Air supply in H.sie mod – New Options Selector 1.6C
 

One of the later changes that H.sie made to his famous patch for SH3.exe (the executable file for Silent Hunter III) was complex code to manage the carbon-dioxide (CO2) production of the crew, with its effect on lowering oxygen in the air of the U-boat. The original (stock) SH3 code apparently allowed underwater travel for three days, which was far too long for realism.

As a result, on the basis of calculations of U-boat volumes of air carried, crew numbers and rates of breathing and CO2 production, H.sie’s hard-code patch allowed about 5 hours of underwater cruising (all U-boat types), and then replenishment oxygen from a coded ‘tank’ of spare oxygen for another 60 hours or so. The ‘tank’ could not be topped up again, even on the surface. H.sie did an excellent job on this – I’ve have a copy of his assembly code and it covers such variables as numbers of crew aboard (affects rate of breathing) and whether silent-running or not, as well as the code needed to operate the reserve tank and the tank meter displayed on screen. He provided algorithms for rate of oxygen consumption and for CO2 production, and the correct maximums of CO2 permitted in the boat.

Owing to disputes as to the time that each oxygen supply should last, the Options Selector (supplied with the H.sie patch) provides two sliders at the bottom which the user can adjust. The original values were 1.0 for each slider, but longer quantities of oxygen-supply can be set with the slider. The recommendation for the NYGM supermod was renewable oxygen = 2.5 and oxygen-tank = 2.0.

However, this basic model is over-simplified. In real life, the U-boat contained compressed air reserves to restore the air in the U-boat while potash cartridges removed carbon dioxide. The same compressed air was used to surface the boat, and the tanks were refilled whenever the U-boat was on the surface. Thus we have a model where air in the U-boat was essentially replenished seamlessly underwater. Cylinders of compressed pure oxygen were used to eke out oxygen supplies during long periods underwater. These cylinders could not be recharged.

From June 1943 U-boats had orders to cross the Bay of Biscay almost completely submerged to avoid air attack. The U-boats were to come to the surface only once at night, for long enough to recharge their batteries (2-4 hours). NOT to recharge their air – I checked this with real U-boat survivors. Thus the U-boats were cruising underwater for up to 22 hours without replenishing their air.

I’ve carried out further tests with SH3, and I consider that values of 3.5 (renewable supply) and 1.0 (non-renewable supply, bottled oxygen) should now be recommended. Maximum permitted underwater times (before use of oxygen tank) with these values (full crew, not silent-running) measured in SH3 thus:
Type II: 21 hours; Type VII 23.5 hours; Type IX 28.5 hours; Type XXI 29.75 hours.

Big problem: the original Options Selector did not allow slider values greater than 3.0 for the air supply (assumed at the time to be the oxygen supply).

Therefore I have created a new version of the Options Selector (version 1.6C) that allows values to be set from 1.0 to 4.5 in steps of 0.5. This new version can be downloaded here:

http://www.subsim.com/mods1/nygm/Hsi...lector_V16C.7z
(Or item 13 after clicking on the NYGM web-page at Subsim, below my signature.)
Stiebler

Sounds like an awesome piece of work. :sunny:

Excellent work!

Many thanks.

Nice work ! :salute:

How does silent running effects oxygen supplie?

Hi Niume
"Oxygen-Supply - by LGN1 (idea) and h.sie (programming)
So far, SH3 models a 100% renewable oxygen (O2) supply. That means: After a long period of diving, say 40 hours, it was sufficient to surface and after that the Uboat was able to dive for 40 hours again and again. With this fix, O2 is divided into two parts: A renewable part and a non-renewable part. The renewable part is the O2 in the air of the Uboat. This part is sufficient for a diving period of about 5-7 hours. During this time the LI informs you about the O2 content of the air, starting at the normal value 21% and slowly decreasing to the critical value of 17%. At 17%, the LI automatically starts to add O2 from the oxygen-supply (contained in pressure bottles). This botteled O2 supply is sufficient for a long diving period of about 30 - 100 hours (depending on Uboat type), but that O2-supply is non-renewable! That means: It is not filled up when surfacing. Only the O2 in the air is restored to the normal value of 21% when surfacing. From now on the Player has to act economically regarding O2 supply, what adds a new strategical component to the game. "

Very nice. Thanks for the hard work and making the patch available. :Kaleun_Thumbs_Up:

In your post, you keep referring to "renewable supply" and "non-renewable supply" or "oxygen tank."

In the actual options selector the modifiable options are "Oxygen in boat" and "Compressed Oxygen." Could you clarify which is which? Can't really figure it out from the readme either.

I'm sure that I am overthinking it (I'm a Physicist, that's what I do + definitions are crucial to me :03: ) It appears that "Oxygen in boat" is the replenishable supply and the "Compressed Oxygen" in not replenishable.

If you could clarify, that would be great thanks. :salute:

"Oxygen in boat" = "renewable supply"
"Compressed Oxygen" = "non-renewable supply"

@RudeWarrier:

Yes, I was a little inconsistent with my words. Sorry about that.

Schlechter-Pfennig's answer is correct:
"Oxygen in boat" = "renewable supply" [Left-hand slider in Options Selector. Preferred value now 3.5]
"Compressed Oxygen" = "non-renewable supply" [Right-hand slider in Options Selector. Preferred value now 1.0]

Stiebler.

Excellent, thank you.

I have sent you a PM regarding your access to h.sie's code and specifically the Torpedo Failure Fix. Please check it when you get a chance.

Again, thank you.

https://en.wikipedia.org/wiki/Submarine_snorkel

From June 1943 U-boats had orders to cross the Bay of Biscay almost completely submerged to avoid air attack. The U-boats were to come to the surface only once at night, for long enough to recharge their batteries (2-4 hours). NOT to recharge their air – I checked this with real U-boat survivors. Thus the U-boats were cruising underwater for up to 22 hours without replenishing their air.

that is why they could cross the Bay of Biscay snorkel was able to give fresh air to the crew and was not designed only for alowing the diesel engines to run underwater for 22 hours

and in 1943 obviously the german submarines have been equiped with snorkel

Welcome to Subsim, Dietrickvonfikt.

In 1943, operational U-boats had not been fitted with the schnorchel. The very first schnorchel-fitted patrols did not begin until about March 1944.

Thus it has been very important to discover how long U-boats could travel underwater before the schnorchel was fitted, if SH3 is to be played correctly. Standing orders during 1943 were to surface once per night to recharge the batteries. (Actually, the standing orders changed several times during 1943, but this was the most persistent order.) Since recharging required 2-4 hours, the air-containers were also refilled (several minutes only) at the same time.

I hope that makes clear any misunderstanding.

Stiebler.

A Warm Welcome To The Subsim Community > Dietrickvonfikt
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