In its recent coverage of the righting of the Concordia the BBC observes that with a Gross Tonnage of 114,000 it is twice as heavy as the Titanic. I suppose they are actually comparing the Gross Tonnage of one with the Gross Registered Tonnage of the other. These are not the same thing, but neither is a measure of weight or more properly mass or displacement. Both are related (in different ways) to the volume of the ship, and different volumes of that: GRT to internal volume and GT to volume to the skin. We may also suspect that a modern cruise ship has a substantial lightweight superstructure contributing to its enclosed volume. So on any measure related to volume two ships one similar to modern cruise ship and one similar to a 1910 ocean liner but of the same displacement the modern design should come out "larger".
From its overall dimensions and a guestimate of its block coefficient we may conclude that the displacement at design draft of the Concordia is ~50-55,000 tonnes. The published displacement of the Titanic at design draft is 52,000 tons (here we are comparing metric tons with long tons but they are close enough for my purposes).
So we see that in terms of weight (displacement or mass) the two ships are very similar.
Saturday, 28 September 2013
Tuesday, 24 September 2013
McHugh's Fundamentals of War Gaming
In the current issue of the US Naval War College Review there is a review of McHugh's book "Fundamentals of War Gaming" on the history and theory of wargaming. This is a reprint of the third edition of 1966. The price quoted is $40, but is available for significantly less from the US Government book store. In addition a scan of the '66 edition is available from DTIC which while in places being tricky to read is free. This is particularly of interest to naval war games as it is effectively the summary of what NWC had learned about war gaming in the first half of the 20th century.
I am currently reading the DTIC download and may write more when I have finished, but right in chapter 1 we have two statements which may be taken as support for Admiral Ugaki's actions in the Combined Fleet's Midway planning games:
With reference to the conduct of manual games: "The results of interactions are evaluated by a control group in accordance with rules and functions which they are frequently permitted to override, or these decisions may be based solely on their professional judgement. New forces may be injected during the game or old ones reactivated, if, in the opinion of the director , such actions will contribute to the purpose for which the game is being played." (page 1-6)
Again on the function of the game director or controller: "He may stop play at any time, when, in his opinion, the game has served its purpose. In case of disputes and disagreements, he makes the final decision. During certain types of simulations the director has the authority to reverse or modify the assessments of umpires or the evaluations made by mechanical or electronic devices." (page 1-7)
Emphasis added by me.
I am currently reading the DTIC download and may write more when I have finished, but right in chapter 1 we have two statements which may be taken as support for Admiral Ugaki's actions in the Combined Fleet's Midway planning games:
With reference to the conduct of manual games: "The results of interactions are evaluated by a control group in accordance with rules and functions which they are frequently permitted to override, or these decisions may be based solely on their professional judgement. New forces may be injected during the game or old ones reactivated, if, in the opinion of the director , such actions will contribute to the purpose for which the game is being played." (page 1-6)
Again on the function of the game director or controller: "He may stop play at any time, when, in his opinion, the game has served its purpose. In case of disputes and disagreements, he makes the final decision. During certain types of simulations the director has the authority to reverse or modify the assessments of umpires or the evaluations made by mechanical or electronic devices." (page 1-7)
Emphasis added by me.
Monday, 8 April 2013
"Hunter Killer" by William T. Y'Blood
I am currently researching the use and performance of the Mk 24 "Mine" (FIDO) air-dropped acoustic homing Anti-Submarine Warfare (ASW) torpedo. I had found a plot (rather poor reproduction) of the main attack by LtCmdr Taylor's Avenger on the I-52 on-line and hoped there might be more such plots available on-line and so conducted a search. The main result of the search was the discovery of the subject of this post "Hunter Killer" by William T. Y'Blood, an account of US Navy escort carrier operations in the Atlantic (mainly ASW but also in support of operation Dragoon the invasion of Southern France).
This post is my comment on this source.
My first comment is that my hopes were disappointed, while there are plots of search patterns and depth bomb, rocket and FIDO attacks they do not really add much to the original plot that I had found. Like the original they lacked scales, but they can be reconstructed from the attack narratives, which should not have been necessary (and still suffer from the ambiguous use of the mile as a unit of distance on occasion, but probably means nautical mile, fortunately most distances are given in feet which are unambiguous). One thing that did emerge was that when used to prosecute contacts made on sono-buoys on non-recently submerged submarines the probability of a successful FIDO attack was very small. More success was achieved by calling in surface ships to prosecute the contact. The high success rate appears to have been reserved for dropping FIDO a few hundred feet ahead of and and a few tens (nearer 50?) feet to one side of the swirl of a submarine that had been seen submerging. This while not exactly what I was looking for in this book is the information that makes the trivial sum that I paid for this volume worth while.
As history this book suffer from the same problem that we see in many popular histories from American authors, the need to recount the detailed activities of the protagonists. It is a heroic style of history more akin to the Iliad than Thucydides. Also it is parochial, the CVEs took part in operations with other forces (I'm thinking operation Dragoon here), but we get no real overview of the operation or of the activities of the other forces involved, just a list of ship movements and narratives of aircraft sorties...
It is not until the very end of this volume that there is any indication that there was/is any controversy about the operations of the US CVEs in the Atlantic, were it is finally revealed that there was disagreement between the UK and the US on the offensive use of Hunter Killer Groups and the tactical exploitation of information derived from Ultra (reading of the U-Boat cyphers).
I would not be surprised if the total absence of any reference to OR/OA also has some significance but what it is either escapes me or will require further research to substantiate my suspicions.
.. to be extended/amended on rereading ..
This post is my comment on this source.
My first comment is that my hopes were disappointed, while there are plots of search patterns and depth bomb, rocket and FIDO attacks they do not really add much to the original plot that I had found. Like the original they lacked scales, but they can be reconstructed from the attack narratives, which should not have been necessary (and still suffer from the ambiguous use of the mile as a unit of distance on occasion, but probably means nautical mile, fortunately most distances are given in feet which are unambiguous). One thing that did emerge was that when used to prosecute contacts made on sono-buoys on non-recently submerged submarines the probability of a successful FIDO attack was very small. More success was achieved by calling in surface ships to prosecute the contact. The high success rate appears to have been reserved for dropping FIDO a few hundred feet ahead of and and a few tens (nearer 50?) feet to one side of the swirl of a submarine that had been seen submerging. This while not exactly what I was looking for in this book is the information that makes the trivial sum that I paid for this volume worth while.
As history this book suffer from the same problem that we see in many popular histories from American authors, the need to recount the detailed activities of the protagonists. It is a heroic style of history more akin to the Iliad than Thucydides. Also it is parochial, the CVEs took part in operations with other forces (I'm thinking operation Dragoon here), but we get no real overview of the operation or of the activities of the other forces involved, just a list of ship movements and narratives of aircraft sorties...
It is not until the very end of this volume that there is any indication that there was/is any controversy about the operations of the US CVEs in the Atlantic, were it is finally revealed that there was disagreement between the UK and the US on the offensive use of Hunter Killer Groups and the tactical exploitation of information derived from Ultra (reading of the U-Boat cyphers).
I would not be surprised if the total absence of any reference to OR/OA also has some significance but what it is either escapes me or will require further research to substantiate my suspicions.
.. to be extended/amended on rereading ..
Sunday, 27 January 2013
Staying Power Models 2
In a previous post I discussed my work on staying power models, and reported how for the two data sets I used the results were indecisive, mainly due to the small size of the data sets. The two data sets were for 1942 American and Japanese carriers subject to bomb attack and Royal Naval cruisers hit by torpedoes (which detonated).
I have now extended the cruiser torpedo hit data set from RN cruisers to now include USN, Japanese and Italian cruisers as well. This data set comprises about 90 records and now shows staying power more or less scaling as the ship displacement. Better yet I have analysed the posterior distribution of the scaling power (the power of displacement that staying power is proportional to) and show that with the previous cruiser data set the analysis was consistent with a wide range of scaling power (at least from 0.3 up to 0.9), while the posterior distribution with the extended data set peaks tightly between ~0.8 and 1.1.
The question now seems to be should I prepare what I now have for publication or continue extending the work.
I have now extended the cruiser torpedo hit data set from RN cruisers to now include USN, Japanese and Italian cruisers as well. This data set comprises about 90 records and now shows staying power more or less scaling as the ship displacement. Better yet I have analysed the posterior distribution of the scaling power (the power of displacement that staying power is proportional to) and show that with the previous cruiser data set the analysis was consistent with a wide range of scaling power (at least from 0.3 up to 0.9), while the posterior distribution with the extended data set peaks tightly between ~0.8 and 1.1.
The question now seems to be should I prepare what I now have for publication or continue extending the work.
 |
| Scatter Plot of the Cruiser Data and 25, 50 and 75% Probability of Sinking Contours |
 |
| Approximate Posterior Distribution of Staying Power RN Cruiser Data Only |
 |
| Approximate Posterior Distribution of Staying Power Full Cruiser Data Set |
Tuesday, 11 December 2012
On Turning Ships
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
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
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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