How fast do Depth Charges sink

[fiendlittlewing]

I sometimes time the interval between splash and boom and compare the values between attacks. This tells me the DDs are setting them shallow or deep. But I was wondering, is there any formula to estimate the depth?

[Admiral8Q]

Great question! I usually do it by ear, but a second by second count-down would help.

[Admiral8Q]

I'd guess about 10 feet per second, or 3 meters per second.

[TorpX]

10 ft./sec. was what I used to use for mental calculations for SHCE, but I don't know what it is in SH4.

I believe it's in one of the game files, and can be changed.

[Admiral8Q]

10 ft./sec. was what I used to use for mental calculations for SHCE, but I don't know what it is in SH4.

I believe it's in one of the game files, and can be changed.


It could be double that, or even triple. Those cans were heavy. I'm thinking from actual experience. In water things tend to move in slow motion.

Maybe 30 feet (10 meters) per second?

[TorpX]

30 ft./sec. seems too fast to me. That would mean about 6 sec. to reach 200 ft. It would be very hard to dodge charges at that rate.

I know different types had different fall rates. The familiar cylindrical type was suited to the racks, but wasn't stable in the water and did not have an optimum drop rate. The British had a large bomb-shaped type that was designed to reach depth quickly.

The weight of the charges isn't really the critical factor, but rather the density and shape. TNT, or TORPEX isn't all that dense, and the steel casings are thin, so they will not drop as fast as a hunk of steel, or rock would.



Edit:

Here is a little info from Wiki on a few types:


The Royal Navy Type D depth charge was designated the Mark VII by 1939.[9] (http://en.wikipedia.org/wiki/Depth_charge#cite_note-campbell-9) Initial sinking speed was 7 ft/s (2.1 m/s) with a terminal velocity of 9.9 ft/s (3.0 m/s) at a depth of 250 ft (76 m) if rolled off the stern, or upon water contact from a depth charge thrower.[9] (http://en.wikipedia.org/wiki/Depth_charge#cite_note-campbell-9) Cast iron weights of 150 lb (68 kg) were attached to the Mark VII at the end of 1940 to increase sinking velocity to 16.8 ft/s (5.1 m/s).[9] (http://en.wikipedia.org/wiki/Depth_charge#cite_note-campbell-9) New hydrostatic pistols increased the maximum detonation depth to 900 ft (270 m).[9] (http://en.wikipedia.org/wiki/Depth_charge#cite_note-campbell-9) The Mark VII's 290 lb (130 kg) Amatol charge was estimated capable of splitting a 7⁄8 in (22 mm) submarine pressure hull at a distance of 20 ft (6.1 m), and forcing the submarine to surface at twice that.[9] (http://en.wikipedia.org/wiki/Depth_charge#cite_note-campbell-9) Change of explosive to Torpex (http://en.wikipedia.org/wiki/Torpex) (or Minol) at the end of 1942 was estimated to increase those distances to 26 and 52 ft (7.9 and 15.8 m).[9] (http://en.wikipedia.org/wiki/Depth_charge#cite_note-campbell-9)
The British Mark X depth charge weighed 3,000 pounds (1,400 kg) and was launched from 21-inch (53 cm) torpedo tubes (http://en.wikipedia.org/wiki/Torpedo_tube) of older destroyers to achieve a sinking velocity of 21 ft/s (6.4 m/s).[9] (http://en.wikipedia.org/wiki/Depth_charge#cite_note-campbell-9) The launching ship needed to clear the area at 11 knots to avoid damage, and the charge was seldom used.[9] (http://en.wikipedia.org/wiki/Depth_charge#cite_note-campbell-9) Only 32 were actually fired, and it was known to be troublesome.[10] (http://en.wikipedia.org/wiki/Depth_charge#cite_note-10)
The teardrop-shaped United States Mark 9 depth charge entered service in the spring of 1943.[11] (http://en.wikipedia.org/wiki/Depth_charge#cite_note-c163-11) The charge was 200 lb (91 kg) of Torpex with a sinking speed of 14.4 ft/s (4.4 m/s) and depth settings up to 600 ft (180 m).[11] (http://en.wikipedia.org/wiki/Depth_charge#cite_note-c163-11) Later versions increased depth to 1,000 ft (300 m) and sinking speed to 22.7 ft/s (6.9 m/s) with increased weight and improved streamlining.[11] (http://en.wikipedia.org/wiki/Depth_charge#cite_note-c163-11)
Although the explosions of the standard United States' 600 lb (270 kg) Mark 4 or Mark 7 depth charge used in World War II were nerve-wracking to the target, an undamaged U-boat’s pressure hull would not rupture unless the charge detonated closer than about 15 ft (4.6 m). Placing the weapon within this range was entirely a matter of chance and quite unlikely as the target maneuvered evasively during the attack. Most U-boats sunk by depth charges were destroyed by damage accumulated from a long barrage rather than by a single carefully aimed attack. Many survived hundreds of depth charges over a period of many hours; U-427 (http://en.wikipedia.org/wiki/Unterseeboot_427) survived 678 depth charges in April 1945, though many may have detonated a considerable distance from the target.

[fiendlittlewing]

I found this (http://www.subsowespac.org/tactics/def_maneuvering.shtml)

Other studies have determined the rate of depth charge descent as 200 ft takes 18 seconds, 300 ft takes 28 seconds and 400 ft takes 38 seconds.This would imply ~ 10.5-11' / sec

[Sailor Steve]

The main Japanese depth charge, the type 95, sank at 6 f/s. The later Type 2 sank at about 10 f/s.
http://www.navweaps.com/Weapons/WAMJAP_ASW.htm

The Standard British Mk VII was also about 10 f/s. Later mods increased the sink rate dramatically.
http://www.navweaps.com/Weapons/WAMBR_ASW.htm

The Americans were about the same.
http://www.navweaps.com/Weapons/WAMUS_ASW.htm

[TorpX]

A lot of interesting stuff there.

I never saw the details of the Squid or Mousetrap before.

Neat stuff! :)

[razark]

The main Japanese depth charge, the type 95, sank at 6 f/s. The later Type 2 sank at about 10 f/s.
http://www.navweaps.com/Weapons/WAMJAP_ASW.htm
According to the link, the Type 95 had depth settings for 98, 197, or 295 feet. How accurate would these settings have been, and was this information known at all during the war?

Has anyone modded this into the game?

[Sailor Steve]

According to the link, the Type 95 had depth settings for 98, 197, or 295 feet. How accurate would these settings have been, and was this information known at all during the war?
The 295-setting only came later in the war. Early on the US Navy knew about the 197-foot maximum setting, and used it to their advantage. The Japanese had no idea about what the Americans knew until the secret was inadvertantly revealed by US Congressman Andrew J. May in June 1943. The Japanese may have already been preparing the deeper setting before May's revelation, but after that they certainly knew the truth.
http://en.wikipedia.org/wiki/Andrew_J._May

Has anyone modded this into the game?
Of that I have no idea. I believe there was one, but I can't find it now.

[Armistead]

Be funny to set them in game to drop at 30ft per sec. Someone should do it with TMO and see how fun it is.

[razark]

Early on the US Navy knew about the 197-foot maximum setting, and used it to their advantage.
Do you know if they actually knew it was a maximum setting or did they think the Japanese were just setting them too shallow?

The Japanese had no idea about what the Americans knew until the secret was inadvertantly revealed by US Congressman Andrew J. May in June 1943.
I guess I removed that reference before I posted. I couldn't remember his name, though.

[Red Devil]

it also depends on saline density :know:

[Sailor Steve]

Do you know if they actually knew it was a maximum setting or did they think the Japanese were just setting them too shallow?
Sorry I missed this the first time. No, I don't know for certain, but I suspect the latter.

[Red Devil]

I do know that the Japanese, for quite some time, thought no sub could go below 200 feet.

[razark]

Sorry I missed this the first time.
No problem. It wasn't really directed to you, but to the room in general, anyway.

No, I don't know for certain, but I suspect the latter.
That does make sense. With the codebreaking efforts, perhaps someone knew and passed information down the line, suggesting strongly that below 200 feet was a good place to hide?

[Red Devil]

Gato Balao and Porpoise could do 300, and a bit. Tench 400 as I recall.

[Admiral Halsey]

Be funny to set them in game to drop at 30ft per sec. Someone should do it with TMO and see how fun it is.

Well for one TMO would become impossible at that point.

[merc4ulfate]

Well if they are set to drop 30 ft/S then I'll just stay shallow and let them blow up below me.

[Admiral Halsey]

Well if they are set to drop 30 ft/S then I'll just stay shallow and let them blow up below me.

That brings an interesting point up. What happens when a Depth Charge hits bottom in game? I tend to stay away from the shallows at all possible times(Thu why I normally do Pearl Based careers) so i've never see what happens.

[Sailor Steve]

Gato Balao and Porpoise could do 300, and a bit. Tench 400 as I recall.
The listed test depth and what they actually "could do" are not the same. American boats were expected to do 1-1/2 times the test depth, and sometimes did more. The Balao class was listed as having a test depth of 400 feet. USS Pampanito went below 600 feet on her first patrol.

[razark]

What happens when a Depth Charge hits bottom in game?
Based on what I saw last night, the campaign ends. :nope:

I got caught in the shallows, and it appears that the charge dropped through the sea floor, and then exploded.


The listed test depth and what they actually "could do" are not the same. American boats were expected to do 1-1/2 times the test depth, and sometimes did more.
I recall one story of a fleet boat in the '50s or '60s that lost power, and was later calculated to have gone below 1000 feet. The pressure hull was damaged enough that the boat was scrapped afterwards, but still not bad for a 25-20 year old boat rated for 400.

[TorpX]

Be funny to set them in game to drop at 30ft per sec. Someone should do it with TMO and see how fun it is.


Well for one TMO would become impossible at that point.

That's what I was thinking.



Apart from making life harder (and shorter) for our subs, there are other things to consider. If the charges sink too fast, the ships could end up blowing themselves up. They needed a certain amount of time to reach a safe distance.

Does anyone know if there is a minimum depth the game uses?

[Admiral Halsey]

I recall one story of a fleet boat in the '50s or '60s that lost power, and was later calculated to have gone below 1000 feet. The pressure hull was damaged enough that the boat was scrapped afterwards, but still not bad for a 25-20 year old boat rated for 400.

That would be the USS Chopper.

[razark]

That would be the USS Chopper.
That would be the one. I thought it started with a "C", but the only name that came to mind was the Copperfin.

[Red Devil]

Based on what I saw last night, the campaign ends. :nope:

I got caught in the shallows, and it appears that the charge dropped through the sea floor, and then exploded. Well, thats one way to sand blast the barnacles off the hull :doh:

[Red Devil]

In das boot, the uboat sat on the Med floor at around 700m, until the british sailed away.

[Sailor Steve]

In das boot, the uboat sat on the Med floor at around 700m, until the british sailed away.
No, it was 280m, which translates to 918 feet. 700m would be almost 3000 feet, not possible even in today's submarines.

In May 1941 U-109 was estimated to have survived reaching 300m, but just barely.

[Red Devil]

Sorry sailor, you are absolutely right. As they said it i presume it was in feet, but thought, being german, meters. But its been a while. *glug*

I do recall in Walkers book, Walker RN that the U202 'went deep sir' - but unaccountable depth. They recognised the fact that their charges would not go that deep. Instead Walker said, we wait, he must come up at 0002 hrs; and he did! Shelled and sunk. Walker was an expert in ASW even when it was unfashionable.

[merc4ulfate]

Depth charges in the game do three things. They explode at set depths, they explode if they touch the submarine and they explode upon hiting the bottom. Hedghogs will explode upon contact with anything larger than a shrimp.

I was hedghoged in shallow water once and the concussion was so great it lift my U-boat to the surface where the crafty submarine though it was surface time and did not return to its below water level after exposing us all to a hail of escort gun fire and promptly sinking 300 yards off shore in Portsmouth Harbor.


Modern submarines can go to 3000. No, I will not explain.