Rugged Mil-Spec Connectors Strengthen Military System Deployment

By John Koon | September 17, 2019

A tour of the West 2019 conference turns up new mil-spec connectivity products that meet size, weight, and power goals, and deliver peak performance under pressure.

For military and aerospace applications, the consequences of system failures are unthinkable. To accomplish mission-critical tasks, these systems depend on the high-reliability performance of rugged mil-spec connectors and cables. Performing without failure in these punishing environments is not easy. Mil-spec connectivity products must tolerate extreme temperatures, shock, and vibration and ruggedly withstand atomic oxygen corrosion, a range of atmospheric pressures, and various other hazards — including dust, dirt, water, and chemicals — and still be able to reliably deliver speeds of up to 10Gb/s. In some cases, the temperature specification of these products ranges from -150°C to +150°C. Additional must-haves for mil-spec connectivity products include being lightweight and small with EMI/RFI protection and resistance to wear and tear.

Successfully designing high-quality mil-spec connectors requires a thorough understanding of their attributes. Matt McAlonis, engineering fellow at TE Connectivity, said relevant factors include impedance, the relationship between vibration and harmonics, what types of coating materials are more effective at preventing corrosion, and how gold and tin affect connector mating cycles. “When you work with systems that operate in the gigabit range, it is important to understand the characteristics of materials and design, such as how solder volume consistency would impact the impedance and conductivity of a connector,” McAlonis said. Additionally, it is important to pay attention to the failure mode of a design. New designs need to be compared with the old ones to ensure the original problem will not occur again.

Mil-spec connectivity products Glenair Series 180

Glenair’s Series 180-183 mechanical transfer (MT) fiber-optic ferrule connectors and cable sets pack up to 24 fibers in a lightweight ferrule and perform well in extreme heat.

During the West 2019 conference, Glenair demonstrated a range of rugged mil-spec connectivity products designed for use in military and aerospace systems, including the 180-091 MIL-DTL-38999 Series III type Fiber Optic Connection System, which offers a wide selection of sizes and materials. The circular shell size ranges from 0.8 to 1.6 inches and materials include aluminum alloy, stainless steel, composite, and marine bronze. The number of termini connections range from 2 to 37, while the diameter of fiber size choice is from 9/125 micron to 1000 microns in both single and multimode. To ensure these connectors can endure rugged environments, they go through stringent testing processes, including temperature cycling (-65°C to +175°C), temperature life (+150°C for 1,000 hours), thermal shock (-55°C to +150°C for five cycles), and shock testing of 300g peak load.

Mil-spec connectivity products

MT breakout cables come in many different forms, including ribbon.

Glenair’s Series 180-183 is a family of mechanical transfer (MT) fiber optic ferrule connectors and cable sets. The industry-standard MT design packs high-density commercial interconnects with up to 24 fibers in a compact and lightweight ferrule. By packaging these popular commercial MT ferrules in the MIL-DTL-38999 Series III MIL-DTL-5015, reverse-bayonet, and Mighty-Mouse-type connector shells, Glenair has created a rugged MT ferrule mil-spec connector system. Twenty-four fibers can be packaged in one single-size 11 D38999 Series III type connector and four of these can be combined to create a single 96-fiber connector. These MT ferrules are RoHS-compliant, meet the ruggedized MIL-DTL-5015 standard, and can be terminated with ribbon, jacketed ribbon, or round cable. Ideal  applications include high-density commercial aircraft wiring.

Mil-spec connectivity products from Hartmann

Housed in a rugged package, the HARTMAN smart current sensor is pin-configurable to sense five different currents.

To meet size, weight, and power (SWaP) requirements, TE Connectivity takes a different integration approach to mil-spec connectivity products. At the West 2019 event, TE demonstrated its configurable HARTMAN smart current sensors, which combine five products into a single lightweight package for use in the commercial aerospace and military ground vehicle sectors. The smart current sensor is pin-configurable to sense:

  • 200 AMP thermal breaker trip times
  • 300 AMP thermal breaker trip times
  • 400 AMP thermal breaker trip times
  • Reverse load detection/trip
  • Turn-off thermal breaker

The unit outputs 0.5 to 4.5VDC with sensed load from -20A to 600A. Its input voltage ranges from 16 to 32VDC. Weighing just 200 grams (0.44lbs), it also complies with DO-160 EMI and DO-160 specifications.

Mil-spec connectivity products TE AMPLIMITE D-SUB

TE Connectivity’s cadmium-free AMPLIMITE D-Sub connectors are made with stainless steel and employ industry-standard 20 or 22AWG crimp contacts.

Building D-Sub mil-spec connectors with cadmium materials has been the norm for quite some time but now there is a push for the military and aerospace sectors to phase out its use, due to its classification as a cancer-causing material. TE now offers a cadmium-free AMPLIMITE line of D-Sub mil-spec connectors made using stainless steel and industry-standard 20 or 22AWG crimp contacts. These mil-spec connectivity products also comply with RoHS directives and meet the MIL-DTL-24308 requirement of 500 hours of salt spray resistance.

Military and aerospace systems are only as strong as their weakest link. Connectors have serious responsibilities in field operations and a low-quality connector choice could easily result in failure. Look for mil-spec connectivity products that have stood up to rigorous testing, meet stringent industry standards, and are manufactured by companies with extensive experience in the field of rugged product design.

John Koon is the president of Tech Idea Research and has held management roles at several Fortune 500 companies. As a technology editor and writer, he covers aviation, AI, autonomous driving, robotics, automation, medical innovations, wireless technologies including 5G and low-power WAN, Fog Computing (beyond cloud) and edge, IoT, NB-IoT, LoRaWAN, cybersecurity, blockchain, digital twin, m2m, MEMS, and sensors-related software, fiber optics and interconnects, aerospace/defense, manufacturing, semiconductor, power and battery, COTS advancements, and emerging technologies. He has a BS in engineering from California State Polytechnic University, Pomona, and an MBA from San Diego State University. He can be reached at [email protected].

Like this article? Check out our other Connector Basics, Harsh Environment, and 2019 articles and our Military & Aerospace Market Page.

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