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Comment by arandomusername | Hacker News Reader

> I wonder if the bunker buster was used

Most certainly was. It's underground (Fordow is ~60m?) so it's either that or nukes.

As I understand it enrichment is by gas centrifuge or thermal diffusion. An earthquake bomb would disrupt both. You wouldn't be starting the feed cycle up rapidly, but since we're told Iran has stockpiles, this goes to sustainable delivery of materials more than specific short term risk.

As a strategy, I see this as flawed. A dirty bomb remains viable with partially enriched materials.

(This does not mean to imply I support either bombing or production of weapons grade materiel. It's a comment to outcome, not wisdom)

Iran is prone to earthquakes, would an earthquake bomb do more damage than that?

Even if it just damages the centrifuges, as far as I see it, it would just delay their enrichment process, severely less than total destruction of their underground base.

Yes that's basically my point. They recalibrate, tighten the pipes, and flush the contamination back out of the chain. 6 to 8 weeks/days/whatever later it's back in cycle.

If they can even get back in

Uranium, especially highly enriched uranium, is not very radioactive. That's one of the reasons its useful for weapons. UF6 is chemically really nasty, but it's heavy and also you have criticality issues that limit how much you can pack into a confined space before it explosively disassembles. That is to say, it would make an extremely poor dirty bomb that would do very little. It'd scare people of course but there are far easier things they could use to achieve that.

Far more concerning is the possibility that they give it away to someone else. Enrichment is nonlinear, going from 60% to the 90% needed for weapons is a fairly trivial amount of work.

> It'd scare people of course but there are far easier things they could use to achieve that.

I wouldn't discount it, though. Remember, feelings matter more than facts. Magnitudes more people die on the road than in the air, but we know how well that translates to fear and action.

I mean heck, how about 9/11 compared to COVID? Wearing a mask for a while: heinous assault on freedom, Apple pie, and the American way. Meanwhile, the post-9/11 security and surveillance apparatus: totally justified to keep America safe

Yeah, my point is there are much better options that would also induce fear and actually be effective. Fentanyl strapped to an explosive, or any of a ton of other chemical agents. Iran would do far more damage -- and create a deep source of fear that would likely have lingering consequences for decades -- by giving their HEU away rather than making an ineffective dirty bomb. There is no way anybody who knows what they had would use it that way. Even the most fanatical member of the Iranian regime understands what to do with the material better than that.

While true, the problem is it wouldn't meaningfully change the security situation for Iran.

Deliverable nuclear weapons make you invasion proof - nobody wants to risk it. A "dirty bomb" isn't something that can come flying in on an ICBM and eliminate large chunks of your nation - the threat of it is more likely to enhance aggression rather then deter it.

I'd say the same could be said for 9/11, which didn't really achieve anything positive for anyone but did make for a large bit of "The US hurt itself in its confusion"

    > Enrichment is nonlinear

Can anyone explain the science behind this statement? To be clear: I believe it, and I have seen multiple reputable sources say that Iran can enrich to 90% within a few months. I was surprised that it is so quick.

You start with natural uranium, which has .72% U-235. Getting from that to 20% is _hard_. You need large cascades of centrifuges to do this because it's only .72%, so each stage gets you just a wee bit more enriched. You do this over and over and over again until you get to higher enrichment. Once you have HEU enriching further is very easy for the same reason that it was hard when it was unenriched: now the stuff you don't want (U-238) is much less. To get from 80% HEU to 96% is trivial using the same centrifuge cascades, and how long it takes really depends on a) how much 80% HEU you have, and b) how much 96% HEU you want. If you have 100lbs of 80% HEU then to get to 10lbs of 96% HEU might really only take weeks if not less when it might have taken years to get from .72% to 80%.

Yep, https://web.mit.edu/22.812j/www/enrichment.pdf is a good starting point if anybody wants to learn more about the economics/logistics of enrichment. Though, it's a notoriously confusing topic so it could take some reading.

Tl;dr is that the amount of energy required to separate a mixture of gasses (U238 waste and U235 product) is roughly proportional to the logarithm of the ratio of the U238 percentage and the U235 percentage. So as your feed stream becomes more enriched in U235, it becomes much easier to do subsequent separations. This log relationship is an approximation, but arises out of the statistical mechanics of separating two mixed gasses and the resulting decrease in entropy.

Edit: a key point most people I'm guessing aren't aware of: centrifuges don't really care what you feed them, whether the feed is natural or 20% or 89% enriched, they just get increasingly more efficient so that a single "pass" through them produces a greater amount of separation as the feed stock becomes more enriched. They do a fixed amount of "separative work" each pass. The same machines can be used to enrich from natural to 20% as 20%-90% (with some relatively minor caveats), and in fact it takes far fewer machines to do the 20-90 step at the same rate as natural-20.

You know how Shannon entropy works in CS, compression and stuff? Atoms work the same way: their mixing entropy is that same x*ln(x) sum which is an extremely steep function near its boundaries. That's your non-linearity. That statistical entropy corresponds to macroscopic thermodynamic properties, enthalpy and work. The starting uranium atom ratios, 0.7%/99.3%, are a very unbalanced mixture deep into that non-linearity side.

https://en.wikipedia.org/wiki/Entropy_of_mixing

(The other half of it is that, as you progressively enrich, you start to discard the "depleted" part of the mass flow, and work only with the, gradually smaller, "enriched" mass flow).

Remember that Israel had more nuclear bombs than China and never signed any international as tmy treaty.

China is estimated to have approximately 600 nuclear warheads. China is rapidly expanding and modernizing its nuclear arsenal and is projected to reach at least 1,000 operational warheads by 2030.

Israel is widely believed to possess around 90 nuclear warheads.

Israel never acknowledged that. It is claimed that the US president at the time demanded that Israel kept this a secret to avoid embarrassment to the US.

Iran repeatedly calls for death to Israel and the USA. Israel never did that.

Israel doesn't talk about destroying Gaza, it just does it.

They absolutely do talk about it. Maybe you should ask yourself why you never heard about it though.

> Iran repeatedly calls for death to Israel and the USA. Israel never did that.

Calling for it and being actually able to do it are two very different things.

It is similar to swearing at someone "Fuck you". It doesn't mean you're actually able and willing to.

So based on your logic we should just let them gain that ability and see what happens?

> It is similar to swearing at someone "Fuck you". It doesn't mean you're actually able and willing to.

Since they conducted decades of terrorism against Israel the USA and our allies a more apt example would be a person who repeatedly stabbed our friends is trying to get a bomb that could kill us all.

It's amazing to me how people are willing to give the benefit of the doubt to people who literally led terrorist attacks against their country. To people who would stone gay people and punish women for the crime of rape. But won't give a similar benefit of doubt to the people opposing them. Who won't consider that, maybe, just maybe, the stuff you read on the internet isn't the whole truth.

> Since they conducted decades of terrorism against Israel the USA and our allies a more apt example would be a person who repeatedly stabbed our friends is trying to get a bomb that could kill us all.

I'm going to play a childish game with you: who started it first?

> Who won't consider that, maybe, just maybe, the stuff you read on the internet isn't the whole truth.

Are you saying people on the internet lie?

> I'm going to play a childish game with you: who started it first?

You can say that the CIA. Not Israel. But again that's a child's game just like you said.

How many Jews conducted suicide bombings in Germany after the holocaust?

We moved on, I can't say forgive and forget but we go to Germany and Austria. We talk and we live.

> Are you saying people on the internet lie?

Yep. And exaggerate and simplify the wrong things.

> A dirty bomb remains viable with partially enriched materials.

A dirty bomb is basically Hollywood nonsense, and wouldn't use uranium to begin with because it isn't very radioactive.

The premise is that you put radioactive materials into a conventional explosive to spread it around. But spreading a kilogram of something over a small area is boring because you can fully vaporize a small area using conventional explosives, spreading a kilogram of something over a large area is useless because you'd be diluting it so much it wouldn't matter, and spreading several tons of something over a large area is back to "you could do more damage by just using several tons of far cheaper conventional explosives".

Also anything that is dangerous enough to actually be scary in dirty bomb form, like Cobalt-60, would be impossible to handle without providing a lethal dose of radiation to anyone working with he material within minutes if not seconds (presumably a reasonablely large & dangerous amount of this material is involved). At least, not without incredibly expensive equipment. And by the time you factor in those prerequisites it's just not worth it.

The toxicity of the Uranium would be a bigger problem than the radioactivity

And has the same issue with dilution, and is even more boring because there are much cheaper things with more chemical toxicity than uranium too, like lead.

It isn’t any more toxic than lead, which this bomb probably was filled with.

> earthquake bomb

https://en.wikipedia.org/wiki/Earthquake_bomb for others who haven't heard the term

Kinda reminds me of how depth charges work

> As I understand it enrichment is by gas centrifuge or thermal diffusion.

Centrifuges. They got them via the A. Q. Khan network. We learned about if circa 2005 from Qaddaffi who gave up his to secure peace and his safety (and it didn't turn out well for him because Obama did not respect the gentleman's deal Qaddaffi had with Bush).

Whatever about bombing Iran with conventional weapons, being the first president since Truman to nuke another country would split Trumps support base, and also legitimize using nuclear weapons in regional conflicts which would be extremely bad news for Ukraine

the bunker buster, if used, will almost certainly be nuclear. estimated tonnage: 300 kt

The GBU-57 was most likely used, which is non nuclear

MOP is a conventional weapon, 30,000 lbs. Only the B-2 is rated to carry it.

https://en.wikipedia.org/wiki/GBU-57A/B_MOP

Genuinely surprised that Israel couldn't push one out of their c-130s

Do they even have access to this variant? I thought they had access to the older ones that weren't as advanced.

They do not.

The MOP isn't particularly 'advanced', it's basically refined version of the Korean-vintage Tarzon guided earthquake bombs. It's just too heavy for most military aircraft to carry.

The IDF has the F-15I which has a centerline hard point rated for 5,000lb load. That's immense for a fighter but a magnitude too low for the MOP.

There are a variety of smaller US penetrating bombs that the F-15 can handle, but they don't have the mass and structure to penetrate as deeply.

Don't think the C-130s can fly high enough with a single 30,000lb bomb. The graphic at bbc site show it would be dropped from about 12km (~40,000 ft) in order to gain the speed needed to drive it some 60m underground.

From 40,000 feet, the bomb would take ~ 50 seconds to fall and would impact at mach 1.5.

Israel hasn’t degraded Iranian air defenses that much. The stuff that can’t threaten a F-35 can still trouble a C-130.

Why do you say this? Israel only lost 1 drone.

C-130s are very large, slow targets.

The US has B52s that are cheaper, but they used B2s for this operation. It seems they don't believe Iran's air defenses to be toothless.

You are correct but although the B52 can technically carry the GBU-57 MOP, but it was only done that way during the initial testing of the weapon. The B2 is the only aircraft the USAF actually uses for that munition in combat scenarios.

Also the B2 is better suited for extreme endurance missions like this where the plane is in flight for >36 hours. It has a toilet, microwave and a cot for the pilots to use during the more mundane parts of the mission.

According to Israel they fly freely in West/central Iran and use all the plains including F15/16. Initially they relied on the F-35's stealth but as of last week they claim air superiority.

video shows how confused and disoriented are whatever SAM that survived

https://www.reddit.com/r/CombatFootage/comments/1lb8mkc/iran...

Those are likely being jammed.

You can threaten a C-130 with visually guided WWII era flak.

You are unlikely to get an F-35 with it.

yeap. but at this point of time F15/16 and drones are flying freely. so far losses are 3 drones. C-130 could probably find his way to fordow

Various sources are saying 6 to 12 of these bombs were used. So, you'd need a lot of C-130s and those planes are too slow to NOT get shot down.

Israel doesn't have access to the MOP.

The kinetics matter here. The B2 flies much higher than the C-130 which would aid the GBU-57 MOP (almost certainly used here) in it's ability to penetrate to maximum depth. 80% of the 15 ton weight of that bomb is just heavy metal to give it maximum energy as it borrows into the ground.

Also, each B2 can carry 2 MOPs making it a better platform than a C-130, and that isn't even taking the stealth of the platform into account

> Also, each B2 can carry 2 MOPs

Wow. That is amazing. 60,000 lbs. combined.

This is nonsense.

> almost certainly be nuclear

Source:

those of you hating on this comment, the conventional weapons could not possibly work, the facility is too deep

Even after everyone corrected you with information on the specific ordinance used, you're doubling down?

they might be right, but that's why the attack failed and why there's a risk what I said might still come true

i was listening to Al Jazeera, one of the DC flaks they interviewed gave an upper estimate of the facility depth as 1000 ft. The conventional device can go to something like 60m or 200 ft. 6 devices were dropped, they would have to have everything, including geology with repeated strikes on the same point, be perfect to get past 1000 feet, and then they probably would not destroy the whole facility. As far as I know, they don't even have a good map of the layout.

hence, the only real option is a nuclear weapon. this is absolutely being considered inside the pentagon. our government is psychotic. a 1 kt nuclear weapon (laughably small, hiroshima was 15 kt) is 73x more powerful than a 30,000 lb bomb. they would be like, well, it's an underground explosion! The world will forgive us. it's so crafty and smart to use a nuke to stop a nuke (that doesn't exist).

https://x.com/ArmsControlWonk/status/1935741526191100181

"The effectiveness of GBU-57s has been a topic of deep contention at the Pentagon since the start of Trump’s term, according to two defense officials who were briefed that perhaps only a tactical nuclear weapon could be capable of destroying Fordow because of how deeply it is located."

https://www.theguardian.com/world/2025/jun/19/trump-caution-...

Ok, I see the logic, but nuclear weapon use is the brightest red line in the world. If there's anything a government wouldn't be forgiven for, it's that. I can't imagine how the calculus for the US would work out in favor given the risk. (Of course that assumes rationality, which one could certainly argue is lacking, but even still.)

Also 1000ft is an upper estimate, right? It's certainly possible the MOPs were sufficient.

the US has already been forgiven for nuclear weapon use, twice. this would suggest that the US would be forgiven a third time

Very different situation; the norm against use hadn't been established at that point, and it was in the midst of a world war.

It’s possible the MOP was sufficient but I suspect not. Probably parts of the facility are shallower and others are deeper, such is the topology of a mountain.

If you ever engage with what Daniel Ellsberg said, or US plans in north korea or vietnam, you’d know just how close the US comes to actual use in war. It’s never off the table. They are currently concerned with peer competition with China. There is likely a faction that would propose to attempt to show american strength on an unarmed target just like we did with Japan.

However at this juncture i’m starting to think this is all a show and they only care about the optics. Iran has already moved its equipment out of Fordow. However if the Iran war continues, expect things to get increasingly ugly.

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