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WHITE PAPER Development Tactics and Techniques for Small Form Factor RF Signal Recorders mrcy.com 4 mrcy.com Custom designed heat sinks that provide conductive thermal paths to the walls of the recorder 's chassis provides some relief, but chassis walls still require sufficient air flow to be effective. Plenums can be used to create air channels throughout the chassis to provide a more efficient cooling design. Custom heat sinks that are integrated into the plenum's walls provide an ultimate level of cooling by allowing air to be channeled directly through all of the electronics' heat sinks. This allows all system electronics to remain sealed from the outside environment while being adequately cooled. Integrating a fan into the plenum helps assure air flows through the heat sinks, providing an excellent cooling solution. This is ideal for systems running in hot environments like an aircraft idling on the tarmac of an air base or a military vehicle running in the desert. But what about cold environments, like an aircraft pod at high altitude or an unpressurized UAV flying in the arctic? It is equally important that our RF signal recorder is able to run at very cold temperatures. The challenge of maintaining the features and performance of larger form factor recorders is facilitated by the growing solid state storage demand driven by data centers. V-NAND flash technology has enabled solid state drive capacity and write rates to continue to increase in very small package sizes. These inherent advances in solid state technology provide a path for shrinking the data storage array, allowing simpler and smaller designs with performance and features equal to that of far larger systems. Small drive packs, containing an array of solid state devices provide storage speed and capacity previously only available with many individually removable SSDs. By designing the packaging of a storage array into a drive pack, the job of managing a high drive-count system is replaced with the job of managing a single drive pack, providing a tremendous ease-of-use benefit. A single high-insertion-cycle connector designed into the drive pack provides a far more reliable mechanism for the removable storage media than standard SATA connectors typically available in rackmount systems. Well designed drive packs are capable of holding tens of terabytes of data and are capable of storage speeds in the gigabytes per second. Drive packs must be designed for easy removal while the recorder remains mounted in the vehicle or aircraft. CREATIVE THERMAL MANAGEMENT TECHNIQUES ALLOW FOR OPERATION IN HARSH ENVIRONMENTS One of the issues in reducing the package size of the data storage media is maintaining a thermal environment that will allow the drive pack to perform at its highest level. Solid state memory controllers will throttle access speeds if the thermal environment is not properly managed. This issue is not only an important concern for the storage media but for all electronics in our SFF recorder. A set of A/Ds can draw 10 watts or more. FPGAs often draw 25 watts or more. CPUs typically draw between 35 and 90 watts. High performance RAID controllers often draw 15 to 25 watts. And drive packs can draw tens of watts. While efforts can be made to minimize power consumption, heat management is one of the most critical aspects of the recorder 's design. Many RF signal recorders are installed in aircraft pods, naval ships or other outdoor environments with little or no protection from the environment. In order to operate in a wide array of environments it is important to protect all electronics from environmental elements such as water, humidity, sand, dust and salt fog. A hermetically sealed chassis is desirable, but brings with it the issue of heat mitigation of internally mounted electronics. Figure 3: Mercur y 's Talon RTX SFF recorders provide a plenum tube that runs through the chassis. Figure 4: Mercur y 's RTX SFF recorders looking inside the plenum tube. This shows the fan pulling cool air and pushing it across the heat sinks providing conduction paths to all system electronics.

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