[WIP] Improved Ship Physics

[TorpX]

Originally Posted by merc4ulfate

Are you trying to say 1:11?? 1 minute 11 seconds?

Yes, it was easier to write it that way.

Will be interesting to see if there's a percentage change that could address all ships.

If so? A script could be written for 010 to adjust all units in the sea folder.

That would save you alot of work.

I don't really know enough to do this. Perhaps in the future, this could be done.

My goal is to have a good set of guidelines at the end of this project, so anyone who wants to add a new, or custom ship/sub, to the game, can read what I post and figure out the right values with minimal testing. I think this is achievable. I don't know if you can totally eliminate the trial and error part, though.

Right now, I still find the issues with diving and turning somewhat tricky. For example, it is not hard to make a boat dive faster, but it may not take a good angle, or might be sluggish, or go past the ordered depth. With turning, strange things can happen. In one test, the boat started a turn, then started skidding from one side to the other, without being able to continue the turn. I was trying to figure out what was wrong, and I noticed the rudder was at constant 40 deg. and depth control was lacking. Going into the control room I was surprised to find the boat rolling one side to the other. I thought, well, we certainly don't want that.

I'm hoping that the fleetboats will all be similar, and I won't have to do too much trial and error.

[TorpX]

I was playing around with the waves. That is, trying different values for the Sim.cfg file (in the Cfg folder). I can't see what the wave attenuation does. Does anyone know about this?

[Mech]
Waves amplitude=0.2 ;[0,1]
Waves attenuation=0.75 ;>=0

I was thinking of trying to make the weather a little more difficult.

[aanker]

Plug this into Google:
site:subsim.com Waves amplitude sim.cfg sh4

..... also try this if the above is more results than you want:
site:subsim.com Waves amplitude sim.cfg sh4 Ducimus

I recall Ducimus breaking it down....... somewhere : )

[TorpX]

I found some of Ducimus posts, and it seemed he did quite a bit of experimentation with these and related files, but it is not clear that he came to any conclusions.

At one point he thought he was close to a breakthrough, but the thread petered out after that. I think I will follow his advice in being careful about adjusting those, and leave them be for now.

[aanker]

From 2007-ish:
This helped a lot in understanding the AI. I tried finding his post here, I know he posted this in the forum however no luck.

--- Wrong topic : )

[TorpX]

I decided to change my timetable on this mod, in order to read U.S. SUBMARINES THROUGH 1945, by Norman Friedman. I should have done this at the outset. It has some very worthwhile info, and will provide a more authoritative basis for any changes. Why rely on guesses and internet crumbs when there are hard numbers available?

Before I got into the book, I did some work on the battery issue. After a good deal of tedious experimenting, I graphed out the results of the actual underwater range vs. input range. The results suggest that there is a logarithmic relationship where at small values, an increase in input range produces a large increase in actual range, but that, as I continued to increase input range, the increase becomes less and less.

[I suppose the devs mixed up a variable or formula in the code there.]

input range...........................actual range achieved
5 mi. @ 2 kts.________________22 mi. @ 2 kts.
10 mi. @ 2 kts._______________32 mi. @ 2 kts.
15 mi. @ 2 kts._______________38 mi. @ 2 kts.
20 mi. @ 2 kts._______________42 mi. @ 2 kts.
25 mi. @ 2 kts._______________ 45 mi. @ 2 kts.
30 mi. @ 2 kts._______________ 47 mi. @ 2 kts.
35 mi. @ 2 kts._______________ 51 mi. @ 2 kts.
45 mi. @ 2 kts.______________ 54 mi. @ 2 kts.
60 mi. @ 2 kts._______________ 58 mi. @ 2 kts.
75 mi. @ 2 kts._______________ 61 mi. @ 2 kts.
100 mi. @ 2 kts.______________ 64 mi. @ 2 kts.
180 mi. @ 2 kts.______________ 67 mi. @ 2 kts.
250 mi. @ 2 kts.______________ 68 mi. @ 2 kts.

[I think these were done with a -50 'special ability' propulsion specialist; you probably can't get the same results.]

It isn't clear whether there is an upper limit to actual range, per se, or not. For our purposes, it doesn't matter. Simply dialing up the input won't make for acceptable battery performance, because the recharge time is proportional to the input value. At the 100 mi. @ 2 kts. value the recharge is 4:21, and at 250 mi. @ 2 kts. it increases to 10:53. Obtaining proper recharge times is just as important as having the ranges correct.

Using inputs specifying 4 kts., or 6 kts., or whatever, gives similar results. I found no evidence of any "magic combinations" that give better results. Using 48 mi. @ 4 kts. will give about the same mileage as 180 @ 2 kts., along with the recharge times. I couldn't find any benefit to be had here. The game evidently uses some formula to reduce the ranges specs we put in to a certain battery capacity, and it doesn't matter how we specify it.

From my results, I've concluded that manipulating the sim file alone cannot fix the battery shortcomings in the game. I tried hard to find a solution here, that doesn't require resorting to using the "special ability" functions, but it doesn't appear possible. I've already experimented with using a "propulsion specialist" type solution (a la Ducimus), and this is workable, but I haven't settled on specific numbers yet. I have to finish this book to see what there is about battery performance.

[CapnScurvy]

Originally Posted by TorpX

I decided to change my timetable on this mod, in order to read U.S. SUBMARINES THROUGH 1945, by Norman Friedman. I should have done this at the outset. It has some very worthwhile info, and will provide a more authoritative basis for any changes. Why rely on guesses and internet crumbs when there are hard numbers available?

TorpX, one thing you should be careful of is thinking Real Life numbers are going to get you real life results. If the game's model for turning Mass, times Horsepower, into Speed, is anything like how it turns Height, times Angle, equals Range.....you won't be satisfied with the results. The game could have its own set of parameters for figuring Speed, Acceleration, Turning radius, etc. They may not match true physics behavior.

Real life measurements won't add up to anything accurate if the measuring tool is off. I know this to be the case with the Range equation using optical means. Whether it's the same for figuring Speed, and overall ship response, could be the same.

Just don't rely heavily on Real Life numbers until you can test the results in practice. Good luck...I'll be watching with interest!

[TorpX]

Originally Posted by CapnScurvy

TorpX, one thing you should be careful of is thinking Real Life numbers are going to get you real life results. ...
Real life measurements won't add up to anything accurate if the measuring tool is off.

Yes, I know what you're saying.

Some parts of the model are certainly broken, some parts seem to work ok, and with many others it's hard to tell.

As far as turning and diving, many of the critical values are "drag coefficients"; that is, they are dimensionless numbers. So it is hard to even make a guess as to what they should be without testing. Lots of trial and error would seem to be required here. Fortunately, Gato, Balao, and Tench classes are not all that different.

I think the hardest part of this is the diving behavior, because so many different factors affect it, in one way or another. I've improved it some. I'm hopeful that I can improve it further.

[mobucks]

Thankyou for taking the time to work on this. It always annoyed me seeing DDs drag race like a cigarette boat. The AI ships are what really need the work. I've read a few books about fleet boat actions and the way they handled in the mods I've played always seemed at least adequate, when considering dive times at least. No idea about acceleration or turning radius, if that is brought to realistic standards then I'm all for it!

[TorpX]

Originally Posted by mobucks

Thankyou for taking the time to work on this.

You're welcome!


***



I thought I'd be done with the subs by this time, but the more I looked at the diving issue, the less happy I was with it.

I've been trying out various number schemes and testing them. I'll pause the game at intervals and record the time, boat angle, at certain depths to get a profile of the dive. Just timing the dive isn't sufficient. I've done this for a surface to PD dive, and for a PD to 150 ft. dive, as well as for the reverse, 150 ft. to PD change. I'm more concerned with the angles at this stage. [I'm focusing on the Gato class now.]

I want to get things so that the boat will take on what I consider a sensible angle, and hopefully, not overshoot the ordered depth. I've never served on a submarine, so I can only rely on what I've read, and whatever intuitive notions of the physics I have. My idea is that the boat should keep within an target angle that is dependent on the speed it has; say ~ 8 to 10 degrees for 4 kts., perhaps ~ 10 to 12 at 6 kts., or something along these lines. The problem is that the AI crew seems to push the dive planes hard, and push the boat angle as far as they can; they don't pull back on the aft plane angle until they get close to the ordered depth. This tends to require that they must ease the angle of the boat very abruptly as they approach the ordered depth. This doesn't seem very good to me. I can lower the plane drag coefficients, but while this slows the angles rate of change, it isn't clear that it really limits the maximum angle. It tends to increase until the crew finally reverses the aft plane angle, and this only happens when they get close to the ordered depth. I don't know if there is a good remedy for this.

Periodically, I've taken a step back, to make some simple experiments to learn if a particular variable is doing what I thought it was doing. This is tedious, but has allowed me to figure out things I would not know otherwise. For instance, the RFB (and stock) files have zero drag coefficients for the front and rear dive planes. I thought this meant that the planes imparted no force to the ends of the boat (the dive angle resulting from buoyancy/trimming factors). This turned out to be false, however. Even with drag coefficient of 0, the value of the prop factor, increases the angle.

Long story short; this stuff takes a long time to sort out.

[Sniper297]

I didn't mess with the dive planes at all, just doubled the mainBT flood speed and diveBT flood speed numbers so it don't take 2 minutes to get it underwater. Also changed rudder drag to 5 and prop factor to 20, gives about the same rate of turn you would get if it was actually possible to back the screw on the inside of the turn.

As far as range and recharge time, I suspect SKWAS either got the values backwards or there's another file affecting this, for a Salmon/Sargo on up the standard is about 50 miles range with a 2 hour recharge time. I changed the numbers to;

miles=1
knots=45

That gives me a range of 63 miles at 2 knots before the battery is down to 10%, with a 14 hour recharge time. The range and speed numbers seem to have a bigger effect on recharge time than anything else, and the results are all over the place. I never tried any supercrewmen, tests were all with default starting crews.

[TorpX]

It's not that I can't get the sub to dive fast. I want the darn things to dive in a proper manner where the planes give the boat a reasonable angle. I don't know - maybe I'm being too fussy about this.

I could zero out the planes and make the boat go down like an elevator, but that isn't what I want. Ideally, a maximum down angle of say 1.5 to 2 degrees per knot of speed would be good. The AI planesmen have other ideas, though. They seem to want to drive the boat down at 30 deg., if they can. I've noted that the interiors of both the RFB fleets and TMO fleets have inclinometers calibrated up to 15 deg. This suggests that they rarely exceeded this angle. That certainly seems reasonable to me, but I may have to let the AI crew have their way.

Just to see what would happen, I doubled the plane drag numbers, and ordered a 400 ft. depth while going at 8 kts. The boat took on a very steep angle as it plunged down. I have no way to measure angles above 15, but it appeared to be ~40 deg. The crew reversed the rear plane to try to reduce the angle, but the boat seemed to just keep plunging (out of control). I expected it to go all the way to the bottom, but around 400 ft., it leveled out (blowing bow buoyancy tank - apparently this is automatic and quite effective), and only overshot the ordered depth a short distance. Going back to PD was the reverse; ~40 deg. up angle, rocketing past 64 ft. and the bow poking up out of the water before the AI crew got it back down again.

The way I see it, diving behavior involves 3 elements:

1. flooding ballast tanks (the main factor going from full surface to ~30 ft. or so)

2. using the planes to achieve a down/up angle (the main factor in changing depths when below the surface)

3. maintaining a sensible target angle and reducing it in such a way as to reach the ordered depth quickly

The first element is easily adjusted with the flood rate, and this seems straightforward without any nasty computer based surprises. The second can be manipulated with the plane drag coefficients, prop factors and UD drag coefficients, but is not so simple. The last element seems to be totally lacking. The AI crew is apt to either go past the ordered depth, and reverse the planes before the finally settling into the correct depth (sometimes they must do this twice), or level out too soon, so that going the final 5 or 10 feet takes a very long time. They're just not very good at this part. Unfortunately, I can't see any way to adjust this part of the game.

[I should note that I'm using a mission where the crew is "competent"; at least that's what I put into the editor. I hope "elite" crews would be better.]



As far as the battery issue is concerned, I've given up on the sim file, and intend to implement Duci's technique. I wasn't able to obtain performance near spec. in any other way.

[CapnScurvy]

The AI crew is apt to either go past the ordered depth, and reverse the planes before the finally settling into the correct depth (sometimes they must do this twice), or level out too soon, so that going the final 5 or 10 feet takes a very long time. They're just not very good at this part. Unfortunately, I can't see any way to adjust this part of the game.

[I should note that I'm using a mission where the crew is "competent"; at least that's what I put into the editor. I hope "elite" crews would be better.]

I think you may have found your answer.

The difference in crew capabilities can easily change the subs "reaction time" to your maneuver orders. I think if you were to stick with a particular sub .sim setting.....yet have identical missions with different crew competency settings, you may find the sub reacts quite differently. It could be you'll find the lowest crew competency setting is the base you need to start with.....figuring the rest will only get better.

[aanker]

Originally Posted by Sniper297

I didn't mess with the dive planes at all, just doubled the mainBT flood speed and diveBT flood speed numbers so it don't take 2 minutes to get it underwater. Also changed rudder drag to 5 and prop factor to 20, gives about the same rate of turn you would get if it was actually possible to back the screw on the inside of the turn.

As far as range and recharge time, I suspect SKWAS either got the values backwards or there's another file affecting this, for a Salmon/Sargo on up the standard is about 50 miles range with a 2 hour recharge time. I changed the numbers to;

miles=1
knots=45

That gives me a range of 63 miles at 2 knots before the battery is down to 10%, with a 14 hour recharge time. The range and speed numbers seem to have a bigger effect on recharge time than anything else, and the results are all over the place. I never tried any supercrewmen, tests were all with default starting crews.

The SALMON/SARGO are different, I don't have time to open them up however here is my GATO:

Following Ducimus, I edited my GATO sim's (for example) to 15.19 knots @ 14138.4 nm.... mostly for superstition and also to give credit to him, it was his idea after all. Each class is different and the numbers are different.

Using those numbers, that's 15+/- knots and around 12,000 - 14,000 nm distance depending on conditions.

Also edited the CFG's to:

AllStop=0.00
AheadSlow=0.25
AheadOneThird=0.50
AheadStandard=0.75
AheadFull=0.90
AheadFlank=1.00

For me satisfaction enough, finally, SHCE distances and speeds, and closer to reality; what I've been reading in the Patrol Reports! No more putting around the Pacific at 10 knots. Furthermore, by editing the Special Abilities UPC to:

[SpecialAbility ]
ID=Ability-Propulsion-Specialist
NameDisplayable=Ability-Propulsion-Specialist-Name
Description=Ability-Propulsion-Specialist-Description
AbilityType=BatteryConsume; FuelConsume <-- comment out FuelConsume
AbilityValue= -41; -5
AbylityActsIn= PropulsionRoom
SkillRequiredLeadership= 0
SkillRequiredMechanical= 0.7
SkillRequiredElectrics= 0.7
SkillRequiredGuns= 0
SkillRequiredWatchman= 0

- and placing a Propulsion Specialist ability crewman (edit him in) to the PropulsionRoom, submerged distances upwards of 95 nm at 2 knots are easy. Ducimus initially suggested -45 but IMO that gave more distance than what these fleet boats could manage in reality - unless there are figures that show they could do 105 - 110 nm submerged... Recharge times are from 4+ hours at all stop to 9 hours at standard speed (14 - 15+ knots) which is what the patrol reports read.

I did away with the speed boost the Engines-Expert - Propulsion Specialist gives as well as the fuel boost. Those shouldn't be available.

[SpecialAbility ]
ID=Ability-Engines-Expert
NameDisplayable=Ability-Engines-Expert-Name
Description=Ability-Engines-Expert-Description
AbilityType= DiveSpeed; SurfaceSpeed, SubmergedSpeed <-- comment out

Unsure atm what I did with DiveSpeed ability.... I read somewhere that boats couldn't go out on patrol unless they could dive in less than a minute. Wish I kept better notes.

Somewhere in my notes I have comparison charts & graphs similar to what CCIP was posting.

Regarding the diving issue - obviously 'crash dive' can only be used when there is no ASW nearby.

During ASW my 'solution' is to order 600' to dive as fast as possible at 2 - 3 kts, and then order my desired depth when within 50' +/- of where I want to be... like 400' - whatever. If they do know where I am, I can increase speed, and then go silent and turn - or not turn.

Also edited DiveSpeed ability however I don't recall the effect, don't have time to re-test, so I don't want to send you on a wild goose chase with that.

[TorpX]

Originally Posted by CapnScurvy

I think you may have found your answer.

The difference in crew capabilities can easily change the subs "reaction time" to your maneuver orders. I think if you were to stick with a particular sub .sim setting.....yet have identical missions with different crew competency settings, you may find the sub reacts quite differently. It could be you'll find the lowest crew competency setting is the base you need to start with.....figuring the rest will only get better.

Yes, I expect you are right. I decided to use the middle level of crew ability, as it was too much work to make separate tests for each level.

I tested a set of numbers today, that I consider very good. I set aside my displeasure with the crews desire for steep dive angles, and let them have their way. They seem to prefer 30 degrees if they have space and speed enough to get it. My only alternative would be to nerf the planes to the point where they are nearly useless, and I don't want to do that. I'll have to test this with an elite crew and see how it goes. If anything, they might dive too fast.



***

- and placing a Propulsion Specialist ability crewman (edit him in) to the PropulsionRoom, submerged distances upwards of 95 nm at 2 knots are easy. Ducimus initially suggested -45 but IMO that gave more distance than what these fleet boats could manage in reality - unless there are figures that show they could do 105 - 110 nm submerged... Recharge times are from 4+ hours at all stop to 9 hours at standard speed (14 - 15+ knots) which is what the patrol reports read.

I tested this with - 40, I think. It seemed pretty good. I'm not too concerned with the exact range figure, though. My inclination is to give a little better than min. spec. It's not clear to me that the listed values are what they tested at, or just Gov. spec (the later, I think). In reality, we would lose battery capacity, as they go through recharge cycles, until we got new ones in the next refit.

The thing about the special ability number is that I have to pick one value that will work well for every class of boat.