Attack-class submarine
The Attack-class submarine is a future class of submarines for the Royal Australian Navy based on the Shortfin Barracuda proposal by French shipbuilder Naval Group (formerly known as DCNS) to replace the  submarines. The class will enter service in the early 2030s with construction extending into the late 2040s to 2050. The Program is estimated to cost $50 billion and will be the largest, and most complex, defence acquisition project in Australian history.

The Program to replace the Collins class began in 2007 with the commencement of the Defence Department acquisition project SEA 1000. Australia's unique operating environment (including significant variations in ocean climate and conditions) and rejection of nuclear marine propulsion had previously driven it to operate in the Collins class the world's largest diesel-electric submarines, capable of transiting the long distances from  to their deployment areas.

In the early phases of the replacement project, four design options were identified: purchase a Military-Off-The-Shelf (MOTS) design, modify a MOTS design for Australian conditions, design an evolution of the Collins-class, or create a new design. Nuclear propulsion has been ruled out due to the lack of an indigenous nuclear industry in Australia and public opposition to nuclear technology.

In 2009, the Australian Government's Defence White Paper announced that a class of twelve submarines would be built. The selected design was to be built in Australia at the ASC Pty Ltd shipyard in South Australia, but, if a company other than ASC was selected to build the submarines, they would be granted access to the government-owned facility. Concept work was to start in 2009, with a winning design to be identified by 2013 and design work to be completed by 2016, enabling the construction of the first submarine to be completed before 2025. However, there were significant delays in implementing the project, with meetings to define intended capabilities not occurring until 2012, which pushed the start of construction beyond 2017.

By the end of 2014, operational capabilities had still not been defined, amidst increasing speculation that the Australian government would purchase  submarines directly from Japan, skipping any tendering processes and ignoring previous commitments to build the boats in Australia. However, in February 2015 the Abbott Government announced a "competitive evaluation process" between competing Japanese, French, and German designs.

On 26 April 2016, Prime Minister Malcolm Turnbull announced the Shortfin Barracuda, a conventionally-powered variant of the Barracuda-class nuclear submarine by French firm DCNS, as the winner.

Background
Australian diesel-electric submarines operate in a wide range of geographic and oceanographic conditions, from the cold Southern Ocean to the tropics of the Coral, Arafura, and Timor Seas – requiring the submarines to handle significant variances in temperature, salinity, density, and climate. Australian submarines provide a deterrent towards military aggression against Australia, by patrolling the waters of Australia and nearby nations, and in addition, gather intelligence through the interception of electronic communications by foreign nations, and assist in the deployment and retrieval of special forces operatives. Because RAN submarines operate from , and because some of Australia's strategic interests are located as far afield as the Persian Gulf and the North Pacific, Australian submarines have to transit long distances to reach some of their potential patrol areas. This requirement for range and endurance resulted in the 1980s Collins-class design incorporating a large fuel load, large engines and sufficient batteries to transit these long distances, although technological improvements since then have enabled smaller diesel-electric submarines such as the German Type 214 submarine and Dutch  to achieve similar range and endurance as the Collins-class. It has also been noted that the transit distances Australian submarines travel could be reduced by operating the submarines from  in Darwin, rather than HMAS Stirling in Western Australia.

The Collins class were the first diesel-electric submarines specifically designed for Australian conditions of long transit distances and diverse sea states, and thus represent an 'orphan' design with no evolved design to replace them. The submarines were enlarged and heavily modified versions of Swedish shipbuilder Kockums' . Built during the 1990s and 2000s, the Collins-class submarines have a predicted operational life of around 30 years, with the lead boat  due to be decommissioned around 2025.

By November 2014, initial capabilities had not been decided on, and recommendations were to be made across 2015. In December 2014, the Australian Coalition government ruled out using a tender process to identify a new submarine design, blaming the limited time left before the Collins-class were scheduled to begin leaving service. Although there was speculation at the time that the Australian government would purchase directly from Japanese shipbuilders, in January 2015, Defence Minister Kevin Andrews stated that the government was still considering the options offered by European shipbuilders: ThyssenKrupp Marine Systems of Germany, Saab of Sweden, and a partnership of the French companies Thales and DCNS.

In mid-December 2015, the Japanese Self Defence Force allowed a journalist from the Australian Broadcasting Corporation (ABC) to tour the newest of the class,  (black dragon), at its base at Yokoska and speak to the commanding officer, Commander Takehiko Hirama, and several other personnel.

2015 policy announcements
On 8 February 2015 the Abbott Government signalled that both the selection of a design and selection of construction options would be competitive, and on 9 February 2015 announced a "competitive evaluation process" with the possibility of construction in Australia. On 20 February 2015 the Australian Government publicly announced three key strategic considerations that would be taken into account in the competitive evaluation process, these being: that the future submarines would have a similar range and endurance to the Collins class, superior sensor performance and stealth compared to the Collins class, and that the combat system and Mark 48 Mod 7 torpedo jointly developed between the United States and Australia would be the future submarines' preferred combat system and main weapon. The government also announced a three-way competition between ThyssenKrupp, the Thales-DCNS partnership and a Japanese design, while Saab was excluded. The process was expected to select the design for the submarine by the end of 2015. It was indicated that the number of submarines would likely be reduced to eight, with specifics to come in the defence white paper slated for later in 2015.

Technical considerations

Propulsion
Deciding the future submarines' propulsion system is closely tied to determining its operational range, endurance and stealthiness. Two basic options are presented in submarine propulsion: nuclear propulsion, and conventional, diesel-electric propulsion. The option of nuclear propulsion effectively gives submarines an unlimited range and endurance, only restrained by maintenance and human crew requirements for resupply and rest, and removes the necessity for surfacing to recharge batteries, an unstealthy and risky process. Australian governments have repeatedly rejected the nuclear propulsion option due to the lack of an Australian nuclear power industry (Australia would be the only non-nuclear nation to operate nuclear submarines), related issues of operational sovereignty were Australia to operate an American nuclear powered submarine such as the , rendering it dependent on American technical support, and public opposition to nuclear technology.

The second alternative is to operate a conventional diesel-electric submarine with sufficient fuel and battery power to transit the large operational ranges required by Australia, and to provide maximum range, endurance and stealth (operating underwater), before having to resurface to snorkel and recharge batteries. Previously, this design brief led to the construction of a relatively large conventionally powered submarine, the Collins class, possessing a large diesel electric engine, fuel load and sufficient batteries capable of transporting the submarines from their remote location at HMAS Stirling to their operational areas, without having to resurface for extended periods.

A further innovation in diesel electric propulsion which might be considered for the Collins-class replacement is air independent propulsion, which is not operated in the existing Collins class, but is operated in a number of more recent submarine designs including the German Type 214, Japanese Sōryū class, and French Scorpène class. Air independent propulsion performs the role of an auxiliary engine, providing submarines with increased stealth by allowing them to operate submerged for longer. The German Type 214 submarine employs advanced polymer electrolyte membrane fuel cells that assist in delivering it comparable range and endurance to the Collins class.

Batteries
Batteries are an important component of diesel-electric submarines, allowing them to operate underwater for extended periods of time before having to resurface to recharge them. Improvements in battery technology in recent years have allowed smaller diesel-electric submarines to operate with greatly improved range and endurance. Future submarine designs might use improvements in Lithium-ion battery technology. The Collins-class replacement might operate battery technology superior to that of the existing Collins-class.

The Australian Government's announcement on 20 February 2015 that the future submarines will have a similar range and endurance to the Collins class increases the possibility that an evolved MOTS or completely new design will be selected.

Weapons capabilities
The 2009 Defence White Paper identified a land strike capability as an important addition to torpedo, mine and anti-ship missile weapons. In February 2015 the Australian Government identified its preference for the future submarines to have a US weapon system and heavyweight torpedo.

 Torpedo 
 Mine 
 Anti-ship missile
 Land attack cruise missile

Design

Candidates
 
In the 2009 Defence white paper, the replacement submarines were outlined as a class of twelve vessels of up to 4,000 tons displacement, fitted with land-attack cruise missiles in addition to torpedoes and anti-ship missiles, capable of launching and recovering covert operatives while submerged, and carrying surveillance and intelligence-gathering equipment. The submarines would likely be fitted with the United States AN/BYG-1 combat system.

There were four possible routes for the SEA 1000 project to take, in order of increasing design complexity and risk:
 Buy a Military-Off-The-Shelf (MOTS) design without modification
 Develop a modified MOTS design to better suit Australian service conditions
 Design an evolution of the Collins-class 
 Design an entirely new submarine

Designs initially considered for the various MOTS routes included the German-designed Type 214, Japan's , the French-designed , the Spanish , and an evolved Collins class. The Spanish S-80 class was dropped from consideration due to serious design issues that had been noted in the public domain. An evolved Collins-class design was also considered in 2013 but was officially dropped from consideration in 2015, due to it being assessed that the work required equated to composing a brand new design. In addition, Saab pushed an enlarged variant of its Swedish A26 submarine, but was excluded from further consideration in February 2015 due to Sweden having not designed and built a submarine independently for twenty years. Pure MOTS submarines were initially ruled out by the project in March 2011, but were put back on the table in December 2011.

Evolved designs of the Scorpène class have been offered, while ThyssenKrupp Marine Systems, in additions to options for an evolved Type 214, has proposed the development of a brand new design, the Type 216, to specifically match Australian requirements.

Selected: Shortfin Barracuda (France; DCNS)
On 30 November 2015, DCNS with Thales delivered its proposal for the Shortfin Barracuda Block 1A design (a diesel-electric variant of the Barracuda-class nuclear submarine under construction for the French Navy) to the Commonwealth of Australia’s Department of Defence. It includes a Government to Government Agreement from the Ministry of the Armed Forces's Direction générale de l'armement (DGA) with a binding written agreement for aspects of the deliverables. "While exact details remain confidential, DCNS can confirm the Shortfin Barracuda is over 90 metres in length and displaces more than 4,000 tons when dived," said Sean Costello, CEO DCNS Australia.

DCNS was chosen by the Australian Government on 26 April 2016 to build 12 of the Shortfin Barracuda Block 1A variant at a projected A$50 billion.  Much of the works will be undertaken in Adelaide, South Australia.

According to the Royal Australian Navy the Shortfin Barracuda will displace 4,500 tons (surfaced), measure 97 metres in length, have an 8.8-metre beam, use pump-jet propulsion, have a range of 18,000 nautical miles, a top speed of greater than 20 knots, an endurance of 80 days and a crew of 60.

Construction

Initially, the Australian government promised that the government-owned ASC, the company responsible for building the Collins class, would build the new submarines. In a May 2009 announcement about plans to release a request for tender, the Labor government indicated that if a company other than ASC was the successful tenderer, that company would be granted access to ASC's shipyard in Osborne, South Australia. Despite ongoing support for the submarines to be built in South Australia by successive Coalition and Labor governments, in July 2014, the Abbott-led Coalition government abandoned their pre-election commitment to ASC-based construction and opened up the likely possibility of building the submarines at a foreign shipyard. In February 2015 the Abbott Government in announcing a 'competitive evaluation process' noted that the government would not approach the submarine decision with an 'open cheque book', but would rather allow a competitive process in which various construction options would be explored, including construction in Australia, overseas, or a 'hybrid approach' of foreign and local construction, along with estimated costs and schedules.

Original plans for construction indicated a 25-year period from work starting to final completion. Because of the lengthy construction period, building the submarines in evolving 'batches' was under consideration; ongoing research and innovation would see updated equipment and designs incorporated into new submarines as built, then added to existing submarines during refits. The SEA 1000 submarines are predicted to remain in service until the 2070s.

In July 2017, Malcolm Turnbull opened the Future Submarine Project office in Cherbourg. Design work on the submarines is currently ongoing.

The class was named the Attack class in December 2018, with the first of class to be designated HMAS Attack.

Cost
When announced, the Collins replacement project was identified as the most expensive ever undertaken by the Australian Defence Force. In December 2010, an update to the 2009 Defence Capability Plan forecast the cost of the project as over A$10 billion. However, the Australian Strategic Policy Institute has predicted that the new submarines will cost over A$36 billion to design and build, with construction of each submarine valued between A$1.4 and A$3.04 billion. Government predictions in 2014 estimated a total cost of up to A$80 billion for 12 Collins derivatives built by ASC, although ASC contests this with claims of a cost of A$18–24 billion.

An unspecified number of Sōryū-class submarines, built in Japan by Mitsubishi Heavy Industries and Kawasaki Shipbuilding Corporation was estimated at A$25 billion. European shipbuilder offers in 2014 were valued by the shipbuilders as costing around $A20 billion or otherwise being competitive with the Japanese valuation.

Submarines in class