The U.S. government’s plan to sell Australia three to five attack submarines (SSNs) in the 2030s as part of the AUKUS pact could lower U.S. SSN stocks by that many boats for upwards of 20 years compared to the current 30-year shipbuilding plan, according to a recent Congressional Budget Office report.
An annual CBO report on the Navy’s fiscal year 2024 30-year shipbuilding plan, released October 26, said that a “major uncertainty in the Navy’s plans for attack submarines is the effects of the tripartite security arrangement between Australia, the United Kingdom, and the United States known as AUKUS.”
As part of this effort to help Australia field nuclear-powered SSNs, the U.S. plans to sell a mix three to five new and used Virginia-class attack submarines in the 2030s before the new SSN-AUKUS class submarines would be ready for Australia to deploy in the 2040s.
While the shipbuilding plan said the Navy “anticipates building additional Virginia-class SSNs in the 2030s as replacements for submarines sold to Australia,” CBO underscored that possibility is not included in the plan’s three alternative projections.
Like the previous year, the FY ‘24 30-year shipbuilding plan includes three alternatives: two without large Navy shipbuilding funding increases and a third with a significant funding increase over recent years.
The existing shipbuilding plan estimates the Navy will buy 16, 21 or 18 SSNs between 2030 and 2039, depending on the alternative
“To purchase 3 to 5 additional replacement submarines during that period, the Navy would need to build 1.9 to 2.6 SSNs per year, depending on which alternative it followed,” the report said.
However , it underscored the U.S. submarine industrial base is already struggling to meet current demands. The Navy is trying to buy two SSNs per year while also starting to build the 12 Columbia-class ballistic missile submarines (SSBN), which will ramp up to procurement at one per year from 2026 to 2035.
CBO said the Navy has reported the submarine shipyards, General Dynamics’ [GD] Electric Boat and HII’s [HII] Newport News Shipyard are jointly building fewer than 1.5 SSNs per year currently as the Columbia-class ramps up and the builders are already dealing with a backlog of work.
The report argued “it would be very difficult and expensive” for the submarine industrial base to build and deliver two SSNs and one SSBN per year and increase production further to make up for AUKUS sales. The CBO cited the time between funds appropriated for SSNs and delivery has increased from six years, when the Navy only built one submarine annually, to nine years currently.
Therefore, the report envisions AUKUS sales to Australia as reducing the numbers of submarines available to the U.S. Navy, rather than being easily replaced.
CBO developed three scenarios of how the AUKUS sales could affect U.S. submarine stocks, taking the long-term shipbuilding plan’s Alternative 1 plan as a baseline.
The first scenario has the U.S. sell two used and one new Virginia-class SSNs to Australia in the 2030s, with used ships having about 20 years of remaining service life, thus coming from the Block IV set of boats. The new SSN would be the first of Block VII, which the Navy plans to order from 2030 to 2036.
The second scenario has the U.S. sell five SSNs from 2032 to 2044: two used Block IV boats and three new Block VII boats.
CBO argued under these scenarios, instead of the U.S. Navy attack submarine force growing from 50-plus ships by 2034 to up to 60 by 2053, the Navy would have three to five fewer submarines from 2033 to 2053.
The last CBO scenario envisions the U.S. selling two used and three new SSNs to Australia, but also buying four submarines in the 2030s to replace them, mitigating much, but not all, of the dip in U.S. submarine stocks for that 20 year period.
The report said this would require the U.S. Navy to spur production of two SSNs per year throughout the 2030s. Then, by 2056 the U.S. Navy would have more submarines than the base Alternative 1 plan envisions.
Notably, CBO said trying to buy replacement submarines under the first two scenarios is harder because of the higher baseline production rate while the industrial base is catching up on SSN production and building the SSBNs.
“In those cases, attack submarine production would exceed 2 SSNs per year for several years,” the report said.
CBO’s scenarios assume Australia will buy the smaller Virginia-class submarines without the Virginia Payload Module on newer models.
The first two scenarios “represent the minimum and maximum potential capability, respectively, that Australia could acquire from the United States under the AUKUS pact, considering the time required to build new submarines,” the report said.
The CBO said the government has to consider if China might be less deterred if the U.S. lowered its own SSN numbers to help Australia develop its own submarine force, but since the U.S. and Australia are close allies “improving the Australian Navy’s capability could help offset the U.S. Navy’s potential loss of capability.”
“That loss might even be more than offset because the Australian submarines would be based in the Western Pacific region and therefore could respond more quickly to any conflict with China involving Taiwan or other issues in the South China Sea. However, Australia would control its own submarines, and their participation in any particular conflict would not be guaranteed,” CBO said.
The report noted in 2020 the Australian defense minister said they did not promise to support the U.S. if a conflict erupts between Taiwan and mainland China.