Comment by greenavocado | Hacker News Reader

Comment by greenavocado | Hacker News Reader

While technically possible, carrying a 500 kg payload at depths beyond 50 meters is extremely challenging and would typically involve commercial diving teams, saturation diving techniques, or the use of ROVs.

Handling a 500 kg payload is more feasible at shallower depths due to lower pressure and shorter decompression requirements.

At 30-50m depths, the challenges increase, and more sophisticated equipment (e.g., lift bags with remote controls) is likely required.

Typically, multiple large lift bags are used to make the payload neutrally buoyant or slightly negatively buoyant. The operation of these bags requires at least two divers, but ideally, a team of 3-4 divers should manage the lift bags to control the ascent and descent accurately. The payload needs to be guided and stabilized during the descent to prevent it from spinning, tilting, or drifting. This typically requires 2-3 divers focusing solely on keeping the payload steady.

At such depths, safety divers are essential. They provide assistance in case of emergencies, such as a diver getting entangled with the payload or a lift bag malfunctioning. At least 2-3 safety divers would be advisable. A dive supervisor or lead diver should be responsible for overseeing the operation, managing communications, and coordinating the divers' actions.

Minimum Team Size: Lift Bag Management: 3-4 divers. Payload Control: 2-3 divers. Safety and Supervision: 2-3 divers (including a dive supervisor). This brings the total minimum team size to around 7-10 divers.

In addition to the divers in the water, a surface support team, including a dive supervisor, tender, and possibly a medic, is essential. If available, remotely operated vehicles (ROVs) can assist with the operation, potentially reducing the number of divers needed for direct handling.

It is bizzare that one arrest warrant was issued when many people were involved.

It sounds like many of these requirements are for safety and reliability.

I can imagine that participants in a war would be much more risk-tolerant than a typical team of professionals would be. Maybe they're okay with a high-ish chance of failure, injury, or death, and so they resource the mission within the limits of what they have, or what they believe will pass unnoticed?

The Germans believe that there were several people. Not 10, but several. The constraint was that they had to be able to pose as vacationers.

Skepticism is warranted for sure, but we shouldn't underestimate what highly motivated and courageous people can do.

Losing a 500 kilogram bundle of explosives in the Baltic Sea is also not an acceptable mistake.

Worth the risk. That's like a single bomb.

I still don't understand why Denmark and Sweden said they believed that “several hundred kilograms” of explosives were used. It's bizzare.

What makes you think that’s bizarre? Presumably one could calculate this from seismic data of the blast, after accounting for the fact that there was still gas in the pipeline despite it not being in use.

"Handling a 500 kg payload"

1kg would be enough to breach a pipe. A single determined diver, not necessarily following OSHA rules could do it.

The question I have is, what side is Germany on? They're cutting or suspending military aid, they are indicting Ukrainians, they are blowing up their own energy production making them more dependent on Russian natural gas. WTH?

https://www.politico.eu/article/germany-halt-new-ukraine-mil...

https://www.reuters.com/world/europe/germany-halve-military-...

In a letter to the U.N. Security Council from Sept. 29, three days after the incidents, Denmark and Sweden said they believed that “several hundred kilograms” of explosives had been used to damage the pipes, each of which measures more than three-and-a-half feet in diameter and is made from steel encased in weighted concrete.

https://www.nytimes.com/2022/10/25/world/europe/nord-stream-...

https://archive.is/00tvb

The German security, media, and political establishment has been completely infiltrated by Russia over the past 30 years. So many of Germany's bad decisions over the past few decades can be explained by this.

Germany taking in millions Syrians is often viewed by critics through the lens of "(naive) empathy". But they were just helping Russia get rid of anti-Assad Syrians.

> While technically possible, carrying a 500 kg payload at depths beyond 50 meters is extremely challenging and would typically involve commercial diving teams, saturation diving techniques, or the use of ROVs.

Those conditions would be challenging during the day, but what about at night? That seems downright impossible without a huge professional operation, not some poor maintained pleasure boat.

The closest equivalent I can think of is cave diving but those tend to have guidelines placed by expert teams and those often take many expeditions over several years to fully place.

Visibility is bad in the Baltic Sea. At 80m depth there's not much ambient light so little difference between day and night.

Once the pipeline has been located, the divers can just go straight down and up the anchor line. There's no need for them to navigate, or follow a guideline like in cave diving.

Where does the 500kg figure come from? I don’t see it in the article.

I’m also surprised about the 220lb figure mentioned in the article. Assuming a steel twinset, and 4 extra cylinders, we barely get to 60-70kg. Where do the remaining 30-40kg come from?

It was an estimation made up early in the coverage by experts when they didn't even know what kind of explosives were used (it's Octogen).

If its HMX (Octogen) then two kilograms is a bit more than sufficient to get the job done. Even 1.2kg is likely sufficient.

Is that 500kg mass or negative buoyancy? Because 500kg of octogen (density of 1.91g/cm³) which thus would take up 261800cm³. An item of that volume and mass would only be 230kg negatively buoyant in sea water.

Still very heavy, but basically neutral with 2 large lift bags (you can easily find 150kg pyramid lift bags for about 1-200€ each).

How about we go in two trips? Your max divers are cut to 5. Two trips is not operationally impossible, and perhaps the diver swim distance allowed the asset that held the first payload was able to be close enough to make the full payload delivery in two trips. Perhaps we cut down the payload into thirds - 3.3 divers per trip, assume we can round up due to military divers being trained in mission specific tasks and physically conditioned to preform these duties above average diver capability, that could put us even lower.

Why would you need 500kg of explosives? That's massively overkill.

Indeed, describing a gas pipeline which already wants to explode. You just need to provide the ignition. You do not want to make a second attempt, but something more modest seems like it would have been just as effective.

Do the pipelines want to explode? How high is the pressure? There’s no oxygen there so the gas itself won’t explode.

The pipeline must be fairly heavy duty to handle pressure and rough conditions on the seabed. And punching a small whole is probably not enough as it could potentially be fixed?

> How high is the pressure?

It's probably similar to a normal gas tank, as the gas is liquefied inside it.

If it "wants" to explode or not will depend on how it's built. But the one sure thing is that the explosive is on the wrong side of it (outside), so all the important forces are on shear and other secondary effects.

Pressure inside a natural gas pipeline would typically be something around 1000psi (70bar). They are built from a strong steel pipe surrounded by a layer of concrete. If you beach both layers with an explosion then the pressure of the contained gas may cause a larger structural failure in that pipe section. As others have pointed out, the natural gas in the pipe wouldn't literally explode, just burst out.

Anything can be repaired if you have enough money but obviously that won't be done until the political issues are settled.

A 85-95% methane, ethane, propane, and butane environment like that which was found in Nord Stream 2 is not flammable because there is no oxidizer present (typically oxygen) under water. Carbon dioxide and Nitrogen are non-combustible and made up the remainder of the gases in the pipeline.

You are arguing against a strawman and I don't think you know much about tech diving. No one has claimed that the divers set a 500kg charge on a single dive. The recent articles have claimed that several hundred kg (no exact amount) of explosives were used across several pipelines, so obviously they weren't all taken on a single dive. The boat crew could have clipped a bag of explosives to the anchor line and let it sink down on its own without even using a lift bag.

The stories claimed that six people were on the boat, with others involved on land. The investigators have only named one suspect. So I don't know why you would think it bizarre that only one arrest warrant was issued. (I hope they all get away with it.)

Do you really think that a team blowing up a pipeline as part of an on ongoing war is necessarily going to follow all best practices and safety recommendations?

I think your comment is bizarre. Did you use an LLM to write it? I don't think many humans would write Lift Bag Management with L, B, M in upper case like that.

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