If the next generation of U.S. subs has quieter propellers or includes unmanned craft, those subs will be the grandchildren of the $64 million SEAWOLF (SSN-21) scale model docked here at Sandpoint, Idaho.
Long after the first SEA WOLF class attack submarine is launched, the self-propelled, computer-controlled model here will continue to be useful, says the Admiral in charge of the SEA WOLF program, Rear Admiral Milfard Firebaugh. “I envision that this vehicle will be used to test propellers for many generations of submarines to come.” he said in an interview last summer. Trained as a naval architect, Firebaugh is overseeing the design and construction of the Navy’s first new class of attack submarines in 18 years.
Firebaugh was in Bayview last June to review progress on the testing of quieter propellers, a major component of the work at the David Taylor Naval Ship Research Center’s acoustic research detachment in Bayview, which is near the northern tip of the Idaho Panhandle.
Here at the foot of 40-mile long and 1,100-foot-deep Lake Pend Oreille, the Navy has tested submarine models and propellers since 1942.
Because quiet running is a major goal of submarine warfare, underwater noise researchers here were among the first people to see what the SEAWOLF class subs will look like.
“We kind of had the first look at it because we had the first models,” said George Guedel, the manager of the acoustic research station at Bayview.
In addition to running the working model through an underwater forest of hydrophones and other listening devices, the Navy has buoyancy-propelled models used to test the noise generated by a hull as it travels through the water.
For those tests, researchers use a· non-self-propelled model nick-named “Kamloops.” The model is hooked to a cable, pulled to the bottom of the lake and then released. Researchers train their sonar on it as it rises.
“There are two areas of development.” said Guedel, — “one is to reduce the noise the sub makes as it moves through the water and the second is to reduce the noise which the sub radiates which can be detected.”
The first is the bow area noise the sub makes as it pushes through the water which interferes with its own sonar. The second is noise from people and machinery inside the sub.
Most test runs occur at night, when the lake’s waters are quietest. The sensors listening to the sub would be overwhelmed by a small outboard motor on the lake five miles away, rain or the water, or waves whipped up by wind.
The use of the self-propelled model marks a radical change in Navy propeller design testing and in the type of research at Bayview.
In the past, new propeller designs were tested by manufacturing full-sized prototypes, which had to be placed on full-sized submarines and tested in the ocean, where background noise can overwhelm sensitive listening devices.
The prototypes were expensive to make and the testing work took working subs out of service for lengthy periods of time.
So, when the SEA WOLF program got under way, the Navy decided to try testing propellers a new way: quarter scale on a scaled-down model in Idaho’s Lake Pend Oreille.
Built in San Antonio by Sperry Corp., the self-propelled model is nick-named “Kokanee” after a local land-locked salmon. It was delivered to the research base by rail and launched from a special launching track built in the backyard of a local sawmill.
Standing in a dry dock at the bow of the 88-foot-long model, Firebaugh said the battery-powered, computerized sub has already shaved years off the design of a quieter propeller.
Despite whistleblowers’ claims that the model has never worked properly, Firebaugh said it was pressed into service more quickly than he expected and is now working well.
Captain Davis, who is overseeing the acoustic testing program said the Navy has been able to test five different propeller types in six months with the “Kokanee.”
Contrast that with prior propeller testing. When the propeller was designed for the now-aging LOS ANGELES class subs, it took 10 years to test it, Davis said.
In the process of building a sophisticated propeller tester, the Navy has developed one of the largest and most responsive underwater vehicles around. “As a hydrodynamic test vehicle, this is more sophisticated than anything the Navy labs employ,” said Firebaugh.
The computer navigation and operation equipment may have some interesting uses in the future, the admiral said, though he declined to specify whether the Navy is working on an underwater “drone” similar to the Israeli Army’s remotecontrolled air reconnaissance drones. “It is certainly an interesting technology. The Navy is interested in the technology of autonomous underwater vehicles.”
As the SEA WOLF project has moved forward, the base at Bayview has grown. In 1986, the base employed about 20 people. Now there are about 35 government employees and 75 federal contractor employees at the base.
In the fall of 1986, the Navy floated a $3 million barge onto the lake to house research equipment. Two stories tall and 190 feet long by 60 feet, it was custom built by the Dix Corp. of Spokane to house the SEA WOLF model. And last spring, the Navy added a 140-by-7-foot barge at Bayview to hold a $1 million workshop. The base is also, at times, used by private firms doing government contracts and by NATO scientists, particularly the British.
Dean S. Miller