TECHNOLOGY AREA(S): Battlespace, Electronics, Sensors

ACQUISITION PROGRAM: PMS 401, Submarine Acoustic Systems Program Office.

OBJECTIVE: Develop an innovative low-cost miniature electrical connector for towed arrays that has high-density connections and can withstand high-pressure marine environments.

DESCRIPTION: Currently for its towed arrays, the Navy uses high-density miniature electrical connectors that contain 7-12 pins and meet the harsh environmental requirements inherent in the use of towed arrays and other marine sensors. Existing Navy miniature electrical connectors do not provide effective electrical and mechanical isolation between individual pins over the lifecycle (~5 years) and range of conditions experienced by towed arrays during Navy operations. While these connectors provide adequate isolation as new assemblies, their effectiveness quickly deteriorates due to the environmental, chemical, and mechanical forces experienced by the connectors during their lives. Additionally, these connectors do not provide sufficient protection against electrical contact fretting caused by the relative motion of the mated connectors and insufficient plating (i.e., thickness, material selection or both). The current connectors, while relatively inexpensive to procure (~$100 per pair), are expensive to install due to the density of connections and means afforded to affix wires to each connector. Combined, these shortcomings lead to lower system reliability and availability, which results in significant costs to the Navy both in terms of forcing Navy platforms to leave their missions to replace failed towed arrays as well as the costs associated with troubleshooting, repairing and maintenance, and shipping costs for the failed array. Currently available commercial technologies fail to meet the Navy’s needs on one or more of these factors (i.e., size, cost, environmental ratings).

The Navy is seeking an innovative connector that provides a solution to the problems of (1) degradation of mechanical isolation between pins, (2) contact fretting from motion and insufficient plating, (3) wire density, and (4) expensive methods of connecting wires in the connectors. The solution will reduce total ownership cost through low up-front costs (lower than $100 per pair); low assembly, repair, and maintenance costs; and improved reliability. The solution will provide improved electrical isolation (greater than 1 MOhm at 500V) between individual pins (even in the event of a failed pressure seal); improved mechanical sealing (no leakage at 2500 psi) against pressure (e.g., hermetic seal); improved resistance to fretting via better plating, better prevention of relative motion, or both; and reduced cost of manufacturing processes by at least 25%. Cost reduction will result from improved fixtures, tooling or procedures that lower the time, skill or costs to assemble the current connector. Separate fixtures or tools that allow for improved connector manufacturing are acceptable solutions to the issues of ease-of-use and affixing wires during array assembly/repair.

While individual single conductor pins are acceptable, it is desirable to have at least one or more pins that maintain coaxial conductors through the connector with a characteristic impedance of 50+/-2 Ohms. If such a coaxial pin can be achieved, it would be counted as 2 conductors (2 pins) for the total count in the connector. For example, while 7-12 coaxial pins are not desired or required, a 1 coaxial and 5 single pins solution would be superior to the currently available solution. The current Navy miniature electrical connector only offers single conductor pins. Fitting a coaxial pin in this form factor, that is also affordable to manufacture, will require innovative solutions not currently available in the commercial or military market. This is a goal, not a threshold requirement.

The proposed solution must meet at least the following set of conditions: (1) The connector will be exposed to vibrations up to those described in MIL-STD-167-1A (with requirements extended up to 50Hz) and MIL-STD-810G. (2) The connector will be exposed to temperatures of -40.0C up to 65.0C, and must survive without any damage or performance degradation; however, it is only expected to properly operate over the range of -2.0C to 50.0C. (3) The connector will be exposed to hydrostatic pressures up to 1200 psi, and must survive without damage or allowing fluid into the interface between the connected halves.

The connector is housed in the vicinity of other wires as well as components that are vulnerable to damage due to abrasion and cutting. As such the proposed connector must not have any sharp edges on the mated body (no features smaller than 0.005”). Due to the limitations of available space in current Navy towed arrays, the connector must fit within a maximum diameter of 0.635 inches and not exceed 1.25 inches long when mated. Note that the proposed connector need not have a circular cross-section as long as all other requirements are met. The mated connector will be exposed to bending loads of 10 pounds when simply supported (with 5 pounds applied at each end). The connector must not suffer any damage or degradation due to repeated (up to 10,000 cycles) bending loads.

The wires will attach to the connector with solder cups that will support up to 20-gage wire. The connector must allow for the use of potting, such as urethane, to seal the back end of the wires as they enter the connector.

The proposed connector must have both male and female connector types that provide a feature to prevent misalignment when mating. Each half (male and female) of the un-mated connector must provide an external indication of the alignment feature such that the connector can be visually aligned by an operator prior to attempting to mate the halves.

The pins must be capable of handling 500V at a maximum current of 3.0 amps (goal). If desired, a separate connector design could be proposed with few pins (minimum 3) to handle high voltage and current. In that case, the 7-12 pin connector would be required to handle 200V and 2.0 amps (threshold). The insulation resistance between any two pins and between the pins and case must be a minimum of 1.0 giga-ohms when measured with a megohmmeter at 500V.

Critical design aspects of the STTR effort are: (1) development of an innovative method to seal the mating pins against external pressures, (2) development of a low-cost manufacturing method (at least 25% improvement), and (3) minimization of the relative motion of the mated pieces during towed array operations. The connector must be easy to use, have solder-ability, meet Navy environmental performance standards described earlier in this description and electrical properties. The environmental compatibility test of the unit will be in accordance with MIL-STD-810G [Ref 4] and MIL-STD-167A [Ref 5]. The Government will assess the electrical properties of the connectors using standard processes (where available) or will develop test procedures with the company where standard processes are not available. The Government will assess the suitability of the connector prototype using the criteria described in the previous paragraphs. The technology will provide innovative solutions to the issues present in the current Navy connector (e.g., electrical isolation, procurement cost, manufacturing cost, mechanical sealing, fretting), while also meeting the environmental and electrical requirements of Navy towed arrays.

PHASE I: Develop a concept for a low-cost, high-density, harsh environment, high-pressure miniature electrical connector. Address the critical performance factors, laid out in the Description, related to electrical isolation, procurement cost, manufacturing cost, mechanical sealing, and fretting. Demonstrate feasibility through analysis and modeling of the key elements (e.g., mechanical packaging model, current carrying capacity calculations, finite element analysis, manufacturing cost model). 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.

PHASE II: Deliver a prototype for testing. Demonstrate its ability to meet the requirements described in the Description. Deliver test results to the Government, which the Government will verify by conducting independent functionality and environmental testing of the connector. Prepare a Phase III development plan to transition the technology for Navy production and potential commercial use.

PHASE III DUAL USE APPLICATIONS: Assist the Government in transitioning the final connector design to allow for Navy acquisition. Support installation of the connectors into a Government prototype towed array, which will be subjected to standard array performance and reliability testing to verify the suitability of the connector for towed array applications. After successful verification, produce connectors for insertion into prototype and future production towed array systems such as TB-29X.

This connector would prove useful in oceanographic research vehicles (manned, unmanned or remotely operated), downhole oil drilling, oil and gas exploration, harsh environment industries (e.g., chemical manufacturing), and oil/gas refineries.

REFERENCES:

1. Lemon, S. G. "Towed-Array History, 1917-2003." IEEE Journal of Oceanic Engineering, Vol. 29, No. 2, April 2004, pages 365-373. http://ieeexplore.ieee.org/abstract/document/1315726/

2. Antler, Morton. “Contact Fretting of Electronic Connectors.” Special Issue of Electromechanical Devices and Their Materials, Vol. E82-C, No.1, January 1999. http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.29.8048&rep=rep1&type=pdf

3. Barnes, Howard E. and Gennari, Jervis J. “A Review of Pressure-Tolerant Electronics (PTE).” Naval Research Lab, Washington DC, June 1976. http://www.dtic.mil/dtic/tr/fulltext/u2/a027967.pdf

4. MIL-STD-810G, Department of Defense Test Method Standard: Environmental Engineering Considerations and Laboratory Tests. http://everyspec.com/MIL-STD/MIL-STD-0800-0899/MIL-STD-810G_12306/

5. MIL-STD-167-1A, Department of Defense Test Method Standard: Mechanical Vibrations of Shipboard Equipment. http://everyspec.com/MIL-STD/MIL-STD-0100-0299/MIL-STD-167-1A_22418/

KEYWORDS: High Density; Low Cost Electrical Connector; Towed Array; Miniature Electrical Connector; Coaxial Conductors; Electrical Contact Fretting; Degradation of Mechanical Isolation Between Pins