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NEWS | Sept. 13, 2022

Acoustic Research Detachment: Carderock’s Hidden Gem for Acoustic Signatures Testing

By Edvin Hernandez, NSWC Carderock Division Public Affairs

Home to the world’s largest unmanned submarine, Naval Surface Warfare Center, Carderock Division’s Acoustic Research Detachment (ARD) in Bayview, Idaho, is the Navy’s hidden gem for acoustic signatures testing. The detachment, which occupies 25 acres next to Farragut State Park and sits on the shore of Lake Pend Oreille, evaluates the acoustic performance of large-scale submarine and surface ship models.

The lake, according to ARD Site Director Seth Lambrecht, is ideal for testing because of its geographical location and quiet waters.

“The rivers and inlets are all on the North side of the lake, so the entire South end of the lake is an almost laboratory static environment that is 1,100 feet deep,” he said. “The flat bottom of the lake and its isothermal condition – 100 feet below the surface – make it ideal for mathematical analysis.”

Lambrecht is responsible for ensuring the safety, security and environmental aspects of the detachment in tangent with achieving Carderock’s mission. He joined the command in 2005, starting at the West Bethesda, Maryland, headquarters, before moving to Idaho where he has worked for the past 12 years.

In 1942, the Pacific Northwest base was used as a World War II training facility, and was eventually transferred into Carderock’s possession in the 1960s.

“Once the Navy realized that Lake Pend Oreille was one of the best locations for acoustic testing around the world, they started bringing different test platforms for evaluation,” Lambrecht said. “Since then, everything has evolved and continued to grow here.”

Testing at ARD requires careful planning and manpower. Take Cutthroat, the Large Scale Vehicle 2 (LSV 2) and world’s largest unmanned submarine, as an example. John Becker, the LSV chief engineer, said it takes about a third of the ARD workforce to prepare, operate and analyze data for a typical LSV 2 underway.

“As the chief engineer, my primary responsibility is to ensure the LSV operates safely and meets Naval

Sea Systems Command (NAVSEA) requirement for the LSV program,” he said. “LSV 2 is a one-third scale Virginia-class submarine model, which is different from its predecessor – LSV 1 – which was a quarter-scale SeaWolf-class submarine model. When it goes out for testing, it is a full day’s work – we start early and end late.”

The detachment uses long-range arrays and the Intermediate Scale Measurement Systems (ISMS) to provide unique acoustic test capabilities, including radiated noise and onboard data collection.

“The testing done here at ARD has contributed to many improvements in submarine systems and features including propulsors, bow area designs, treatments, sonar systems and many others,” Test Operations Manager Steve Finley said. “There are four major ranges here on the lake. The oldest one is a buoyant vehicle range, which consists of haul-down that pulls the model down to the bottom of the lake to take on onboard data. The LSV range is similar to a full-scale submarine range; it has two vertical arrays with the LSV running between them for making radiated noise measurements. The ISMS range is the most complex underwater structure in the world. It consists of 158 hydrophones and 36 projectors – all to take target strength measurements as well as radiated noise measurements and test advance sonar and underwater systems. Finally, the yellow barge, which is in 600 feet of water just 1 mile from our Bayview site is where calibration and smaller model and UUV testing is done.” 

The data acquired from these ranges is important to the greater Navy because it offers critical evaluation and analysis of submarine signatures underwater, target strength testing and attributes to keeping the warfighters safe at sea.

“All of the data that is transferred to West Bethesda from model testing here in Bayview is processed and used to answer questions on full-scale submarine platforms,” Lambrecht said. “We look to improve them and make them more effective for our fleet.”

LSV 2, which is named after the cutthroat trout, follows suit in a local tradition at ARD that names its vessels after local fish species. When a group of students from an elementary school toured the naval base on a field trip, they were given the choice to make the name permanent. The rest, as they say, is history.

“Our Cutthroat model has similar systems that a full-scale submarine would have,” Becker said. “The front part of the vehicle is almost all batteries – there are 1,680 lead acid batteries just for the main motor. We also have a computer system that contains the autonomous software that allows the LSV 2 to operate on the range. The model is used to predict full-scale acoustic performance for submarines.”

Cutthroat is not the only submarine model that is tested at ARD. In August, Carderock employees at the detachment recovered their Pike model, a Columbia-class submarine model, from the ISMS range after testing and craned it in to one of their shops.

“The Pike model, once deployed on the ISMS range is tested underwater for one to eight weeks at a time,” Finley said. “We take nearly continuous data on it through the fiber optic cable and process all range and onboard sensors and transducers. Everything is controlled and recorded via the 14-mile fiber-optic cable in the laboratory, back at the base. Once the testing is completed, the model is pushed back into this Model Engineering Support Facility and configuration changes are made while the data is processed and analyzed, typically by West Bethesda personnel.”

SeaJet is another model that is docked at the facility and, unlike Cutthroat and Pike, is a surface ship model generally representative of USS Zumwalt (DDG 1000). It is a quarter-scale model that supports radar cross section and underwater electromagnetic testing.

There are some challenges to collecting acoustic data at the base, however. The noise produced by public boat traffic, for example, is one way that data can be contaminated, as well as inclement weather. Lambrecht added that the lake is unpopulated for the most part and said testing is sometimes executed at night for the best conditions.

“All of the acoustic testing on Lake Pend Oreille is guided under the Environmental Impact Statement,” he said. “We follow that guidance to avoid any natural damage to the environment and native species that inhabit the lake. Every test that is conducted here goes through extensive planning so we can get the best results.” 

Apart from supporting the Navy, ARD has previously partnered with private industry, academia and U.S. allies for various missions.

“The purpose of this detachment is to bridge the gap between full-scale testing and initial concept design small-scale testing,” Lambrecht said. “Our models are large enough to capture all of the relevant structural features of full-scale testing at a significantly cheaper cost. We validate all of the acoustic properties of full-scale fleet designs and ensure that the Navy meets all of its acoustic requirements.”

Though ARD is on the opposite side of the country from its West Bethesda headquarters, there is no doubting its importance to Carderock and America’s fleet.