Here's What You Need to Remember: An adversary observing a missile launch from an American SSGN might mistake it for a nuclear first strike. “These missiles shouldn’t be launched from anything resembling an SSBN,” Robert Farley, a University of Kentucky political scientist, noted on his blog.

The U.S. Navy has confirmed that the Block V version of its Virginia-class attack submarines will be the first vessels in the fleet to carry a new hypersonic missile the service is developing.

Arming the Block V Virginias with a hypersonic missile could help the Navy to fill the gap that the four Ohio-class guided-missile submarines will leave in the service’s overall firepower when the aging boats begin leaving service in the mid-2020s.

There are naysayers, however. Some critics question the Navy’s plan to concentrate so much of its missile capacity in its submarine force. The fleet in 2020 possesses 56 Los Angeles-, Seawolf- and Virginia-class attack submarines and Ohio SSGNs. Under current planning, that number would drop to a low of 41 or 42 boats in 2028.

The Navy’s $207-billion budget request for 2021 cuts billions of dollars from shipbuilding, potentially slowing or even ending the fleet’s attempt to grow from 294 front-line ships to 355. But the budget includes $22 billion for research and development, a billion dollars of which the fleet wants to spend on the so-called “Conventional Prompt Strike” weapon.

CPS is a hypersonic land-attack cruise missile. A vehicle qualifies as “hypersonic” if it’s maneuverable and can travel faster than five times the speed of sound. Such high speed makes a missile more responsive to moving targets and harder for the enemy to intercept compared to slower missiles.

“The CPS program develops warfighting capability to enable precise and timely strike capability in contested environments across surface and sub-surface platforms,” the Navy’s budget documents explain.

The Navy’s CPS missile is a version of a weapon that the fleet is co-developing with the U.S. Army. The U.S. Air Force also was part of the joint effort until early 2020, when it signalled its intention to develop a unique hypersonic missile to arm its bombers and fighters.

CPS builds on the Common Hypersonic Glide Body that the Navy and Army are developing and adds a 35-inch booster. The Navy’s budget documents for 2021 state the service’s intention to arm the Block V Virginias with the new high-speed missile before adding the weapon to surface vessels.

The Navy earlier had considered arming the four Ohio-class guided-missile subs with the hypersonic missile. But those SSGNs, which are conversions of surplus nuclear-ballistic-missile boats, are more than 30 years old. Their reactors will wear out in the mid-2020s, compelling the fleet to decommission them.

Each SSGN packs a whopping 154 cells for Tomahawk cruise missiles and other weapons, making them by far the most powerful vessels in the fleet for land-attack missions. The four converted Ohios together account for 600 of the fleet’s roughly 6,000 Tomahawk launchers.

The Navy anticipated a big dip in fleetwide missile capacity in the late 2020s resulting from the SSGNs’ decommissioning. To help fill the gap, the service developed the new Block V version of the Virginia-class attack submarine, adding a “Virginia Payload Module,” hull extension holding four large-diameter missile tubes, each of which can carry seven Tomahawks or a smaller number of wider missiles.

The VPM modification boosts the missile capacity of the Virginia class from 12 in early boats to 40 in Block V and later versions. The Navy in late 2019 cut a $22-billion contract with submarine-builders Electric Boat and Newport News to build nine Block Vs through 2023. But in a surprise move, the Navy in its 2021 budget asked for just one Block V, down from two in earlier projections.

Besides embedding a new missile capability in a younger class of vessel with a much longer potential service life, adding hypersonic munitions to the Block V Virginias solves another problem. The Ohio-class SSGNs are identical in appearance and acoustic signature to the Navy’s 14 SSBN ballistic-missile boats that carry nuclear-tipped ICBMs.

An adversary observing a missile launch from an American SSGN might mistake it for a nuclear first strike. “These missiles shouldn’t be launched from anything resembling an SSBN,” Robert Farley, a University of Kentucky political scientist, noted on his blog.

But the Virginias might not be the best platform for land-attack, experts recently told Defense News. Submarines are expensive. And they’re getting easier for enemy forces to detect. A robotic surface ship might make a better missile platform, the experts said.

David Axe served as Defense Editor of the National Interest. He is the author of the graphic novels  War Fix, War Is Boring and Machete Squad. This article first appeared last year.

Image: Flickr.