With Silent Service due to release in early March I thought it would be nice to review ASW warfare from the perspective of sub, surface and air platforms using the Basic Training tutorial scenarios. We'll start looking at the engagement from the ship perspective. The USS Stockdale is a DDG 103 Truxtun (Burke) Class Destroyer, circa 2015.
It has the following ASW Sensors ...
An AN/SQS-53C(V)1 Hull Active/Passive sonar operating in the LF band. It shows nominal range of 40nm and early 1990s tech. Also the TB-37/U MFTA passive towed array sonar operating in the VLF band. It shows a nominal range of 70nm and early 2010s tech. Notice that the hull sonar can provide search range, speed and heading info as well as the general Underwater Search capability? That means precise info can be delivered from using the hull sonar in active mode. The TASS can only provide Underwater Search, meaning that heading, speed, depth and range all have to be derived from TMA (target motion analysis) over time.
The Stockdale has 3 ASW weapons. Two triple Mk 32 324mm torpedo tubes holding Mk54 LHT Mod 0 torpedoes facing the port and starboard arcs. Eight RUM-139C VLA (Mk54) VL ASROC weapons in the Mk41 VLS. And a SH-60B maritime patrol helicopter carrying Mk54 LTH Mod 0 torps. Each weapon system uses the Mk54 LHT torpedo as it's terminal ASW tool, the difference between them being the range they can engage from. Typically the MK 32 torp tubes are a close defense weapon, the VLA providing a bit of standoff range (9nm) and the SH-60B providing the longest range for ASW operations for the ship (100+nm).
From this we can see the Mk54 torp itself has a 4nm anti-sub range, a kinematic range of 6nm, a Sub PoH of 85% and can engage targets down to -1510ft. Additionally the torp has Search Pattern, BOL and Re-Attack Capabilities. When dropped from a helo, deployment range is typically somewhere in the realm of 0.3nm from an altitude of 1000' or less. Finally, its' seeker is active & passive, has a 1nm range and operates in the HF band.
Let's take a look at the map display rings around the Stockdale.
The first one to note is the dark green inner circle. This is the longest range organic ASW weapon mounted, the RUM-139C VL ASROC, at 9nm. The next is the first Convergence Zone, the shaded annular zone starting at 25nm and stretching to 30nm, with a second CZ starting at 52nm and stretching to 57nm. Finally we have the outer light green ring, maxing out at 70nm. We can infer that the TASS has the ability to extend to two CZs in the current water environment based on this graphic. It is likely that both the TASS and hull-mounted sonar can hit the first CZ based on range values.
Now the Stockdale moves forward quickly into contested waters at 20kts, hunting for a sub.
Contact! A conventional sub at bearing 187 degrees, estimated 12nm range. The stated range estimate is just that, an estimate, and no speed, heading or depth info is available. Looking at the contact trace we can infer a few things. First, it's a direct path contact that begins at 7.3nm and stretches to the inner limit of the first CZ. Selecting the target, we can see it was only detected by the Stockdale's TASS. The TASS trails below the thermocline while the hull sonar is above (obviously). This may indicate that the contact is below the layer at this range.
Now what to do? First off I'll cut speed to Creep (5kts) to reduce self noise. In reality changing course could reduce the TASS' effectiveness until it straightens again, but I'm not sure how or if such degradation happens in Command. Given the range I'll turn a bit more perpendicular to the target to slow down closure. Checking Stockdale I see that the change in Passive Sonar signatures is just +0.5-1dB by changing the aspect. I figure it's worth it. At the same time I launch my ASW-configured SH-60B helo.
After the turn is completed the Seahawk is now up, contacts continue via the TASS (so no maneuver penalty), the range estimation has shortened to 7.5-12nm. Could be a potential VLA shot but I'll let the helo handle it. Moving the Seahawk in at 200' and Loiter speed (55kts) the bearing shifts a bit but the range estimate shrinks to a 9.8-11nm zone. Laying a couple of sonobuoys should firm up the contact, toot-sweet.
There it is! A North Korean Romeo below the thermocline making 2kts on a course of 310. It's just out of VLA range from the Stockdale. So it's up to the Seahawk to get the kill. Swinging around, the helo makes a low pass and drops a Mk54 at close range, then follows it up with an active sonobuoy at both deep and shallow depths to follow the sub as it evades.
Saw sub. Sunk same.
< Message edited by Primarchx -- 2/20/2018 10:24:46 PM >