h.sie's Oxygen-Supply fix question

[CaptBones]

First, let me assure everyone that I really appreciate and enjoy the work that h.sie and the others who helped him, put into his hardcode fixes for SH3.

However, from my experience the Oxygen-Supply fix is not entirely correct and I’m hoping someone (perhaps even h.sie) can provide some help to “fix the fix”.

The idea for the fix and the basic approach are fine, but in the real world there is one significant difference that I have found slightly annoying. Oxygen content monitoring in an enclosed atmosphere is not usually done directly, especially with 1940’s technology; what you monitor is the CO2 content. That’s for two reasons; first because the CO2 content is actually more critical and second because direct detection of the O2 content is not as easy or as accurate as detection of the CO2 content.

Would it be possible to revise the Oxygen-Supply fix such that the LI reports the CO2 level instead of the O2 level? I suspect...and am hoping…that could be done by changing the text and the function that generates that text report, such that 21% O2 equals 0% CO2, 20% O2 equals 1% CO2, and so on, down to 17% O2 equals 4% CO2, at which time the bottled O2 supply is used to “restore” the atmospheric quality. I know that isn’t exactly, technically, chemically correct, but it would be “close enough for government work”.

I started to fix this to my own taste by changing the report given when the boat surfaces and the O2 content is restored to normal. I changed “en.menu” line 4816 to read ”Ventilate the boat.” I also changed line 4817 to read “CO2 level high. Using oxygen supply.” But, when I started to think about tinkering with line 4815, I decided to ask for help first, since I don’t know how the % oxygen is calculated and making a “simple” change to the apparent arithmetic might break the whole thing.

I was also wondering if the optional O2 gauge part of that fix could be retained in the LI’s slide-out gauges, while also keeping the CO2 gauge above the compressed air control manifold in the Control Room functioning as a CO2 gauge (I noticed the face of that gauge still reads “CO2“).

Thoughts anyone…hints, tips…”here’s how to do it” directions?

[LGN1]

Hi CaptBones,

you are right, a fully correct implementation of the air renewal mechanism should include both CO2 and oxygen generation/consumption. Both limited the time submerged and for both there were different tools to keep them under control: oxygen bottles and cartridges to keep the CO2 limited.

However, SH3 has only one 'variable'. Thus, in order to keep the 'fix' simple, one has to decide to either model O2 consumption or CO2 generation. Since I have never read anything about the cartridges limiting the submerged endurance, I think the current implementation focusing on O2 (and neglecting the CO2) is preferable.

In addition, the CO2 content was kept at 1.5% while the O2 content was kept at 17.5% (see the original handbook of the VIIC: http://www.uboatarchive.net/Manual/Manual.htm , page 84). Based on this handbook it seems the O2 could be measured. From where did you get the information that O2 was not measured back then?

Regards, LGN1

PS:

-Concerning having both CO2 and O2: This would require some major changes to H.Sie's code (and the game code). I don't think there is anyone around here who would like to do this.

- There are some interior mods which have also corrected the CO2 to O2 on the gauge in the control room.

[CaptBones]

Thanks LGN1...

It wasn't the answer I was hoping for, but it was the one I expected. I guess I'll just live with the two little report text changes I made.

I didn't say they couldn't, or didn't, measure O2 directly. About the only type of somewhat easy-to-use and reliable gas analyzer available in those days were the Orsat type devices (which were supposedly provided on the U-Boats). We had them in the Guppy boats and they are nice and simple to use, when you're sitting at a desk in a laboratory. But sampling, filling a burette or tube with a reagent, leveling, testing, and then emptying, rinsing and re-doing the whole procedure separately for each gas to be tested for, is time consuming and a pain-in-the-behind. In the USN, before gas monitoring systems were introduced during the mid-70s, we also had Bacharach analyzers, which are a lot easier to use (pre-filled and disposable reagent tubes). Of course, now days it's a snap to measure just about any "standard" atmospheric gas with galvanic probes and other electronic marvels. But, back when chemical testing was all there was, the easiest and fastest way to do the testing was to just run a CO2 test...unless something was amiss, it told you everything you really needed to know.

After all, O2 content down to 17% or less is still survivable, provided that neither CO2 nor CO is greater than 2 or 3% and there aren't any other noxious or poisonous gases in the mix. Hypoxic saturation diving mixes go even further than that, down to 10% O2, where the partial pressure of the O2 becomes more important than the percentage by volume in the mix.

Anyway, thanks again...for the answers, as well as for the work you did to put this MOD into h.sie's fix.

[LGN1]

Hi CaptBones,

thanks for sharing your experience. Very informative

Indeed, the VIIC manual mentions the Orsat device. My guess is that the crew did not measure the O2 content during all dives, but relied in most cases on experience and just estimates based on elapsed time. In particular, because (as you mention) a lower level would not be immediately lethal.

If you had the choice would you prefer a CO2 model or an O2 model? Or are you just not happy with the messages?

Regards, LGN1

[CaptBones]

Hello again LGN1,

You're welcome...and thank you.

Personally, I would prefer the CO2 model. Within the context of "realism" and given the limitations of the game engine, it would seem to be the closest method of capturing the "feel" of how things were done in a practical manner back then.

On the other hand, how would the problem of limiting the submerged endurance due to CO2 build-up be reconciled with the ability to extend that limit? The CO2 content could be allowed to increase to an unrealistic level of 4% before using absorbent or adding "anti-CO2". Would you still be able to label that absorbent/"anti-CO2" as an O2 Supply and display that on the gauges? There's no doubt that having a "CO2 Gauge" is not realistic for the technology available at that time; the LI's text report of CO2 level is quite correct and completely adequate IMHO.

As I mentioned, the messages were "annoying", in that I (as the CO/KL) would expect to get regular reports on the CO2 level and/or the presence of any other unwanted gases in the boat (CO, H2S, NOX, SOX, CL2/chlorides, etc.), but would seldom expect to get a report on just the O2 content. So, if a bigger, better fix is not workable, the changes I made to the messages will suit my personal tastes.

BTW, I made another little change to the "en.menu" text reports to suit my own experiences at sea. Lines 4814 and 4818 became "Visibility is improving, Herr Kaleun" and "Visibility is deteriorating, Herr Kaleun".

Warm regards; sink 'em all!

[LGN1]

Hello again CaptBones,

in a purely CO2 model I would miss the 'long-term' planning of saving oxygen. In the current implementation I really like this.

Do you know whether the Guppy boats were limited by O2 supplies or 'CO2' cartridges? Or did the Guppy boats have a different air renewal system than the u-boats?

Regards, LGN1

[CaptBones]

Yes, I suppose that would be a missing feature of the CO2 model. I was hoping there might be some way to still have the non-renewable O2 supply by applying it as some sort of "anti-CO2" but still relabeling the face of the gauge as indicating the level of "bottled" O2. Oh well...guess I'll just live with the text report changes I made.

Well, remember that Guppy boats were just converted Fleet Boats. But, they were "Luxury Liners" by comparison to the U-Boats. We had lithium hydroxide CO2 scrubber systems that operated on continuous circulation with the boat's HVAC system and chemical candle O2 generators (installed units, water cooled) that were used when required. But, I don't personally recall any occasion when that was required...it was "peacetime" after all. There were also emergency lithium peroxide individual breathing devices. There might have been some developmental lithium peroxide CO2 scrubber/O2 generator units installed in the last iteration of the Guppy's...I don't remember for certain though.

Later "conventional" boats also had electrolytic O2 generators and catalytic convertors to handle CO/CO2 and H2 scrubbing all at the same time; I don't think any of the Guppy boats ever got that equipment. Of course, snorkeling was the primary means of refreshing the atmosphere. You didn't run on battery until the cans were flat (batteries nearly exhausted); IIRC, you'd typically run down to 70-75% or even 50-60% and then snorkel to recharge and ventilate the boat.

[LGN1]

Thanks for the reply, CaptBones!

I once visited the Pampanito in SF. A very special 'Luxury Liner'

Regards, LGN1