General Dynamics plans upgrades to Knifefish unmanned minehunting submarine as Navy eyes full production

May 13, 2021
The Knifefish UUV is based on the Bluefin 21 UUV, which Bluefin Robotics in Quincy, Mass., developed for research and counter-mine operations.

WASHINGTON – Unmanned underwater vehicle (UUV) designers at General Dynamics Corp. are upgrading early developmental versions of the Knifefish minehunting UUV under terms of a $72.8 million contract announced late last week.

Officials of the U.S. Naval Sea Systems Command in Washington are asking the General Dynamics Mission Systems segment in Quincy, Mass., to make improvements to five Knifefish Surface Mine Countermeasure Unmanned Undersea Vehicle (SMCM UUV) systems to operate at deeper depths, in more complex target environments, and with more precise localization than the first versions had.

The contract calls for General Dynamics to retrofit five Knifefish SMCM UUV systems to the Block I configuration and provide engineering support services.

General Dynamics began low-rate initial production (LRIP) of Knifefish Block 0 versions in September 2019. Knifefish is being built in blocks to incorporate new technology as it matures. Planned block upgrades will improve the minehunting UUV's sensors and automated target recognition software to keep pace with advancing mine threats.

Related: Navy asks Raytheon to upgrade AN/AQS-20 mine-hunting system with high-resolution synthetic aperture sonar

For nearly the past two years General Dynamics has been building a small number of Knifefish UUVs for initial operational test and evaluation, and started tooling-up for full production sometime next year. Navy officials plan to buy 30 Knifefish systems -- 24 for the littoral combat ship (LCS) and six for other Navy vessels.

Knifefish is for deployment from the LCS, other suitable surface vessels, or from shore to detect and classify buried, bottom, and volume mines in high-clutter environments. Volume mines are suspended at shallow depths and are designed to break the keels of ships passing over them.

The Knifefish system has two UUVs and support systems, low-frequency broadband sonar, and automated target-recognition software to act as an off-board sensor while the host ship stays safely away from the mine field.

The Knifefish minehunting UUV has a common open-systems architecture that offers modularity to enable the undersea vessel to carry out a wide variety of countermine, surveillance, and reconnaissance missions. Planned upgrades will improve its sensors and automated target-recognition software to keep pace with mine threats, Navy officials say.

Related: General Dynamics eyes full-scale development on unmanned Knifefish minehunting UUV for LCS, other Navy ships

Navy experts supervised testing in 2019 off the coasts of Massachusetts and Florida against a deployed simulated target field. Sailors during testing performed mission planning, launching and recovering the system, monitoring the sorties, and processing data.

The unmanned undersea vehicles were deployed from a support craft in the vessels of opportunity configuration for all test events in order to provide a characterization of the performance of the entire Knifefish system, including the launch and recovery subsystem.

The Knifefish UUV is based on the Bluefin 21 UUV, which Bluefin Robotics in Quincy, Mass., developed for deep-dive research and counter-mine operations. General Dynamics acquired Bluefin Robotics in 2016.

The Bluefin 21, on which Knifefish is based, is 16.2 feet long, 21 inches in diameter, and weighs 1,650 pounds. The unmanned undersea vehicle can operate to depths to 14,763 feet, and can operate for as long as 25 hours between battery recharges.

Related: Navy moves to low-rate initial production of minehunting unmanned surface vessel

The undersea vehicle can store as much as 13.5 kilowatt-hours of energy in nine 1.5-kilowatt-hour batter packs. Powering the Bluefin-21 is a gimbaled ducted thruster, and navigation comes from inertial navigation, remote operation, and Global Positioning System (GPS) satellite navigation.

The UUV has an integrated GPS, radio-frequency, Iridium, and strobe antenna, and communicates with operators via radio frequency links, Iridium satellite communications, and acoustic communications systems.

The Bluefin-21 data capability includes a four-gigabyte flash drive for vehicle data storage. Standard payloads include the EdgeTech 2200-M 120/410 kHz side-scan sonar, EdgeTech DW-216 sub-bottom profiler, and Reson 7125 400 kHz multibeam echosounder.

On this contract General Dynamics will do the work in Quincy and Taunton, Mass.; and in Greensboro, N.C., and should be finished by April 2023. For more information contact General Dynamics Mission Systems online at, or Naval Sea Systems Command at

About the Author

John Keller | Editor-in-Chief

John Keller is the Editor-in-Chief, Military & Aerospace Electronics Magazine--provides extensive coverage and analysis of enabling electronics and optoelectronic technologies in military, space and commercial aviation applications. John has been a member of the Military & Aerospace Electronics staff since 1989 and chief editor since 1995.

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