The following is mainly drawn from discussions between "S" and Pete on the Comments thread for Air Independent Propulsion (AIP) Issuesof April 23, 2015. A big thankyou to S for doing the estimates and providing other comments.
S advises that originally Stirling AIP was unpopular in the Japanese Navy, because of its low power (2.5knots) and complicated operation. For Japan AIP was only a temporary measure on the Soryu until Lithium-ion batteries (LIBs) became a more mature technology.
Looking at the Table at the bottom of this article you will see the first tranch/group of what may eventually be 12 Soryu submarines are known as “16SS” in red. 16 is the last two digits of the Soryu’s first of class’s “Building no. 8116” and “SS” means conventional submarine. The “Soryu” 16SS was commissioned in 2009. 16SS is diesel-electric with lead-acid batteries and Stirling AIP.
Published figures for 16SS range/speed (see sidebar of Wiki) would most likely be for semi-submerged snorkel/snorting mode. 16SS fully submerged (no snorkel use) figures are classified but S’s estimate for submerged speed and endurance is 6 knots for 3 days.
The aim of S's input is to give an estimate for the fully submerged range/speed of the second tranche of Soryu’s further down the Table, known as 28SSin red. The first of class 28SS may be commissioned in 2022. It will not have AIP but instead will have new Lithium-ion batteries (LIBs).
As a yardstick for comparision the Collinssubmarine, has lead-acid batteries totalling 400 tonnes. Its range/speed is480 nautical milesat 4 knots
S estimates 28SS submerged speed/range and duration may be 5,040 nautical miles at 7 knots for 30 days.
HOW SPEED/RANGE AND DURATION ARE WORKED OUT
This 28SS estimate is based on a Japanese Navy (Japan Maritime Self-Defense Force (JMSDF)) estimate 10 years ago that LIBS have 1.5 times to twice the capacity and power (or is that twice the capacity and 1.5 times the power?) of lead-acid batteries.
While 16SS has AIP space and can carry only 500 low capacity lead-acid batteries (cells?) the 28SS will probably have five times more battery space = 500 LIBs + 2,000 LIBs in the space that used to house the AIP = 2,500 LIBs.
On the assumption that the submerged speed for 16SS is 6 knots and knowing power is proportional to the cube of velocity. Submerged speed for 28SS = 6 knots x 1.15 (cubic root of 1.5) = 7 knots.
Assuming the submerged duration for 16SS is 3 days the submerged duration for 28SS = 3 days x 2 (capacity ratio of 28SS/16SS) x 5 (batteries ratio of 28SS/16SS) = 30 days
Submerged range for 28SS = 30 days x 7 knots x 24 hours = 5,040nm.
COMMENTS
One must remember that the above are estimates based on several assumptions. Still, it indicates much greater submerged performance for the second tranche of Soryus (28SS) that will come into service from 2022.
Australia would want a transit speed (Fremantle to around Darwin and alternatively Freemantle to Sydney) of perhaps 12 knots. After that an Australian sub may rely on much more fully submerged LIB use in order to stay out of view of Chinese satellites (keeping away from Chinese undersea sensor arrays is another problem).
Variables that are difficult to predict are whether the next tranche of Soryus (28SS) is larger or smaller than 16SS or whether Japan may build an Australia-only version.
LIBs may well surpass expectations ever considered for AIP. But they still will not compare to the performance of nuclear propulsion.
S used the following two web documents when doing the estimations:
- http://en.wikipedia.org/wiki/Drag_(physics), “Drag at high velocity”“Power” (in fluid dynamics 6 knot/h is high velocity).
- https://samueldavey.files.wordpress.com/2013/04/fluid-dynamics-submarine-report.pdfan Australian Maritime College paper of 30 pages. This is especially interesting. It draws on Australian Defence Science and Technology Organisation (DSTO) findings. It explains why submarines are shaped as they are and what modifications can make them move more efficiently.
For further information on LIB issues and other Soryu issues see many more articles on Submarine Matters, including:
Technical issues and the Soryu - Lithium-ion batteries no AIP of February 12, 2015 and
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THIS TABLE IS BASED (BASED ON WIKI)
| Building no. | Pennant no. | Name/Namesake | Laid down | Launched | Commissioned | Built By | |
|---|---|---|---|---|---|---|---|
| 16SS | 8116 | SS-501 | Sōryū (そうりゅう) / Blue Dragon | 31 March 2005 | 5 December 2007 | 30 March 2009 | Mitsubishi |
| 8117 | SS-502 | Unryū (うんりゅう) / Cloud Dragon | 31 March 2006 | 15 October 2008 | 25 March 2010 | Kawasaki | |
| 8118 | SS-503 | Hakuryū (はくりゅう) / White Dragon | 6 February 2007 | 16 October 2009 | 14 March 2011 | Mitsubishi | |
| 8119 | SS-504 | Kenryū (けんりゅう) / Sword Dragon, Stegosauria | 31 March 2008 | 15 November 2010 | 16 March 2012 | Kawasaki | |
| 8120 | SS-505 | Zuiryū (ずいりゅう) / Auspicious Dragon | 16 March 2009 | 20 October 2011 | 6 March 2013 | Mitsubishi | |
| 8121 | SS-506 | Kokuryū (こくりゅう) / Black Dragon | 21 January 2011 | 31 October 2013 | (March 2015) | Kawasaki | |
| 8122 | SS-507 | Jinryū (じんりゅう)/ Benevolent Dragon | 14 February 2012 | 8 October 2014 | (March 2016) | Mitsubishi | |
| 8123 | SS-508 | ? | 2013? | 2015? | 2017?) | Kawasaki | |
| 8124 | SS-509 | ? | 2014? | 2016? | 2018? | Mitsubishi? | |
| 8125 | SS-510 | ? | 2015? | 2017? | 2019? | Kawasaki |
28SS 8128 SS-513 ? 2018? 2020? 2022? Mitsubishi?
Again thankyou S for doing most of the work :)
Regards
Pete