Submarine & Other Matters

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November 17, 2022

REVISED Japanese Sub LIB distributions, Other calculations

Anonymous has provided much improved revisions of article:

"Japanese Submarine LIB distributions & other calculations." of Nov 11, 2022

Below are very simplified diagrams of Japanese subs with the estimated number and distribution of Lithium-ion Battery (LIB) modules in yellow.

All this highlights the advantages of the Japanese all LIB Taigei-class subs over the 50 tonne lighter all LIB Soryu Mark (MK) IIs (namely JS Oryu and JS Toryu). The LIB distribution

Propulsion Motor	Diesel	Officer	Command	Command	Torpedo	Bow Sonar
		LIBs a	Crew/eating	Mechanical
		LIBs	LIBs	LIBs
		b	c	d

Figure 1. Schematic structure of Toryu/Oryu (Soryu MK IIs)

- 5 Bulkheads: Propulsion Motor/Diesel/LIBs(ab)/LIBs(c)/LIBs(d)/Torpedo Room

- Double hull: Propulsion Motor, Diesel, Torpedo Rms

- Single hull: Other Rooms except bow sonar

- Number LIBs = 640 = 80 (a) + 80 (b) + 240 (c) + 240 (d)- Higher center of gravity due to 80 LIBs in higher LIBs "a" section -

- Higher center of gravity due to 80 LIBs in higher LIBs "a" section

- LIBs in "a" section increases vertical stray magnetic problems.

- Stray fields can be more easily electro-magnetically detected by ASW enemies. Strays fields can also upset - delicate electronic equipment in the submarine.

- Regarding "Fuel/Water" (omitted from Figures 1. and 2.) once the Diesel Fuel is consumed the fuel tank is filled with seawater to maintain constant weight distribution (important for buoyancy and trim)

Propulsion	Diesel	Officer			Command			Torpedo	Sonar
		Crew/eating			Mechanical
		LIBs	LIBs	LIBs	LIBs	LIBs	LIBs
		A	B	C	D	E	F

Figure 2. Schematic structure of Taigeis - much improved from Toryu/Oryu (Soryu MK IIs)

- Greater number of LIBs for longer full submergence / more discrete = 720 LIB modules = 120 x 6 in each of (A, B, C, D, E & F) sections
- Less vertical stray magnetic fields
- Lower center of gravity, better for calculating and maintaining buoyancy and trim.
- Less potential leakage of dangerous gases caused by fire from battery sections to upper sections.

- Easier to deploy downward traveling fire suppressant gases as all batteries are contained in bottom deck of a Taigei.

- Fewer Bulkheads: maybe as low as 4 ie. Propulsion Motor/Diesel / LIBs (ABC) /LIBs (DEF) / Torpedo rooms.

Based on official report of Japanese MoD information, a decrease in numbers of bulkheads was estimated to be four in Taigei-class submarines [5-7], while numbers of bulkheads in Soryu MK Is and IIs are five.

[5] Study on structural type of submarine by MoD (FY2012)

Implementation plan (completed): FY2013-2015 (budget implementation 554 million yen) Prototyping (by MHI) , FY2014-2015 (budget implementation 504 million yen) Laboratory testing (by MHI)

Needs (excerpt): Elongation of the compartment based on the new structural type of submarine is needed to contribute to the rational installation of the equipment inside of submarine..

[6] If length of submarine does not change, “elongation of compartment” may suggest decrease in numbers of bulkhead.

[7] Taigei was laid down in 2018, and its length is as same as Soryu.

Stern Bow

+-	+-	+-	+-	+-	+-	+-	+-	+-	+-
-+	-+	-+	-+	-+	-+	-+	-+	-+	-+

Figure 3. Top views of series connection (from bow to stern) of 20LIB modules in Oryu/Toryu/Taigeis.

Size of 20 LIB-modules 444cm[D] x 83.2cm[W] x 166.7cm[H] or 431m[D] x 88.8cm[W] x 166.7cm[H]

Stern Bow

20LIB-modules

Fig 4a. Top view of 20 LIB-modules in Oryu/Toryu (a and b in Figure 1)

Stern------------ Bow

20LIB-modules

Fig 4b. Top view of 20 LIB-modules in Ouryu/Toryu/Taigei (c/d in Figure 1, A-F in Figure 2)

Soryu MK. I has two lead acid batteries [LAB: 444mm(D), 432mm(W), 1665m(H), 880kg, 2V] sections [c and d in Figure 1]. In each battery section, 240 LAB modules are connected in series generating 480V (=2V x 240).

Two battery sections are connected in parallel (480V).

In Oryu/Toryu/Taigeis, 20 LIB-modules [each, 444mm(D),431mm(W),1667mm(H),770(kg), 36V] (Figures 3, 4) are connected from bow to stern in series generating 720V (=36V x 20), where 20 LIB-modules seem to be folded in two (10 LIB modules x 2) to cancel stray magnetic field from bow to stern. All 20 LIB-modules are connected in parallel (720V).

Battery arrangements of LABs (c/d in Fig1, Soryu MK. I) and LIBs (c/d in Fig 1. Soryu MK. II, A-F in Fig 2. Taigei) should be the same because they install batteries with the same dimensions and weight. Their arrangement is according to multiples of 3, 2 and 5. But, 80 LIBs are arranged in c/d of Oryu/Toryu, and their arrangement is according to multiples of 2 and 5. Then, series connection of LIB module is based on multiples of 2 and 5 and minimize stray magnetic field. Possible arrangements are 10 LIBs (360V) and 20 LIBs (720), higher voltage (720V) is electrically more efficient.

Anonymous on November 8, 2022 provided extra calculations, which are reproduced below:

Energy of total Japanese submarine LIBs (codenamed “SLHs”) is estimated to be 62-74MWh and 70-83MWh for Oryu/Toryu (ie. The Soryu Mk IIs) and the Taigeis, respectively. This suggests maximum fully submerged endurance of 9-11 days and 10-12 days respectively [3].

Calculations:

[1] https://www.gs-yuasa.com/gyt/jp/products/space/ [Japanese doc . Just right-click mouse to Translate to English.] High performance lithium-ion battery for spacecraft (eg. satellites and “space probes”): energy density 168Wh/kg, 130(Width) x 50(Depth) x 271(Height) all in mm

Energy density of this battery is ca.20% higher than [2] suggesting energy density of [2] is 140Wh/kg.

[2] https://www.gs-yuasa.com/gyt/jp/products/lithium_l.php [Japanese doc . Just right-click mouse to Translate to English.]

Large lithium-ion battery for space: energy density 140Wh/kg

[3] Estimated energy of submarine (Oryu/Toryu, Taigeis) with SLH (weight 770kg) based on [1] and [2]. If 10% of SLH is used for "frame" [does this mean for internal battery function, eg. keeping battery warm enough to be efficient?] and so on, then energy of SLH is 0.097-0.116MWh

(770kg x 140Wh/kg x 0.000001 MW/W or 770kg x 168Wh/kg x 0.000001 MW/W)

Energy: 62-74MWh [Oryu/Toryu, 640SLHs], 70-83MWh [Taigeis, 720SLHs]

(0.097MWh x 640 or 0.116MWh x 720 for Oryu/Toryu)

If daily energy consumption at surveillance speed [<4knots] is 6MWh [4] and depth of discharge is 90% for SLH, then maximum endurance is 9-11days [for Oryu/Toryu] and 10-12days [ for the Taigeis].

(62MWh / 6MWh x 0.9 or 74MMWh//6MWh x 0.9)

[4] Considering the significant electrical needs of submarine sonar systems and other non-propulsion electrical “hotel load”, then requirement may be 200kW. Energy requirements for propulsion at surveillance speed may be 50kW. Then daily energy consumption is 6MWh (=(200kW+50kW) x 24hours).

The approximately 50kW [minimum] estimate for propulsion motor is based on the Japanese National Defense Standard (NDS) (at https://www.mod.go.jp/atla/nds/F/F8004_2.pdf , in Japanese) F8004-2 (General rules for submarine electric propulsion equipment - Part 2 submarine equipped with AC propulsion motor = Soryu MK. I).

- Low speed 1 is rotation speed of propulsion motor (19 - 45rpm) [ F8004_2.pdf (44/52) 4.4.1 table].

- 19 rpm is the minimum rotation speed of propulsion motor which is 10% of maximum rotation speed at maximum speed in water (= 20knot/h) [ibid (9/52) 4.4.2. table1, item 4 or 7].

- Output of propulsion motor is 56.8kW at rotation speed of propulsion motor (39rpm) [ibid (38/52) 4.4.2. table].

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For more launch dates and other details of all these Japanese submarines see Submarine Matters Oyashio-Soryu-Taigei Table here.