More powerful. Lighter. Cooler. These are the key criteria for the design of Line Replaceable Units (LRUs) in next-generation Unmanned Aerial System (UAS) platforms, which continue to grow in importance to military organizations worldwide. The ability of these platforms to provide persistent surveillance of targets while eliminating the need to put warfighters in harm’s way makes them indispensable assets to commanders. The effectiveness of these platforms in the field is governed by their sensor payload and their processing systems. Next-generation UAS designs, such as the Navy’s Unmanned Combat Air System Carrier Demonstration (UCAS-D), require high levels of processing power for multiple onboard sensors, and all that power must be delivered in a lighter, cooler configuration that minimizes the size, weight and power (SWaP) envelope of onboard electronics subsystems.

COTSCurtiss- Wright Defense Solutions has supplied Northrop Grumman with the dual Integrated Mission Management Computer (IMMC) subsystems used as the redundant flight control processors aboard the Global Hawk UAS since the program’s inception in 2000.
Unfortunately, designing LRUs that meet next-generation UAS program requirements is a challenge. Commercial off-the-shelf (COTS) single board computers (SBCs) are available that provide key functionality for everything from feature recognition and video surveillance, to target identification and tracking. But not all SBCs are ideal for LRUs destined for new UAS platforms. Most do not have the processing power required. Some that do have the processing power require too much real estate in available chassis configurations, while others may offer the right mix of processing power and compact size, but cannot be cooled properly to meet rugged operational requirements. LRUs built on open architecture 3U VPX form factor modules offer the optimal balance of size, weight and power for a variety of UAS applications.

More Functionality in Less Space

Whatever the configuration of the sensor payload, the key to the effectiveness of a UAS once it is deployed is how long it can remain in the air collecting, processing and delivering sensor information to operators and commanders. If the payload is too large and too heavy, it will have an impact on fuel consumption and how long the UAS can stay in the air. Therefore, the more information processing that can be accomplished with smaller, more compact and more capable SBCs, the more valuable the LRU is to a system integrator and, ultimately, to the commander and operator in the field.

The compact 2-slot rugged 3U MPMC-9321 mission computer supports up to 2 single board computers or one SBC and one mezzanine card carrier board. (Curtiss-Wright)
New LRUs configured with SBCs built on the 3U VPX open standard offer a number of benefits. Compared to systems built on the 6U VME or even 6U VPX standards, LRUs configured with 3U VPX cards offer more processing power in a smaller form factor. As a result, system integrators need fewer cards and fewer LRUs in the same system to deliver the same functionality of a 6Ubased subsystem. For example, 6U VPX designs that may have previously required two LRUs can now be built with one LRU, thereby cutting size, weight and power allocations by as much as 50 percent.

Beyond functionality, 3U VPX SBCs are also a more cost effective option. With fewer SBCs needed to deliver the required functionality, development and build costs are lower. Once deployed, the open standard architecture makes life cycle maintenance and management easier, and makes tech insertion a less costly operation.

Pre-Validated Reference Design Architectures

Despite the benefits, leveraging the 3U VPX SBCs for next-generation UAS platforms can be difficult.

One of the biggest challenges that system integrators face is ensuring COTS-based SBCs will work as intended in a specific LRU design configuration. Like all COTS-based solutions, 3U VPX COTS SBCs are designed and built by COTS solution providers to perform a specific function, such as network routing, switching, or graphics processing. The manufacturer rarely knows how their board will ultimately be used in a LRU, and integrators can use the board to provide its function in a variety of LRUs destined for a variety of platforms. Often, the same board can be used in multiple LRUs to enable different applications.

To speed time to deployment of their COTS-based LRU subsystem in next-generation UAS platforms, system integrators can opt to leverage pre-validated 3U VPX SBC architecture-based reference designs.

Test Processes and Tools

Regardless of the design approach, all 3U VPX SBCs must be tested to ensure they deliver the required functionality once integrated into a LRU with the other COTS modules that comprise the particular subsystem. Although COTS manufacturers will test a board to ensure it performs its intended function, testing for capabilities beyond the basic function is not a requirement and is usually undefined.

Curtiss-Wright's MPMC-9351 rugged 3U 5-slot system is an example of an LRU designed to reduce space, weight, power and cost for UAS subsystems. (Curtiss-Wright)
Exacerbating the testing challenge is the fact that COTS SBCs are not usually delivered with system integration support tools that will speed the integration process. As a result, integrators must focus significant time and effort on developing and executing test software and processes.

To minimize the cost and time associated with testing and integration of any COTS SBC into a UAS platform, integrators should opt for 3U VPX SBCs from suppliers who offer solutions that enable testing of:

  • The hardware: for specific performance parameters;
  • The software: to ensure it provides the proper commands to the LRU for a specific function;
  • Both hardware and software: to ensure that they operate together to provide reliable, predictable results every time.

Getting 3U VPX Designs to Deployment Faster

Ultimately, although next-generation UAS applications can best be addressed using rugged, high performance, size, weight and power (SWaP)-optimized processing systems built with open architecture 3U VPX modules, system integrators should choose the shortest route to deployment. Some COTS component manufacturers provide that path with a complete pre-validated subsystem solution approach that offers the pre-packaged boards and test support tools integrators need to reduce program risks and development cycles with new 3U VPX designs. The COTS board and subsystem vendor knows the components they produce best. Therefore, they are better able to select and package the right COTS components that will work together in an LRU to deliver the required functionality with the optimal balance of size, weight and power for a variety of UAS applications. This makes it easier to design advanced LRUs for next-generation UAS platforms that can carry multiple onboard sensors, stay in the field longer, and process more information faster.

Examples of pre-validated rugged, SWaP-optimized VPX systems are provided by Curtiss-Wright’s family of open architecture Pre-Qualified Multi-Platform Mission Computer (MPMC) Subsystems. These fully integrated mission computers are certified to meet the demanding MILSTD- 810, MIL-STD-461 and RTCA/DO- 160 military and aviation environmental engineering standards. They eliminate the need for customers to undertake their own time-consuming, costly, and riskfraught process of building new systems from the ground up in order to meet demanding performance requirements. Prevalidated systems can save customers tens of thousands of dollars and multiple weeks (typically 8-12 weeks) of development time that would otherwise be required to meet MIL-STD-810/MIL-STD- 461/ RTCA/DO-160 testing requirements. They also save significant amounts of time before environmental testing even begins, because the lead-time to delivery of the first testable system can shrink from the typical 10 months-to-2 years frequently seen for a customer’s internal hardware development phase, to a matter of several months.

This article was written by Jacob Sealander, Chief Architect, Integrated Systems, Curtiss-Wright Defense Solutions (Ashburn, VA). For more information, Click Here .


Aerospace & Defense Technology Magazine

This article first appeared in the May, 2015 issue of Aerospace & Defense Technology Magazine.

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