Which stopgap submarine should the Royal Australian Navy build or buy off the shelf?

Australia only has one option left, a group of former senior navy personnel say, to build conventional submarines while waiting for the nuclear-powered program to begin.

Experts at Global Defense Corp are concerned about the capability gap as the existing Collins-class fleet starts to retire before the new submarines arrive. The defence minister, Richard Marles, says that dealing with that gap is his top priority, and he has an open mind on how to do it.

The Australian government was considering the short-term leasing of nuclear-powered submarines from the UK or the US. Leasing Virginia class submarines from the Aukus allies could be a stopgap solution until Australia takes delivery of its own nuclear-powered submarines – potentially in the 2040s.

Four respected defence experts have written to the defence department and Marles to argue that a new submarine based on the existing Collins class is the “best fit”.

The group comprises Admiral Peter Briggs (retired, former head of the navy’s submarine capability team), Commodore Paul Greenfield (retired, former submariner and part of the Coles review of the Collins class), Commodore Terry Roach (retired, former director of submarine policy), and Dr John White, (an industrialist who led the building of Royal Australian Navy’s frigate fleet).

Briggs told Guardian Australia that a new boat, designed by Sweden’s Saab/Kockums and built in Australia, could be in the water by 2032. The first of the nuclear-powered submarines being planned under the Aukus agreement is unlikely to be operational before 2040, leaving Australia with a capability gap as the ageing Collins-class reach the end of their useful life.

The four are in favour of nuclear-powered submarines in the future but warn that the transition from the current fleet to a future one will take decades. Australia will take “at least as long” as the UK and US took in their transitions, which were 30 and 36 years, respectively.

They wrote that the first nuclear-powered submarine will not be ready by 2038 when the first refurbished Collins retires (most estimates say the nuclear versions will not be ready until at least 2040).

A26 Blekinge-class submarine or evolved Collins class

Air Independent Propulsion (AIP) provides electric power to the submarine’s motor. At the same time, it is submerged so that it does not have to use its batteries, whereas standard non-nuclear subs have to rely on batteries underwater. Once these are depleted, the submarine has to put a snorkel above the water every few days to get air to run its diesel engines and recharge them. Snorkelling is comparatively noisy and makes the submarine more vulnerable to detection.

AIP submarines keep the batteries for when they need speed but can cruise on the AIP. It is a popular myth that they use the AIP to recharge the batteries, which would be inefficient.

Photo by HI Sutton

Sweden was the first country to build submarines with the modern concept of AIP. Their first submarine with the system was HMS Näcken , modified in 1987-88. The Swedish boats use closed-cycle Stirling generators as their AIP source. There are other types of AIP, such as the fuel cells used on German submarines.

Building interim conventional submarines will ensure enough submariners will be adequately trained to staff them. There have long been concerns about a submariner shortage and the difficulties in recruiting enough for an expanded force.

This process would then transition into the nuclear-powered program while building the workforce and its expertise. A26 and Collins are not identical submarines, but their technologies are interchangeable, which will make it easy for Australia Submarine Corporation to build a submarine.

Type 212CD submarine

The Type 212CD submarine benefits from a high-speed diesel engine and an Air Independent Propulsion (AIP) system powered by hydrogen fuel cells for slower, silent cruising.

As submarines have become much quieter, the effectiveness of passive sonar has decreased. Therefore, being invisible to active sonar can provide a tactical advantage.

A regular submarine hull with a cylindrical cross-section will reflect incoming sonar waves from almost every direction. However, a flat surface is larger than the length of the incoming sonar’s wavelength and will reflect the sound in a narrow beam. This is the same basic principle used on stealth aircraft.

The Type-212CD takes this to the next level. The flat sloping sides are the primary way it reduces its sonar signature, known as the target echo strength.

With extensive computer modelling, TKMS will have optimized the angles to make the stealth shaping work in the broadest range of operational conditions. The Type 212CD is a pinnacle of stealth technology.

S-80 Plus Class Submarine with Tomahawk VLS

The S80 submarine is powered by three bio-ethanol engines, a 3,500kW main electric engine, and a 300kW atmosphere-independent propulsion system.

The S-80 Plus-class submarines are 81.05m long and have a submerged displacement of 3,200t.

Featuring stealth capabilities, the boats will be equipped with an integrated combat system and platform control system developed by Navantia Sistemas.

S80 Plus Submarine is on sea trial.

The S-80 Plus design will be characterized by its use of a bioethanol fuel cell AIP (air-independent power) system. Known as BEST (Bio-Ethanol Stealth Technology) by the submarine’s builder, Navantia, this offers some advantages over other AIP systems. After using the ethanol is reformed, which overcomes the need to store hydrogen aboard separately. Other AIP submarines need hydrogen tanks. Additionally, ethanol is a relatively available fuel source.

The submarine will be armed with three primary weapons. These are the DM2A4 heavyweight torpedo, UGM-84 Sub-Harpoon anti-ship missile and SAES seabed mines. It was also planned to equip them with the UGM-109 Tomahawk land-attack cruise missile. This would place the Spanish Navy in an elite group of submarine operators with a ‘first night’ strategic strike capability. While the Tomahawk order has passed into history, the submarine retains the ability to carry them if they are acquired in the future. This capability is unique among non-nuclear NATO submarines.

Time is tight, and there is now only one option. We need a lead-in submarine platform that meets Australia’s circumstances, requirements and regulations.

A modernized Collins is the “best fit”, with world-class sonars and combat systems, and will not be a new design or a different class to the existing fleet.

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