LuftWolf and Amizaur's Realism Mod Poll #11: Nuke Speeds

[Amizaur]

Originally Posted by Kazuaki Shimazaki II

If you want to improve the Akula, give us sensitivity or washout speed improvement.

It's not about improving, it's about realism...

The game interface does a good enough job of modeling Russian sonar inferiority that you don't need a Nrd differential anyway...

Did you know, that in late 80's and early 90's Russians themselves estimated that their best sonars has 3 to 10 times shorter det ranges than US sonars ? Yes, subs were very quiet, but sonars were much worse... time has passed but how much this gap have closed ? With western technology still improving all the time ? So, having 30% det range penalty is just fantastic thing to have in DW :p in russian subs which are (with exeption of SW) faster, deeper diving, and have better (with exeption of ADCAP) and more universal armament ?

Or change the SS-N-27's airdropped torp back up to 55.

And this would be justified by what ? Do you expect very small and not most modern russian electric torpedo that is used in SS-N-27 system to have speed of 55kts ??

Or reduce the 688I's diving depth to 300m, since some sources suggest its dive depth is reduced to cram in the speed and reactor. With the Advanced Torp Mod, it has the effect of not allowing it to use depth to slow the approaching torp - in torp evasion, relative speed is important.

This is much better proposition. 688 diving depth is often stated as 300m (984ft) with 450m (1476) crush.

But I'm afraid we can't simply put correct values into database (even that they would be only little less than now from 492m --> 450m). Because if we put correct crush depth into DB, then not much changes - just like now every 688 in game would be runing 10m above crush depth... in game you are sure that nothing wrong will happen. In real life I suppose no one sane captain would dive even CLOSE to his boat's crush depth even if running for life... at this depth sub is supposed to collapse, so even 10% less would be very, very dangerous, probably more dangerous than torpedo that is chasing him. I don't think (personally) that anyone would exceed 400m in RL with 300m test and 450m crush depths - even in worst situation .

But we can't also set 300m into db as crush depth - in RL subs can go deeper if needed, just not all the way to crush depth. Maybe we should assume some % of crush depth that in RL would be maximum used, and set it in DB - for 688i it would I think be not less than 350 (1150ft) but not more than 400m (1312ft). And rework all sub's depths with this scheme.

Currently crush depths are:

492m for 688s (1614ft)
656m for Seawolf (2150ft)
569m for Akulas (1866ft)

[Bubblehead Nuke]

Originally Posted by Amizaur

In real life I suppose no one sane captain would dive even CLOSE to his boat's crush depth even if running for life...

When a weapon is in the water, and you are the target, all bets are off. You use every bit of the performance envelope that you have. Redline a reactor plant for the extra knot or 2?? Take her deeper cause there is a layer 200 feet deeper but not quite at crush that MIGHT save your butt?? Oh yeah, count on it. You would 'break the rules' on the performance envelope if you have to in order to stay alive and come back to kill the OTHER guy.

We used to have discissions about it all the time in the division and with other divisions on the boat. Little "What if's" in the corners of the boat while tossing cards around. We even joked about it. It ended with 'the shipyard can fix it if we are still around to get it there.'

Added:

One thing here that probably irks us real bubbleheads is that there are operating limits and absolute limits on submarines. The game deals in absolutes while we think in terms of the operational limits that were imposed on us. You have a safe range of speed and depth that work inside of. Outside of this range you are getting into dangerous areas. Too fast and too deep mean you hit your crush depth before you can recover from flooding etc etc. Crush depth is an UNKNOWN thing till you find it the hard way.

I think the game does a good job in balancing the the various classes but what needs to be done is something on the same order. I realize that is can not be done my a mod probably. What you do is make variable ABSOLUTE limits and impose operational limits. That way a player has an envelope to play in but then makes a choice to operate outside those limits and risk breaking things or crush.

Put down that a 688i has a safe operating max depth of 800 feet (otherwise known as test depth). Crush depth is something deeper than 1200 feet but put a variable on it. It might actually be 1141 for that ship. Maybe the welders had a good day and on another ship of the same class crush depth is 1487 feet. Make it random each time you dive for each ship. That way you can not guess how deep you can REALLY go.

Why did I bring this up?? With all the discussions of changing speed someone asked what does a knot or 2 matter? It can literally be the difference between life and death. Remember back when I started posting I said something about how FAST a bell is answered. That normally the throttleman will NOT cavitate unless ordered but when told to GO, he answered it quickly and without hesitation. When torpedo's are in the water speed IS life. You will get told to stand on the power and the boat will speed up REALLY quickly. Speed gets you out of the detection cone of the weapon. Speed gets you clear of the datum and tosses his solution out the window. Speed makes the boat more manuverable. Speed is more imporant than depth in a lot of ways when weapons are in the water.

[Amizaur]

Originally Posted by Bubblehead Nuke

We used to have discissions about it all the time in the division and with other divisions on the boat. Little "What if's" in the corners of the boat while tossing cards around. We even joked about it. It ended with 'the shipyard can fix it if we are still around to get it there.'

Yes, but crush depth is a depth at which sub is supposed to collapse, it's designed to it... of course it can withstand little more, but maybe little less... So I don't think anyone would dive to crush depth even if a evading torpedo, because... shipyard can't fix this kind of damage and you won't get back.
Something like diving a fighter plane below ground level to avoid a missile... or better, to dive a fighter plane, in a fog, to or below 0ft altitude to avoid a missile...

P.S. After reading the add on I see that actually we agree in general

One thing here that probably irks us real bubbleheads is that there are operating limits and absolute limits on submarines. The game deals in absolutes while we think in terms of the operational limits that were imposed on us. You have a safe range of speed and depth that work inside of. Outside of this range you are getting into dangerous areas. Too fast and too deep mean you hit your crush depth before you can recover from flooding etc etc. Crush depth is an UNKNOWN thing till you find it the hard way.

This is exactly what I had in mind writing. There are NO operational limits in game, that anyone would care about them. Maybe if game penalized after the mission if operational limits were exceeded... something like with friendly fire but not that serious. So we have ABSOLUTE limits only in game. To get people to behave realisticaly (and dive within operational or emergency limits, but NOT crush depth) we would probably have to set not exceeded in real life even in emergency... isn't it called "safe excursion depth" or something like that ? Never exceed depth ?

There is IIRC 150% safe margin in US designs between operational (test?) depth and crush depth... Or was it 175% ? I remember german standards are 200% of operational depth.

Put down that a 688i has a safe operating max depth of 800 feet (otherwise known as test depth). Crush depth is something deeper than 1200 feet but put a variable on it. It might actually be 1141 for that ship. Maybe the welders had a good day and on another ship of the same class crush depth is 1487 feet. Make it random each time you dive for each ship. That way you can not guess how deep you can REALLY go.

In game manual is written (again IIRC, didn't read it for long time ) that real crush depth is randomised each mission, so you don't know HOW MUCH you can exceed crush depth actually. However it doesn't simulate that real crush may be LESS than is written, so we should set game crush limit to something less than crush depth we want to use.

[Bubblehead Nuke]

Originally Posted by Amizaur

Yes, but crush depth is a depth at which sub is supposed to collapse, it's designed to it... of course it can withstand little more, but maybe little less... So I don't think anyone would dive to crush depth even if a evading torpedo, because... shipyard can't fix this kind of damage and you won't get back.
Something like diving a fighter plane below ground level to avoid a missile... or better, to dive a fighter plane, in a fog, to or below 0ft altitude to avoid a missile...

P.S. After reading the add on I see that actually we agree in general

As was pointed out in an earlier post, there is a HUGE amount of hull penetrations in the pressure hull of a submarine. There is no 'designed' hull crush depth. They factor cyclic stress from surfacing and diving over the projected life of the hull, add a few fudge factors for the estimated weakest penetration and then put in a 30% safety margin (30% is a GUESS here folks). They call this number on american subs test depth. It is the normal maximum operational depth that a sub can operate at.

Everything is calculated by some big egg head in the sky and we only hope they lubed up the slide rule before they figured all this out. As the ship age and go thru ship alts they modify this number. Some of the older nuke boats actually had their max depth REDUCED because they had exceeded the calculations based on life of the ship.

This is exactly what I had in mind writing. There are NO operational limits in game, that anyone would care about them. Maybe if game penalized after the mission if operational limits were exceeded... something like with friendly fire but not that serious. So we have ABSOLUTE limits only in game. To get people to behave realisticaly (and dive within operational or emergency limits, but NOT crush depth) we would probably have to set not exceeded in real life even in emergency... isn't it called "safe excursion depth" or something like that ? Never exceed depth ?

See above. We called it test depth. The number by the way is variable based on ships speed. As a general rule, the deeper we went, the slower we operated. It had to do with PEACETIME rules and our ability to recover from certain casualties

There is IIRC 150% safe margin in US designs between operational (test?) depth and crush depth... Or was it 175% ? I remember german standards are 200% of operational depth.

Sorry, can't help you there. I can not tell you if you are even close.

Any OPERATIONAL limit would have to be self imposed by the player as it is a set of numbers designed to keep you operating in a safe enviroment (such as it is). It could be imposed by the manuevering limits of the ship. If you go back thru my posts you will see me commenting on the depth excursions exibited by a sub throwing a hard rudder on at high speed. As I said, this comes on MUCH faster and creats FAR more of a depth excursion than is currently modelled in game.

Want to know what I like about this dicussion? With all of the THOUSAND of ex-bubbleheads out there, nobody has given out the real numbers.

That makes me PROUD of the Silent Service.

[LoBlo]

Originally Posted by Bubblehead Nuke

They factor cyclic stress from surfacing and diving over the projected life of the hull, add a few fudge factors for the estimated weakest penetration and then put in a 30% safety margin (30% is a GUESS here folks). They call this number on american subs test depth. It is the normal maximum operational depth that a sub can operate at.

Everything is calculated by some big egg head in the sky and we only hope they lubed up the slide rule before they figured all this out. As the ship age and go thru ship alts they modify this number. Some of the older nuke boats actually had their max depth REDUCED because they had exceeded the calculations based on life of the ship.

I got my undergraduate degree in engineering. In almost all cases of structural design work I've seen we usually see about a 100-200% safety margin. But those were all civillian engineering applications (bridges, building frames, etc.) We calculated the maximum stress that the structure needed to withstand and then designed the loading points to fail under twice that amount. However, estimation, conservative guessimates and worst case scenario are factored into just about every point in those estimates with the true failure stress of a load point really an unknown. It really is a shot in the dark, but one could probably be reasonable to think that a new sub without any damage could sustain alot more than its crush depth and live to tell about it, like you've already mentioned.

As far as Russian subs go... man, its hard to say. The russians don't have a very good reputation for safety that's for sure. One *could* think that the double hull design of the Russian subs would give them a relatively deep crush depth... but then again would the same stress safety margins apply to their structural design in the first place? Perhaps the russian *crush depth* isn't as conservative an estimate... or maybe its more conservative... impossible to tell. I wouldn't be opposed to a 2000ft ingame crush depth for the Akula. Perhaps if even just an ingame reflection of the will of the Russian navy to push safety limits... (also a blatant stereotype)

[Amizaur]

Originally Posted by LoBlo

We calculated the maximum stress that the structure needed to withstand and then designed the loading points to fail under twice that amount. However, estimation, conservative guessimates and worst case scenario are factored into just about every point in those estimates with the true failure stress of a load point really an unknown. It really is a shot in the dark, but one could probably be reasonable to think that a new sub without any damage could sustain alot more than its crush depth and live to tell about it, like you've already mentioned.

All you say is truth... Me too thinks that NEW sub can withstand little more... But what you say that nobody really knows what is the real load at which structure fails... If you are designing a bridge, and are not sure if your safe margin is perfectly safe, and are not sure if it REALLY can withstand what numbers say... you just increase the margin. You don't have money to build whole section of a bridge and make destructive test on it anyway...
But you can't make it with submarine, or airplane - just increase the margin to be sure. You have to be quite sure what it can take. So for so important projects like aircrafts and submarines people from time to time test such things just to have idea of what they REALLY can withstand :-), and then base on those tests for some time, and then make new tests while designing new construction... I know that whole sections of submarines were tested for fail pressure when designing really NEW (new designs, new materials) constructions, like when the Russians tested sections (or maybe whole hull?) of first titanium submarine. I could bet that sections of hull from new (HY-100?) steel were tested to fail too... and maybe even material tiring tests - somone someday tested this to know today what limits put on aging sub...
When they build new aircraft today, B-777 or Airbus A380, they know really good what the plane can withstand. I remember an destructive test of wing strength made on whole big passenger airplane airframe. They were bending the wing to the point it failed. This point was, if I remember, around 102% of calculated value... so it was calculated quite precisely :-).
I - personally - wouldn't try do dive a sub below given crush depth, even new one... but of course it's an open question and either of us can be right :-)
Probably it can really withstand some more, if new... but on the other hand, just like you said, even if the hull as a whole take it, one of thousands small thing like opening in the hull or internal pipe that is weaker... and it can kill whole sub and crew... remember the australian Collins accident lately...? They said they were close, very close... It can happen even on less than crush depth, but while closing and passing crush the probability of such thing increases by factor of ten probably...

About Seawolf speed - yes, it can have much more powerfull reactor, but it is also much bigger than LA. And correct me if I'm wrong, it's not reactor that counts, it's first the steam turbines limit (this is reason that nuclear carriers had same max speed as conventional - they had different steam generators, one conventional, second nuclear, but the turbines were the same and had same output power...) and secondly how much power the propeller can transfer to the water... (but yes, IIRC the LA is rather reactor-limited, all other parts of chain being more capable).

The Alfa and Papa, speed record breaking subs, were just big metal-cooling reactors and machinery monsters with not much place left for other things... SW is normal submarine with much place for weapons, sensors ect. similar like LA class... I really wouldn't expect it to break those records... it can be quite possibly the fastest OPERATIONAL sub in the world (with all Alfas decommisioned long ago), but wouldn't take the words as absolute record breaker...

I think if we have an hydro enginer here, with help of few smart programs like NavCad or it's free analogs, can quite accurately estimate drag of SW hull (or at least difference between LA hull and SW hull) and maybe even the propeller efficiency, although it's a water jet... there are good programs for determining ordinary propeller performance but don't know if for waterjets... In most simple case we could compare drag increase of SW hull to LA hull and compare this with official data of output shaft power, and see what speed could we get... the question is if we can trust the values that are given for SW propulsion...? ;-)

[FERdeBOER]

Originally Posted by Amizaur

And correct me if I'm wrong, it's not reactor that counts, it's first the steam turbines limit (this is reason that nuclear carriers had same max speed as conventional - they had different steam generators, one conventional, second nuclear, but the turbines were the same and had same output power...) and secondly how much power the propeller can transfer to the water... (but yes, IIRC the LA is rather reactor-limited, all other parts of chain being more capable).

I'm not correcting, I'm just asking: are not the nuclear carriers bigger than conventional ones?
If so, the engine power of the nuclear reactor should be bigger than conventional to move them at same speed.

[LoBlo]

[quote=Amizaur]

Originally Posted by LoBlo

About Seawolf speed - yes, it can have much more powerfull reactor, but it is also much bigger than LA. And correct me if I'm wrong, it's not reactor that counts, it's first the steam turbines limit (this is reason that nuclear carriers had same max speed as conventional - they had different steam generators, one conventional, second nuclear, but the turbines were the same and had same output power...) and secondly how much power the propeller can transfer to the water... (but yes, IIRC the LA is rather reactor-limited, all other parts of chain being more capable).

yep, In fact, I'm almost 100% certain that that's the origins of both the SW's quieting and its improved poweroutput of its S6W reactor over the older S6G reactor of the LA, I'ld garantee that the S6W has supplemented a traditional coolant loop cycle (like the S6G) with an additional natural circulation cooling loop providing a "silent" (i.e. no coolant pump needed) mode to 20 knots with activation of its traditional coolant pumps for full power. The combination of the two is what neccessitated the larger diameter hull and would also provided increased peak turbine flow (with the maximum flow volume of the steam turbine cycle dictated by the maxmum steam -> water cooling rate of the sub). The addition of a NC cycle, provides a "quiet mode" and boost the maximum steam flow rates at the same time.

At least that's my completely and utterly amateur theory anyway.

The SW, when compared to the Akula II, is smaller, lighter, has a more advanced propulsor, larger "powerplant" spacing, and I believe a improved peak output power. A 4-6 knot speed advantage is reasonable to me. (33 knots for the Akula II vs 38knots for the SW, or 35knots for the AkulaII vs 40knots for the SW).

btw, I'm not an expert by any means, but I did do some elementary fluid dynamics training in college. I could share some of the simple and basic stuff I remember if it would help and if anyones interested. Don't remember enough to give any hard calculations though.

[Kazuaki Shimazaki II]

Originally Posted by Amizaur

It's not about improving, it's about realism...

I'm wondering how they figured out (even guestimated) the washout speed. I suppose you can guestimate sensitivity by looking at the array size and making some estimates as to the influence of processing power, but washout speed - beyond the general assumption the US would have a higher one?

Did you know, that in late 80's and early 90's Russians themselves estimated that their best sonars has 3 to 10 times shorter det ranges than US sonars ?

I read something similar, except it was 1/3rd as sensitive, which roughly collaborates with what L/W seems to be shooting (2Nrd difference = 4dB, = 2.5 times difference), but that correlates with a lot less than 3 times, depending on conditions. 10 times might hold true at higher speeds or in wierd hydroacoustic conditions - hard to see it in normality.

And I entirely agree with this general concept, except:
1) Does the mentioned difference (from the sources) take account the Display Influence?
2) "-8" (or =TB-16, 2Nrd less sensitive vs new TB-23) is more than fair for the Improved Akulas, which are rough contemporaries of the 688I and in accordance to the 1/3rd as sensitive guide. But not the Akula-IIs, which are roughly contemporary with SW. Assuming this +2Nrd sonar lag holds, the Pelamida II should have a sensitivity of closer to -10 to compare with the SW's -12 (or was it -14?) - take the higher washout of US arrays into account as well...

And this would be justified by what ? Do you expect very small and not most modern russian electric torpedo that is used in SS-N-27 system to have speed of 55kts ??

OK, maybe not 55, but 50. This is like 10+-year old tech (French NTL-90 came in about '92), so even assuming the usual 10-year gap it is not unreasonable to assume the Russians would have gotten around to it in their newest ASW weapons. Besides, some sources suggest making a 50-knot small torp is not impossible for the Russians.

This is much better proposition. 688 diving depth is often stated as 300m (984ft) with 450m (1476) crush.

Since MaxDepth in DW = Max 100% Safe Depth, I suggest initial calibration can be set for Never Exceed Depth (in the Ak, it is 1804 feet according to GlobalSecurity, which is similar to what's there now).

Fine calibration between that and crush (estimated at about 1970-2160 feet) to aim for a 50% chance, with the condition that Never Exceed Depth should be perfectly safe.

For those without Never Exceed Listed, I suggest starting out halfway and then calibrating within the gap between test (300m for LA) and crush (450m) so that at the real crush, we get roughly a 50% chance of death as possible.

[LuftWolf]

modern akula II class submarines were at least as quiet as the 688i and I don't think this is modelled in the game (vanilla or lwami mod).

GD, yes this is modelled in LWAMI. The Akula II's are more quiet than the LAi's up to about 6-7 kts. At higher speeds, the Akula II's are known to be louder than the LAi's because the active noise cancellation systems used on the AKII's are ineffective above low speeds.

I like the figures Amizaur listed.

688/688i - 32kts
Akula -35kts
Seawolf - 37kts

Cheers,
David

PS Keep in mind, if you are worried about play balance, you have to keep in mind that this is in the context of LWAMI4, in which the torpedoes are by far going to be the biggest balancing factor. Interestingly, the strength of the ADCAP over the UGST (the gap between the torpedoes is much wider in LWAMI4) will help the 688i considerably, while the overall changes to the torpedoes such as "basic" torpedo physics and wirelength limits will help tone down the power of the SeaWolf. All in all, I think the game will be even more balanced once these changes are all implimented.

PPS And for the record, this should be LWAMI Poll #12. :-P

[Molon Labe]

In terms of depth, the way the game works now is that it chooses at random an actual crush depth that is somewhere below the given crush depth. Every little bit you go below increases the risk of implosion.

[Amizaur]

Originally Posted by Kazuaki Shimazaki II

I'm wondering how they figured out (even guestimated) the washout speed. I suppose you can guestimate sensitivity by looking at the array size and making some estimates as to the influence of processing power, but washout speed - beyond the general assumption the US would have a higher one?

I have no idea what washout speed are or should be. So I just don't take a position in any discussion about it, leave it to others...

I read something similar, except it was 1/3rd as sensitive, which roughly collaborates with what L/W seems to be shooting (2Nrd difference = 4dB, = 2.5 times difference), but that correlates with a lot less than 3 times, depending on conditions. 10 times might hold true at higher speeds or in wierd hydroacoustic conditions - hard to see it in normality.

I have read that Russians thought it was 10x det range, but actually it was not that bad and about 3 times

And I entirely agree with this general concept, except:
1) Does the mentioned difference (from the sources) take account the Display Influence?

Don't know, I don't touch sensors. But this influence SHOULD BE MEASURED I think, and measured on more than one comp to see if GFX card makes any difference between US and Russian interfaces.

OK, maybe not 55, but 50. This is like 10+-year old tech (French NTL-90 came in about '92), so even assuming the usual 10-year gap it is not unreasonable to assume the Russians would have gotten around to it in their newest ASW weapons. Besides, some sources suggest making a 50-knot small torp is not impossible for the Russians.

Only most modern electric torps like MU-90 with very advanced batteries are said to be in 50kts class speed. The torpedo used in SS-N-27 system is MPT-1UE very small electric torpedo, not designed for it and used previously in russian eqiuvalent of CAPTOR mine. Not most modern probably, some years design.
Very small, very light (that's why they used it instead of great APR family - oh yes, APRs ARE fast, but too heavy for that system... but APRs could be raplacement for Stallion torps).

From the link you gave, do you thought about 400 mm (15.75") APSET-95
torp ? Come on, 30.000m of range for 400mm torp ? It's very questionable one, probably two different torpedos are mixed here, the name from one and specs (guessed) from another...

Since MaxDepth in DW = Max 100% Safe Depth, I suggest initial calibration can be set for Never Exceed Depth (in the Ak, it is 1804 feet according to GlobalSecurity, which is similar to what's there now).

Fine calibration between that and crush (estimated at about 1970-2160 feet) to aim for a 50% chance, with the condition that Never Exceed Depth should be perfectly safe.

For those without Never Exceed Listed, I suggest starting out halfway and then calibrating within the gap between test (300m for LA) and crush (450m) so that at the real crush, we get roughly a 50% chance of death as possible.

100% agreed I would like to do it exactly this way !

[XabbaRus]

I'd go with SCX speeds.

Henson, Russian subs use PWRs the Alfa was the only operational Liquid Metal reactor sub.

[Henson]

Originally Posted by XabbaRus

I'd go with SCX speeds.

Henson, Russian subs use PWRs the Alfa was the only operational Liquid Metal reactor sub.

Good gouge, thanks.

And it makes sense. I got the info off a public interview by some old soviet bubblehead.

[Kazuaki Shimazaki II]

Originally Posted by Amizaur

Only most modern electric torps like MU-90 with very advanced batteries are said to be in 50kts class speed. The torpedo used in SS-N-27 system is MPT-1UE very small electric torpedo, not designed for it and used previously in russian eqiuvalent of CAPTOR mine. Not most modern probably, some years design.
Very small, very light (that's why they used it instead of great APR family - oh yes, APRs ARE fast, but too heavy for that system... but APRs could be raplacement for Stallion torps).

We can try that last too as a hypo. In my experience at least, the present situation is such that you basically would never carry a Stallion. Its torpedo is inferior (and will remain so after even this latest downgrade of the torp on the SS-N-27). The missile itself has greater range but of limited utilitity since you won't really shoot that far anyway and the SS-N-27 has more than enough reach...

From the link you gave, do you thought about 400 mm (15.75") APSET-95
torp ? Come on, 30.000m of range for 400mm torp ? It's very questionable one, probably two different torpedos are mixed here, the name from one and specs (guessed) from another...

Well, I suppose it won't be at 50 knots for 30000 (too far out of the zone for battery driven), but if I assume it can run 10-12 km at 50 knots (reasonable considering it is supposed to be a 90s torp itself and larger than Mu-90), 30000 yards may well be possible at say 30-35.