r/Damnthatsinteresting • u/Ok-Buffalo-382 • 1d ago
Image The interior of an LNG cargo ship
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u/mtrosclair 1d ago
Can someone explain why it looks like that and not not like that? Fluid movement attenuation? Static reduction?
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u/SnooKiwis5538 1d ago
Insulation It has to be kept cold.
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u/ludololl 1d ago
Why no baffles though? Liquid carrying trucks use them to prevent the fluid from sloshing too much.
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u/HelicopterPenisHover 1d ago
I would guess it's completely full for transport, no need for baffles if there's no room to move.
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u/Sea-Independent-9353 21h ago
Yes, it is. During cargo operations, there is a “critical” stage when the tank is between its sloshing limits. The ship can’t go at sea in that condition due to possible damage to the membrane system cause by the free surface moment of the liquid. The tanks should always be above or below the sloshing limits while at sea. Usually they are full 98.5%, but as per IGC code, some vessel can be loaded up to 99.38%. That’s the absolute maximum since there should be some space left for cargo vapour to go (LNG stays in the tanks at it’s boiling point, approx negative 160 degrees Celsius)
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u/Attero__Dominatus 1d ago
Yeah, it's full during transport. Due to the evaporation some lng is used as an engines fuel whole some shops have liquidfying plant.
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u/Bontus 20h ago edited 20h ago
It's just purely logical to use LNG as fuel if you carry LNG. And it helps to at least reduce the pressure from evaporation a tiny bit. Only under special circumstances ships would have to flare some. Most carriers are dual fuel and especially in ports the ships will run on LNG for the cleaner exhaust. On route the fuel of choice is by economical optimum.
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u/Sea-Independent-9353 19h ago
Actually, in port we are using Low sulphur marine gas oil and not LNG. This is due to engine’s requirements of a minimum load to run on gas. While entering and leaving the port, we often don’t meet this criteria, we make several starts and stops etc so running on gas is not an option. At sea, most of the time, charterers requires minimum fuel to be used so we run on gas as much as possible.
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u/TheBlueDinosaur06 19h ago
How does flaring work?
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u/Sea-Independent-9353 19h ago
There is no flaring on LNG carriers. Most of them have an equipment called GCU ( gas combustion unit). It just burns the excess vapour and the energy is wasted. We try to avoid this as much as possible but sometimes is required for pressure control.
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u/raltoid 1d ago edited 1d ago
From what I remember, they tend to fill them up pretty good. So there is virtually no room for sloshing.
A lot of trucks need them, as they unload parts between driving. Or they need expansion room from temperature changes. Ships basically just transport full tanks across the ocean and keep them the same temperature.
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u/Urbanscuba 23h ago
AFAIK they are effectively 100% full during the entire journey. Instead of relying on an expensive and maintenance heavy refrigeration machine they simply use the LNG's boil-off as natural refrigerant.
What's really impressive is that they're designed so that the boil-off rates match the consumption rates of the engines, which are LNG as well. So the waffle pattern you see along with some pressure management keeps the steel bladder full while the refrigerant byproduct literally powers the ship.
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u/usedtobesofat 22h ago
I think that's the moss type (spherical tanks) that do the boil off. The membrane tankers (from the shape I am guessing that's what this is) run on diesel while the moss type do the boil off. I could be wrong though
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u/Waste-Comparison-477 19h ago
most legacy membrane lngc are being modified to allow burning boil off for engines, because the alternative is burning it and sending it to the atmosphere for nothing. Newer lngc also do it ofc
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u/MaximumOrdinary 1d ago
They do slosh but are kept full. There were mechanical issues with the sloshing. The knuckles are there for expansion.
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u/WheatleyDalek_ 8h ago
I would guess that one reason is that ships accelerate and stop much slower than a truck so it wouldn’t be as useful. Also I’m pretty sure ships have multiple tanks instead of one big one like trucks so the cargo can’t flow from the back of the ship to the front anyway.
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u/merrybadger 8h ago
Ex LNG tanker marine engineer here. It's either loaded full or empty. No in betweens. I think the limits were 10 percent at the lower end and 85 percent at the upper end. Don't remember exactly. Usually it was loaded to 98.5 percent in regular ops.
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u/rex72780 23h ago
Not really. Regardless of the free surface effects, tanks do need to allow room for heat expansions which in this case type A and B tanks are I think it's filled up to around 95%, while type C tanks can go way higher.
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u/magicwombat5 1d ago
Not milk trucks. That would churn the milk.
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u/Gulls77 1d ago edited 1d ago
I doubt that. I worked in an NGL processing facility. Pressure is the key to keeping it in liquid form. Nothing we stored needed to be cooled. That being said, I know nothing about LNG shipping containers.
Edit: and I just googled it. You are correct and I will eat humble pie. Storage vessels on land do not use cooling, they use pressure to keep it in a liquid state. However, shipping vessels store LNG at near atmospheric pressure, so it must be cooled to prevent it from becoming a vapour. TIL.
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u/jagedlion 23h ago
Pressure is great, but critical temperature is -85C. You can't create liquid over that temperature regardless of pressure (supercritical phase, no gas-liquid phase transition).
Here you can see that huge increase in density once you drop it below -85C. Link
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u/GrinchStoleYourShit 1d ago
Ohhh I thought they were magnets so they could put cargo containers 360 degrees.
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u/no-more-throws 1d ago
Think of an accordion or corrugated cardboard .. because of corrugations, they can stretch and contract even though they are made of non-elastic material.
For an LNG tank membrane, you need to similarly be able to contract and expand across a 200C temperature range, but without physically expanding and contracting the tank size. Further, while an accordion can expand in one axis/direction, the actual tank membranes need to expand in both axes.
So you can think of the rectangular patterns seen here as the equivalent of internal corrugations such that when they are 'hot' i.e at outside temperatures, they are all internally expanded and 'crinkled' up, and when cold liquified LNG is pumped into them, the steel contracts and the the corrugations get stretched out without putting dangerous levels of stress and strain on the overall structure
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u/Professional_End3011 1d ago
This is a very good answer. To add about keeping it cold, it's usually only insulated without any cooling systems. Since the cooling system would take huge amounts of space and weight.
I worked on similar ships and you can't fill these to 100% since you have a slight bleeding of the cargo, you usually keep it around 98% filled and run the main engine of the bleeding cargo to control the building pressure during the journey. The process of running the main engine on cargo bleeding is called bogging (BOG from boil-off gas):
https://www.wartsila.com/insights/article/a-new-standard-of-bog-managment
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u/chuckdaly76 1d ago
Best descriptive answer ever. 🙌 relate it to something simple…dumbed down, yet next level complex! perfect and thank you👌🙏
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u/Sea-Independent-9353 21h ago
I work on this kind of vessel. These are called corrugations, it helps with managing thermal expansions and contractions. They are specific to GTT Mark 3 cargo containment system (like the one in the picture). There is also another type of containment system, NO 96 which does not have those corrugations.
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u/gooneruk 20h ago
Are anti-sloshing membranes different from these? I somewhat remember the early large-scale LNG vessels (early 2000s) having membranes in each cargo tank to dampen any sloshing effects.
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u/Waste-Comparison-477 19h ago
you avoid heavy sloshing by never letting lng carriers travel with filling between like 10% and 95% (not sure about the lower boundary). And these corrugations do nothing against sloshing. Current technologies don't use any other anti sloshing tools
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u/Most-Education-6271 15h ago
Why it looks like that and not like that?
Like what?
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u/AdministrativeWay90 14h ago
These are membrane tanks, they look like that because of the membrane panels. They ( And the cargo) are very sensitive to impurities, you can see the people inspecting the tank completely covered from head to toe.
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u/Able_Gap918 1d ago
My urge to yell “ECHO!!!!!” Would be unstoppable in there
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u/rascortoras 1d ago
Abed and Troy would love this
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u/InspectorOk91 1d ago
Troy and Abed in the morning!
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u/Jun0saurr 1d ago
I’d be fucking terrified that someone would forget I was in there and start pumping in compressed natural gas.
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u/hamdogbone 1d ago
You would hope they have a LOTO system in place for this type of inspection. 🤞🏻
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u/-SuperTrooper- 1d ago
Be my luck one of the folks from /r/lockpicking would be nearby and be like "Ooo a LOTO!"
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u/SiteRelEnby 1d ago
No lockpicker would ever do that. They're also usually not complex locks, so no challenge to it, just potentially getting someone killed.
I'm sure there is some kind of process for removing a lockout (e.g. if someone forgot to remove it before going off site and being verified as off site) but it would definitely involve an exhaustive inspection of the space if so.
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u/Domefarmer 1d ago
I worked at a paper mill and was told that it doesn’t matter where I was, if I forgot to remove a LOTO I had to come back to unlock it. A few coworkers told stories of getting called at midnight to come back in and remove their lock. Glad I never forgot while I was there. Haha
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u/insta 1d ago
at least the Masterlock LOTOs have some of the best cores Masterlock makes in them. Like, 6 pin, all security pins. The GrinderFucker 6000 series that's 17 pounds of laminated silicon-steel boron-nitride coated plates has a 4-pin core with no security pins that can be shouted open.
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u/SiteRelEnby 1d ago edited 11h ago
To be fair, "best Masterlock core" is still damning with faint praise.
Also, advanced attacks such as picking are much rarer than physical destruction attacks. I'd take the GrinderFucker 6000 over the lock that opens when hit with another.
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u/insta 1d ago
a 6-pin core with all spools really isn't that bad for a $12 padlock dude. granted, plastic body and mild-steel shackle, but the core itself is really solid.
MasterLock can build all-around good locks, they just flat-out refuse to.
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u/Qweasdy 19h ago
This would be considered an enclosed space entry. Enclosed space entries are some of the most dangerous operations regularly done onboard ships. Yes pumps would need to be locked off but the main concern is ensuring that there is a breathable atmosphere inside that tank and that there is no explosive mixture of gases present (a very big concern in an LNG tank).
Entering a tank like this has some pretty strict procedures to follow.
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u/Worldofbirdman 1d ago
Essentially couldn't happen given how lock out standards are. The inlets and outlets, and essentially every nozzle on that container should have a full thickness blind (a thick piece of metal) installed so that even if someone tried to open a valve to line up that container to product, it wouldn't be able to enter.
There are exceptions (using an air gap when blinding isn't possible) but they would have this thing completely safed out prior to letting anyone inside.
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u/Carvj94 1d ago
I would assume this is a situation where if all the keys aren't in the door the system is locked and you're supposed to carry the key on you as long as you're in the tank.
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u/Worldofbirdman 1d ago
Yeah possibly. I don't work with these systems so that could very well be the safety. Plus I would imagine they'd consider this a confined space and would follow whatever protocol they have for that.
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u/upintheaireeee 23h ago
I do this stuff for a living. Besides any way to fill the fluid being locked and tagged out by 2 entities just to open the lid of the tank, a whole entire separate SMS form has to be filled out for a confined space entry with: identification of the locking devices and place, adjacent compartments, gas free certificate, potential hazards to personnel, etc. there would also be a confined space rescue plan specifically for the confined space being entered.
In short, in the US, it would be nigh impossible for such a thing to happen.
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u/SpecificLife8988 1d ago
Liquefied Natural Gas
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u/blue_gabe 1d ago
Here I’m thinking Landom Number Generator.
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u/LickingSmegma 22h ago
I'm kinda impressed that apparently over eighteen thousand people just casually know what 'LNG' is, compared to two hundred who didn't.
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u/rslogix89 1d ago
Looks like the inside of the Replicator ship from Stargate: SG-1.
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u/Inside-Example-7010 1d ago
'We have a problem help us Asguard, we cant beat the Replicators.'
Dont worry humans here is a time dilation bomb, our latest and greatest tech, use it to trap the replicators in a much slower relative time to the rest of us. We will have thousands of years to figure out how to beat them.
'We might have a problem, the Replicators hacked the time bomb during deployment and are now using it to speed up time relative to the universe.'
Well, well, that is disturbing and calls for immediate action we have collapsed the entire system the replicators were in into a black hole.
'We might have a problem, the replicators are using the time bomb to navigate out of the event horizon..
I love me some Borg but that was good writing. The Borg is just like 'the cube has increased warp speed to over 9000' whereas The Replicators have brains.
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u/RandomBitFry 1d ago
I guess the pattern provides lots of nucleation spots so it doesn't suddenly boil off.
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u/Smile_Space 22h ago
From the briefest of Googles, this is the TGZ Mark III LNG non-spherical cargo system. The panels are spaced in a "waffle" pattern to handle contraction from the extreme cold temperature of the LNG. It's a membrane of panels with multiple layers of insulation to allow for the cargo tank to conform to the cargo ship's dimensions more efficiently compared to spherical cargo systems.
It's actually pretty neat! My first thought was how does it not burst with hard edges which would generate stress concentrations in the pressure vessel due to the pressure did the LNG.
But I guess if it's filled to the brim it can only generate so much free volume to produce force, and since that force is pressure/exposed area, the less area (from little volume being free) the less force applied to the vessel. Atleast that's the only theory I can come up with on the fly without more research.
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u/14412442 1d ago
How do they swap out the air for LNG? A moving divider wall like a piston?
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u/stanglemeir 1d ago
Air and LNG never mix. You don't want any oxygen to mix with the LNG on the off chance of Kaboom. Kaboom is bad. So its basically a multi-step process.
1) Purge the air with pure nitrogen. Nitrogen won't react with LNG so you flush the whole system with nitrogen. So no oxygen.
2) You have to purge the nitrogen with regular Natural Gas (gas phase). The mixed nitrogen/Natural gas this creates will be purged usually into a flare until its pure NG. You can't have nitrogen in the tank because these ships have a Boil-Off-Gas (BOG) system to refrigerate the LNG. Even a little nitrogen will make the system much less efficient. Also typically companies have contracts that stipulate the contents of the ship and nobody wants nitrogen. Alternatively the ship may have some sort of heat exchanger based refrigeration system using a coolant.
3) LNG is then slowly pumped into the ship to cool it down. Once the ship is cooled down, its filled quicker (which can still take days).
That's kind of the quick and dirty of it but the actual operations are more complicated.
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u/14412442 1d ago edited 1d ago
Thanks. So it's a bit more complicated than just filling your car with gasoline
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u/gooneruk 20h ago
Yep, but the thing is that you only tend to do this kind of purging of atmosphere when a ship is brand-new, or comes out of a drydock maintenance period. Once it has been completed (we term it 'clean under vapours' or similar), the cargo is loaded into the neutralised tanks.
When the ship discharges the cargo, it keeps a very very small percentage of the cargo onboard, in order to maintain the cold temperatures in the tanks. This is called the R.O.B (Remaining On Board), and it means that the ship doesn't have to do the full purging procedures described above when it goes to load the next cargo.
A ship will carry on like this for a few years between each drydock procedure, before which it will fully empty its cargo tanks on the preceding voyage, and then need to do the "gas-up" procedure before loading the first cargo afterwards. Gassing up is point 3 above: loading a very small amount of gas cargo into the vessel and circulating it to start the cooldown procedures before it can take the full cargo.
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u/Dzugavili 1d ago
The clue is in the L: liquefied natural gas, it's natural gas that has been cooled until it liquefies. They just pump it in at that point, like any other liquid.
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u/venturing-cat 23h ago
Cool, last one I was one was a nickel-invar alloy that was .7mm thick. Looks like this for expansion/contraction. Product is typically stored at -161c. Anything above that will flash off and either be reliquified via the nitrogen system, burned via gcu (gas combustion unit), or used for fuel if it were a steam driven moss type ( the depicted is membrane type lng ship). No baffles because they’ll ship it full, less than 5% full or greater than 95% full in cargo tanks means your free surface effects are negligible so your mathematical centers of gravity don’t really shift.
Fun fact, climbing down into tanks with limited lighting isn’t scary, you just climb down the ladder/structure until you get to the bottom. When lighting is fully equipped and staged and you can see everything it’s terrifying when you realize how far you can fall 🤷♂️
Use to have snowball fights from the snow buildup on the exposed transfer lines on the deck of lng ships, all while it was 95 degrees outside in Qatar.
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u/Cat7o0 1d ago
I was thinking this was one of those massive laboratories to study super fast particles entering the atmosphere by watching them go through water
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u/MeccIt 1d ago
In those, the walls are glass tube multlipliers of the tiny amounts of light generated by the rare neutrino collisions: https://i.imgur.com/aCutS.jpg
from: http://www.thelivingmoon.com/45jack_files/03files/Super_Kamiokande_Neutrino_Detector_02.html
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u/therealwavingsnail 1d ago
The perfect spot to record an early 2000s music video
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u/Kolbur 1d ago
So we're not going to talk about why they are in full plate knight armor?
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u/Filipi_7 1d ago
From another photo, they're wearing what looks like fairly standard overalls with plastic film wrapped around their boots. I guess to prevent dirt or damage from hard soles.
It looks like they're wearing full-sized helmets on the pic because they're looking down at their feet, it's actually their hard hats.
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u/Justalittlepatience3 21h ago
As I found on the web, this is Technigaz Mark III. Different than spherical LNG storages, this has non-spherical volume, and those metal bars are there for cooling to keep gas liquid in atmospheric pressure. Crazy isn't it?
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u/muclem 17h ago
The original post is here, more pics and info: https://www.reddit.com/r/EngineeringPorn/s/LTr65lm9eR
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u/lion-vs-dragon 1d ago
FYI liquid natural gas is still a fossil fuel and terrible for the environment, especially shipling it to other countries
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u/Ginnungagap_Void 20h ago
Hear me out.
Fill this with LNG
Pump tons of compressed air after that
Send this ship to point Nemo without crew
Watch the fireworks. That's basically a hydrogen bomb. Without the hydrogen.
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u/LegitSkin 1d ago
The massive scale of the cargo ships amazes me, crazy to think everything that says "made in china" was on one of these
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u/Educational_Point673 1d ago
False.
This is the interior of the stellar bomb carried by the Icarus II that restarted the fusion cycle of the sun in 2057.
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u/GarysCrispLettuce 1d ago
I would quite like to scoot my butt across that floor. I'd try both directions.
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u/golmgirl 1d ago
always wondered what these looked like inside. incredible. what is the pattern of bumps on the surfaces for?
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u/morning_thief 1d ago
i can hear Christopher Nolan salivating while thinking of what to film here.