The rows below show:
- current Soryu Mark
1s (Stirling AIP & LABs)
- future Soryu Mark
2s (LIBs only) and
As well as two hypothetical Soryu models:
- Soryu X (Fuel
Cell (FC) AIP & LABs), and
- Soryu Y (Stirling
AIP & LIBs))
Soryu modes of
electrical propulsion are compared according to criteria in the first column.
70 day mission =
20days transit
+ 50days surveillance
|
Soryu Mark 1s (AIP & LABs)
|
Soryu Mark 2s (LIBs only)
|
Soryu X
(FC-AIP & LABs)
|
Soryu Y
(AIP & LIBs)
|
Numbers of batteries 1] [2]
|
480 LABs
|
576 or 672 LIBs
|
480 LABs
|
480 LIBs
|
Submarine size (length)
|
length 84m
|
78-83m
|
same
|
same
|
Crew shifts
|
3 shift crew routine
|
Same
|
Same
|
Same
|
max fully submerged period in theory
period - (actual)
in days [3]
|
LABs+AIP
16-17 days
(15 days)
|
LIBs
7-8.5 days
(6-7.5 days)
|
LIBs
+FCAIP 32
(33)
|
LIBs+AIP
20
(19)days on
|
Percentage LOX unused
|
most LOX kept in reserve
|
N/A
|
30% of LOX kept in reserve
|
most of LOX kept in reserve
|
frequency of snorting/recharge [7]
theory
(actual)
|
6-12 hours LABs
|
Within 6 days
(1-2 days)
|
1-2 days on FCAIP+LABs
|
5days
(1-1.5days) LIBs
|
none
|
Lithium Nickel Aluminium oxide (NCA)
|
none
|
Lithium Nickel Aluminium oxide (NCA)
|
|
The future? [6]
|
No Soryu Mk. 1 new builds after 2014 [5]
|
Evolved LIBs or Li-Sulphur Batteries (LSBs)
|
none
|
none
|
[1] Although
the combination of AIP + LIBs had some advantages the JMSDF preferred
increasing the number of LIBs (576 or 672 LIBs on Soryu Mark 2s) compared to only 480 LABs
on current Soryu Mark 1s). Major reasons for the change in propulsion were the
low utilisation ratio of AIP and need for high speed performance.
[2] The reasons
why the Japanese Navy (JMSDF) gave up AIP for the Soryu Mark 2s (LIBs only))
are not clear. Possible reasons are:
i) poor endurance of Soryu Mark 1s due to weight and bulk of the 2 x LOX tanks
i) poor endurance of Soryu Mark 1s due to weight and bulk of the 2 x LOX tanks
ii) low frequency
of AIP use
iii) complex
operation of diesel engines, AIP and LABs
iv) demand for high
speed performance, which low submerged speed Stirling AIP cannot efficiently
contribute to
v) LIBs last more
years than LABs ie. LIBs can function for more cycles. Lithium Titanate (LTO) shows an extremely long life time, and total life
time cost may be the same or less than for LABs.
vi) Though there is
an another attractive option, ie. AIP+LIBs, instead of increased LIBs, AIL+LIBs
was not selected. This suggests that the contribution of increased LIBs (96 or
192 LIBs) was greater than that of AIP. Presumably based on operational
experience and submarine tactics, the JMSDF prioritize high speed performance (such
as longer period at max silent submerge speed) over long submerge period at low
speed provided by AIP.
[3] The fully submerged
period of a Soryu Mark 1 (LABs + AIP) is said to be as short as 2 weeks. So AIP
is possibly not used for ordinary missions. Possible uses of AIP are as follows:
i) emergency such
as combat
ii) modulation of snorting-recharge
timing to avoid undesirable timing which may be caused by Low energy density of
LABs.
The maximum
discharge of LABs and LIBs are assumed as 30% and 90%, respectively. Further discharge
leads to irreversible damage to batteries.
[4] 12 years ago
the JMSDF demonstrated that the energy density of prototype LIBs was twice that
of LABs. The LIBs for Soryu Mark 2s are much better than the LIBs prototype.
[5] See the SORYU-Oyashio Build, Launched and Commissioned Table of March 22, 2017 (below).
[6] A future sub with AIP and LIBs may have an
excellent indiscretion ratio. But, improved LIBs or Lithium-Sulphur Batteries (LSBs) are a more feasible option for the JMSDF.
[7] For LABs, more frequent snorting-recharge
avoids the submarine running out of electrical power at a bad place and/or time.
For LIBs, frequency of snorting-recharge drastically decreases. A lower longer frequency
for LIBs of snorting-recharge every 6 days is possible, but, after 6 days snorting-recharge
takes longer.
Anonymous and Pete
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