Air Independent Propulsion (AIP) Comparative Noise and Youtube

Australia's future submarines will operate against a much more formidable strategic opponent (China). China is developing and installing much better sensors to detect the sound of the loud (heavy truck like) submarine diesel engines that the future submarine needs to run about once every two days. China is filling out the strategic South China Sea with increasing numbers of anti-submarine sensors. This Sea may become a standard operating area for our subs.

When the diesels are being run is called low discretion. Ways to improve discretion include choosing nuclear propulsion, using better batteries and/or using Air Independent Propulsion (AIP).

Australia's future submarine debate appears to involve unquestioned assumptions of rejecting AIP in favour of a new fairly untested battery type, Lithium-ion Batteries (LIBs), that have never been used operationally.

Choosing Japan will involve choosing LIBs and rejecting AIP because Japan is specifically rejecting AIP.

Germany (TKMS) and France (DCNS) may adopt or retain AIP and use the old lead-acid battery type or, if encouraged, adopt LIBs.

To rejects AIP while adopting LIBs is a $Multi Billion dollar gamble for Australia.

This makes it all the more important to revisit (now and then) the relatively arcane subject of AIP - below .

AIP Section Loudness 

In recent Submarine Matters comment threads there has been increasing discussion about the comparative loudness or silence of AIP systems. This has come from comments of observers standing in submarines AIP sections on Youtubes or by viewers of the Youtubes.

There are several variables which could distort the sound for listeners within AIP sections including:

- their hearing adjusting up or down (were they last in quieter front of sub or in louder engine room)

- is the AIP being run near its max workload, low workload, or basically in neutral or turned off?

- how close are they to the AIP engine?

- is their hearing focussing more on the AIP because they've been asked to focus on it?

To someone listening to the AIP on Youtube variables can be:

-  the sound quality/distortion/age of the Youtube

-  how loud they've turned the Youtube up

-  are they relying on a mic within the AIP section?

-  do they already know through knowledge/reading whether the average loadness of an AIP is higher or lower than other AIP systems? At what submarine speeds (4 knots? 7 knots?).

1. Are there any good online links comparing AIPs (with tables, graphs and curves)?

2. What real significance does the sound of an AIP have to an observer within the submarine anyway?

3. Isn't the main attribute the ability of a strategic opponent's fixed or mobile passive sonar/SOSUS/microphones to hear the sound of AIP?

Comparing AIP Systems

David Schueler, a Seattle Base Member of United States Submarine Veterans Inc 

presented an interesting Youtube commentary on Air Independent Propulsion Submarines" on May 1, 2010. Most of the information seems up to date. As the US isn't building AIP for submarine an American perspective may be more neutral.

 (David Schueler's Youtube starts off quietly. Sound kicks in at 00:25 (25 seconds).

---

First 14 minutes maybe less interesting is about:

-  fairly well accepted (non-nuclear) definition of AIP. 

-  danger of 1940s onward for German, US, UK, Russian experiments with hydrogen peroxide AIP

-  US, Russia then UK steadily adopted nuclear "AIP" then US-UK full use of nuclear. 

-  up until about the 1980s no safe, practical AIP for submarine.

Youtube most interesting:

14:25 - detailing and implicitly comparing current AIP systems 

15:05 - Closed Cycle Diesel Engines no-one using – trialled many on years ago on a Type  205 but never adopted. Still offered by German Nordseewerke (?) for retrofitting?

17:00 - Closed Cycle Steam Turbine system engine active in French MESMA many efficiency limitations. High power delivery. Three Pakistani Agostas using.

18:55 - Stirling Engines. Simple mechanism, quiet. But large for limited power output, LOX heavy with usage effecting whole submarines buoyancy. Since 2010 Saab involved in development of more advanced Stirling.

[Existing use by Sweden and Singapore. For 2010 very advanced information on then new use on Soryu and on Chinese Type 041 Yuan. 

China may have reverse engineered, autonomously researched and parallel engineered, bought or illegally acquired dual use technology from Sweden. Or all of these methods.] 

23:00 - Fuel Cells (Polymer Electrolyte Membrane (PEM)) only exhaust product is water, low heat, stackable parallel arrangements depending on electrical need. Low power output (not good for high power use Combat Systems).

[Used on TKMS Type 212, Italian Todaro class, Dolphin 2, Type 214 (and soon 218). Maybe Lada using but insufficient information. Since 2010 increasing interest in developing more stable Direct Methanol Fuel Cell (DMFC). Also see. Likely future/current Chinese and Russian interest.]

26:45 - what AIP can do and not do. Good for slow gradual (no quick acceleration) movement. Not good for quick sprints. Pure hydrogen or pure oxygen can be dangerous.

Pete's Comments

The ease or difficulty a strategic opponent in a military setting can hear AIP counts more than reporter's perceptions in AIP sections. 

Variables for a strategic opponent may include ability to hear your AIP under different conditions of distance, direction, AIP sub hiding in holes and behind rocks (littorals), behind icebergs, depth/water pressure, water temperature, salinity differences(?):

Sound detection devices and networks available to strategic opponent: 

-  the sensitivity of passive sonar/SOSUS/microphones of (say):

   =  one listening submarine using bow and hull sonars and/or towed array sonar

   =  SeaWeb collection of many microphones on many platforms to triangulate your AIP. 

Basically it seems there is continuing interest in Stirling (with unknown Chinese adoption). Sweden and maybe China are steadily improving Stirling.

Main interest in Fuel Cell (including from French, Russian and Spanish(?)) especially Direct Methanol Fuel Cell (DMFC). US and Japanese civilian interest and development as well. Germany busy improving submarine uses.

Australia does not appear to be interested in AIP for the future submarine. This may prove dangerous for any 2+ week Australian missions in the South China Sea or further north than that.

BACKROUND ON AIP TECHNOLOGY

-  Air Independent Propulsion (AIP) Issues, April 23, 2015, and

-  Air independent propulsion (AIP) Technologies and Selection, August 5, 2014.

Pete