damagelethality of depth charges

[el cid again]

ORIGINAL: spence

In WitP there are "hits" a la combat report which seemingly cause cumulative damage and there are "hits" in the animation which seemingly show explosions on or immediately adjacent to the submarine.  One of those is should inflict catastrophic damage on the submarine, perhaps not fatal but a 'mission kill' anyways.  I do not dispute that it generally took a lot of depth charges thrown into the water to get the one that "hits". 

WitP does not (to my knowledge) allow escort types to finish off of a submarine which has been damaged by depth charges with gunfire or ramming (or by the crew scuttling a severely damaged boat.  Thus for the purposes of the game those "finishes" must be included in the "hits" caused by depth charges or other ASW weapons.  Reading throught the UBoat Fates Section at Uboat.net I noticed there did not seem to be any differentiation between killed by a depth charge or killed by a hedgehog.  It reports that the first hedgehogs were deployed in 1943 so I think it is safe to say that any uboat reported sunk by surface ships before '43 were killed outright using depth charges or so severely damaged by depth charges that they surfaced and were finished off with gunfire, ramming, torpedoes, or scuttling (all of which for game purposes would have to be included in depth charge hits).  The "Fates" section also lists the personnel casualties involved in the loss of each boat.  There is a strong correlation between boats lost with relatively light personnel losses and ones that were finished off by something other than depth charges.  "Lost with all hands" goes hand in hand with "sunk by depth charges from HMS/HCMS/USS...."

Of the Uboats reported sunk by ships (264), 22 were torpedoed by Allied submarines (mostly British).  Of the boats reported scuttled a like number reported scuttled were in fact scuttled after depth charge attacks so damaged them that they were unable to either fight, run or hide.  So the total of uboats effectively sunk by surface ships stays about the same.  And well over a hundred of those Uboats were killed by surface ship depth charges (with the aforementioned game qualifications about scuttling, gunfire etc) before 1943.   

This is a mixed bag - but it also clearly is a serious attempt at analysis. So I will break it down:

1) Early in the war the German doctrine was to attack on the surface. This is the reason that the Naval Escort Service was created - you were not going to contest a raider or the Graf Spee with a single 5 inch gun - but you were dangerous to a submarine. It is probably not valid to assume that any losses before 1943 were caused by depth charges. U boats were, in that era, more submersable torpedo boats, and even submersable gunboats, than submarines. It is likely a significant number were damaged for taking such risks in range of guns of escorts and auxiliaries and merchants - not to mention planes in cooperation with them.

2) The absolute number of submarines lost to depth charges - whatever it is - and I will stipulate it should be over 100 in the Atlantic campaign alone - does not in itself imply a high lethality for any single depth charge. It remains probable that WITP overstates this lethality - likely by a gross amount. Submarine survivability in WITP is clearly less than history. This is for two causes: it is far to easy to detect them - because (like Donitz U boats) they are surface raiders - but in WITP they NEVER are submarines EVER for detection purposes; and probably DCs are way too lethal.

3) You make a somewhat valid point about no surface action after DC damage. However, on the other side, WITP has subs on the surface when it is suicide - slugging it out with guns when no skipper ever would consider it. I hope you don't see this in RHS - but I had to "trick" the code - and if I am lucky it worked in the sense that statistically this will happen a lot less. [What I did was limit ammo for guns. A Japanese submarine - a big one - carried 17 ROUNDS - not salvos. WITP uses a shot system - and I decided a "shot" in this case means 6 rounds - so an I boat gets 3 shots. Once it has used up these shots, it must engage with torpedoes - so it won't try to use the guns. Some subs get 4 or even 5 shots - if they were gun oriented - but most get 3. This is in line with other WITP code- which does not track every round - just shots of several rounds. How they got such huge values for subs is beyond my kin? But I suspect they wanted subs to be a neusence - not effective - as they explicitly wrote about mine warfare. They KNOW they modeled mines wrong - and do not want to model them right.]

[el cid again]

ORIGINAL: spence

Some figures from the Pacific: DATA FROM IJN SUB TROMs at COMBINED FLEET

IJN subs sunk by surface warship alone (subs forced to the surface by ASW weapon damage and finished off with guns, torpedoes or ramming by the same surface ships are included (since WitP does not model this sequence of events - the number of such incidents is roughly 15 or about 25% of the total with more of the incidents relating to depth charge damage than hedgehog damage):

PRINCIPLE ASW WEAPON

DEPTH CHARGE - 44 KILLS

HEDGEHOG - 19 KILLS

MOUSETRAP - 1 KILL

There were three additional surface ship kills but the TROM did not specify what sort of weapon delivered the fatal attack. In one case there was no mention of weapons used; in the other 2 both depth charges and hedgehogs were used.

All very interesting - and possibly a crude indicator of the cause of losses. One problem is the total is too high - particularly if you bear in mind airplanes got some and unknown causes got some. But OK - lets conclude that many of those lost were lost to depth charges. That needs to be compared to the number of DC dropped to get the lethality PER ROUND. Better still, the number of patterns - the lethality per pattern - and I would also like to know the size of the patterns that worked? IF we could get the data - you would not be impressed with the kill chance of a DC - even if the target is a real sub and not a whale. It was a crude weapon, for which you usually had to guess a depth setting, and directed by sensors that easily could contain errors greater than a miss distance. Add to that the sub might turn right or left, or reverse, or both, or spring ahead, or stay in place - none of which could be known when the charges were set. Tough problem. A proper ASW attack might last many hours - even a day or two. Underwater a sub cannot go very far - and it can't stay down there forever! Well - it can - and we are trying to make it do just that - but it does not want to stay down forever - so it will try to escape - sooner or later - if it is still alive. Our problem is, even if we kill it, we don't know we did, so we have to hang around in case it is only playing dead.

[el cid again]

ORIGINAL: ChezDaJez

Wonder how many Large Fish, Dolphins, Whales, Sharks and such were shot....

Well, as someone who once "bombed" a disappearing radar contact (determined to be a whale a short while later) with active sonobuoys, I would say probably quite a few!

Torpedo suppository anyone?

Chez

It is estimated than on the order of a hundred whales were killed in 1982 - by RN - in a campaign in which the enemy had one effective - one ineffective - one non-operational - and one ancient submarine (unable to submerge but still operating - as a surface transport!).

[DuckofTindalos]

Well, better safe than sorry...

[Speedysteve]

Ho on earth did they log the number of whales killed?!? Did someone seriously do this el cid?

[DuckofTindalos]

They probably didn't...

[spence]

Should anyone be interested the total number of attacks delivered with whichever ASW weapon is noted in the TROMs for the IJN subs.  Going through them was a wee bit tedious but my impression is that hedgehogs killed subs with fewer though in most cases multiple attacks.  I recall only a relative few where a single salvo/pattern of either hedgehogs or depth charges did the trick (2 for depth charges I believe).

What needs to be addressed is the "effect" of the ASW routines.  The Japanese Player is given the chance to change history by instituting convoys and forming ASW groups right from the start.  Thus Allied submarine losses are likely to be higher in any PBEM game or Allied AI game.  Thus really the only "measuring stick" would be the historical effectiveness of Allied ASW efforts in the game which are as follows re sub kills:

1941 - 1 (by Enterprise SBD a few days after PH), 1 also was lost in a collision with another sub, the sub that collided with the sunken sub was heavily damaged as well and returned to Kwajalein where it suffered more damage in the February 42 raid and was never operational after that.

1942 - 14 (does not include the accidental one mentioned above)

1943 - 26

1944 - 50

1945 - 28*

Accidental losses (6) ARE included in the totals above:  Other than the collision mentioned above, the Japanese seemed to have had a problem remembering to close the main induction valve when diving - the cause of the other five losses.  One of those instances was sort of the result of Allied action:  a sub in port at Attu or Kiska dove to avoid an air raid but sank because the valve was open.  Unknown causes (10) and losses to mines (2 for sure (?)) are also included though there may be some overlap between the former and the latter cause.

*The drop in losses for 1945 is probably mostly due to a relative paucity of targets for Allied ASW.  Kaitens destroyed in '44 and '45 are not included - all losses are I or RO boats.   

[rtrapasso]

i suspect some marine biologists/scientists estimated the numbers on before and after surveys of whale populations in the area, which are pretty carefully monitored worldwide.

[spence]

The German raider Pinguin took out practically the whole Norwegian whaling fleet in 1941 or early 42. That surely helped whale populations rebound.

I also suspect that studies of whale populations were pretty shoddy (oriented towards exploitation for sure) or non-existant before WWII. It was quite some time after WWII that any treaties or legislation bubbled to the forefront. I wouldn't be surprised if much of the data that precipitated the laws/treaties actually originated with military studies whose purpose was to avoid "wasting costly ammo" on marine mammals, fish, plankton and so forth.

[spence]

Just for comparision IJN sub kills by year...(don't bet the farm on the figures/causes for Dutch and British subs.  Accidental losses not included. 
 
1941 - 1 US (bombed in Cavite), 4 Dutch (2 to mines I think)
 
1942 - 3 US, 3 Dutch (scuttled in port)
 
1943 - 16 US
 
1944 - 14 US
 
1945 - 8 US, 3 UK (2 to mines I think)

[bradfordkay]

"Should anyone be interested the total number of attacks delivered with whichever ASW weapon is noted in the TROMs for the IJN subs."


And how did they get these reports from the sunken subs?

[spence]

    In rare cases the escorts picked up a survivor who identified his ship.  In most it was a post-war correlation of an ASW ships AAR (particularly the sighting of wooden or cork debris, oil and/or human remains with the "disappearance" (from the IJN perspective) of a sub operating in a certain area.  In some cases the identity of the sub sunk is noted as "probably the I-#/RO-#".  As an example of the situation in such cases though one might ask the question:
"What subs did the IJN lose in the Gilbert Islands in Nov '43?" 
a) I-#
b) I-##
c) I-### 
d) RO-#
e) RO-##
f) ALL OF THE ABOVE (the correct answer) 

[spence]

IJN Submarine I-12


--------------------------------------------------------------------------------

Date of Action: 13 November 1944
USCG Unit(s) Involved: USS Rockford, PF-48, a Coast Guard-manned frigate [in concert with US Navy's USS Ardent, AM-340.]
Sinking/Capture/Assist? Probable sinking, credit shared between Rockford and Ardent.
Location of event: 31'- 55" N x 139' - 45" W
Credit by US Navy? Yes, probable sinking (see below).
Enemy warship's Commanding Officer: ??
Enemy casualties: 114 officers and men
USCG casualties: None.
Misc:

Details/Updates:

The USS Ardent (AM-340) and the Coast Guard-manned frigate USS Rockford (PF-48) escorted a six-ship convoy from Honolulu to the United States' mainland in November 1944. As they approached the midway point of the voyage, the Ardent made a sonar contact ahead of the convoy. She began plotting the contact and made two hedgehog attacks with negative results. The Rockford then made a "well conducted attack" with a 13-charge hedgehog pattern. Fifteen seconds later the crew heard three distinct hedgehog detonations and four minutes later they heard numerous underwater explosions. Water and air bubbles were then observed "boiling" on the surface, along with diesel fuel and debris, including teak deck planks (one with Japanese builders' inscriptions), ground cork, pieces of a vegetable crate covered with labeling in Japanese, pieces of varnished mahogany with tongued and grooved material, and one piece of smoothly finished wood from instrument case, with loose screws around the edges, and inscribed with Japanese writing.

The subsequent analysis concurred that three hedgehog charges detonated against the submarine, causing its destruction. Both warships were given equal credit in the probable destruction of a Japanese submarine. The only Japanese submarine operating along the west coast of the United States at that time was the I-12, which had attacked and sank the SS John A. Johnson on 30 October.

Technically their claim remains unconfirmed as the sinking was not corroborated by Japanese documentation captured after the war. Japanese sources indicate that the submarine was active through December and is listed as having been lost in January, 1945 from unknown causes. Nevertheless, due to the clear sonar contact, the accuracy of the attack including three hedgehog explosions, and the debris recovered, it is most probable that the Rockford and the Ardent did, in fact, sink the I-12.

Click here for a history of the USS Rockford.


--------------------------------------------------------------------------------

Sources:

Memo, COMINCH, United States Fleet, Incident No. 7282, "Analysis of Anti-Submarine Action By USS Rockford (PF-48) and USS Ardent (AM-340)."

W. J. Holmes. Undersea Victory: The Influence of Submarine Operations on the War in the Pacific. Garden City, NY: Doubleday & Company, Inc., 1966, p. 413.


--------------------------------------------------------------------------------

[Historians' Office] [WWII Combat Victories]

[USCG Home Page]
Added: December 2001

30 October 1944:
North Pacific. Cdr Kudo attacks a convoy enroute from San Francisco to Honolulu. At 2110, the I-12 hits the 7,176-ton American "Liberty" ship JOHN A. JOHNSON with two torpedoes. The 1-12 attacks but misses another transport.

The JOHNSON is abandoned and breaks in half. The I-12 surfaces and shells both sections of the ship. They both sink at 29-36N, 141-43W. The I-12 rams a lifeboat then makes its way among the JOHNSON's lifeboats spraying the survivors with machine guns and pistols killing six men. That day, the remaining survivors are picked up by the USS ARGUS (PY-14) on patrol out of San Francisco.

20-31 December 1944:
The I-12 reports sinking a transport and a tanker in mid-Pacific.

15 January 1945:
Cdr Kudo sends a message that he has been spotted by the enemy N of the Marshalls. This is the last signal received from the I-12.

31 January 1945:
Presumed lost with all 114 hands in the mid-Pacific. The cause of the I-12's loss remains unknown.*

10 August 1945:
Removed from the Navy List.


________________________________________________________________________________________________
*Some sources credit the USCG cutter ROCKFORD (PF-48) and the minelayer USS ARDENT (AM-340) with sinking the I-12 in the Central Pacific on 13 November 1944, but Cdr Kudo's last message belies that claim.

Author's Note: Special thanks for help in preparing this TROM go to Dr. Higuchi Tatsuhiro of Japan.
– Bob Hackett

There are problems figuring out what really happened - especially with ASW. The above are first; the official US Coast Guard Historian's record of a combat victory in the Pacific War and second; the reconstructed TROM of the I-12 from Combined Fleet. Presumably, copies of the messages recieved from I-12 subsequent to its alledged sinking do exist. But the physical evidence collected by the ROCKFORD combined with the recorded 3 hedgehog detonations makes it seem very likely that somebody died that day in that location.

[Cmdrcain]

ORIGINAL: jwilkerson

ORIGINAL: Drex

Has anyone ever sunk a sub with one depth charge hit? It seems to me that if a DC "hit" a sub the explosion would damage the shell bad enough to cause massive flooding but in WitP it seems to take 2 or more "hits" or a series of a hit and near misses to sink the sub. So how close does the DC have to be for it to effective to sink? or is that possible in this game?

I just LOST a sub to 1 depth charge hit.

On the other hand, I taken 25 hits and survived.

Note that in the new 1.7.9.5 system, and "hit" is not necessarily a "hit" .. some "hits" (most?) are "rattles". The 25 were probably all "rattles" .. the one that sank with one hit .. was clearly a "real" hit. One "real hit" should be enough if it is the right hit ... though many misses ... should be quite normal.

In my current "test" game against the AI ... I'm in Feb 44 and I've lost 24 US subs (tracking pretty darn close to historical rate) ... 14 to air and 10 to surface ... and I am using them "very" aggresively ( i.e. historically ) they are camping all over the home islands and the SRA.

With 1.8x Do "rattles" do any type of damage at all?

I've noticed some are asterisked * ** ***
as if the sub was getting very close near misses.

Seems to me for realistic combat, very close near misses should give damage at least a point or so of system damage to sim the burst pipes etc and so
enough close near misses would accumulate enough Sys damage to have a sub return to port for repairs.

Subs did return to ports without getting hit direct but suffering damage from close rattling near misses that required repairs..

So do near misses like those with asterisks give damage?

Or are all near misses even those sating taking on water are just eye candy?

[el cid again]

ORIGINAL: bradfordkay

"Should anyone be interested the total number of attacks delivered with whichever ASW weapon is noted in the TROMs for the IJN subs."


And how did they get these reports from the sunken subs?

The author of War Benieth the Sea is explicit: we did not get reports from sunken IJN subs. He credits two by name with exceeding the time underwater record set by USN - and one German sub - but says it is "certain" other IJN subs also broke the record - but didn't survive the war so we could read their logs.

[el cid again]

ORIGINAL: Cmdrcain

ORIGINAL: jwilkerson

ORIGINAL: Drex

Has anyone ever sunk a sub with one depth charge hit? It seems to me that if a DC "hit" a sub the explosion would damage the shell bad enough to cause massive flooding but in WitP it seems to take 2 or more "hits" or a series of a hit and near misses to sink the sub. So how close does the DC have to be for it to effective to sink? or is that possible in this game?

I just LOST a sub to 1 depth charge hit.

On the other hand, I taken 25 hits and survived.

Note that in the new 1.7.9.5 system, and "hit" is not necessarily a "hit" .. some "hits" (most?) are "rattles". The 25 were probably all "rattles" .. the one that sank with one hit .. was clearly a "real" hit. One "real hit" should be enough if it is the right hit ... though many misses ... should be quite normal.

In my current "test" game against the AI ... I'm in Feb 44 and I've lost 24 US subs (tracking pretty darn close to historical rate) ... 14 to air and 10 to surface ... and I am using them "very" aggresively ( i.e. historically ) they are camping all over the home islands and the SRA.

With 1.8x Do "rattles" do any type of damage at all?

I've noticed some are asterisked * ** ***
as if the sub was getting very close near misses.

Seems to me for realistic combat, very close near misses should give damage at least a point or so of system damage to sim the burst pipes etc and so
enough close near misses would accumulate enough Sys damage to have a sub return to port for repairs.

Subs did return to ports without getting hit direct but suffering damage from close rattling near misses that required repairs..

So do near misses like those with asterisks give damage?

Or are all near misses even those sating taking on water are just eye candy?

It appears to me that near misses cause increase in ops points. They also are stated to cost fuel points. Both are realistic and better modeling than I expected.

[Cmdrcain]

ORIGINAL: el cid again

ORIGINAL: Cmdrcain

ORIGINAL: jwilkerson




I just LOST a sub to 1 depth charge hit.

On the other hand, I taken 25 hits and survived.

Note that in the new 1.7.9.5 system, and "hit" is not necessarily a "hit" .. some "hits" (most?) are "rattles". The 25 were probably all "rattles" .. the one that sank with one hit .. was clearly a "real" hit. One "real hit" should be enough if it is the right hit ... though many misses ... should be quite normal.

In my current "test" game against the AI ... I'm in Feb 44 and I've lost 24 US subs (tracking pretty darn close to historical rate) ... 14 to air and 10 to surface ... and I am using them "very" aggresively ( i.e. historically ) they are camping all over the home islands and the SRA.

With 1.8x Do "rattles" do any type of damage at all?

I've noticed some are asterisked * ** ***
as if the sub was getting very close near misses.

Seems to me for realistic combat, very close near misses should give damage at least a point or so of system damage to sim the burst pipes etc and so
enough close near misses would accumulate enough Sys damage to have a sub return to port for repairs.

Subs did return to ports without getting hit direct but suffering damage from close rattling near misses that required repairs..

So do near misses like those with asterisks give damage?

Or are all near misses even those sating taking on water are just eye candy?

It appears to me that near misses cause increase in ops points. They also are stated to cost fuel points. Both are realistic and better modeling than I expected.

Well not direct damage then, but if fuel and Ops (I take it time on station like 45/180 becoming 60/180
say ..just an example... and so reducing length could stay before a RTB(return to base) That is as good, means all my near misses on USA subs at choke points by my ASW fleets is affecting them [:D]