Rising to the Challenge of Airborne Storage
Mil-aero equipment has to record, process and analyse more data than ever before. The capability to integrate the required performance within space and weight constrained form factors presents a challenge, reports Caroline Hayes.
Intelligence, Surveillance and Reconnaissance (ISR) equipment is expected to be deployed in smaller, lightweight formats, which has led to changes in design. As video throughput and resolutions increase, unmanned aircraft systems and unmanned vehicles rely on embedded computing systems that have more processing and storage capability, yet without changes to Size, Weight and Power (SWaP). The system is also expected to maintain the thermal performance of the earlier generation.
According to Mark Littlefield, Defense Portfolio Manager, Kontron, storage is “an almost ubiquitous requirement, from the smallest to the largest systems.” Other factors, however, complicate product design. “There are many industry forces pulling in all directions—ruggedness, storage size, form factor, encryption and security, processor architecture choice, etc.,” he says. Storage suppliers have to offer different products to meet different needs. One things is certain: “Solid state storage seems, however, to be the most important thread,” he concludes, “as its capacities, speeds and ruggedness make it ideal for mil-aero applications.”
Responding to the conundrum of capacity and performance without penalties in SWaP, Littlefield fears: “There is no easy way to address this. There is no magic bullet.”
“Compression allows greater storage without increasing SWaP, but it requires processing that might not be available on a constrained system,” he adds. Developers have to make trade-offs in design, using a choice of modules, boards and systems, which means that a company’s offering has to be flexible, with interconnect and format choices.
Standard groups and consortia help in providing flexibility across the industry, says Littlefield. As well as playing a role in keeping future technologies backwards compatible, they ensure greater ease of system integration, he says. “Systems have become more and more complex, and standard form factors give developers the confidence to select components with the expectation that they are interoperable and function together in a system,” he believes.
Ken Grob, Director of Embedded Technologies, Elma Electronics, agrees on the importance of standards, saying: “The evolving Open VPX VITA 65 and VITA 48 are playing large roles in standardizing interconnect and packaging and cooling.”
The introduction of next-generation processors also brings design choices. Developers can integrate multiple processing cores, with dual and quad cores in a single package, offering hyperthreading.
Elma Electronics uses dual 10GbE ports with integrated TCP/IP offload engines to free up the Intel Core i7 processor in its StorSys-3000 high capacity Networked Attached Storage (NAS) mission system. The Intel Gen 3 Core i7CPU clocks in at 2.5GHz and is freed up to focus on mission compute tasks and preserve link speeds on each input port, says the company.
A four-slot storage array supports over 8-TByte of solid state Multi-Level Cell (MLC) storage, and high-speed data access speeds of 1.2-GByte per second. The 3U VPX mission computer is protected to IP65 and operates at temperatures between -40 °C to +75 °C for high bandwidth, intensive data processing in electronic warfare, radar, thermal, hyperspectral, sonar imaging and Signals Intelligence (SIGINT) gathering applications.
Grob observes: “We are seeing the need to support 10Gb-KX4 [the Ethernet standard which operates over four backplane lanes, using the same physical layer coding as 10GBASE-CX4, for copper cabling] and 10G-KR [which operates over a single backplane lane, using the same physical layer coding as 10GBASE-LR/ER/SR for optical fiber] for Single Board Computer (SBCs), as well as PCIe Gen 3 speeds for interconnect.”
Another processor architecture driver is the Intel Xeon D architecture. It is used in Kontron’s VX30583U VPX blade (Figure 2). The eight-core architecture supports dual 10GbE and PCI Express 3.0. As well as DDR4 memory, it has mezzanine options for XMC, storage, graphics and I/O. There is also M.2, which allows smaller and more flexible formats than the mSAT standard, to shrink end devices. It also uses the company’s switch technology and VxFabric. The latter allows an Application Program Interface (API) to extend the TCP/IP protocol over the PCI Express infrastructure to boost I/O bandwidth for radar, sonar, imaging systems, airborne fighter and UAV radar.
Grob also identifies storage trends, with an increase in demand for multi-TByte Solid State Drives (SSDs) in both MLC and Single Level Cell (SLC) technology, and storage solutions that address FIPS-140 [Federal Information Processing Standards, the U.S. Government computer security standards for cryptography modules].
As the hardware count increases and spacing between each is reduced to meet the constrained spaces allocated, more heat is generated, presenting thermal management issues.
The StorSys-3000 uses fanless, conduction cooling and has a high Cubic Feet per Minute (CFM) front-to-back airflow to dissipate heat. “Thermal management is always a key, and sometimes challenging design criteria,” concedes Littlefield. “Extended temperature components that can operate in temperatures from -40 °C to +80 °C is extremely important,” he says. “Highly ruggedized components that are resistant to high shock and vibration are also critical, as is EMI and conducted emission for some environments (think secure systems).
Shift to Small Form Factor
“We see more designs shifting to 3U VPX or to Small Form Factor designs,” says Grob. Littlefield agrees—in part. He says, “Strict SWaP-limited applications will need the smaller sized 3U, whereas radar, sonar and compute-intensive applications will need the performance delivered in a 6U [form factor]. With 6U, Original Equipment Manufacturers (OEMs) will get greater processing (and storage) density, as there is less real estate used for non-core functions such as power supplies, mechanicals etc.” As with all choices, the trade-offs are dictated by the application’s requirements, he says. “It really depends on the functional and performance requirements of the system or application versus the amount of SWaP available to deploy the system.”
Flexibility of design to suit applications is also reflected in Elma’s 3U OpenVPX backplane. It is designed to meet VITA 65 and can be used in either optical or RF applications (Figure 3) where integrated data processing or data collection requires optical or RF connectivity, says the company.
Slots two and three accept a VITA 66.4 optical mode or a VITA 67.1 four-cavity, RF module. The optical module accepts Mechanical Transfer (MT) Multi-fiber Push On (MPO) fiber ferrules. The optical ferrules of the backplane support 12 or 24 discrete fibers or equivalent fiber ribbons. Slot one is designed for a conventional 3U VPX module. It has dedicated Fat Pipe connections to slots two and three. All three slots accept MultiGig-compatible cables, and there are also coaxial contacts to support flexible, semi-rigid or rigid RF cabling.
The data planes support 6.25Gbaud per lane or 25Gbaud per Fat Pipe. Applications that can require optical or RF connectivity, with high-speed connections to a processor slot are mission management and navigation for avionics systems as well as night vision systems and shipboard systems for target tracking and High Definition (HD) displays.
While companies strive to offer as much flexibility and choice as possible, the mil-aero industry in particular commonly requests custom storage solutions, says Littlefield. Grob concurs, adding “VPX backplanes are generally specific, and with higher-speed interconnects, they will become more so.”
As the industry moves to pack more capability into smaller, lighter embedded systems, standards bodies and manufacturers will continue to provide as much choice as possible for the ever-changing challenges.
Caroline Hayes has been a journalist, covering the electronics sector for over 20 years. She has worked on many titles, most recently the pan-European magazine, EPN.