N221-066 TITLE: New Water-Blocking Chemicals/Materials for Zero Longitudinal Seawater Flow through Navy Outboard Cables

OUSD (R&E) MODERNIZATION PRIORITY: General Warfighting Requirements (GWR)

TECHNOLOGY AREA(S): Materials / Processes

OBJECTIVE: Develop new outboard cable water-blocking chemicals/materials system that prevent the longitudinal movement of seawater through a cable after the watertight integrity of the cable jacket or connector is breached (thereby allowing seawater to enter the interior of the cable).

DESCRIPTION: When the watertight integrity of an outboard cable is breached, the navy depends upon a water-blocking compound within the interior of the cable to slow/prevent the movement of seawater down the length of the cable. Seawater moving through the interior of a cable will eventually reach either end where it will come in contact with sensors, power supplies, and other electrical components and connectors. This often results in extensive and costly damage to these crucial pieces of equipment and could trigger system failures that can compromise the ability of Navy ships and submarines to perform their assigned missions.

The objective is to develop new saltwater-blocking materials that will prevent the longitudinal movement of seawater through the interior of a breached/flooded outboard cable both at high (500 - 1000 psi) and low (25 psi) hydrostatic pressure conditions. The governing military specification for outboard cables (MIL-DTL-915G; reference 1) contains two water-blocking requirements: section 4.5.12 (hydrostatic/open end � high pressure) and section 4.5.17 (water tightness - low pressure). Although reference 1 allows some water flow through the interior of cables undergoing these tests, the goal of this SBIR topic is to develop a water-blocking chemical/material system that prevents any saltwater from flowing through the cable segments used in these tests. Commonly used Navy outboard cable jacket materials include polychloroprene, polyurethane, poly (vinyl chloride), and chlorosulfonated polyethylene. The water-blocking chemical/material in a non-compromised/flooded cable must allow individual conductors within the cable to be easily accessed and separated from other conductors/wires.

The chemical composition of the most commonly used water-blocking materials used in outboard cables is unknown to the Navy. The material is soft and rubbery and typically performs acceptably during the MIL-DTG-915G hydrostatic/open end test. We believe it is successful because the high hydrostatic pressure allows the formation of a compression seal with the water-blocking compound. It typically allows some water to pass through the interior of the cable during the MIL-DTG-915G water tightness test (presumably because the much lower hydrostatic pressure is not sufficient to form a pressure seal). For the purposes of this SBIR topic, the Navy will not forbid or restrict the use of any particular materials/chemistries for the new water-blocking material, but materials of low toxicity and environmental impact are preferred over those of high toxicity and environmental impact. New water-blocking materials may utilize non-reversible chemistries as long as the longitudinal flow of saltwater is prevented (proposers may assume the breached cable will be scrapped/never used again upon return of the vessel to port); the goal is to protect the equipment attached to the ends of the cable. The Navy notes that it has tested super water absorbent gels (e.g., sodium polyacrylate) as a possible candidate for a new/improved cable water-blocking material. However, the results were disappointing since the absorption of water by such materials is impeded by the presence of dissolved ions in the water, so this material does not work well with seawater. The Navy will consider modified versions of super water absorbent gels that have been modified to work acceptably (per the MIL-DTL-915G requirements) with seawater. For example, the new water-blocking material could be a polymer system that reacts irreversibly with seawater to form a water-block; however, the material should be designed to react with seawater flooding a cable, but not with water diffusing through the cable jacket. The flexibility/bendability of the affected cable need not be retained once the water blocking reaction is triggered.

Major goals/considerations for this SBIR topic:

The new water-blocking chemical/material MUST:

1. Work with SEAWATER.
2. PREVENT/STOP the longitudinal flow of seawater through a cable at both high (up to 1000 psi) and low (25 psi) hydrostatic pressures.
3. NOT be triggered by (fresh) water diffusing through the cable�s outer jacket.
4. BE COMPATIBLE WITH the outboard cable manufacturing process
5. Have as low an ENVIRONMENTAL and TOXICITY impact as possible

PHASE I: Define and develop a concept for innovative water-blocking materials/chemistries that could be used inside Navy outboard cables to prevent saltwater from flowing longitudinally through such cables. "Simulated cables" (rubber tubes filled with the proposed water-blocking material) may be used to demonstrate proof of concept. During phase I, the emphasis should be on the chemistry of water-blocking material. The proposer will be expected to contact cable manufacturers to verify that the proposed chemistries would be compatible with commonly used cable manufacturing processes. The Phase I Option, if exercised, will include the initial design specifications and capabilities description to build a prototype solution in Phase II.

PHASE II: Develop and deliver a prototype of at least three different types of navy outboard cables of sufficient length to be tested for hydrostatic pressure/open face and water tightness in accordance with a modified version of the MIL-DTF-915G tests that will substitute seawater for freshwater. Both kinds of hydrostatic testing shall be conducted and no passage of seawater through the cables should occur. Refinement of the water-blocking chemistry/material will be conducted, as necessary. The new water-block chemical/material will be tested with the commonly used cable jacket materials noted in the "description" section.

PHASE III DUAL USE APPLICATIONS: Support the Navy in transitioning the technology to Navy use through one or more commercial cable manufacturers to incorporate the new water-blocking material/technology into operational Navy outboard cables used by the sponsoring Navy Program Office. Work with the Navy to obtain approval for Navy use of such cables by the appropriate Navy authority.

Potential employment for this technology in the private sector is good. Outboard submerged cables can be found on civilian ships, submarines, and unmanned undersea vehicles. Additionally, this cable technology has use on submerged civilian marine infrastructure such as seabed power and communication cables.

REFERENCES:

1. MIL-DTL-915G, "Detail Specification: Cable, Electrical, for Shipboard Use, General Specification for," 22 August 2002. (Note: This document has been approved for public release; distribution is unlimited).
2. Worzyk, T, Submarine Power Cables: Design, Installation, Repair and Environmental Aspects, Springer Science and Business Media, 2009, 296 pp.
3. Powers, W. F., "An Overview of Water-Resistant Cable Designs," IEEE Transactions on Industry Applications, 29, 5, 831, (1993), doi: 10.1109/28.245702 https://ieeexplore.ieee.org/document/244196.
4. Ma, X., and Wen, G., "Development History and Synthesis of Superabsorbent Polymers: A Review," J. Plym. Res., 27, 136, (2020), doi: 10.1007/S 10965-20-02097-2 https://link.springer.com/article/10.1007/s10965-020-02097-2.

KEYWORDS: Underwater Cables; Hydrostatic Pressure; Water-blocking; Water-Proofing; Water-Tightness Testing; Super-Absorbent Polymers.