Along time ago, in a galaxy far far away I wrote a paper [1] on the relationship between ship tactical diameter size and speed. In that paper I used a hand waving argument based on geometric similarity and hydrodynamic forces scaling with the square of speed to conclude that the tactical diameter should be independent of speed and proportional to length.
Here I just want to observe that this result can be deduced from dimensional analysis. The variables of interest are D the tactical diameter (we could use turn rate but when converted back into tactical diameter we would get the same result), L the ship length (or the cube root of displacement, since we are considering a geometrically similar family of vessels these scale in the same way) and speed v. The only dimensionless quantity that can be formed from these is D/L (ignoring powers of this ratio which will give the same result in the end). Thus the only dimensionally correct relation between the variables is essentially of the form D/L=k a constant. Thus we get that the tactical diameter is independent of speed and proportional to length.
The more-or-less independence of speed is supported by the data presented in [1], though the length dependence is rather poorly supported. presumably because the ships considered are not geometrically similar.
References
1. Larham R. “On Turning Ships”, Summer 1983, Battlefleet (Journal of the Naval Wargames Soc.)
https://www.researchgate.net/publication/312472208_On_Turning_Ships
Tuesday 11 December 2012
Saturday 27 October 2012
The Ignorance of Crowds (on naval matters)
There is an interesting display of ignorance and knee jerk reactions in the comments section of Ed Brayton's blog post on Romney's comments on the relative (absolute?) strength of the USN today and in 1916 on FreeThoughtBlogs.
Some absurdities:
Criticising a methodology (not Romney's a different assessment that scores in relative terms the USN today as more powerful than the RN at the height of its power, which has the feel of possibly being a correct conclusion, though always worth another look) without reading (or reading but not understanding) the references. (As usual the references can be argued with, but that is a different discussion, and one between friends). My advice, if someone makes an assertion based on a reference that is easily accessible, read the reference before ridiculing the claim. Failure to do so just makes you look stupid.
Jingoism.
Failure in large measure to understand that naval power is not only generated by ships and their weapons, but also by land based systems (and when some cognisance is taken of this failing to realise it cuts both ways).
..and many more but I am getting tired of typing now, but not as tired as I am of the idiocy/stupidity of American election campaigns.
Some absurdities:
Criticising a methodology (not Romney's a different assessment that scores in relative terms the USN today as more powerful than the RN at the height of its power, which has the feel of possibly being a correct conclusion, though always worth another look) without reading (or reading but not understanding) the references. (As usual the references can be argued with, but that is a different discussion, and one between friends). My advice, if someone makes an assertion based on a reference that is easily accessible, read the reference before ridiculing the claim. Failure to do so just makes you look stupid.
Jingoism.
Failure in large measure to understand that naval power is not only generated by ships and their weapons, but also by land based systems (and when some cognisance is taken of this failing to realise it cuts both ways).
..and many more but I am getting tired of typing now, but not as tired as I am of the idiocy/stupidity of American election campaigns.
Sunday 15 January 2012
More on the Japanese Midway Games
Never being one to leave things alone I want to say more about the last two sentences from the quote from [1] in the last post.
We can answer this at least partially by assuming that The Japanese believed that a deck load strike from a fleet carrier could mission kill or sink two carriers. This is what Wayne Hughes, page 100 [2], tells us was the belief of US carrier forces at the time. This is consistent with the hit rate achieved in the Indian Ocean raid by the Nagumo force, and probably consistent with initial inflated reports of the results of the 5th Carrier Division attacks at the Coral Sea.
The Japanese estimated that the Americans had two fleet carriers available to defend Midway, thus if the Japanese credited the Americans with the same level of performance they credited themselves with, a first strike from the Americans would neutralist four carriers. If this occurred before the Nagumo force launched a counter strike, in the initial games this would have left the Japanese with two operational carriers, sufficient to eliminate the US carrier force since the Nagumo force in those games had the full six fleet carriers. If the Nagumo force had only four carriers, as in the second set of games and on the day, then it would have been mission killed (and with subsequent American strikes probably all the Japanese carriers would have been sunk).
Now it is likely that the Japanese did not credit the Americans with comparable capability as they thought they themselves had. So now assume that the Japanese credited the Americans with the ability to mission kill or sink a single carrier with a deck load strike. Then the two American carriers, with a first strike before the Japanese had the chance to launch, would have neutralised two of the Nagumo force's carriers, leaving sufficient forces to eliminate the American carriers with a counter strike. Note, according to Hughes [2] this is the level of effectiveness displayed (more-or-less) by both carrier forces in the battles of 1942. While in the main games of the second set (24/25th May) when the American sortied the two forces exchanged strikes the level of Japanese casualties incurred are consistent with this assessment.
It seems that the Japanese were well aware that if the Americans got lucky the game would be up, and orders were issued to minimise the chance of such luck (pages 67-8 of [3]). On the day the game was up because the Americans did get lucky, and they had three rather than two carriers available.
With an average amount of luck on both sides, on the day we might expect an initial exchange of strikes with the result of three US carriers mission killed or sunk, and the same number of Japanese carriers mission killed or sunk. Then the Japanese would have been able to follow up and probably sink any US carriers still afloat from their remaining operational carrier. Since after the first strikes there are no remaining US carriers the Japanese have the chance to save any of their carriers that were not sunk.
It should be pointed out that even a loss of two carriers by the Nagumo force as a price for the elimination of the American carriers might have been too high a price for the Japanese. The Midway campaign was just a part of the Japanese plan for the second stage of the Pacific war, and the loss of two carriers might have been sufficient to compromise the viability of the subsequent operations in the South Pacific and against Johnston and the Hawaiian islands.
References
1. Caffrey M., History of Wargames:Toward a History Based Doctrine for Wargaming , Jan 2000, http://www.strategypage.com/articles/default.asp?target=WARGHIS2.htm&reader=long
2. Hughes W. P., Fleet Tactics and Coastal Combat, Naval Institute Press, 2000
3. Parshall, J.B., Tully A.P, Shattered Sword, Potomac Books 2005
Still, Admiral Ukagi failed to address the issue the loss of his carriers in the wargame should have brought up - what if the American's get in the first hit? Would we have enough strength to win anyway?
We can answer this at least partially by assuming that The Japanese believed that a deck load strike from a fleet carrier could mission kill or sink two carriers. This is what Wayne Hughes, page 100 [2], tells us was the belief of US carrier forces at the time. This is consistent with the hit rate achieved in the Indian Ocean raid by the Nagumo force, and probably consistent with initial inflated reports of the results of the 5th Carrier Division attacks at the Coral Sea.
The Japanese estimated that the Americans had two fleet carriers available to defend Midway, thus if the Japanese credited the Americans with the same level of performance they credited themselves with, a first strike from the Americans would neutralist four carriers. If this occurred before the Nagumo force launched a counter strike, in the initial games this would have left the Japanese with two operational carriers, sufficient to eliminate the US carrier force since the Nagumo force in those games had the full six fleet carriers. If the Nagumo force had only four carriers, as in the second set of games and on the day, then it would have been mission killed (and with subsequent American strikes probably all the Japanese carriers would have been sunk).
Now it is likely that the Japanese did not credit the Americans with comparable capability as they thought they themselves had. So now assume that the Japanese credited the Americans with the ability to mission kill or sink a single carrier with a deck load strike. Then the two American carriers, with a first strike before the Japanese had the chance to launch, would have neutralised two of the Nagumo force's carriers, leaving sufficient forces to eliminate the American carriers with a counter strike. Note, according to Hughes [2] this is the level of effectiveness displayed (more-or-less) by both carrier forces in the battles of 1942. While in the main games of the second set (24/25th May) when the American sortied the two forces exchanged strikes the level of Japanese casualties incurred are consistent with this assessment.
It seems that the Japanese were well aware that if the Americans got lucky the game would be up, and orders were issued to minimise the chance of such luck (pages 67-8 of [3]). On the day the game was up because the Americans did get lucky, and they had three rather than two carriers available.
With an average amount of luck on both sides, on the day we might expect an initial exchange of strikes with the result of three US carriers mission killed or sunk, and the same number of Japanese carriers mission killed or sunk. Then the Japanese would have been able to follow up and probably sink any US carriers still afloat from their remaining operational carrier. Since after the first strikes there are no remaining US carriers the Japanese have the chance to save any of their carriers that were not sunk.
It should be pointed out that even a loss of two carriers by the Nagumo force as a price for the elimination of the American carriers might have been too high a price for the Japanese. The Midway campaign was just a part of the Japanese plan for the second stage of the Pacific war, and the loss of two carriers might have been sufficient to compromise the viability of the subsequent operations in the South Pacific and against Johnston and the Hawaiian islands.
References
1. Caffrey M., History of Wargames:Toward a History Based Doctrine for Wargaming , Jan 2000, http://www.strategypage.com/articles/default.asp?target=WARGHIS2.htm&reader=long
2. Hughes W. P., Fleet Tactics and Coastal Combat, Naval Institute Press, 2000
3. Parshall, J.B., Tully A.P, Shattered Sword, Potomac Books 2005
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