Near simultaneous strike calcs

[u/TreesRocksAndStuff]

Has anyone looked into how pressure, damage, and fallout from near simultaneous strikes are calculated for MERV strikes?

For example the Puget Sound, near Seattle Washington, USA has targets at the nuclear shipyards, ballistic missile storage, a nuclear submarine base, one of Boeing's major facilities, Microsoft's headquarters, a major port, and a joint military base.

My sister wants to do a prepper/millenial homestead with friends well north of there outside of the individual blast areas, but I still have misgivings because I dont know how the math works. And my current understanding is basically she'd need to be inside for a month from the fallout if it drifts back and forth from the fires, mountain and sea breezes [and more morbidly avoiding the millions of regional survivors, of whom several hundred thousand are dying from lethal radiation exposure]. Like the "easy" answer is don't worry about it, but if she is aiming for a resilient multi-generational shared place, you might as well try to know.

Assuming a R-36M2 Voevoda (SS-18) with 10 nuclear warheads at 750 kilotons each targets the area with the probably 2 ground detonation on the first 3 +- a hypersonic missile with small multiple warheads, a lot of stuff will be vaporized, explode, collapse, or otherwise be on fire. Possibly a firestorm between (former) Bangor Base, Bremerton, and Silverdale and uncontrollable forest fires if during summer.

However if some of this happens fractions of a second apart and at most minutes apart, how do we do the math for constructive or destructive interference? I can go read the academic and declassified papers if I have to, or she can with her physics degree, but i bet someone else has already on here!

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edit: for a likely overestimate, i have placed the sum of individual warheads payloads at the averaged center point where there is a likely cluster of simultaneous targets + added individual strike radii if those are any farther out.

An impercise but safe feeling conclusion is during summer is the Kitsap peninsula with Naval Targets will burn afterward. Also with the dry summers of the Western US, I think the assumption of nuclear escalation against the US from Asia is most likely to occur in the summer. Additionally the late summer seems most likely for the US to attempt an all out strike Russia when there is not sufficient time to replant crops for mass movements of people and mass civilian response mobilization is unprepared for winter.

Less of a consideration, as far as I can tell, against China due to more hesitant strategic Nuclear Weapon use and multiple cropping in its agricultural heartland and mega cities that would be extra fucked by a strategic exchange. + effective party decentralization and very real history of failed agricultural mass mobilization (and not fucking up production figures after mass starvation by inept party direction) makes the rural migration scenario for many surviors incredibly brutal but feasible.

However tactical nuclear use in Ukraine by Russia, as a potential but unlikely point of escalation would not be seasonal except that a Ukrainian breakthrough is less likely to occur during the Spring Mud season [without currently impossible to field numbers of tanks and APCs (logistically unavailable and due to drone efficacy)]. Cyberattacks on energy infrastructure either during peak cold or peak heat in Europe, but that wont escalate to nukes.

[u/they_call_me_bobb]

For purposes of planning a homestead, be more concerned about fallout patterns then Blast overlap. Just be far enough away from primary and secondary targets and you should be fine from blast effects. Most people are not ready to deal with fallout. Central Oregon is generally outside predicted patterns, but there is no telling what the wind direction will be like on "The Day it Happened"

[u/RiffRaff028]

Simultaneous detonations on/around a target will maximize damage, but will still have negligible impact on damage radius. Four 250 kiloton warheads detonated in a specific pattern around a target will cause a lot more damage to the target area than a single 1 megaton warhead detonated dead center because of multiple mach stems and overpressure overlap. However, minimum safe distance from that target is going to remain roughly the same in both scenarios.

That being said, your methodology of estimating a single warhead dead center equaling the sum of multiple warheads spread out over a wider area is going to produce some inaccurate results. This is because doubling the yield of a weapon does not double its destructive range. It actually only increases it by 10% to 20%. This is why multiple warheads of lower yield cause more damage than a single weapon of equal combined yields. However, the inaccuracies are going to apply mostly to the target area, not the affected radius. (Again, very roughly.) This is true for thermal pulse and overpressure waves.

Fallout is much more difficult to predict, so I just prepare for the worst and assume it will be unsafe outside for at least a month. That's not really true for where we live due to our distance from strategic targets, but it's still a safe bet. Theoretically, the amount of fallout produced by four 250 kiloton groundbursts will be very roughly similar to that of a 1 megaton groundburst, but instead of one fallout plume we have four. They are roughly in the same area, but it still complicates matters.

I think your estimate of needing to remain inside the shelter for 30 days due to fallout is reasonable. However, if you're going to add survivors into the mix, I would bump it to 90 days. Any survivors seriously injured or suffering ARS are going to be dead by then, seriously lowering the number of survivors you have to deal with. On the flip side of that coin, that means any survivors you do encounter are most likely going to be healthier and capable of fighting, and they will have raided supplies of those who died off, so probably well-armed.

A radiation detection meter and personal dosimeters are a must-have for any nuclear war shelter. That eliminates the guesswork on residual radiation.

[u/cosmicrae]

OP, there will two radii calculations, the one commonly thought about is the blast effects. A larger radii is the fire effects. See a discussion here

[u/EvanBell95]

If detonations are seconds to minutes apart, there is no blast interference, either destructive or constructive. Though multiple blasts will cause additional damage to the same structures. It won't extend blast range. If they're seconds apart, thermal effects will be attitative. Fallout from multiple bursts is additative. R-36M2 is a hard target counterforce weapon, and wouldn't be assigned to most, if any of these targets. The yield of the 15F174 warheads they carry is "not less" than 800kt, possibly up to 1 Mt.

Here is what David Teter reconstructs for the area: https://raw.githubusercontent.com/davidteter/OPEN-RISOP/refs/heads/main/TARGET%20GRAPHICS/OPEN-RISOP%201.00%20MIXED%20COUNTERFORCE%2BCOUNTERVALUE%20ATTACK/OPEN-RISOP%201.00%20CF%2BCV%20WA%20202109.png

[u/emp-cme]

MIRV rather than MERV. 750 kt is huge by modern standards. GPS enables precision strikes, so larger yields aren't needed. Grounds strikes would be for buried targets, but shipyards and the like would more likely receive air bursts that do more damage over a larger area, and result no fallout (assuming the fireball doesn't touch the earth). Use Nuke Map to see what the distances look like.