Shadow Zone Explained

FPSchazly · 05-09-19, 11:31 AM

Hey, all.

A while back, I made a video called "Dangerous Waters Concepts: Sound Speed Profile," explaining the three different sound speed profiles in Dangerous Waters: bottom limited, surface duct, and convergence zone. I mentioned the "Shadow Zone" in passing, but felt it needed further discussion. The "Shadow Zone" is the area beneath the layer where you cannot hear / be heard by things on the other side of the layer. However, it's actually not as simple as saying, "below the layer means you're in the shadow zone." I also found experimentally the distance where the shadow zone starts based on layer depth and what that means for you tactically. Check out the video here:

p7p8 · 05-09-19, 03:29 PM

Thank you for video (i watched it earlier)

I think you should remind something about TACTAS. Most ASW warships in DW uses TA sonar. This sonar can be deployed under layer. For example Perry's TA can reach*:

1030 ft (315 m) at 15 kts
1230 ft (375 m) at 10 kts
1480 ft (450 m) at 5 kts

It means: shallow layer can be penetrated easily by FFG TA
Of course greater speed (needed for tactical operations) sets TA antenna shallower. Sometimes surface ASW group cannot reach under layer and in this case shadow zone works like in your video

Would be nice to see sound propagation for antenna below layer.

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This is my sound propagation drawing for DW
It's little simplified because main reason was to use it as hint for understanding sound velocity gradient.

(Red lines for TA are more accurate for VDS with active regime of work than passive TACTAS - but it's still good hint for DW)

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Here is gif from database srceens for AI SQR-19 Towed Array (like on Perry class FFG)

Blue marked on left shows sensor used for Shallow, Medium or Deep position of TA

Green means maximum speed for this position of TA antenna

Blue on right shows depth in meters at current speed (green value)

[Yes - sensor for specific speed range is physically changed in DW for AI warships]

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

* in RA mod

05-09-19, 11:31 AM	#1
FPSchazly Good Hunting! Join Date: Apr 2014 Location: Maryland Posts: 771 Downloads: 15 Uploads: 1	Shadow Zone Explained Hey, all. A while back, I made a video called "Dangerous Waters Concepts: Sound Speed Profile," explaining the three different sound speed profiles in Dangerous Waters: bottom limited, surface duct, and convergence zone. I mentioned the "Shadow Zone" in passing, but felt it needed further discussion. The "Shadow Zone" is the area beneath the layer where you cannot hear / be heard by things on the other side of the layer. However, it's actually not as simple as saying, "below the layer means you're in the shadow zone." I also found experimentally the distance where the shadow zone starts based on layer depth and what that means for you tactically. Check out the video here: __________________ Your friendly neighborhood modern submarine YouTuber. My videos: Exclusive Look at Modern Naval Warfare! Dangerous Waters Liu Doctrine (LwAmi Learn to play Dangerous Waters

05-09-19, 03:29 PM	#2
p7p8 Seasoned Skipper Join Date: Nov 2006 Posts: 742 Downloads: 136 Uploads: 6	Thank you for video (i watched it earlier) I think you should remind something about TACTAS. Most ASW warships in DW uses TA sonar. This sonar can be deployed under layer. For example Perry's TA can reach: 1030 ft (315 m) at 15 kts 1230 ft (375 m) at 10 kts 1480 ft (450 m) at 5 kts It means: shallow layer can be penetrated easily by FFG TA Of course greater speed (needed for tactical operations) sets TA antenna shallower. Sometimes surface ASW group cannot reach under layer and in this case shadow zone works like in your video Would be nice to see sound propagation for antenna below layer. -------------------------------------------------------- This is my sound propagation drawing for DW It's little simplified because main reason was to use it as hint for understanding sound velocity gradient. (Red lines for TA are more accurate for VDS with active regime of work than passive TACTAS - but it's still good hint for DW) -------------------------------------------------------- Here is gif from database srceens for AI SQR-19 Towed Array (like on Perry class FFG) Blue marked on left shows sensor used for Shallow, Medium or Deep position of TA Green means maximum speed for this position of TA antenna Blue on right shows depth in meters at current speed (green value) [Yes - sensor for specific speed range is physically changed in DW for AI warships] -------------------------------------------------------- in RA mod __________________