Practical ranges

Guns, torpedoes, mines, bombs, missiles, ammunition, fire control, radars, and electronic warfare.
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tommy303
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Re: Practical ranges

Postby tommy303 » Mon Jan 21, 2013 7:16 pm

One of the main limiting factors of radar directed gunfire was the problem of identifying the target on the screen as friendly or hostile. Unless the firing ship has an IFF interrogator and all friendly ships in the area have responders with appropriate codes and are operational (like any other piece of equipment there can be problems which might prevent it from operating properly--battle damage, power failures, etc.), a target on the screen is not necessarily an enemy which should be taken under fire. Thus even with IFF present, a commander would always have a certain amount of doubt and might prefer to make a visual ID before ordering his ship to open fire.

This was a problem, I believe, for the Germans during the Barents Sea action. At Surigao Strait, West Virginia, California, and Tennessee were able to track the oncoming Japanese and obtain early fire solutions, but waited until the range was down to 22--23000 yards before opening fire. The other three of Oldendorf's battleships had less capable radars; Maryland was eventually able to find the target by spotting shell splashes from the other ships, Pennsylvania could not find a target at all, and Mississippi only fired one broadside in the whole action. Why West Virginia, California, and Tennesse waited until the range closed to open fire, even though having obtained solutions earlier, might have been a tactical necessity rather than a limitation imposed by their radars. Oldendorf's battle line had, I believe, been largely assigned to fire support and had only limited amounts of APC on board, and waiting for the range to drop to below 23,000 yards would have assured an adequate hit percentage for the limited stocks of AP ammunition.

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Dave Saxton
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Re: Practical ranges

Postby Dave Saxton » Mon Jan 21, 2013 8:23 pm

tommy303 wrote:This (IFF) was a problem, I believe, for the Germans during the Barents Sea action..


This is correct. Kummetz re-called his destroyers prior to opening fire at 0936 to avoid mixing them up with the enemy and clobbering them with his own cruiser's fire. Kummetz made a point to enter into the KTB how difficult it was to determine friend from foe, and how frustrating the situation was. Stange recalled Z31 twice in the hour before 10:40 hours to avoid loosing track of it. At 10:40 hours Luetzow and the German destroyers accompaning it were perfectly positioned to destroy the convoy, whose escorts were pre-occupied with Hipper to the north per Kummetz's battle plan. Luetzow's radar located the ships of the convoy and gunnery officers begged for permission to open fire, but KzS Stange refused to open fire because he was unsure if the radar located targets were friend or foe. Had he thrown caution to the wind and opened fire, the battle would certainly have turned out different.

A similar IFF ambiguity was a factor at Surigao St. Gunnery officers begged for permission to open fire but that permission was denied over and over again as the CIC scambled to confirm that US destroyers were finally clear following their torpedo attacks. Conserving AP ammunition was also a reason for waiting to open fire according to the Action Reports.
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Re: Practical ranges

Postby Dave Saxton » Mon Jan 21, 2013 8:36 pm

alecsandros wrote:I thought Lutzow acquired the target (Obdurate), opened fire and continued to shoot at it using radar only.
But now that I think of it, it's nonsense, as the "target", from Lutzow's stand point, could easily have been a German destroyer. :D So optical confirmation was a must.

Luetzow did open fire on Obdurate using radar only. This was the second time it opened fire and there was no question about the location of other German warships by then. The first time it opened fire, it opened fire on a steamer belonging to the convoy. This was done first with an optical solution but quickly followed by full radar control.
Entering a night sea battle is an awesome business.The enveloping darkness, hiding the enemy's.. seems a living thing, malignant and oppressive.Swishing water at the bow and stern mark an inexorable advance toward an unknown destiny.

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Re: Practical ranges

Postby Dave Saxton » Tue Jan 22, 2013 2:49 pm

alecsandros wrote:Another word on this, allthough it doesn't concern radar plot of fall of shot, but it does concern firing accuracy: both Hipper and Lutzow fired remarkably accurate salvos at Barents Sea, despite the weather conditions (rough seas, poor visibility, etc). This shows that the fire control system used on German capital ships was very precise and capable of very fine tuning...

A little know fact about Barents Sea is the brief re-engagement which occured 30 minutes after Kummetz turned for home. Burnett was shadowing via radar and the Germans apparently thought there were too close. Suddenly without warning Luetzow straddled both British cruisers in turn, forcing Burnett to turn away to the north west. The interesting thing about this; is that this was well after twilight period and during a period of very poor visibility. The Luetzow's radar was able to discriminate between the two targets and accurately target each one in turn. The British also straddled the Luetzow with return fire.
Entering a night sea battle is an awesome business.The enveloping darkness, hiding the enemy's.. seems a living thing, malignant and oppressive.Swishing water at the bow and stern mark an inexorable advance toward an unknown destiny.

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Re: Practical ranges

Postby sineatimorar » Sun Jun 23, 2013 11:49 am

Accuracy wise, ranges above 27,000 meters was less than 5%. This accuracy issue related to practical mechanics of manufacturing of the cannons, shell, powder and the physical mounting of the canons in relationship to each other ( interference ). Highly accurate sights and radar would not have helped all that much unless you add more cannons to the equation.

When you look into art of range charts and predicted ranges and variations you realize quite quickly how unpredictable results can get.

Using modern external ballistic programmes, you actually end up with more questions than answers.

One such extra question I have is the long range shots with elevations between 30 to 55 degrees.

What I found was the historical charts show the expected decrease in striking velocity with increases in range then an increase occurs at elevations mentioned. My argument against this is as follows ( I included a chart example with variations shown )

Comparison range chart between officially published values [o p v ]and ballistic computer results.
range chart USA 40.6/50 mk 7 canon with 2,700 lbs. (1,224.5 kg) AP Mark 8 muzzle velocity of 2,500 fps

Range -- Angle of Fall /o p v --Striking Velocity /o p v -- Time of flight/o p v -- elevation/o p v

10,000 yards -- 5.23 / 5.7 -- 2012 / 2,074 fps -- 13.3/13.2 -- 4.66

15,000 yards -- 9.46 / 9.8 -- 1789 / 1,892 fps -- 21.2/np -- 7.82

20,000 yards -- 14.99/ 14.9 -- 1581 / 1,740 fps -- 30.2/29.6 -- 11.4 /17,650yds@10degs

25,000 yards-- 21.99 / 21.1 -- 1388 / 1,632 fps -- 40.3/np -- 15.72 / 23,900ys@15degs

30,000 yards--30.15/ 28.25 -- 1210 / 1,567 fps -- 51.8 /50.3 -- 20.6 / 29,000yds@20degs (most accurate of comparison)

35,000 yards -- 40.22/ 36.0 -- 1043 / 1,556 fps -- 65.8/np -- 26.46 / 33,300yds@25degs

40,000 yards -- 50.18 / 45.47 -- 962 / 1,607 fps -- 80.8/80.0 -- 32.66

42,345 yards --53.92 / 53.25 -- 931 / 1,686 fps -- 88.2/np -- 35.65 / 39,500yds@35degs

np= not published
Except for a noticeable strike velocity difference most values are within acceptable tolerances.

Now while the explanation as to why at certain barrel elevation above 30 degs will travel further down range than otherwise indicated in a vacuum(45 deg is max range in vacuum) is logically acceptable. The reason being the reduced air pressure at altitude reduces the drag experienced while at that altitude which reduces the rate of reduction in velocity for that time period only. The shell still has to experience the same amount of drag on decent at any given altitude. Even in a vacuum the shell would still experience the effects of gravity (hence the curved flight path) any increase in velocity would be limited by the terminal velocity particular of that shell which is the same for any given altitude and if the shell does increase its momentum [ something I do not believe possible; Conserve maybe, but not increase] there would be an increased in both parasitic, aerodynamic drag as the thicker atmosphere is encountered and that would counter any increases so I refuse to believe that there such an increase in final velocity. This is confirmed if the reader takes the time to plug some different height values into the free fall equations found online at .http://hyperphysics.phy-astr.gsu.edu/hb ... lq.html#c1 which confirms there is no increase in velocity due to any increase in height that would effect any vertical component of the shell's momentum. Flight time and range are the same or very close as is clearly shown.

Can anyone give me logical answer other than the Rout answer "That is what was believed to be the case at the time so it must be true!"

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Re: Practical ranges

Postby tommy303 » Sun Jun 23, 2013 7:17 pm

You may want to ask Bill Jurens about this since he is an expert in ballistics. Having made that suggestion, I would comment that the equations of which you speak are for a sphere, which in projectile terms is the least efficient in terms of drag and weight, and presupposes that the sphere starts at rest. A long range battleship-type projectile is still supersonic at the time it begins its descent and has a much better, lower drag shape than a sphere. At extreme range, it will begin its descent in thinner air where acceleration due to gravity is greater than the amount of drag being imposed on the shell.

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sineatimorar
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Re: Practical ranges

Postby sineatimorar » Fri Jul 12, 2013 4:22 am

All find and dandy if the gun fired spheres for the other ranges. Clearly it did not and effects of the shell shape would be similar across the ranges and is expressed by the overall increase in performance over that of a sphere. The basic premise of my example still holds. Suggest you look into the other thread I started in this forum about range charts.

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Re: Practical ranges

Postby Byron Angel » Fri Jul 12, 2013 11:49 am

sineatimorar wrote:All find and dandy if the gun fired spheres for the other ranges. Clearly it did not and effects of the shell shape would be similar across the ranges and is expressed by the overall increase in performance over that of a sphere. The basic premise of my example still holds. Suggest you look into the other thread I started in this forum about range charts.



..... Take Tommy's advice and speak with Bill Jurens if you really do want to sort this out.

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Re: Practical ranges

Postby sineatimorar » Fri Jul 12, 2013 1:46 pm

Ok I will see if he can explain it to me. I already emailed navweap.com and got a answer that talked around the issue but no details. I took a couple of hours to read us navy 1935 training manual that was suggested would answer my question( other stream on this forum) pg 105 plate iv shows ballistic chart for 16 inch weapon and there is no sign of this phenomenon in the chart or supporting text. So we will see.

Byron Angel
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Re: Practical ranges

Postby Byron Angel » Sat Jul 13, 2013 2:19 pm

sineatimorar wrote:Ok I will see if he can explain it to me. I already emailed navweap.com and got a answer that talked around the issue but no details. I took a couple of hours to read us navy 1935 training manual that was suggested would answer my question( other stream on this forum) pg 105 plate iv shows ballistic chart for 16 inch weapon and there is no sign of this phenomenon in the chart or supporting text. So we will see.



..... See my response on the other thread (problem with range charts) related to this point.

Byron

sineatimorar
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Re: Practical ranges

Postby sineatimorar » Sat Jul 13, 2013 5:13 pm

Thanks chaps. Bill did sort me out. Took the time and patients to go into great detail as to what's what.
Now I have a little job of understanding the method used and some interesting results will hopefully come from it..Well interesting to me anyway.


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