Volume 6, Issue 1 - Naval Sea Systems Command - The US Navy

SEAFRAME
28
By
William
Palmer
Core equities
Saving At-Sea Acoustic Trial Costs
Through Computer-Based Analysis
Recently, researchers at the Naval
Surface Warfare Center, Carderock Division,
were tasked to measure the acoustic
signature of USS Florida (SSGN 728), a
former Ohio-Class submarine which had
been converted to the SSGN submarine class–a class
capable of carrying payloads to support special warfare
operations. Initially, the plan was to measure the boat’s
signature with an outer appendage, called a Dry Deck
Shelter (DDS), attached, and also without the DDS,
for comparison purposes. Due to changing schedules
and demands on the boat’s operating schedule, only
one trial, with the DDS attached, could be executed.
But the researchers came up with a way to measure the
submarine’s “bare-hull” configuration without putting the
boat through a second trial.
The method, called signature decomposition
analysis, was created from a process called beamforming,
which enables trial personnel to pinpoint a noise source.
The Florida’s trial was done in FY 07 and lasted for five
days, during which the sub’s signature was measured.
But, instead of putting the boat through a second
trial, members of Carderock Division’s Performance
Assessment, Modeling and Simulation, and Special
Projects branch adapted the beamforming procedures to
SIGNATURE
DECOMPOSITION
ANALYSIS
predict the Florida’s bare-hull signature. Since the rest
of the Ohio-Class fleet operates bare-hulled, there was
plenty of prior trial data to corroborate the prediction.
And the results were accurate, so accurate that the
researchers presented their findings to program sponsors
at NAVSEA’s SSGN program office, which concurred
with the prediction, permitting the modeled signature to
stand as a valid representation of the Florida’s signature.
As a result, about $350K was saved in trial
expenses. These savings were realized across a broad
range of concerns, such as eliminating logistical,
hardware and operational risks associated with
conducting such a trial; 5 to 6 days of ship time spent
conducting the trial; and the cost associated with
installing and removing a DDS. Because of their success
in closely modeling the bare-hull signature, and because
the model closely agreed with prior Ohio-Class data, the
Carderock personnel have won the support of the Ohio
Replacement Program. “This was one of the first of these
types of analyses,” says Steve Jackson, a mechanical
engineer, acoustic trials program manager, and liaison
between the NAVSEA program office and Carderock
Division. “It was a first on the SSGN/SSBN class. It’s
SIGNATURE DECOMPOSITION (Continued on page 30)