Australia’s next submarine – Will it be the Soryu?

After some confusion the project to acquire Australia’s next submarine seems back on track.  A logical procurement process has been developed that should see a decision on the specific type of submarine to replace the current Collins class announced during the late 2016 election season.
A review of Australia’s strategic needs and operational requirements against the three submarine types being considered foreshadows the possible outcome.

Strategic Needs and Operational Requirements

The previous Chief of the Australian Navy, Rear Admiral Ray Griggs, defined the major operational task for Australia’s submarine force as: “sink hostile surface ships and submarines.” In contrast, other roles such as intelligence collection, transporting special force teams and land strike using cruise missiles are very much secondary, and not significant design drivers.
In being so optimised to destroy hostile naval forces, Griggs considers Australia’s new submarine force will comprehensively deter potential aggressors.
The area of operations seems clear. Admiral Briggs considers the South China Sea as the area of most interest. This large sea area north of the Indonesia archipelago through which any would-be aggressor must transit to reach Australia seems an obvious region of concern.
The South China Sea covers 3.5 million square kilometres; bounded by several ASEAN nations and China it is almost an inland sea.  To the west and north it covers a continental shelf and is shallow, to the south and east though it is very deep, with the China Sea Basin in particular averaging 4,000 metres in depth.  While any submarine can undertake operations in deep waters, the size of a submarine influences its capability to operate in shallow water.
In this, the size of Australia’s new submarine is driven by a key planning assumption. Rather than deploying forward to bases near the South China Sea, the new submarine is intended to operate directly from HMAS Stirling near Perth. Accordingly, as Peter Briggs advises, the new submarines will need to be able to transit some 7,000km to their operating area and then remain on station for some 30 days.
Given current technology this range requirement means that Australia’s new submarine will need to be of the order of some 80-90 metres in length.
Such boats can come into water as shallow as 40 meters on carefully planned intelligence collection missions, but to freely manoeuvre in three dimensions and conduct war fighting operations a depth of more than a 100 metres is more realistic.
Large submarines are thus better suited for deep water war fighting than for shallow water operations.  Given this, Australia’s new submarine will be more appropriate for operations in the South China Sea’s southern and eastern parts where the water is deep rather than in the shallow waters of the Sunda Shelf that borders Malaysia, Singapore, Indonesia and southern Vietnam.
There is a second key planning assumption that also has a significant impact: the new submarine must incorporate a specific American combat system (the AN/BYG-1 or developments of it) and use American weapons, in particular the Mk-48 torpedo.  This requirement means that no existing submarine type is suitable, one cannot be bought off the shelf so a new submarine must therefore be developed. This requirement further means that the US has a strong, possibly decisive, interest in source selection.

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