Realism- and gameplay-related hardcode fixes for SH3.EXE

[h.sie]

During our PM correspondence some weeks ago, LGN1's arguments sounded very plausible to me, and since I found no better / historical information, I decided to rely on his point of view and started to program accordingly.

[Wolfstriked]

That is so kool!! I love these realism tweaks so thanks to maker and the guys pushing him.

One question is,what happens to the CO2 that is produced by crew?I understand adding in pure O2 as its used up but can't understand how the CO2 increase does not matter.

[h.sie]

@Wolfstriked: Without huge programming effort, sh3.exe can only model CO2 or O2. So far, CO2 was modelled: The longer the diving time, the more CO2 and (not modelled directly, but as a consequence) the less O2.

Modelling both components, CO2 and O2, separately and independently would cause a HUGE programming effort, so we decided to model O2 instead of CO2, because, as LGN1 mentioned, the O2 supply is the most critical and restricting factor of strategical importance. Now we have: The more O2 in the air, the less CO2.

That is still not exact, because CO2 and O2 are not 100% depending on each other, and the reduction of CO2 using potassium(?) = Kalipatronen is still not modelled. We decided to not model them, because that would require a lot programming and we don't know details: How many Kalipatronen were available? How much CO2 could be reduced with one Kalipatron? And so on.

My opinion: Still not 100% exact, but nearer to "reality" than before.

But if anyone has more detailed information: let us know.

[LGN1]

Originally Posted by Wolfstriked

One question is,what happens to the CO2 that is produced by crew?I understand adding in pure O2 as its used up but can't understand how the CO2 increase does not matter.

Hi Wolfstriked,

the CO2 is bound chemically. See here for an example:

http://en.wikipedia.org/wiki/Sodalime

Cheers, LGN1

[Wolfstriked]

Great stuff again,thanks guys! I think that modeling just O2 is perfect since I would imagine that they stored a ton of lime to combat the CO2.

[Salvadoreno]

I downloaded my SH3 from D2D. I read your directions carefully, however i think since my copy of Sh3 comes patched to 1.4, i cannot install. Now let me make sure i got this right

I installed Sh3 to my E drive.
Downloaded your fix..
Made a folder called sh3 fixes on my e drive and extracted the contents of the patch to the folder.
Copied my sh3.exe found in my e drive.
Pasted the copied sh3.exe in the sh3 fix folder containing your fixes.
Ran the fixes, did not work.

Something i missed? Since my version is already patched does it make it unusable?

[UltimaGecko]

Originally Posted by h.sie

@Wolfstriked: Without huge programming effort, sh3.exe can only model CO2 or O2. So far, CO2 was modelled: The longer the diving time, the more CO2 and (not modelled directly, but as a consequence) the less O2.

Modelling both components, CO2 and O2, separately and independently would cause a HUGE programming effort, so we decided to model O2 instead of CO2, because, as LGN1 mentioned, the O2 supply is the most critical and restricting factor of strategical importance. Now we have: The more O2 in the air, the less CO2.

That is still not exact, because CO2 and O2 are not 100% depending on each other, and the reduction of CO2 using potassium(?) = Kalipatronen is still not modelled. We decided to not model them, because that would require a lot programming and we don't know details: How many Kalipatronen were available? How much CO2 could be reduced with one Kalipatron? And so on.

My opinion: Still not 100% exact, but nearer to "reality" than before.

But if anyone has more detailed information: let us know.

Someone interested in modding for a subsim already seems to be looking into the problem in some places, but maybe I can help out here.


First a few useful figures:

The lowest safe 'partial pressure' of oxygen is 16kPa or approximately 15.8% of standard air temperature and pressure (STP). Below 17% fatigue and a feeling of shortness of breath will occur and going lower a person may fall unconscious. Natural oxygen content in the atmosphere is about 21% (giving you about 4% of the oxygen in the uboat to work with while submerged - before you need to start pumping more in immediately).

In general carbon dioxide levels above 1% are to be avoided (with standard atmospheric composition at 0.4%). Above 1% people may experience flushed skin (as the heart works harder) and lethargy (a tendency to feel slow and tired). A partial pressure of carbon dioxide of 5kPa or about 5% can result in disorientation and even unconsciousness. At 10kPA or about 9.8% convulsions may occur, unconsciousness is very likely and - with prolonged exposure to such high levels - death may occur (although the other symptoms are basically signs of impending death in an increasingly hypoxic environment, anyway).


NASA says average oxygen usage for a flight crew member is about 1.76lbs (or 0.8kg) per person per day (at 14.7psi, which is effectively equal to 1atm). Other reports say 550L at STP (approximately 0.77kg) or 0.85kg. My calculations below use 0.85kg (about 600L at STP). Carbon exhalations are slightly less than this (with less volume, since carbon dioxide has a higher molar mass than oxygen).


With those numbers out of the way, we can search for more useful hard data about the boats.


For hard numbers:

The USN's Naval Technical Mission in Europe reports list useful numbers. The IXC40 report covers a decent amount with some hard numbers. Unfortunately, NavTecMisEu's most relevant reports (309-45 and 310-45) only seem to be available in an actual physical archive. As far as I'm aware the same chemical reactions were used for both the VII and IX.


Of note for the IXC:

More elaborate air purification and oxygen renewal systems have been installed. Removal of CO2 is accomplished by insertion of sodium hydrate cartridges into special manifolds attached to the ventilation exhaust line. Measurement of CO2 concentration is made with use of air sampling tubes, a Drager-measuring apparatus, or an Orsat testing setup.

...

The air purification and oxygen renewal systems are based on the requirements of 44 men during 72 hours total submergence. For air purification, a total of 315 canisters, each capable of absorbing 400 liters of CO2 [about 0.7kg], are provided.

For oxygen renewal a total of 13 flasks, each containing 50 liters of oxygen under 160 atmospheres (2275 p.s.i.) pressure, are installed. 44 sets of emergency breathing apparatus are carried on board.

And for the XXI:

The capacity is based on the requirement of 50 men during 150 hours of use.

24 oxygen bottles, each containing 1.77 cu. ft. [50.1L] at 2130 p.s.i. pressure, were placed on board. In addition, a total of 25 oxygen generating cartridges are carried for insertion into a special manifold on the ventilation exhaust line. Each cartridge is able to generate in 50 minutes 53 cu. ft. [1500L] of oxygen at atmospheric pressure.

For C02 removal an improved system over that used on earlier submarine types has been installed. Two large chambers, each capable of holding 35 lbs. of a calcium compound (formula unknown), are placed in the recirculating line running to the small recirculating blower. 450 spare containers, each with 6.5 lbs. of compound for filling the chambers, are carried on board. An air flow meter and regulating valve is attached to the chamber so as to properly adjust the air flow through the line.

More nebulous information for the boats (including internal volume):

The internal volume of air in a Type VII is about 525 cu. m (or about 10.5 cubic meters/person). At normal atmospheric composition this gives about 29.4kg (or about 830 crew hours) of breathable oxygen (after that time you'd be approaching an unsafe level of 17%).

Internal volume of a Type IX is about 625 cu. m (or about 11.5 cu. m/person). That is 35.0kg or 988 crew hours of breathable oxygen.

That seems like a substantial amount of oxygen (more than 18 hours), but the diesels also output carbon dioxide, carbon monoxide and eat up oxygen, meaning the internal atmosphere of the uboat is likely not exactly the 21% oxygen /0.4% carbon dioxide blend outside). But I have no idea how to determine those values at the moment.

Also it's probably best not to tempt fate by dipping below 17% oxygen if possible.


Gas generation and concentration:

The oxygen-generating cartridges in the XXI provide about 2.1kg of oxygen, but more importantly provide approximately the amount of oxygen the crew will be breathing in the same time frame (e.g. in the 50 minutes the reaction is taking place a crew of 50 will in total breathe about 1.8kg of oxygen then factor in non-breathing waste). So this is about 1 extra day of air that other types of uboats won't have.


The tanks of compressed oxygen in both cases seem to be designed to support about 10-15 crew per day with oxygen (depending on exertion) or the whole crew for 6 to 8 hours per tank/flask. Depending on pressure they hold approximately 9.4 to 9.8kg of oxygen each. This is about 124kg for the IXC (or approximately 145 crew days of oxygen (e.g. 3.3 days with 44 crew)) and 228kg for the XXI (or 268 crew days of oxygen (5.36 days with 50 crew)).


Chemical reactions:

The NavTecMisEu implies that the carbon dioxide scrubbers on the IX (and by proxy the VII) used sodium hydroxate (aka sodium hydroxide/lye or "Ätznatron").

2NaOH + CO2 → Na2CO3 (sodium carbonate) + H2O

The air seems to have been pulled through the ventilation tubes, putting it through the scrubbers. The report says one catridge cleans 400L of carbon dioxide from the air. It also says the IX carried 315 or so catridges, or approximately enough to remove 220.8kg of carbon dioxide (or around 260 crew hours of CO2 scrubbing). Approximately 5 days.

Keep in mind that engine exhaust and internal damage may foul a scrubber before it's completely used up, so it's unlikely that the grand total of 315 could all be used purely for exhaled breath.


In a type VII, without being able to change scrubbers CO2 levels could reach over 1% concentration in under 3 hours (e.g silent running/combat situations). Much more dangerous levels of 5% could be reached in less than 24 hours.


The Kalipatronen seem to have been a chemical analogue to sodium hydroxide (albeit more expensive to produce) - potassium hydroxide (aka caustic potash or "Ätzkali"). Its reaction takes part in two steps

2KOH + CO2 → K2CO3 + H2O
K2CO3 + CO2 + H2O → 2 KHCO3

(sorry for the abundance of numbers and letters side-by-side, BB code doesn't like subscript numbers)

Thus it was favored in the Dräger Tauchretter (escape set), because it could use exhaled breath and exhaled water vapor to remove more carbon dioxide (and also provide an exothermic reaction that could help heat the water around the wearer). Although I believe sodium hydroxide can also perform both steps of this reaction.

The NavTecMisEu doesn't identify the XXI's CO2 scrubber, but there's a good bet they're larger than the older subs' versions.


As far as I am aware chemicals that produced oxygen and scrubbed CO2 weren't reliably used until after the war had ended.


So I guess the CO2/O2 debate is whether you think 6-12 hours of renewable + 80 dedicated hours of reserve oxygen is more or less important than 2-4 hours of renewable and 120 hours of dedicated effective CO2 scrubbing.

Depending on the size of the crew and how hard they're working, of course.



(if you're going to take silent running into account, may I recommend having less experienced crew members actually use more air during silent running as a panic/hyperventilation reflex that would probably put them on par to breathing the same amount of air as if they were actually working maintaining torpedoes and such? At least, since it's probably difficult to gauge when the crew is actively under imminent threat)

Originally Posted by Salvadoreno

I downloaded my SH3 from D2D. I read your directions carefully, however i think since my copy of Sh3 comes patched to 1.4, i cannot install. Now let me make sure i got this right

I installed Sh3 to my E drive.
Downloaded your fix..
Made a folder called sh3 fixes on my e drive and extracted the contents of the patch to the folder.
Copied my sh3.exe found in my e drive.
Pasted the copied sh3.exe in the sh3 fix folder containing your fixes.
Ran the fixes, did not work.

Something i missed? Since my version is already patched does it make it unusable?

It should work, mine came all patched when I bought it from the disk and ran fine, dive and surface if the 1 WO goes to the bridge your fixes should be on. If not try the enabler program to select which fixes to use, I think you may need to check the ones you want to use.

[Hitman]

Now the crucial question is whether u-boats could produce pure oxygen AND also recover their Alkalipatronen. As far as I know they could not. I've never read anything about any machine on a u-boat that could do that. In addition, I've read about one account where a boat was almost sunk in the Bay of Biscay because the commander wanted to save oxygen for the patrol area and therefore did not travel submerged. In the context of the Norway campaign I've also read about a boat returning to base (among other things) because of low oxygen supply.

I can confirm that, though probably from having readed the same sources. Nevertheless, the great explanation by Ultimageko definitely settles the matter

Magnific realism adittion, hSie and LGN1

[Wolfstriked]

What about a realistic view thru scopes.I play with stabilize view off(more on that below)and when I click on the UZo my brain says GAME!!But in reality the submariners had to deal with the ocean mucking around with the view thru scopes.



Thing is though the game was developed wrong so that doing readings is almost impossible.I am talking about the stadimeter button and that you have to click off the scope control and click on the stadimeter button.This causes the scope to get thrown off so its pretty much useless.....forcing the player to play with stabilize view on.You can play with stabilize off easier with the RAOFB method.Use proper technique of diving as low as possible to settle the boat and take your scale readings which takes skill but is not impossible.

Any ideas to fix the stadimeter.....and is it possible to remove the UZO always having stabilize view on??

I was thinking that possibly making the Rmouse button to force stabilize view on while in game....you then can move the mouse and now the stadimeter scale moves up and down and when your ready you click Rmouse again and it unstabilizes view and sends the measurement to TDC.The thng is though that stabilize view forces the vertical and horizontal to center so it may look weird when it snaps into this position.

EDIT....maybe its possible to mod a button to click on stadimeter(Rmouse)and it slowly starts lowering by itself so that all the player has to do is to keep the bottom line on water line and click off stadimeter when the top line reaches the meausre point.

[Myxale]

Great post Gecko!! Some parts went over my head...but some stuck!
This was probably the first technical run-down on that matter i have ever read.

[Hitman]

What about a realistic view thru scopes.I play with stabilize view off(more on that below)and when I click on the UZo my brain says GAME!!But in reality the submariners had to deal with the ocean mucking around with the view thru scopes.



Thing is though the game was developed wrong so that doing readings is almost impossible.I am talking about the stadimeter button and that you have to click off the scope control and click on the stadimeter button.This causes the scope to get thrown off so its pretty much useless.....forcing the player to play with stabilize view on.You can play with stabilize off easier with the RAOFB method.Use proper technique of diving as low as possible to settle the boat and take your scale readings which takes skill but is not impossible.

Any ideas to fix the stadimeter.....and is it possible to remove the UZO always having stabilize view on??

I was thinking that possibly making the Rmouse button to force stabilize view on while in game....you then can move the mouse and now the stadimeter scale moves up and down and when your ready you click Rmouse again and it unstabilizes view and sends the measurement to TDC.The thng is though that stabilize view forces the vertical and horizontal to center so it may look weird when it snaps into this position.

EDIT....maybe its possible to mod a button to click on stadimeter(Rmouse)and it slowly starts lowering by itself so that all the player has to do is to keep the bottom line on water line and click off stadimeter when the top line reaches the meausre point.

Only some of the early war UBoat types were equipped with stadimeters in their periscopes. Most UBoats throughout the war had none and the IWO or Captain estimated distance by eye or with the aid of the reticle.

Agree with you on the stabilization, though, but I believe that can be solved via Silent Editor and the cameras file.

[LGN1]

@UltimaGecko:

Thanks for the long and detailed comment In addition to the documents you mentioned I also read the original handbook of the VIIC. In the section dealing with the CO2... they use a volume of 400 m^3 air in the VIIC and an average consumption of 30l/h per each crew member. Where did you get the 525 m^3 for the VII from? One problem is that I never found a source giving the air volume of the II and IX

@Wolfstriked:

There are mods around that have removed the stable UZO via the cameras.dat file. IIRC, Sergbuto's free cam mod was the first Just look for it. If you use a modded cameras.dat, you can see how Sergbuto did it back then and implement it in your cameras.dat.

Cheers, LGN1

[Hitman]

Where did you get the 525 m^3 for the VII from? One problem is that I never found a source giving the air volume of the II and IX

In any case you can calculate the proportion basing on the tonnage of the UBoat, as in general the proportion between internal air volume and size will be very similar.

[Wolfstriked]

Originally Posted by Hitman

Only some of the early war UBoat types were equipped with stadimeters in their periscopes. Most UBoats throughout the war had none and the IWO or Captain estimated distance by eye or with the aid of the reticle.

Agree with you on the stabilization, though, but I believe that can be solved via Silent Editor and the cameras file.

Didn't know that.So how did the captain actually go about it.Did he use the scale to read the tickmarks for mast height and scream it to the WO who entered it into the TDC?Or did the cap'n count the tick marks and then use the RAOFB and send all the info it gives to the WO?I am so lost in how a uboat actually operated.