The Line it is Drawn: The Critical Issues for Australia’s Future Undersea Warfare Capability (Part III of 'Six Years On')

The RAN’s existing Collins fleet will remain its most important submarine asset over the next two decades, providing operational capacity and supporting development of new technologies. It provides the only element of risk mitigation in transitioning to an SSN force and the future management of the class should be more carefully considered.

The Government’s discourse on the RAN’s subsea warfare capability over the next quarter of a century promotes a vision based on an increasing number of nuclear powered submarines (SSNs). In reality, the Navy’s subsea force over most of this period will be provided largely by its existing Collins class submarines and Ghost Shark Autonomous Underwater Vessels (XL-AUV). The Collins will remain the most numerous crewed Australian submarine into the 2040s.

The schedules for the acquisition of RAN SSNs are extremely long term. Even the most optimistic expectations of the program to provide three interim US Virginia class SSNs will see it occupying the 2030s. The British designed SSN-AUKUS class will begin delivery in the early 2040s, followed by a boat from the Adelaide yard of ASC Pty Ltd every three years.

Consequently, all Collins submarines would have retired before the third Virginia entered Australian service, leaving the RAN without an operational submarine capability.

To avoid this, each of the Collins will have a Life-of-Type-Extension (LOTE) to allow an extra 10 years of service, beginning from 2028. The LOTE includes changes to diesel generator sets, propulsion motors and electrical distribution systems. There is, however, some current speculation that the LOTE for the earlier submarines might not include changes to propulsive machinery because of a potential risk to schedule.

The LOTE will enable four of the Collins to serve into the 2040s, with the last retiring just before the end of that decade. It is these refurbished boats that constitute the RAN’s real deployable submarine capability until the SSN-AUKUS build is established. The Collins LOTE constitutes the only Plan B that the RAN can employ should the American or British designed SSNs be disrupted, delayed or denied.

Yet the Collins LOTE as planned will be largely overwhelmed by emerging subsea warfare technologies that will change the way that underwater operations are conducted.

More nations are deploying submerged sensor systems linked to artificial intelligence analysis that will make submarine missions increasingly difficult. Just how, and to what degree, broadly will depend on who’s listening, why they’re listening and what they can do about it. When a country such as Indonesia deploys a submarine detection system covert passage between the Indian and Pacific Oceans will become problematic, especially for large SSNs that can proceed only via the Lombok Strait.

Indonesia may harbour no ill intent but release of transit data, say, to support Indonesia’s interpretation of its archipelagic status, could compromise other nations’ submarine deployments. Submarines based at HMAS Stirling would become merely an Indian Ocean flotilla were Indonesia ever prompted to close the Strait (hence the planning for an Australian east coast submarine base).

The Collins LOTE would be faced from the 2030s onwards by contemporary boats (Link to Part 2) with LMB energy systems offering up to four times the submerged performance. Without a LMB energy system the class will be a regionally inferior submarine, with diminishing operational utility.

Deploying various AUVs during submarine operations to counteract hostile activity is seen as a likely means of improving submarine survivability and effectiveness. Diverting roles to XLUUVs such as Ghost Shark, either independently or under submarine control, further supports the survivability of crewed submarines. Mine laying is an immediate task for large AUVs and the RAN is expecting them to perform anti-shipping missions in the near future and land strikes by the 2040s (p.11).

The development of these capabilities are covered by the AUKUS Undersea Robotics and Autonomous Systems project but will require research and development demanding sea days aboard an RAN submarine to be operationally deployed. Most of these will have to be provided by the Collins class. However, the obsolete LAB energy system of the Collins class has limited energy capacity, and it is unclear how effectively it could test and support off board digital systems.

The Collins LOTE, therefore, is not only the RAN’s Plan B for sustaining future submarine warfare capability, it is also necessary to ensure the most effective implementation of the AUKUS Plan A. The RAN’s resistance to refitting the Collins with a light metal battery energy system is curious, to say the least, as PMB Defence (the manufacturer of the Collins’ LAB system) is offering advanced battery systems designed for ease of integration into existing submarines.

Yet it might be the case that the developing technologies in subsea warfare portend a paradigm shift in the concept of submarine operations. The spread of surveillance technologies, the improved performance promised by SSEs and extended reach available with autonomous systems may signal a change in the heretofore dominant concept of operations, that of deploying submarines to an enemy’s shipping focal areas. The PLA-N appears to think so. China is not emphasising acquisition of SSNs; rather it continues to methodically build and improve its Yuan class SSK to sustain its conventional submarine force of around 60 vessels [link to Part 1]. With the technology and shipbuilding capacity to further expand its subsurface forces it should be expected that China will have effectively closed the East China Sea before 2040.

Thus, Australia’s SSN force will have been dealt out of its major role before it becomes operational. Unable to approach China’s coast and islands, the issue then becomes should Australia focus its subsea operations more tightly in harmony with its national defence strategy of denial. By the time that Australia has an operational SSN capability its subsea warfare inventory would then be built around fixed sensors, intelligent mines, autonomous underwater gliders, autonomous surface surveillance craft like BlueBottle and the progeny of Ghost Shark. The role of crewed submarines would remain important but be more focused, and their acquisition will be evaluated in the context of the financial and personnel constraints of the integrated undersea warfare system.

In the meantime, what seems prudent, if not outright fundamental, is that Australia should maintain as many options as possible for supporting its undersea warfare potential while the AUKUS program remains a distant and uncertain objective. Securing the future operational effectiveness of the Collins class is a central first step in sustaining this goal.

Derek Woolner and David Glynne Jones

6 October 2025