WW II ASDIC/Sonar

[Sardaukar]

I didn't know that apparently Brits developed ASDIC able to determine depth.

That  IMHO increased depth charge efficiency a lot., being able to bracket sub more accurately.

https://weaponsandwarfare.com/2021/08/07/asdic/

 Britain also developed a specialized sonar (Type 147B) for accurate depth determination.

An advanced Type 147 ASDIC set was developed later in the war that tracked U-boats in three dimensions, giving readouts of bearing as well as range and depth. Note: All Western Allied navies adopted the U. S. Navy term for ASDIC in 1943: sonar.

[DougRichards]

Depth charges were indeed useful, but Hedgehog didn't need depth readings, as it was contact fused.

[Sardaukar]

7 minutes ago, DougRichards said:

Depth charges were indeed useful, but Hedgehog didn't need depth readings, as it was contact fused.

Yep, it was major improvement, in forms of Hedgehog/Mousetrap/Squid.

[shep854]

Nice article.  I had read about the 'dead zone' close to the attacking ship and thought that there was an issue with directing the sonar emissions directly downward.  It was stated that the sub's depth was estimated from the moment contact was lost and the ship's speed.

[BJE]

9 hours ago, Sardaukar said:

Yep, it was major improvement, in forms of Hedgehog/Mousetrap/Squid.

It was Squid who needed the type 147 to work. The detonation depth was set automatically in the mortar bombs just before launching to ensure that the pattern of six bombs exploded over and under the submarine.

[Rick]

Visual information.

https://www.youtube.com/watch?v=jyRLJPLTCGA

 

[Argus]

On 12/23/2021 at 10:56 PM, Rick said:

Visual information.

https://www.youtube.com/watch?v=jyRLJPLTCGA

 

The internet is a wonderful place when a bloke in Indiana can link to recording of an Australian broadcast of BBC doco from 20 years ago

Type 147 made a difference to all forms of attack, when it actually got into service having a depth took the last of the guesswork out for hedgehog (allowing lead to be calculated properly) and made huge difference to depth charge attacks, particularly setting the fuses. 

[Markus Becker]

It did massively. 

A Hedgehog fired two dozen projectiles with a 25% kill rate per salvo. 

The single Squid fired three mini depth charges and had a 50% kill rate, the double Squid six and was pretty much a guaranteed kill. 

[DougRichards]

Obviously the Squid was the superior weapon, two comments however: It first came into service in 1943, and it was too heavy to be installed in the Flower Class, which had to persist with the Hedgehog, and depth charges, until the end of the war.

 

[CaptLuke]

The US and the UK seem to have come down on different sides of the Hedgehog vs. Squid debate; the US developed and widely used the stabilized and power-trained Mark 15 Hedgehog post-World War II instead of the Squid (or a Squid equivalent).  I have no comment on what's right/wrong in this, but these are a couple quotes from Navweaps:

Quote

First USN Hedgehog projectors, adapted from the British 24-spigot mortar. More popular and more successful with the USN than with the Royal Navy, possibly because of better sonar detection practices.

Quote

In the USN, this weapon [the Squid] was fitted the frigate USS Asheville PF-1 in 1944 and to the destroyer escort USS Dealey DE-1006 in 1954. Both evaluations determined that Squid was not much, if any, better than Hedgehog and so it was not fitted to other USN warships.

 

[shep854]

The USN may have felt that direct contact gave better results.  Until a recent thread on TN, I thought that Squid was a direct contact munition, rather than a depth charge.

[Markus Becker]

1 hour ago, CaptLuke said:

The US and the UK seem to have come down on different sides of the Hedgehog vs. Squid debate; the US developed and widely used the stabilized and power-trained Mark 15 Hedgehog post-World War II instead of the Squid (or a Squid equivalent).  I have no comment on what's right/wrong in this, but these are a couple quotes from Navweaps:

 

A lot of "Hogs in inventory? 

[Argus]

Squid isn't a depth charge either, it was a time fused projectile. I can't recall what the issue with a hydro pistol was. But Squid fired at a fixed range, so time of flight and sink rates would have been constants making things pretty straight forward. 

[CaptLuke]

6 hours ago, Markus Becker said:

A lot of "Hogs in inventory? 

In addition to the wartime ships, the Forrest Sherman-class destroyers (roughly 1953-59) were built with Hedgehog.

The follow on Charles F. Adams-class destroyers (roughly 1958-64) switched over to ASROC.

[DougRichards]

3 hours ago, CaptLuke said:

In addition to the wartime ships, the Forrest Sherman-class destroyers (roughly 1953-59) were built with Hedgehog.

The follow on Charles F. Adams-class destroyers (roughly 1958-64) switched over to ASROC.

And about this time the DASH system was 'being put into service'.  (never worked of course).  Then the ASROC

The RN and RAN had moved to the Ikara, with twice the range of the ASROC but as for the USN, as it was 'not invented here' there was no chance of it being adopted or, more importantly, developed into something useful for the USN.. 

[DougRichards]

Would a Hedgehog have been useful for close naval land bombardment?  😁😁😁

After all, a Hedgehog projectile with 30 pounds of torpex would have have been too far short of the amount of HE in an 8" gun projectile?

THE USMC would have been delighted.

[Rick]

1 hour ago, DougRichards said:

Would a Hedgehog have been useful for close naval land bombardment?  😁😁😁

After all, a Hedgehog projectile with 30 pounds of torpex would have have been too far short of the amount of HE in an 8" gun projectile?

THE USMC would have been delighted.

Not enough range.

[DougRichards]

Did you really think that I was being serious?  😁😁😁

 

[Argus]

But but - it was used for bombardment!

[R011]

15 hours ago, DougRichards said:

And about this time the DASH system was 'being put into service'.  (never worked of course).  Then the ASROC

The RN and RAN had moved to the Ikara, with twice the range of the ASROC but as for the USN, as it was 'not invented here' there was no chance of it being adopted or, more importantly, developed into something useful for the USN.. 

DASH did work - when properly maintained and operated by trained specialist staff rather than semi-random sailors and officers.  At least that's how things went in the JMSDF compared to the USN.

[DougRichards]

16 minutes ago, R011 said:

DASH did work - when properly maintained and operated by trained specialist staff rather than semi-random sailors and officers.  At least that's how things went in the JMSDF compared to the USN.

And the Army used them for a while for target towing.

The problem with nearly every cutting edge piece of military equipment is that is has to be used by those trained specialists, but often all you have available are those 'semi-random' personnel.  It is likely that any specialists who could have used the DASH effectively would have gravitated to slots where their skills could be used in a way that kept them personally satisfied.  I mean, if you could operate DASH then you could probably fly a real helicopter and want to do that.

[R011]

Just now, DougRichards said:

And the Army used them for a while for target towing.

The problem with nearly every cutting edge piece of military equipment is that is has to be used by those trained specialists, but often all you have available are those 'semi-random' personnel.  It is likely that any specialists who could have used the DASH effectively would have gravitated to slots where their skills could be used in a way that kept them personally satisfied.  I mean, if you could operate DASH then you could probably fly a real helicopter and want to do that.

You don't fly helos with guys who just happen to be on board.  Some types of system just require dedicated ratings and officers.  Nor did flying a DASH and flying a Seasprite or Wasp take anywhere near the same expertise or training - or space aboard ship.

[sunday]

There were also Limbo and Weapon Alpha.

[DKTanker]

If squid uses a timer then it must rely on a quite accurate distance/depth estimate.  An estimate resolved from sonar returns.  I wonder how those measurements were affected by thermoclines and if there was a detrimental affect, could that be why the USN stayed with Hedgehog?

[Argus]

2 hours ago, DKTanker said:

If squid uses a timer then it must rely on a quite accurate distance/depth estimate.  An estimate resolved from sonar returns.  I wonder how those measurements were affected by thermoclines and if there was a detrimental affect, could that be why the USN stayed with Hedgehog?

This is why it needed depth data in addition to range and bearing, but I believe it was essentially just an adapted time fuse as per AA shells.

You could be on to something there,  the USN could well have seen an advantage in the 'simplicity' for whatever specific reason.