An Educated Guess of RN & VMF Battleship Ballistics

[fnord_disc]

Since Lesta gives us the name of the shell used, I had some fun looking at the historical shells and what their ballistics are in the game. I was very happy to notice that with only a few inexplicable exceptions, the way Lesta derives drag constants is relatively simple and easy to understand. Since muzzle velocity and weight is also well-documented, it's possible for me to predict ballistics for these battleships with a fair amount of accuracy. There is always a chance that Lesta uses experimental or poorly documented shells, in which case the prediction is obviously wrong.

 

To make it more relatable, I'll compare the arcs to similar arcs in the game.

 

Where the drag coefficient comes from

 

The drag coefficient seems to be almost exclusively based on the shell's crh value, which represents the length and curvature of the shell nose or ballistic cap, whichever is applicable. Here is an image from navweaps:

 

 

4 crh means the nose is 4x as long as the radius of the shell. If two numbers are given (such as 4/10 crh) then the second number corresponds to the curvature of the shell. 6/infinity shells for example (common IJN shell) means that the cap is not curved but looks like a conical hat and is 6x as long as the radius. Obviously a long and streamlined nose gives better ballistics than something blunt.

 

Generally, 4crh is quite bad and leads to in-game drag constants between 0.4 and 0.45. 5-6crh gives okay drag constants around 0.33-0.36 depending on curvature (common shell design on many ships in the game), and 10 crh (common on WW2 German BBs) is really good and gives around 0.27-0.28 drag. Lower drag is better.

 

Lesta seems to take some liberties with these, since Yamato has roughly 7crh shells and the drag is only 0.29 when it should be a little higher in my opinion.

 

Royal Navy

 

16" Mark I (Nelson)

~800 m/s MV, 930kg, 6/infinity crh

= decent arcs very similar to Nagato/Amagi

 

14" Mark VII (KGV)

757 m/s MV, 721 kg, 6/12 crh

= decent arcs, slightly worse than Warspite and better than Fuso/Kongo

 

15" Mark II (experimental KGV)

836 m/s MV, 879 kg, 5/10 crh

= decent arcs almost identical to Warspite

 

16" Mark II-IV (Lion)

747m/s, 1080 kg, 6/12 crh

= decent arcs, should be slightly better than Nagato/Amagi

 

Basically, all these guns have very similar ballistics to Warspite and Nagato/Amagi, so you get a solid all-round performance. Not as flat as Bismarck or Yamato, but good.

 

Soviet Navy

 

16" Vickers (WW1 Paper Projects)

757 m/s MV, 1116kg, probably standard 4crh old British shells

= terrible arcs

 

16" B-37 (Soyuz)

830 m/s MV, 1108kg, looks like 6/10 crh in pictures

= flat arcs, same or slightly worse than FdG/GK

 

12" SM-33 (Stalingrad)

950 m/s, 467kg, looks like 10 crh or more

= insane lasers

 

If you like this and want me to predict more stuff, you can suggest it.

[creamgravy]

How about the 18" BL Mark I from HMS Furious. A 8crh HE shell should make her the biggest scumbag at tier 4.

 

http://www.navweaps.com/Weapons/WNBR_18-40_mk1.php

 

 

[fnord_disc]

How about the 18" BL Mark I from HMS Furious. A 8crh HE shell should make her the biggest scumbag at tier 4.

 

 

http://www.navweaps.com/Weapons/WNBR_18-40_mk1.php

 

 

 

That's really good drag, and the shells are very heavy, but they're also very slow. So the arcs would be pretty good but nothing truly amazing.

[Vanhal]

After reading that title, i expected angry, barely coherent rant about Russian bias, and instead i've got exactly what was supposed to be under it. Refreshing

 

[Historynerd]

A very interesting factor; you have my thanks.

 

It's neither a RN nor a VMF naval shell, so I won't ask you to predict a Model 1934's APC shell drag cohefficient, but I am not too worried about it...

 Besides, I can't find a half decent pic of it... didn't we at least keep at least one of them in a museum or something? 

 

 

[fnord_disc]

The perspective makes it hard to judge, but it looks like the cap is about as long as the shell, and according to navweaps the shell was 167cm. Radius 19cm = about 9crh, maybe even 10. So 0.28ish drag.

 

With the high weight of 884kg and the 850 ms/ MV, that means extremely flat arcs, even flatter than Bismarck and Yamato.

 

This is confirmed by checking the impact angles on navweaps: 5-37.6° for 10000 yards to 35000 yards versus 5.8-40.3 for Bismarck.

 

So these guns would have the flattest and fastest arcs of any ship in the game except maybe Moskva (but even this is dubious and the Italian guns are probably flatter).

[Historynerd]

So these guns would have the flattest and fastest arcs of any ship in the game except maybe Moskva (but even this is dubious and the Italian guns are probably flatter).

 

 

 

Sorry, I just had to do this! 

 

'Sides, we all know these things will fire one round per ten minutes, so no big deal.

Thanks for the answer, buddy! 

 

[SparvieroVV]

A very interesting factor; you have my thanks.

 

It's neither a RN nor a VMF naval shell, so I won't ask you to predict a Model 1934's APC shell drag cohefficient, but I am not too worried about it...

 Besides, I can't find a half decent pic of it... didn't we at least keep at least one of them in a museum or something? 

 

 

 

 

About the 5:10 mark for a good view.

[fnord_disc]

Yeah, that looks like 9 crh.

[mr3awsome]

How about the 18" BL Mark I from HMS Furious. A 8crh HE shell should make her the biggest scumbag at tier 4.

 

http://www.navweaps.com/Weapons/WNBR_18-40_mk1.php

 

 

Warning, Large Shell. 

 

 

[SparvieroVV]

Anyone know what the Russian shells looked like for the modern 305mm? As I imagine the Novosrossiysk premium might be the last refit planned by the Russian navy. 

 

http://www.navweaps.com/Weapons/WNRussian_12-62_m1948.htm

[fnord_disc]

Those would have been the Stalingrad guns also used for SM-46 railway guns. They are insane lasers. Very streamlined and look to be using some kind of rocket assistance.

[mtm78]

Rocket assisted 'shell' = kinetic 'missile'?

 

Borderline if so, WG said no missiles

[SparvieroVV]

Rocket assisted 'shell' = kinetic 'missile'?

 

Borderline if so, WG said no missiles

 

Hopefully that is the case. Hasn't introducing atgm to that other game caused only grief?

[GhostRiderMax123]

 

Hopefully that is the case. Hasn't introducing atgm to that other game caused only grief?

 

Indeed it has ATGM's basically ruined WT for me.

[Eruantien_Aduialdraug]

Rocket assisted 'shell' = kinetic 'missile'?

 

Borderline if so, WG said no missiles

 

The difference between a rocket and missile is (generally) a missile has some kind of guidance/steering. The main issue is that is changes the trajectory a bit, because it's getting some propulsion the entire way there (or at least most of the way). And that means new code.

 

Missiles in WT don't really work because the game wasn't designed with them in mind, they work in  AW because they were always intended to be there.

[fnord_disc]

RAP means the shell has a little rocket motor in the back that gives the shell extra velocity and range. It's not guided and I doubt it would fall under WG's missile prohibition, so it could be legitimately included.

 

Still, Lesta might not want to include rocket-assisted projectiles because they don't follow the normal ballistics. A normal shell has a muzzle velocity that it starts losing immediately after leaving the barrel. A RAP keeps accelerating or conserves its velocity for a fair distance after firing, so Lesta would have to code a modified ballistic model for this particular shell to account for the rocket motor.

 

Since the game uses lookup tables anyway, it wouldn't be a prohibitive amount of work to include rocket-assisted projectiles, but it would surprise me if they were implemented.

 

The result in gameplay terms would be that the arc would be hilariously flat and even at very long range there would be little velocity bleed. Since the muzzle velocity of the Stalingrads is 950 m/s, it's probably resonable to assume an average shell velocity of 1000 m/s for the first 20 kilometers or so. Since shell flight is also accelerated, the Stalingrads could fire to 20km in about 7-8 seconds inside the game.

[mtm78]

RAP means the shell has a little rocket motor in the back that gives the shell extra velocity and range. It's not guided and I doubt it would fall under WG's missile prohibition, so it could be legitimately included.

 

Still, Lesta might not want to include rocket-assisted projectiles because they don't follow the normal ballistics. A normal shell has a muzzle velocity that it starts losing immediately after leaving the barrel. A RAP keeps accelerating or conserves its velocity for a fair distance after firing, so Lesta would have to code a modified ballistic model for this particular shell to account for the rocket motor.

 

Since the game uses lookup tables anyway, it wouldn't be a prohibitive amount of work to include rocket-assisted projectiles, but it would surprise me if they were implemented.

 

The result in gameplay terms would be that the arc would be hilariously flat and even at very long range there would be little velocity bleed. Since the muzzle velocity of the Stalingrads is 950 m/s, it's probably resonable to assume an average shell velocity of 1000 m/s for the first 20 kilometers or so. Since shell flight is also accelerated, the Stalingrads could fire to 20km in about 7-8 seconds inside the game.

 

That would actually be hilarious if implemented ( aka: don't give them many idea's they might stick you never know with the Motherland ). 

[fnord_disc]

 

That would actually be hilarious if implemented ( aka: don't give them many idea's they might stick you never know with the Motherland ). 

 

On the flip side, rocket-assisted projectiles tend to have relatively small bursting charges, though this is not necessarily the case. So despite being 30.5cm, they might only have alpha damage comparable to a 20.3cm or 22cm shell.

 

I think it's possible to include and balance the Stalingrad guns if you're really determined to have them in the game.

[BuccaneerBill]

Surely rocket assist will make em widely inaccurate, just for inland bombardment?

[fnord_disc]

Surely rocket assist will make em widely inaccurate, just for inland bombardment?

 

RAPs are widely known for their poor dispersion characteristics, but they're not poor enough to be limited to inland bombardment. RAP was used for anti-ship shells even before the advent of guided projectiles.

[mtm78]

 

On the flip side, rocket-assisted projectiles tend to have relatively small bursting charges, though this is not necessarily the case. So despite being 30.5cm, they might only have alpha damage comparable to a 20.3cm or 22cm shell.

 

I think it's possible to include and balance the Stalingrad guns if you're really determined to have them in the game.

 

Well if they lower alpha, they usually increase rof as they want dpm on the same tier to be somewhat comparable right? I don't see how you could balance low alpha damage high caliber shells without increasing rof which would not fit in the game ( explain the rof differences between Stalingrad with 305's and other ships with 305's to general public.. would also probably break a bit of immersion ). 

[piritskenyer]

 

Well if they lower alpha, they usually increase rof as they want dpm on the same tier to be somewhat comparable right? I don't see how you could balance low alpha damage high caliber shells without increasing rof which would not fit in the game ( explain the rof differences between Stalingrad with 305's and other ships with 305's to general public.. would also probably break a bit of immersion ). 

 

Stalingrad with 305 having higher RoF could be easily explained by technological advancement. I mean take the difference in RoF between a QE-class BB and Vanguard. QE could push out two rounds/minute max due to technical limitations, but I seem to recall that when Vaguard was completed, she achieved a rate of fire of 2.5-2.8 r/m/g (if I'm wrong I'll have Train correct me here), but as you can see, the difference is quite significant, and is due to the hoists and systems behind the gun being more effective.

[mtm78]

 

Stalingrad with 305 having higher RoF could be easily explained by technological advancement. I mean take the difference in RoF between a QE-class BB and Vanguard. QE could push out two rounds/minute max due to technical limitations, but I seem to recall that when Vaguard was completed, she achieved a rate of fire of 2.5-2.8 r/m/g (if I'm wrong I'll have Train correct me here), but as you can see, the difference is quite significant, and is due to the hoists and systems behind the gun being more effective.

 

True, but how much rof increase would be needed to offset the lower alpha? We can only guess, since we don't know what alpha WG would attach to the shells. 

[piritskenyer]

 

True, but how much rof increase would be needed to offset the lower alpha? We can only guess, since we don't know what alpha WG would attach to the shells. 

 

Well, alpha damage is an arbitrary number really. Even within the same calibre, numbers can vary widely.