The Navy’s Virginia-class fast attack submarines are slated to serve for the next 50 years, but service leaders are already debating what submarine or system might replace it.

The Navy’s 2014 30-year shipbuilding plan calls for the construction and delivery of Virginia-class submarines through at least 2043, an acquisition strategy which plans for a total of 48 to 50 boats, Adm. David Johnson, Program Executive Officer, Submarines, told Military.com.

Since the expected service life of a Virginia-class submarine is 33 years, the timeline means they will be expected to serve well beyond 2060, Johnson explained.

“We are starting to think about what upgrades do you need to make to the Virginia class to keep it relevant and competitive out into the mid-century. We’re also looking at options and concept studies of what should the new SSN (attack submarine) do,” Johnson said.

Given the importance of payloads to the future, Johnson said Navy developers are making moves today in order to prepare for the payloads of tomorrow.

“I think a couple things are pretty clear, acoustic quieting and non-acoustic quieting – they matter and payload matters. I don’t envision a small ship.”

Alongside early conceptual discussions of what a submarine platform should look like in 2060, Navy leaders have also engineered the Virginia-class attack submarines so they are upgradeable and can accommodate new technologies, such as payloads or electronics, as they become available, Johnson added.

“The Navy looked to the future with the Virginia-class and designed the submarine to be flexible enough to adapt to and address new requirements and technologies,” Johnson added.

Navy engineers are now working on requirements and early designs for a new, 70-foot module for Virginia-class submarines engineered to house an additional 28 Tomahawk missiles. The Virginia Payload Modules, or VPM, are slated to enter production in fiscal year 2019 as part of a Virginia-class Block V contract. While designed primarily to hold Tomahawks, the VPM is being engineered to handle different and potentially emerging payloads as well.

“You want to build inherently flexible platforms that you can plug in and out payloads as the demand and threat environment changes. You build a very flexible host platform,” Johnson said.

With the VPM, Block V Virginia-class submarines will increase the vertical launch missile capability from 12 to 40, Johnson explained. The missile tubes are engineered such that they could accommodate a new payload, new missile or even a large unmanned underwater vehicle. The fiscal year 2014 budget includes $59 million dollars for VPM development, he said.

Virginia-class submarines, engineered to replace the 1980s-era Los Angeles-class attack submarines, are being built in block increments. Blocks I and II, totaling 10 ships, have already been delivered to the Navy. Block III boats are currently under construction. The first Block III boat, the USS North Dakota, was christened this past November and is slated for delivery this coming April.

The fiscal year 2014 budget passed by Congress appropriated $3.8 billion for two Virginia-class submarines to be built in 2015 and $2.3 billion more for advance procurement dollars for two more submarines to be built in 2016 and 2017.

In total, all eight Block III boats are being built under a $14 billion Navy deal with General Dynamics Electric Boat from December 2008. A contract for Block IV construction is currently being finalized and Block V is slated to begin construction in fiscal year 2019. Blocks VI and VII are planned for the mid to late 2020s and early 2030s.

The Navy plans to build two Virginia-class submarines per year for less than $2.5 billion each and build the Ohio Replacement Program submarine, a next-generation nuclear-armed submarine, for less than $5 billion.

Virginia-class submarine developers have also implemented a software and hardware upgrade rotation in order to ensure that the ships keep pace with technological change and incorporate the latest technical designs and developments, Johnson said.

A program known as Submarine Warfare Federated Tactical Systems model, or SWFTS, involves upgrading all attack submarines (SSNs) and guided missile submarines (SSGNs) sonar, combat system, and imagining systems once every four to six years, Navy officials said. This upgrade utilizes commercial hardware, called technology insertions which are delivered on even years, and open architecture software upgrades every odd year.

“We do an upgrade of the ship. That way we stay ahead on capability because the threat keeps evolving. We’re able to incorporate new sensors like a new towed array,” Johnson explained.

This approach, which involves examining on-board electronics, sensors, combat control systems and imaging, to ensure the submarine avoids obsolescence and remains effective, he said.

This upgrade approach will also be applied to the Navy’s guided missile submarines, or SSGNs, as well as its next-to-be-built nuclear-armed Ohio Replacement ballistic missile submarines, or SSBNs.

The Virginia-class boats will serve alongside the the Ohio Replacement ballistic missile submarines slated to enter service in 2031. Once the Ohio Replacement begins construction, there are several years wherein one of each, one Virginia-class submarine and one ORP, are slated for production.

“We’re going to try to contractually tie those two programs together so that we can use the volume benefit of a multi-year procurement,” Johnson said.