By Kelley Stirling
NSWC Carderock Division
December 11, 2018 – Most people tire of their long commutes to work. Driving in a car in stop-and-go traffic for an hour can get old, but it’s something that most people just get used to.
In Ketchikan, Alaska, the commute to the Navy’s Southeast Alaska Acoustic Measurement Facility (SEAFAC) is a little different; a 20-minute car ride, followed by a 10-minute boat ride to Back Island is what a person has to get used to.
“Rather than planes, trains and automobiles, it’s planes, boats and cars,” said Bill Fagan, head of the Trial Directors, Facilities and Mission Readiness Branch. Fagan himself works out of Naval Surface Warfare Center, Carderock Division’s Bangor, Washington, site, which is responsible for the operation of SEAFAC. “It’s fairly quick, fairly efficient, but a little different than your typical commute; and needless to say, there is not much oncoming traffic.”
Set at the edge of Behm Canal, the little bit of rocky beach SEAFAC sits on is a 15-acre parcel of a publicly accessible island. Naval Surface Warfare Center, Carderock Division leases the land from the U.S. Forest Service for the facility’s operations. The rest of the 100-acre Back Island is home to a forest, offering an ideal location for boaters to stop and go for a hike, or Boy Scouts to go camping.
But the bread and butter of SEAFAC lies under the water a few miles away, right in the middle of Behm Canal, with two sites that service the U.S. Navy’s Pacific Fleet of submarines. At the static site, suspension barges lower a submarine on cables and position it between measurement arrays to evaluate acoustic signatures of individual machinery components. The underway measurement site provides the opportunity to collect acoustic signatures for a variety of speeds and operating conditions as the submarine transits back and forth between the dual bottom-mounted acoustic arrays.
Fagan said every Pacific Fleet submarine comes to SEAFAC about once every four years to get its acoustic health checked, which means they do about 12-15 acoustic trials each year, each taking, on average, about a week of testing.
“The acoustic check on a submarine is an opportunity to go in and check the submarine’s acoustic signature, how much noise it’s putting in the water, all the way from where it’s just going 5 knots through flank bell (a ship’s maximum speed),” Fagan said. “And the static site is a place we can do unique testing on a submarine, where we can have complete control of it and be able to move it to just about any depth we want, to any position we want, any aspect we want, and be able to do testing very rapidly.”
Jennifer Kelso, SEAFAC site manager who falls under Fagan’s branch, said while the primary mission of SEAFAC is to conduct submarine acoustic trials, they can occasionally accommodate other customers, such as hosting a rescue exercise, or even measuring acoustics of cruise ships.
“To have a stable environment, a controlled environment, where we can work with the assets gives us really unique capabilities within the Navy and here in southeast Alaska,” said Kelso, who has been the site manager at SEAFAC for two years. But ultimately, she said it’s all about the submarines.
In 2017, SEAFAC underwent a very complex array replacement that included the recovery and reinstallation of both arrays and associated bottom-mounted anodes of the static site. Kelso gives credit to the contractors who work at SEAFAC for the hard work during this seven-week period. She said they have been instrumental in making so many of the evolutions safe, efficient and effective, whether it be site maintenance or a submarine trial.
“Our number-one priority in all these operations is always personnel safety, as well as environmental safety and then, of course, we are out here to collect good, quality data,” Kelso said. “But that’s only after we come through our operational risk management and agree collectively as a team that we have a safe plan, something that’s achievable with the resources available to us.”
Prior to coming to SEAFAC, Kelso was a test director for large-scale acoustic testing in Carderock’s Propulsor Development Group in West Bethesda, Maryland, just outside of Washington, D.C. She spent a lot of time in Bayview, Idaho, doing tests at Carderock’s Acoustic Research Det., where she developed a love for the outdoors that also keeps her busy and happy in isolated Ketchikan.
Behm Canal is a channel that separates Revillagigedo Island, where Ketchikan sits, from mainland Alaska’s Cleveland Peninsula. The area is well-known for its salmon fishing, hunting and hiking, as well as the average 200 inches of rain it gets each year. Ketchikan itself is situated next to the Tongass National Forest. It is also a main hub for Alaskan cruise ships.
Fagan came to work for Carderock just a couple of years before SEAFAC was established in 1991. He said Carr Inlet Acoustic Range off Fox Island, Washington, became overcrowded and signature testing became difficult with the added noise nearby. Behm Canal’s protected waters are deep and quiet, so it was the ideal spot to do unobstructed signature testing and get good, quality data, Fagan said.
SEAFAC uses a high-gain measurement system with twisted, bi-cone arrays to focus acoustic energy on a ship, allowing the engineers to view the acoustic field at specified frequencies. The underway testing generally lasts for two days; the submarine can perform about two runs per hour, and it allows them to quantify its acoustic signature as the ship moves between the arrays.
Communication between the boat and the operations center are limited during underway testing, unlike the testing at the static site. There, because the submarine is connected by cable and is stationary, the trial directors can also connect communication lines, greatly improving both voice and data communications between the laboratory and the analysts aboard the submarine.
Typically, in addition to Kelso, who is a government employee, there are about 12 contractors who work at SEAFAC supporting the mission on a daily basis. During a trial, an additional 19 engineers, analysts and trial directors come to SEAFAC, with 10 of them generally riding aboard the submarine throughout the test.
“SEAFAC is invaluable to the Navy,” Fagan said. “Every submarine comes here, gets its acoustic health done, it’s checked up, it’s corrected if necessary. And when it goes out to sea, the Sailors aboard know that its acoustic posture is absolutely the best in the world, checked by the best in the world and ready to execute its mission in support of our nation.”