In addition to guided-missile destroyers, the U.S. Navy is building a large number of nuclear-powered attack submarines. The current class being built is the Virginia class, with 22 boats currently in service and an additional 16 authorized or under construction. The 2024 budget calls for two more Virginia class boats; the current price tag is $4 billion each. Navy plans call for a total of 51 boats of this class.
The USS Virginia (SSN 774) entered service in 2004 and additional boats soon followed. The boats are built by General Dynamics Electric Boat in Groton CT and by Newport News in Virgina. I've previously discussed the difficulties with the production rate of these submarines; see previous posts on the issue.
Like many series-produced Navy ships, the Virginia class SSNs have been improved over the years. The early boats have a spherical sonar array in the bow whereas later boats have gone to an improved large aperture bow sonar array in a horseshoe shape. The whole class has other sonar equipment, including side arrays and towed arrays.
Likewise the older conventional single screw has been replaced by a propulsor (see drawing).
The most recently authorized boats have been lengthened considerably -- from 377 feet to 460 feet -- to incorporate additional vertical-launch missile tubes. These have not yet joined the fleet.
One of the 2024 boats is planned to be further modified to conduct seabed operations, which like many submarine activities, are highly classified.
A few basic specs:
-- 377 or 460 feet long
-- 34-foot diameter hull
-- speed submerged "over 25 knots" (35?)
-- max operating depth classified but likely well over 1000 feet
-- Crew of 135
-- Armed with four torpedo tubes and vertical-launch missile tubes with a capacity for 12 cruise missiles (earlier boats) or 40 missiles (longer boats)
This is the class of SSN that is likely to be transferred or built for the Royal Australian Navy.
https://en.wikipedia.org/wiki/Virginia-class_submarine