Diesel Submarines

[Panther Bait]

It's also my understanding that current generation AIP systems are generally limited in regards to power output, at least relative to the diesel engines. The AIP can let them stay below the surface for a long time, but with a limitation on speed, i.e. tactical flexibility.

Mike

[dvresic]

MAD is a great search tool for aircraft. It will pickup deep subs if it overflies one, which is often the case if you setup a patrol box.

[Rory Noonan]

U mad bro?

[I1066]

ORIGINAL: StellarRat
They're not that fast and have limited endurance submerged.

Not sure what you mean by limited endurance, but for example, the Swedish Gotland class can stay submerged for weeks, if not months.

"Gothus sum, cave cornua"

[comsubpac]

ORIGINAL: I1066

ORIGINAL: StellarRat
They're not that fast and have limited endurance submerged.

Not sure what you mean by limited endurance, but for example, the Swedish Gotland class can stay submerged for weeks, if not months.

"Gothus sum, cave cornua"

a 212A crossed (U32) crossed the atlantic in 2013 and stayed submerged for 18 days.

Does AIP actually make sounds? It uses fuel cells and nothing is moving except the screw.

[I1066]

AIP is not a single technique.
The Swedish Gotland uses two Stirling engines to recharge the batteries. The Stirling engine is extremely quiet.
The German subs like 212A uses fuel cells, which has no moving parts at all.


SAAB: Stirling Engine
SAAB: The Gotland class
Wikipedia: Stirling Engine

[thewood1]

ORIGINAL: dvresic

MAD is a great search tool for aircraft. It will pickup deep subs if it overflies one, which is often the case if you setup a patrol box.

But I thought it was broken.

[mikmykWS]

Ease up Wood. It could he disagrees with himself.





https://www.youtube.com/watch?v=At-LrR-vqUk

[thewood1]

That is my point.

[reezing]

Correct me if I am wrong, but I believe the reason why modern diesel subs are highly successful in these military exercises is because they aren't pinging away with active sonar like a real combat environment. If they were, you'd end up with tons of dead marine animals and a huge PR disaster.

[thewood1]

I think that's pretty much true for all submarines...forever. Except in stupid submarine movies.

[reezing]

No I meant the force hunting the subs. I believe that in exercises both sides refrain from using active sonar in fear of harming the marine ecosystem, which would play out to the benefit of the subs.

Similar situation to news reports a while back where Chinese subs surfaced within x miles of US carrier groups. Most likely this wouldn't have happened in a real war scenario with active sonar.

[magi]

It is my understanding that the newer ASW sensors on the Romeo and p8's are very good and people in those communities are very pleased....

[Gunner98]

both sides refrain from using active sonar in fear of harming the marine ecosystem

I suspect that this might be a beneficial by-product of sensors becoming much better through the Cold War. Not many were environmentally concerned in the 60's when passive sonars became the norm. More important was not being found, once you were the hunter became the hunted.

I'm not an expert in any way but I believe that, like electronic emissions, active sonar can be detected well outside its effective detection range - so it might be critical in localizing a target but not in finding it in the first place.

B

[AlGrant]

Found this a couple of days ago .... seems appropriate to the current thread.

Thesis: PASSIVE AND ACTIVE SONAR PROSECUTION OF DIESEL SUBMARINES BY NUCLEAR SUBMARINES

http://www.dtic.mil/dtic/tr/fulltext/u2/a479975.pdf

"The simulation results show that initial detection times of a search follow an exponential trend as a function of SSN speed, diesel submarine speed, detection ranges,
ping interval and detection probability. As a result, as detection ranges continue to decrease due to increases in sound quieting technology, initial detection times during a
submarine search will increase exponentially.

This can render a passive sonar prosecution ineffective when combating a modern diesel submarine. Should an SSN use active sonar, initial detection times can be significantly reduced, especially if combined with an effective search path. The threat to the SSN of using active sonar can be mitigated by judicious consideration of ping interval and search speed with detection probability and active detection ranges"

Conclusion (extract - pg33)
"The simulations suggest that an active search can yield detection times at a fraction of passive searches, but real world exercises are needed to determine the breakpoint at which this occurs."

I think I'm going to lose a few hours this weekend running something close to this test scenario and see how it holds up in Command.
However worth remembering that the results in this thesis are from a simulation .... not real world.

One thing this document does cover is active sonar 'Ping Intervals' something I don't think Command simulates (unless in the background).
This ping interval ranges from a few mins to a couple of hours, where I think in Command if we turn of active sonar then we simply ping constantly.
Could be a useful addition to Command [;)]

Important to note that it also covers a straight forward SSN vs SS scenario with no airborne ASW assets or sonobouys looking for the SSN

[thewood1]

It should be noted that signal processing was still in its infancy in the 50's and 60's, when the core of modern sub detection SOPs were developed. Digital computing has significantly improved, especially in the 90's. That is why in earlier sonars, a number of pings were needed at set intervals. It gave you baselines for the signal processing to filter out noise. Now, with the huge data and processing capacity of small computers, I would imagine you can do a LOT more with a single ping.

I would suspect we on this board and in that paper aren't the only ones to realize this. That paper is almost nine years old. I bet its been tested in the real world already.

To me, all this is saying is that as subs become quieter, active sonar now has a longer detection range than passive. I know there is more to it than that through intermittent pings, that is what I take from it. And...best of all, it makes sense. Radars are heading the same way.

[ultradave]

Submarines aren't going to be using active sonar, whether nuclear or diesel. Diesel subs are just very quiet when running on electric alone, and as a previous commenter stated, a nuclear sub cannot shut down it's reactor, which, while quiet, still makes some noise that can be detected (theoretically).

[thewood1]

I thought the point was because diesels have become so quiet that the only way to get them before they get a noisier SSN is throw a ping out now and then.

[Panther Bait]

In exercises (and at least some of those peacetime intercepts), the ability to detect a diesel sub before it enters attack range can be complicated by the size of the exercise area and starting conditions. That may be appropriate for a sudden shift to a hot war (i.e. the diesel was already relatively close when hostilities start), but it's probably less so in a transit or infiltration scenario, where ASW assets can be brought to bear before a SAG gets into range of the diesel (assuming the diesel starts in the target area/choke point).

Mike