The defense and aerospace market continues to push for reductions in size, weight, power, and cost (SWaP-C) to support advanced sensor/vetronics payloads onboard unmanned platforms. Groundbreaking SWaP-C reduction for processor and network switch systems are enabling UAS (unmanned aircraft system) and UGV (unmanned ground vehicle) platforms to expand their mission capabilities. Several technologies are driving this small form factor revolution, including tightly integrated system- on-chips (SoCs), semiconductor packaging advancements (i.e. smaller nanometer dies, lower voltage chips), and micro-miniature rugged connectors.

(U.S. Army)
The need for ever greater SWaP reductions stems largely from the balance between the small size of many unmanned platforms and the amount of payload electronics that needs to be integrated on those platforms. For the most part UGVs, UUVs, USVs, UAVs are smaller platforms, and generally speaking their mission and purpose is to serve as a sensor host for information gathering. These sensors can include FLIR cameras and other types of imaging technology to conduct surveillance, and capture video or photos or mapping information.

The platforms might also include onboard sensors used to remotely control the aircraft or vehicle, or to allow autonomous operation of the platform. This requires that various processing elements and various sensors are interconnected to gather information. Typically, if there are multiple processors on the platform they will be supported with a data communications network, which is driving the need for smaller processor and network switch connectivity. At the same time, system designers want devices that meet the requirements, from an environmental and EMI standpoint, to operate in harsh environments such as at high altitude or during water ingress. Other notable reliability concerns that need to be mitigated include dealing with “dirty power” that might otherwise damage devices due to high voltage surges or spikes, and also noisy electrical environments aboard the vehicle that may disrupt adjacent devices.

Parvus DuraCOR 310 Quad-core i.MX6 ARM miniature rugged mission computer.
Helping to increase requirements for SWaP reductions is the issue of how weight can affect a mission’s endurance. One UAS customer states that every pound they can eliminate from their combat UAS platform saves them approximately $60,000 in cost for their vehicle. For an ISR (intelligence, surveillance and reconnaissance) mission platform, it’s calculated that it costs $30,000 to add a pound, or inversely saves $30,000 to eliminate a pound. So what are these costs? Where do they come from?

One key contributor is fuel. There’s a tradeoff analysis of how much capability a platform can provide given a specified weight for the electronics, fuel, and ammunition, etc. If one element is removed you can add more of another. But if you can shrink the physical size and weight of the payload electronics you can potentially get more functionality in the same physical space.

Switch Sizing

As an example, a couple of years ago, one of the largest US Army tactical UAS platforms had a requirement for network readiness, involving the integration of an onboard Gigabit Ethernet network. Given that the UAS was a smaller platform, the customer performed a volumetric analysis and determined that the size available for the network switch was roughly the size of a pack of playing cards, and ideally about half a pound in weight.

At the time, when the requirement arose, we had a COTS Ethernet switch that met the functional requirement but exceeded the allowable weight. We had already developed a roadmap for a miniaturized version of the switch and we accelerated the timing to accommodate this program. As a result, we designed, without NRE, a COTS solution that was half a pound in weight and just 10 cubic inches in size. This was 10% of the weight and size of our smallest previous GbE switch product.

Ultra-small form-factor DuraNET 20-11 Ethernet switch supports network backbone upgrades on swap-constrained UAS platforms.
What enabled us to miniaturize the GbE switch? Today, both processors and networking devices are evolving to include more functionality in their physical packaging. While previously the system architecture might require multiple different devices, today we have access to system- on-a-chip alternatives that combine processing, memory, other controllers, interfaces, and physical transceivers all on a single chip. The system-on-chip has been a tremendous tool in the miniaturization of military electronics.

Beyond the miniaturization provided by the SoC, you need to consider the physical packaging of the system, including the metal, the connectors, and the thermal needs of the device. As manufacturers of these next generation SoC devices are reducing the thermal needs of the silicon, they are producing devices that are lower power and, therefore, the system requires less power dissipation in terms of the surface area of the system enclosure. Enclosures can now be smaller and still dissipate the heat that is generated by the device.

Connectors and Computers

The connectors that bring out all the I/O signals for the Ethernet and other computer I/O have also advanced in recent years. The traditional MIL-DTL-38999 connectors are still widely used and accepted. However, next generation micro-miniature versions of the connector are now available that provide the same or better physical, EMI, and electrical performance. These have higher density contacts and the physical size and weight of the connectors are roughly half that of traditional options. Traditional 38999 shell sizes, together with MIL-STD-1472 Human Engineering recommendations for connector spacing, has driven the size of the connector panel and enclosure. With the new micro-miniature connectors, we are able to shrink the physical height of the box. In the case of our miniature GbE Ethernet system, the box is now barely over an inch tall.

Another example of a small form factor component suitable for unmanned vehicles is the recently introduced Parvus DuraCOR 310 tactical mission computer based on a low-power, fourcore NXP i.MX6Quad ARM processor. This ultra-small system measures less than 40 cubic inches in volume, weighs less than 1.5 lbs and requires only 10 watts of power. It supports a high level of I/O flexibility through the use of dual PCIe-Mini Card I/O expansion slots. The mission computer features an industrial grade ARM-based Computeron-Module (COM) tightly integrated with a Flash SSD and system carrier board, which provides a full complement of standard vetronics I/O interfaces including CANbus, USB, Ethernet, serial, DIO, video, and audio. The system’s combination of small size, low-power multi-core processing, and flexible I/O represents the key design targets that system designers for unmanned systems are seeking to be able to add new Command, Control, Communications, Computers, Intelligence, Surveillance and Reconnaissance (C4ISR) capabilities to their platforms.

MQ-1C Gray Eagle in flight. (U.S. Army)
What’s more, these small mission computers need to be rugged to be able to perform optimally in the hard environments endured by unmanned platforms, whether the heat of desert tarmacs or the extreme cold of high altitudes. The use of the low-power ARM processor helps ensure that tiny mission computers can support a full range of military operating temperatures, from -40 to +71°C (-40 to +160ºF) without fans or active cooling requirements. To ensure it’s ability to perform under the extreme shock/vibration conditions, high altitude, and humidity, required by mobile, tactical, aerospace, and ground vehicle applications, the unit will be fully validated through qualification testing to extreme MILSTD-810G, MIL-STD-461F, MIL-STD-1275D, MIL-STD-704F and RTCA/DO-160G test conditions for environmental, power and EMI (thermal, shock, vibration, dust, water, humidity, altitude, power spikes/surges, conducted/radiated emissions and susceptibility). Housed in a rugged sealed IP67-rated (dust and water proof) aluminum chassis with MIL-performance circular connectors, the DuraCOR 310 features advanced EMI filtering and power conditioning to protect against input vehicle/aircraft voltage surges, spikes and transients.

The breakthroughs in SWaP-C reduction resulting from continued increases in device density, packaging improvements and connector size miniaturization will help drive the development of smaller, more effective unmanned platforms. As these platforms expand their mission capabilities, our warfighters will benefit from better, more real-time intelligence.

This article was written by Mike Southworth, Product Marketing Manager, Curtiss-Wright Defense Solutions (Ashburn, VA). For more information, Click Here .

Aerospace & Defense Technology Magazine

This article first appeared in the May, 2016 issue of Aerospace & Defense Technology Magazine.

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