TECHNOLOGY AREA(S): Battlespace, Electronics, Sensors

ACQUISITION PROGRAM: PMS 401, Submarine Acoustic Systems Program Office

OBJECTIVE: Develop an effective Conductivity, Temperature, Depth (CTD) sensor for the Ohio Class SSBN, Ohio Class SSGN, and Columbia-class submarines.

DESCRIPTION: The Navy has a need to improve the capabilities of its current CTD sensors to acquire environmental data aboard its deployed submarines. These sensors measure conductivity, temperature and pressure to estimate the speed of sound and seawater salinity and density. It is imperative that the data accurately represent ambient conductivity, temperature, and depth conditions with no latency and with high degree of accuracy. The Navy�s CTD was a form factor replacement for the legacy sound speed sensor and designed to be installed into the sensor chamber on 688(i)-class submarines. This is not an optimal CTD system configuration for SSGN/SSBN, as it causes inadequate flow to be directed at the CTD sensor resulting in an erroneous measurement of sound speed profiles. A CTD specifically designed for use in SSN sea chests is hampering the ability of SSBN/SSGN and eventually Columbia-class submarines to accurately estimate local sound speed and water density. A sensor designed specifically for the Ohio SSBN/SSGN and Columbia submarine classes is required and will allow for the acquisition of more accurate data. As such, while CTD sensors are commercially available for purchase, they are not specifically designed for the mounting arrangement and unique flow requirement of the SSBN/SSGN/Columbia-class submarines as detailed in platform-specific plans.

The new sensor will fit a maximum envelope form factor of an 18-inch by 18-inch by 18-inch cube to minimize the need to modify the current sensor�s sea chest, and will also be designed to ensure adequate flow to the CTD sensing elements. The design of a sensor that is optimized for the SSBN/SSGN/Columbia class sail CTD intake vents is necessary to enable accurate sensing of these important parameters. This will enable an accurate sound velocity profile to be used in sonar tactical aids. It will enable better weapon presets and better ballast control for both manual and automatic ship handling during assents to periscope depth and hovering operations. This both enhances mission performance and helps to reduce broaching and associated vulnerabilities.

Specific requirements include the following:
1) The conductivity sensor must achieve an accuracy after stabilization of less than 28 �S/cm (micro-Siemans/centimeter) RMS error (threshold) or 14 �S/cm (goal).
2) The temperature sensor must achieve an accuracy after stabilization of less than 0.28�C root mean square (RMS) error (threshold) or 0.14�C (goal).
3) The pressure sensor (supporting depth determination) must achieve an accuracy after stabilization of less than 0.3 decibars (i.e., 50 kPa) RMS error (threshold) or 0.2 decibars (i.e., 20 kPa) (goal).
4) All sensors (temperature, conductivity, and pressure) must achieve a stabilized state after any change in ambient conditions in less than 12 seconds (threshold) and 6 seconds (goal). A stabilized state is equivalent to 95% of the steady state level approached with unlimited wait time.
5) The maximum delay in passing sample water from the free stream outside of the hull boundary through a duct (limit IAW ship drawings, 18-inches)onto any sensor head must be 3 seconds (threshold) or 1.5 seconds (goal) when the boat speed through the water is 5 knots or greater.
6) The CTD system must meet Military Standard (MILSTD) 461 electromagnetic noise requirements for conducted and/or radiated emissions.
7) The CTD system must meet MILSTD 901D requirements for shock qualification standards and MIL-STD-810 Environmental Engineering Considerations and Laboratory Tests.

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.

PHASE I: Develop a conceptual design of a CTD optimized for installation in a SSBN/SSGN sea chest. Demonstrate feasibility of the design through testing, modeling, and/or simulation. Show feasibility of deployment on a submarine through demonstration of fit to the form factor as well as demonstration of transmission through cable length that would be required on a submarine in the required timeframe. Develop a Phase II plan. The Phase I Option, if exercised, will include drawings, schematics, and financial plan to build the prototype in Phase II for the proposed system.

PHASE II: Develop and deliver a prototype CTD sensor. Demonstrate that the system will fit into the existing sea chest. Prepare a Phase III development plan to transition the technology to Navy use. Once a prototype is produced, or if a detailed model is produced, complete testing to verify performance criteria has been met.

It is probable that the work under this effort will be classified under Phase II (see Description section for details).

PHASE III DUAL USE APPLICATIONS: Support the Navy in transitioning the CTD sensor to Navy use. Deliver the sensor to Naval Undersea Warfare Center Division Newport (NUWCDIVNPT) for final inspection. Send a representative to accompany NUWCDIVNPT personnel for installation onto a SSBN, SSGN, or Columbia-class submarine. Perform further receipt-testing of the installed sensor to verify the performance requirements were met.

REFERENCES:

1. "Conductivity, Temperature, Depth (CTD) Sensors.� Ocean Instruments, Woods Hole Oceanographic Institution, Woods Holes, MA, 26 January 2018,� http://www.whoi.edu/instruments/viewInstrument.do?id=1003

2. Urich, Robert J. �Principles of Underwater Sound.� Peninsula Publishing, Westport, CT, 1992, https://www.amazon.com/Principles-Underwater-Sound-Robert-Urick/dp/0932146627

KEYWORDS: Conductivity, Temperature, and Depth (CTD); SSBN and SSGN Sensors; Columbia Class Submarine; Speed of Sound; Underwater Acoustics; 688(i)-class Submarines