A new generation of more powerful unmanned aerial vehicles carry a payload that includes sensors, cameras, processors, and other electronics. Small, lightweight connectors help make their missions possible.
Small unmanned aerial vehicles (UAVs) for military use are getting even smaller and more powerful as trends toward miniaturization in modern military equipment extends to the skies. Like larger conventional drones, military UAVs can be controlled remotely, but since they are far less visible, these little aircraft are helping ground troops cover more territory while also increasing their safety.
Some UAVs, also known as small, unmanned aircraft systems (sUAS), can be hand-launched, like the combat-proven FLIR Black Hornet, the world’s smallest UAV used for surveillance and reconnaissance. In May 2020, the U.S. Army awarded FLIR an additional contract to supply Black Hornet nano-UAVs to platoons and small units as part of the U.S. Army’s Soldier Borne Sensor (SBS) program. The pocket-sized Black Hornet is nearly silent, weighs only 33g, and transmits live video and still HD images, providing the same situational awareness capabilities as larger UAVs.
The U.S. Defense Advanced Research Projects Agency (DARPA) is sponsoring the development of even tinier UAVs: devices about the size of insects. Its Short-Range Independent Microrobotic Platform (SHRIMP) program is developing millimeter-to-centimeter-scale robotics technology for use in disaster relief and for inspecting hazardous environments.
Most military UAVs that fall into the small category are somewhat larger, hand-launched systems, such as AeroVironment’s Raven, or tube-launched models such as Raytheon’s Coyote. These measure just a little larger than a football. The Army is also developing the forward-launched ALTIUS 600, a military UAV that can be launched through a tube from a helicopter in flight or a moving ground vehicle. In a March 2020 demonstration, the ALTIUS 600 was launched at a tactically relevant altitude in forward flight. It can be either flown manually with a handheld remote or programmed by a ground control station to follow a series of waypoints, giving ground troops critical real-time intelligence for situational awareness.
Payloads Increase, Connectors Stay Small
To provide increased surveillance and reconnaissance capabilities, military UAVs depend on payloads that include multiple sensors and cameras for multiple frequencies, such as thermal, infrared, and visible light. Payloads also usually include sophisticated embedded computing and storage devices. Keeping UAV weights down to increase flight time can be a challenge with these larger payloads. That’s also true for connector size and weight.
“The demand for higher-definition imaging, increases in payload, and the need for various types of sensing and detection are being put on UAVs,” said Mark Favale, director of supplier development for high-reliable connectors for distributor Avnet. In turn, these demands are also creating more of a challenge for connector design. Consequently, size, weight, and power (SWaP) and higher transmission speeds are becoming even more vital. “Interconnect companies continue to push the envelope of copper and utilize new contact configurations and materials to meet these requirements,” he said.
Designers are challenged with the problem of how to increase capabilities and electronics on military UAVs, while still maintaining the small device size and necessary operating time or range, said Favale. The space remaining for electronics and interconnects is shrinking, so the challenge becomes maintaining or even increasing connector capabilities and performance within the same or a smaller package. As the needs of UAVs and their applications expand, the demands and requirements placed on the entire interconnect system are changing and evolving, said Favale. This is intensifying the need for both SWaP-optimized designs with high-speed data rates.
Higher Density, Higher Speed, and Quick Disconnects
Connectors for military UAV applications must meet stringent environmental, electrical, mechanical, shock, and vibration specifications in order to maintain a durable, lasting system.
“Several years ago, Glenair saw the need for smaller connector packages that met the rigorous specification of the well-proven D38999 Series,” said Favale. “Out of that vision came the now popular Mighty Mouse connector series.” The company has since added many different contact configurations and accessories to the Mighty Mouse.
High-reliability connectors and cabling solutions from Harwin combine a rugged, lightweight construction with compact size, enabling the power and data needed for military UAVs without adding unwanted bulk to the design. Harwin’s slimline 1.25mm-pitch Gecko Connectors are a high-performance alternative to conventional micro-D connectors. The Gecko-SL features stainless steel screw-locks to provide greater resilience to vibration. In addition, the company’s Datamate Mix-Tek family can combine power, signal, and RF contacts inside a single compact housing to reduce the weight of wire harnesses.
Amphenol’s RADSOK contact system is one example of how connector suppliers are coming up with innovative contact designs, insert materials, and pin layouts to handle the demand for higher speeds and higher power, while reducing size and weight, said Favale. This technology is based on a stamped, formed flat grid twisted into a hyperbolic geometry that provides robust, high-density contact to the mating pin contact. It increases reliability and power, reduces size, and reduces insertion and extraction forces, which makes it a highly versatile contact for applications requiring higher power in a smaller package, like military UAVs.
A method for quickly disconnecting cables in the field is also essential for tasks such as testing or uploading mission data, said Favale. Relevant coupling types include quick disconnect, bayonet, push-pull, and break-away, and the designer’s choice depends on the application and the environment.
“For UAVs exposed to sand or the elements, and with a need to quickly connect for testing or software uploads, a break-away coupling with a contact system using pogo pins can be used,” said Favale. “Pogo pins are uniquely suited to mate with an electrical pad, allowing the pad side to be easily cleaned off. The pad replaces a typical socket contact, in which a good connection can be easily prevented by sand and other debris.”
ITT Cannon’s Nemesis Series connectors are environmentally sealed and have a quick-disconnect coupling with a pogo pin on the plug side and an electrical pad on the receptacle side. This lets the operator quickly and reliably connect and disconnect in the harshest environments.
In some UAV applications, the micro-D, or M83513, is a good solution. This connector handles high vibration in a very small package, with only 0.05” contact spacing, said Favale. Some connector manufacturers, such as ITT Cannon, use a twisted-pin contact with seven points of contact to ensure high reliability under even the harshest conditions.
The choice of packages and shapes for connectors used in military UAVs depends on space constraints, as well as the specific application, said Favale. Designers should ask questions such as the following to determine what’s best for their application: What are the shielding requirements? What are the height, width, and depth specifications? How many signal and power pins are needed? How will the connector be terminated? and What are the cabling requirements? A growing selection of connectivity products are available to answer these questions and help military UAVs take to the skies, in any size.
Like this article? Check out our other Mil/Spec, Connection Basics, and Harsh Environment articles, our Military/Aerospace Market Pages, and our 2020 and 2019 Article Archives.
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