bombs are usually stored in such a way that an accidental detonation cannot cause a chain reaction (though there will be nuclear material spread everywhere). Now, nuclear pulse bombs and nuclear pellets could potentially be set off by a direct hit, though that is academic given the fact that a direct hit will likely vaporize the ship.

[Ulzgoroth]

Originally Posted by Fred Brackin

I can't say whether or not the neutrons from one bomb might set off another bomb is they were touching outer casing to outer casing. It's probablyt an extremely technical (and specialized) question but it is somehting like what happens in a modern multi-stage nuclear device (though both nuclear cores are inside the same casing then).

I'd think it would be a pretty solid no, assuming we mean a proper detonation rather than a possibly damaging misfire.

The neutron flux would certainly induce fission in fissionables. But it won't change that those fissionables aren't arranged in a configuration that allows them to achieve supercriticality.

Neutron flux could easily destroy a fission bomb, but it would be nigh-impossible to cause it to detonate anything like as intended. Unless the incoming flux is so high that it substitutes for the internal neutron density that would be generated during normal prompt criticality... Which would mean that the area around the bomb has been hit harder by the incoming flux than it will be by the energy released from the bomb!

Originally Posted by Fred Brackin

Spaceships hypothetical fusion-only devices are even harder to say anything about as you need temperature and pressure rather than neutrons to set those off. Making large fusion-only nuclear devices explode might be very difficult.

Seems about as plausible as detonating a modern fission device by setting off a conventional bomb next to it - you'll certainly break it, but it's functionally and maybe even physically impossible to do so in a way that makes the active material do its thing.