The BBC, Costa Concordia and the Titanic

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.

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.

"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 ..

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.

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