The last decade has seen a steady reduction in the size and weight of almost all kinds of commercial electronic equipment. Many formerly fixed-base items are now portable, or even wearable. That, in turn, has driven the development of innovative interconnect solutions and the introduction of miniature form-factor connectors.
Even the military market—with its stringent environmental requirements, extended development cycles, and product lifetimes measured in decades—has not been immune to this trend. This article will take a look at some of the factors driving military connection systems towards smaller and lighter connectors, while maintaining or increasing performance and accommodating new mission imperatives.
Heavy Soldier Loads Drive Smaller, Lighter Connectors
Infantry soldiers have long been burdened by heavy loads; even the Roman legionnaire is estimated to have been hauling approximately 80 pounds during extended marches. Although the constituent parts have changed dramatically since that time, today’s soldiers still carry an average load of 87 to 127 pounds on extended foot patrols. According to the U.S. Department of Defense, this literal burden has resulted in increased musculoskeletal injuries. Every decrease in equipment weight reduces fatigue and decreases response time. In combat, those savings can mean life or death, so reducing weight without compromising the mission is a priority.
Micro-miniature and nano-miniature connectors are part of the solution. Such miniature connectors are 10 times smaller in volume and 90 percent lighter in weight than traditional military connectors. Many nano-miniature connectors are available with temperature ranges as wide as -200° C to 200 ° C.
Network-Centric Warfare and the Nett Warrior Program
The modern military doctrine of network-centric warfare (NCW) seeks to translate an information advantage, enabled in part by information technology, into a combat advantage through large-scale data sharing and the robust computer networking of all sizes of fighting units. NCW requires connectors that can provide high-bandwidth performance in a durable, rugged design that withstands harsh, high-shock and high-vibration environments.
At the individual soldier level, there’s the Nett-Warrior program (and the earlier Land-Warrior program), which integrates multiple modules and technologies from different manufacturers. The goal is to provide modular equipment solutions that can vary depending on the mission. To minimize weight, all pieces of equipment must still use a common power source (battery), forcing a rethink of connector strategies across multiple vendors.
Figure 2: A broad array of new connector types are needed for today’s networked soldier. (Source: SoldierMod)
The Drive Towards COTS
In an attempt to take advantage of the best commercial equipment, the military increasingly is looking to commercial-off-the-shelf (COTS) technology. In many cases (communications, for example) the pace development in the commercial sector far outpaces that in the military sector, resulting in more powerful capabilities at far lower costs.
For example, after costs skyrocketed to $85,000 per soldier, the Land Warrior system was saved from cancellation in the late 1990s only by replacing military-spec equipment with commercially available technologies, including parts bought off the shelf from Fry’s Electronics.
The current Nett Warrior program, too, makes use of COTS devices; the end-user device is a Samsung Galaxy Note II cell phone. The devices are purchased at commercial prices and the software modified for military use; they communicate via USB with a hip-mounted radio for network connectivity. This use of standard commercial devices leads to a requirement for military-grade connectors for standard commercial interfaces such as USB or Ethernet.
Figure 2: Military Ethernet connector. (Source: Amphenol Socapex)
New UAVs Are Smaller and Lighter, Pose Special Demands
It’s not only soldier-carried equipment that has new size and weight constraints – take UAVs (unmanned aerial vehicles), for example. Forget about the Reaper with its 66-foot wingspan and 3,800-pound payload. These days, the action is at the smaller end with drones that can be carried and launched by a single soldier. The Black Hornet Nano micro AV (MAV), for instance, measures around 4 inches x 1 inch and weighs just over half an ounce; including the batteries!
However, MAVs present connector designers with problems on two fronts. First, since a given battery flight time is proportional to overall weight, connectors need to be as small and light as possible. Given the MAV tendency towards aggressive landings, they must also meet rigorous shock and vibration requirements. Second, in order to carry out their mission, even MAVs must contain a full complement of sophisticated electronics. The Black Hornet Nano comes equipped with a full-motion video camera, GPS and digital data link, and those connectors must also be protected against EMI and likely EMP threats. In full-size UAVs, connectors and cable assemblies can be protected by encasing them in conductive conduit, but an MAV cannot accommodate the added weight. The alternative—metal-braided shields—forces miniature connector designers to offer a variety of backshell configurations so that there is adequate grounding for EMI/EMP protection.
Applicable Military Standards
As one might expect, the U.S. Military has developed sets of standards describing this new generation of connectors.
MIL-DTL-38999
Miniature, high-density, circular connectors using removable crimp or fixed-solder contacts, are capable of operation within a temperature range of -65° C to 200° C.MIL-DTL-83513
Micro-miniature, rectangular electrical connectors, often referred to as a Micro-D form factor; suited to a multitude of systems such as missiles and their guidance systems, aerospace avionics, radars, shoulder-launched weapon systems, advanced soldier technology systems and military GPS.MIL-DTL-32139
Nano-miniature connectors terminated on printed circuit boards or attached to cable assemblies. The connector contacts are densely packed with 0.64 mm (0.025 inch) spacing between contact centers in the same row; intended for interconnections on printed wiring board (PWB), PWB-to-cable, cable-to-panel or cable-to-cable on miniaturized equipment with low-power requirements.
There’s nothing new in the constant trend in electronics towards systems that are smaller, faster and more efficient—and the military market is no different. The drive for smaller and lighter systems is forcing connector designers to develop systems that are smaller and lighter, capable of increased performance, but still as rugged as existing military-style connectors.