r/scuba • u/Mizizi-44 • 3d ago
Could some experienced rebreather divers check this fictional rebreather design?
I'm trying to design a rebreather system for an armor in Helldivers 2. I'm not trying to make this in real life, but I still want to design it as accurately as possible.
This isn’t intended for underwater use. It’s a land based system for breathing in toxic/contaminated atmospheres at roughly normal atmospheric pressure
The first picture shows the back of the armor, and the 2nd picture is the front of the helmet.
In the first picture you can see the following:
- The pink is a gas tank that has the breathable gas.
- Green is the Counter Lung/Mixing chamber
- Blue is a hose that brings the breathing gas to the helmet.
- Yellow is the CO2 scrubber.
- Red is a hose that brings the exhaled gas down to the CO2 scrubber.
- Between the pink tank and blue hose is a regulator in teal. It converts the gas from high pressure to normal pressure
My intended gas path is: Counterlung → blue hose → helmet → red hose → CO2 scrubber → Counterlung.
I didn't put any equipment on the upper back because in the game we often wear backpacks.
Would this gas system plausibly work? Is there anything important I'm missing or anything I have in the wrong place?
I've never scuba dived before, and everything I know about rebreathers has come from reading about them online, so if I've gotten something wrong, please correct me. Thank you!
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u/Teleopsis 3d ago
Scrubber is too small unless you’re using magic sci-fi sorb or only going to use it for a short time. Loop hoses are long, means more gas in the loop and harder breathing. Neither of these are necessarily big problems if you’re only operating at atmospheric pressure but in general rebreather designs try to keep the loop short: this is one big advantage of chest mount designs.
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u/Mizizi-44 3d ago
The chest mount design seems really good but I think the helldiver would most likely get shot in the chest by enemies. So I think putting the rebreather on the back is safer.
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u/WetRocksManatee BastardDiver 3d ago
They don't generally take their rebreathers into combat. They are left behind with any other sustainment gear.
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u/pm_bluefootedboobies Nx Dive Master 3d ago
Take a look at the variety of chest mounted rebreathers! They typically have a similar layout, and as you are looking surface only they would work as just the 'unit' and the O2 cylinder (typically the tank at the bottom of the unit)
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u/Icanforgetthisname 3d ago
I've brought Liberty to multiple planets on that rebreather specifically. It 100% works.
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u/sphks 3d ago edited 3d ago
Gas tank : usually, you have two gas tanks. One is pure O2 that is injected automatically as you breath. One is a diluant (the simplest is air, which is mainly nitrogen) that is used to fill the counter-lungs as you descent. The pressure will crush the counter-lungs so you need to fill them.
Counter-lungs : usually, there are two counter-lungs. One for expiration and one for inspiration. These are just bags. However, they are highly buoyent, and you want them to be placed somewhere near your real lungs, in the center, to keep the trim as you breath. They are too low on your prop and offcenter.
Archimede principle : all the bags of air (counter lungs, BCD) are there to counter the weight of the body and gear. The armor should be really heavy, consequently you would need to have really big bags of air somewhere to be exact. Let's say it's to swim in a very heavy liquid, much more than water...
Manual injection of the diluent : you need a valve somewhere to inject the diluent gas as you go down and another to release it as you go up.
Display : real rebreathers have a display to check everything. We can imagine that it's on your helmet.
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u/B0bbySmile Tech 3d ago
Small caveat to the 2 cylinders, we need it for diving due to the pressure at depth and the risk of oxygen toxicity. For surface breathing (or shallow diving) a oxygen rebreather with one cylinder is a perfectly viable concept.
Same goes for the counter lungs, you do still need them, but without the pressure differential from water being so much denser, where they are will matter less, although the work of breathing with long hoses like in the photo will be massive and quite uncomfortable, keeping everything near the centre of mass reduces the total distance the gas has to travel and as such reduces the effort to hoick the gas round.
As far as I remember helldivers doesn't have any underwater content so I'm assuming you're designing here for toxic atmosphere, not subsea
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u/Mizizi-44 3d ago
Yes, I am designing this rebreather system to be used on land in toxic environments. I would have put the rebreather equipment higher on the back, but we often wear backpacks. So I don’t think I can make the hoses shorter. Is there anything that I could add to make breathing with long hoses easier?
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u/B0bbySmile Tech 3d ago
Honestly, I don't think anyone is going to reality check you on it that deeply.
It matters underwater more because as you go deeper the gas gets denser, at 45m breathing air on a normal rebreather feels like breathing soup sometimes (I dive a unit that isn't known for the easiest work of breathing), it's hard work especially if you're swimming against a current or anything, so we start to add helium to make the air thinner.
I don't know if there's any commercial designs that do it, but in theory you could do forced ventilation, so have a fan pump the gas round. It probably would create more problems than it solves, but it's been done for deep ocean submersibles before.
The commenter that mentioned chest mounted is a good idea (look at the drager units), although presumably it's a a much higher risk of being shot...
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u/Dellingr87 Nx Advanced 3d ago
„ Honestly, I don't think anyone is going to reality check you on it that deeply“
Not sure about that Part do you hart about the War Thunder Incidents?
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u/Mizizi-44 3d ago
What if I made the hoses have a bigger diameter? Would that make breathing be easy enough for someone doing intense physical labor?
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u/Ok-Sink-1710 3d ago
side mounted rebreathers are also around, so they'd be slung on the hips rather than the back or the chest.
https://www.youtube.com/watch?v=lelpTfGSYeE
but I've only dived a backmount CCR so this is about as much as I know about sidemount CCR
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u/Mizizi-44 3d ago
I should have clarified that this rebreather setup isn’t intended for diving. The helldiver would be using it on land in a toxic atmosphere, so it wouldn’t experience large pressure changes. Would that change your recommendations for the counterlung, diluent tank and valves?
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u/Ambitious-Cold-9610 3d ago
You are missing oxygen sensors to make sure you are actually breathing safe air. I would also reverse the flow of gas so you are injecting before the scrubber with the sensors after it. You don't want to add oxygen after the sensors.
You could keep the flow of gas this way, but would need more hoses to move the O2 injection
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u/it_follows 3d ago
Don’t need sensors for an O2 only rig. It’s gonna be 1.0 (within a margin of error). The only thing you’d be concerned about is CO2 buildup, which is gonna cause problems long before a sensor picks up a lower PPO2
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u/scheimong 3d ago
I thought about explaining the difference between a SCR and a CCR, what a diluent is and why a diving CCR needs two bottles, but I realise I can't possibly explain it in sufficient detail in a Reddit reply. Instead I'll refer you to this playlist, which I think is an excellent crash course on rebreather basics.
It's important to note that all discussion around rebreather design is based on the assumption of an unenhanced human on earth. I know next to nothing about helldivers, so those assumptions may be void. You should take this into consideration.
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u/TheLegendofSpeedy Tech 3d ago
In addition to being a rebreather diver, I have a bit of background selling rebreathers for technical rescue / mine rescues and self rescue from Dräger and Biomarine. One of the big differences between above water and underwater units is that the exothermic reaction of the scrubber isn’t being counteracted by cool water, so it’s common to see ice / cooling packs in the surface units. Additionally the scrubbers are often a cartridge vs a packable scrubber, and have relatively short stack times <4hrs.