In tests managed by GD off the coast of Boston, the Knifefish operated in multiple mine test target fields at-sea, which used buried, bottom, and volume style Navy mine-test targets. GD said the vessel successfully verified its ability to detect, classify, and identify potential mines at various depths.

GD said these trials went beyond previous assessments of the Knifefish because this demonstrated end-to-end performance of the vessel in realistic at-sea scenarios. The trials took place over hundreds of hours of at-sea operations and in over 100 simulated missions.

The Knifefish is an untethered and self-propelled medium-class MCM UUV that the Navy intends to deploy on the Littoral Combat Ship (LCS) and other vessels. It is aimed at replacing the dolphins and sea lions the Navy currently uses to detect mines. This would also reduce risk to personnel by operating as an off-board sensor in minefields while the host ship stays a safe distance from the boundary of a minefield, GD said.

GD is the prime contractor for this UUV and based the Knifefish on the company's Bluefin Robotics Bluefin-21 deep-water autonomous undersea vehicle (AUV).

The Navy has previously said it plans to test this UUV aboard an LCS in fiscal year 2017 before starting fielding in fiscal year 2018.

Earlier this year, a Navy official said the Knifefish had a successful series of contractor tests in Dec. 2016, detecting eight mine-representative targets in Narragansett Bay in Rhode Island (Defense Daily, Jan. 10).

The company noted it designed the Knifefish vessel using an open architecture concept that can be efficiently and swiftly modified to accommodate a range of missions in the future.

"The Navy is pleased with the Knifefish performance during the recent contractor trials, as the system demonstrated its ability to reliably find mines in different environments. Knifefish provides the Navy a critical means to find and identify bottom, buried, and volume mines, providing a much-needed capability for the warfighter," Capt. Jonathan Rucker, program manager for the Unmanned Maritime Systems program office (PMS 406), said in a statement.

Carlo Zaffanella, GD vice president and general manager of Maritime and Strategic Systems, said this set of tests demonstrated continued improvement in the Knifefish performance and that the company is looking forward to Sea Acceptance Trials in 2018 "and continued refinement of the Knifefish system."