A program in development by the Office of Naval Research (ONR) is rapidly moving forward into the fleet to provide much deeper magazine depth for torpedoes on Virginia-class SSNs. The effort is testing and fielding multi-packed 6.75-inch Mark 58 Compact Rapid Attack Weapon (CRAW) torpedoes or 3-inch UAVs in a single 21-inch torpedo tube.
Known as the Multi-Vehicle Torpedo Tube Defense System (MVTTDS) to ONR, the Revolver Multi-Payload (Revolver MP) program is designed to provide Virginia-class SSNs with additional magazine depth, responding to an urgent operational need laid out by U.S. Indo Pacific Command and U.S. Strategic Command. Revolver MP will deliver the capability to salvo a dozen or more torpedoes against submarines or surface ships.
Revolver has its roots in ONR’s Full Spectrum Undersea Warfare (FSUSW) program, which seeks to rapidly develop and deploy new technology for maritime warfare. Efforts to develop the Revolver and Reloader system dates back several years.
“Revolver is a launcher integration kit that is required to integrate the MK 58 [CRAW] torpedo into the [Virginia-class] submarine Torpedo Tubes. The Revolver system is not permanently installed onto the submarine. Instead it is loaded onto the submarine in the same manner as any payload that is stowed in the torpedo room.”
U.S. Navy FY2026 Budget Documentation
The U.S. Navy tested a Revolver MP prototype in 2024, including reload methods for the multi-packed Mk 58 CRAW torpedoes. In FY2025, it is slated to deploy a Revolver and Reloader system at sea onboard a Virginia-class submarine while simultaneously innovating beyond the current design to improve capacity for future payload objectives. In 2026, Revolver-MP will be tested with 3-inch diameter UAVs and unspecified diameter decoys.
The U.S. Navy also expects to award a design contract as a program of record, filed under “PMS-415 Revolver [Program Of Record]” this year.
Part of that POR involves the development of Revolver and Reloader GEN 2, a next generation increment of the Revolver MP and attached Reloader that will fit new payloads, including larger diameter UAVs and UUVs.
The U.S. Navy’s new workhorse torpedo: Mark 58 Compact Rapid Attack Weapon (CRAW)
The Mk 58 CRAW torpedo provides anti-submarine warfare and anti-torpedo capability to the U.S. Navy’s Virginia-class SSN fleet, leveraging lessons from the Anti-Torpedo Torpedo Defense System (ATTDS) to enable a small diameter, compact weapon with long-range lethal effects. ONR has also experimented with small diameter torpedoes, and CRAW also builds off their research.
CRAW is not limited to the Virginia-class 21-inch torpedo tubes either. Seapower Magazine reported on the CRAW’s initial use from SSN countermeasure tubes in 2023, and the U.S. Navy has laid out requirements to enable launch via vertical launch cells.
Penn State University and Raytheon are working on CRAW’s Technology Insertion 1 and 2 respectively: two different variants of the CRAW that aim to achieve different goals in the fleet.
TI-1, led by the Penn State University Applied Research Laboratory (PSU-ARL, aims to rapidly field small-diameter, anti-submarine torpedoes to the fleet to allow for early operational capability (EOC) within two years, demonstrating the system in an operationally relevant environment by FY2026.
“CRAW TI-1 effort acquisition strategy is to fund Penn State University Applied Research Laboratory (PSU-ARL) to complete modification of the existing very-lightweight torpedo design leveraged from the ATTDS program. The CRAW TI-1 effort is being executed as a Middle Tier of Acquisition (MTA) effort and will rapidly develop fieldable prototypes to demonstrate the new very-lightweight torpedo ASW capabilities in an operational environment.”
U.S. Navy FY2026 Budget Documentation
TI-1 is also driving development of the Revolver MP and Reloader, as well as capabilities to launch torpedoes from vertical launch cells equipped on Virginia-class attack submarines. CRAW torpedoes developed under TI-1 will remain in the fleet as a residual operational capability, and TI-2 will become the main torpedo of choice in the CRAW family.
TI-2, Raytheon-led, will improve on TI-1 to improve mass production potential while adding additional capabilities to the weapon, like counter-torpedo capability for both submarines and surface ships.
“The TI-2 effort will update the TI-1 baseline to address obsolescence and improve producibility and supportability so that the CRAW capability can be fielded broadly across the submarine force.”
U.S. Navy FY2026 Budget Documentation
Deliveries of initial TI-2 CRAW torpedoes is expected to begin in FY2026, with initial capability in counter-torpedo and anti-submarine warfare for development testing (DT).
“The TI-2 program is being phased with the TI-1 effort so that the TI-2 program can fully leverage the TI-1 prototypes as proof of design hardware. This will reduce overall cost of the TI-2 program as the TI-2 program will move immediately into development of proof of manufacturing prototypes to support Development Testing that will begin in FY26.”
U.S. Navy FY2026 Budget Documentation
The Mk 58 CRAW torpedo is slated to become a workhorse of the U.S. Navy by 2030, in a move that will change how submarines and surface combatants can engage and defend against a variety of high-end and low-end targets. The Mk 58 offers magazine depth in the dozens for low-cost, high-density, large-salvo missions against large and small surface ships—something INDOPACOM sees as favorable to engage hostile amphibious forces in constrained, littoral areas of the Pacific.
Speaking to Naval News, H. I. Sutton, an experienced undersea warfare analyst and regular Naval News contributor, explained “one challenge that nuclear powered attack submarines have, which was first realized during the Cold War, was that the submarines are so good that they’ll run out of torpedoes before they are themselves sunk. Thus torpedo room capacity aboard top-tier Russian and British boats increased from around 20 rounds to 40. The U.S. Navy however trod a different path, keeping the torpedo room smaller but adding vertical tubes for missiles instead. These vertical systems cannot practically launch torpedoes however. This move now finds a way to increase torpedo room capacity.”
Sutton explained that smaller, and lower cost, torpedoes are a growing area in naval planning: “The realization of these projects, particularly for carriage aboard submarines, will move slowly however. CRAW will ultimately provide submarines with a lower cost way to deal with lower-value targets for which a heavyweight torpedo is over-kill or not efficient.”
“CRAW is a highly capable, yet also rather specialised, weapon. Its requirements are so broad and exacting that the final product is quite exquisite. It will be interesting whether other navies follow the American path, or instead focus on lowering the unit cost of secondary smaller torpedoes for submarines,” Sutton concluded.
