Fat Line Towed Array Aft Stabilizer
AREA(S): Battlespace, Electronics, Sensors
PROGRAM: PMS 401, Submarine Acoustic Systems Program Office
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730-774, which controls dual use items. Offerors must disclose any proposed use
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work permit possessed, and the statement of work (SOW) tasks intended for
accomplishment by the FN(s) in accordance with section 3.5 of the Announcement.
Offerors are advised foreign nationals proposed to perform on this topic may be
restricted due to the technical data under US Export Control Laws.
Develop a passive or active control system that stabilizes the aft end of towed
fat line arrays during operational tow conditions.
Fat Line Towed arrays often operate in hydrodynamic conditions where the flow
field is turbulent. Non-uniform flow causes the aft end of the towed array to
experience low-frequency motion (i.e., roll, and lateral and vertical motion).
These high levels of movement negatively affect the performance and reliability
of towed arrays and associated processing by impacting the acoustic performance
of the array, degrading performance of the magnetic heading sensor in the aft
end of the array, and causing additional stress and failures for components and
modules in that area. A stable array is required for accurate understanding of
the location of detected signals and improved reliability of the aft heading
sensor for array shape estimation. In addition to improving system acoustic
performance, an aft stabilization device (stabilizer) should reduce mechanical
stress and associated failures in the aft components and modules in the array.
The reduction in failures for the towed array components will reduce system
lifecycle costs by decreasing the number of repairs required due to failures;
increasing the time between failures; and reducing the costs associated with the
removal and installation of the system. The Navy is looking for an innovative
solution that provides a passive or active control system (stabilizer) for the
aft end of towed fat line arrays that stabilizes the low-frequency motion
during operational tow conditions. This solution should also be compatible with
current fat line array handling and stowage infrastructure.
Commercial towed systems do not operate in the same speed regime or flow field
as military towed arrays and do not have the same constraints on size or
compatibility with existing array handling infrastructure. The designs and
concepts used in the commercial sector are not applicable to this application.
Critical aspects of the technology development for the stabilizer system
include control methods and devices; flow analysis of array state in a
non-uniform (turbulent) flow field; and feedback and control to mitigate
deleterious motion caused by the turbulent flow field. The towed arrays for
which aft stabilization is desired are approximately 300 feet long with a
diameter of approximately 3.5 inches. The representative specific gravity for
developing concepts is 1.025 +0.07/-0.00. The outer surface of fielded fat line
towed arrays is smooth.
Critical performance factors of the technology development for the stabilizer
system include tow stability, compatibility with the fat line stowage tube and
handling, and retention of full system performance, reliability, and
compatibility with the towed array. The stabilizer needs to be designed such that
any failure modes such as loss of lift or drag will not negatively impact the
towed array performance.
The stabilizer system must fit within stowage tube and bell mouth physical
limitations. The bell mouth is a funnel shape with a bend radius of ~ 60 inches.
The stabilizer is deployed from and pulled into a stowage tube with an inside
diameter of approximately 6.0 inches at a rate up to 100 feet per minute. The
material for both the bell mouth and stowage tube is a Copper-Nickel alloy. A
bell mouth at the interface between the tube and ocean environment mitigates
kinking of the array and its tow cable. Deployment of the array itself occurs
by allowing the ambient differential pressures to pull the array from the tube,
and the stabilizer must not interfere with this passive deployment evolution.
To avoid negative impact on reliability, the stabilizer system must survive a
minimum of 100 deployment and retrieval evolutions without damage. The size of
the stabilizer system is limited to a maximum diameter of 3.5 inches and a
length of 4 feet when inactive or retracted. No more than 100 volts and 0.25
amps of system power are available for stabilizer control and activation. The
stabilizer system must be able to operate for 30 days continuously under
typical tow conditions. Typical tow conditions are speeds from 5-20 knots with
most of the time spent at mid-range speeds. The flow input for the stabilizer
will be based on the Turbulent Boundary Layer (TBL) developed by the array
(cylindrical tow) forward of the stabilizer.
To be deemed suitable for use, the stabilizer system cannot generate acoustic
noise or mechanical vibration that negatively impacts the overall system (or
magnetic heading or acoustic sensors) performance. Proposers should identify
the anticipated acoustic noise and vibration levels associated with their
proposed solution. Failure of the stabilizer system should not preclude the
retrieval or deployment of the towed array from the stowage tube. The
stabilizer is required to mate with the towed array modules. The stability and
performance of the device are higher priority than the specific array
The purpose of the stabilizer system is to mitigate low-frequency movement and
oscillations (roll) of the towed array and demonstrate this ability during
testing under actual tow conditions with an instrumented array provided by the
Government. The environmental compatibility of the unit testing will be in
accordance with MIL-STD-810G [Ref 4]. The Government will evaluate the
compatibility of the stabilizer system with current deployment and retrieval
equipment and procedures by using a mock-up of the stowage tube during static
and towed conditions.
The Phase II effort will likely require secure access, and NAVSEA will process
the DD254 to support the contractor for personnel and facility certification
for secure access. The Phase I effort will not require access to classified
information. If need be, data of the same level of complexity as secured data
will be provided to support Phase I work.
Work produced in Phase II may become classified. Note: The prospective
contractor(s) must be U.S. Owned and Operated with no Foreign Influence as
defined by DoD 5220.22-M, National Industrial Security Program Operating
Manual, unless acceptable mitigating procedures can and have been be
implemented and approved by the Defense Security Service (DSS). The selected
contractor and/or subcontractor must be able to acquire and maintain a secret
level facility and Personnel Security Clearances, in order to perform on
advanced phases of this contract as set forth by DSS and NAVSEA in order to
gain access to classified information pertaining to the national defense of the
United States and its allies; this will be an inherent requirement. The
selected company will be required to safeguard classified material IAW DoD
5220.22-M during the advance phases of this contract.
I: Develop a concept for a stabilizer system that must address the critical
performance factors for a fat line towed array as described in the Description,
including the design of any control system required. Demonstrate feasibility by
analysis and modeling of key elements. Develop a Phase II plan. The Phase I
Option, if exercised, will include the initial design specifications and
capabilities description to build a prototype in Phase II.
II: Design, develop, and deliver a prototype stabilizer system. Ensure that the
prototype demonstrates its ability to reduce the array aft end motion based on
the requirements in the Description. Perform the demonstration at a Government-
or company-provided facility.
Conduct the final system validation on a Navy ship that uses towed arrays.
Monitor the performance of the array using the existing array sensors and
compared to baseline measurements. Measure the reduction in array aft end
motion and vibration during system performance testing to quantify the overall
stabilizer performance. Assess the reduction in damage to sensors and modules
in the array during the testing of the stabilizer performance. Prepare a Phase
III development plan to transition the technology for Navy production and
potential commercial use.
It is probable that the work under this effort will be classified under Phase
II (see Description section for details).
III DUAL USE APPLICATIONS: Assist the Navy in transitioning the fully
functional stabilizer system for Navy use. Support installation of the
stabilizer system into a Government-defined fat-line towed array and provide
assistance during laboratory and shipboard test events.
The developed technology is applicable to any towed system where aft end
stability is required. One example would be the stabilization of dual array
systems where the relative position of the two arrays impacts system
performance. The stabilizer design could be re-sized and modified to work with
this application. Towed arrays are used in undersea surveys, such as oil
Lemon, S. G. "Towed-Array History, 1917-2003." IEEE Journal of
Oceanic Engineering, Vol. 29, No. 2, April 2004, pp. 365-373. http://ieeexplore.ieee.org/abstract/document/1315726/
Obligado, Marin and Bourgoin, Mickael. “An experimental investigation of the
equilibrium and stability of long towed cable system.” New Journal of Physics,
Volume 15, April 2013.
iopscience.iop.org/article/10.1088/1367-2630/15/4/043019/pdf, 15 April 2015; http://iopscience.iop.org/article/10.1088/1367-2630/15/4/043019/meta
Bearman, P.W., Huera-Huarte, F.J., and Chaplin, John R. “The Hydrodynamic
Forces Acting on a Long Flexible Circular Cylinder Responding to VIV.”
MIL-STD-810G, Department of Defense Test Method Standard: Environmental
Engineering Considerations and Laboratory Tests, 31 Oct 2008. https://snebulos.mit.edu/projects/reference/MIL-STD/MIL-STD-810G.pdf
Hydrodynamic; Towed Array; Flow Stabilizer; Towed Dynamics Control System; Flow
Analysis; Turbulent Boundary Layer; Fat Line
** TOPIC NOTICE **
These Navy Topics are part of the overall DoD 2019.1 SBIR BAA. The DoD issued its 2019.1 BAA SBIR pre-release on November 28, 2018, which opens to receive proposals on January 8, 2019, and closes February 6, 2019 at 8:00 PM ET.
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