Cooling electronics in modern military ground and air platforms must balance reliability and cost
In this Q&A with Gerry Janicki, Senior Director at Meggitt Defense Systems in Irvine, California, he discusses design trends in military-electronics thermal management, challenges and requirements in air and ground platforms, and how modular hybrid cooling is solving current thermal challenges while reducing total lifecycle cost.
MCHALE REPORT: Please provide a brief description of your responsibility within Meggitt Defense Systems, your group’s role within the company, and an example or two of where Meggitt’s thermal management systems are used within the military.
JANICKI: I’m responsible for leading the Thermal Management System (TMS) and Environmental Control System (ECS) Programs and Business Development activities for Meggitt Defense Systems, as well as the Business Area Team, which all TMS and ECS Programs report into. I work closely with engineering to develop new products, co-direct internal research and development (IRAD) investments and am also responsible for the development of ECS business and program strategies, market forecasts and assessments, bid and proposal planning and execution, new-program starts, and developing new products and programs.
Meggitt has been developing affordable and reliable global and local thermal-management solutions for military ground and aircraft platforms and systems for over 40 years.
MCHALE REPORT: Your expertise is in the thermal management of military electronic systems. What factors are driving thermal-management designs today in these systems?
JANICKI: Thermal management has become a mission-critical function and subsystem in support of key electronics in combat vehicles and higher energy weapons. Good thermal management is benign, while poor thermal mismanagement can ruin your day.
The current and planned exponential growth in military platforms electronics is driving cooling requirements from several kW to several hundred kW. Network-centric warfare is driving the development of higher-functional-density electronics that need to be implemented on both new and legacy platforms.
To balance global and local cooling requirements, these systems need to be simple, modular, and flexible to cost effectively support commercial-off-the-shelf (COTS) electronics on legacy and future military platforms. Optimized solutions such as hybrid refrigerated (active and passive) forced liquid cooling of COTS electronics still represents a high-value solution for future military platforms.
Modular hybrid cooling provides the best balance of cooling efficiency, power, reliability, and total system thermal management. The limitation of size, weight, and power (SWaP) has led to the development of these efficient hybrid thermal management systems.
MCHALE REPORT: What are the most popular cooling methods for military electronics today and why?
JANICKI: Forced air-cooling and forced (passive) liquid cooling are challenged by tomorrow’s environmental and reduced SWaP; that’s why more applications are using active (refrigerated) forced liquid cooling.
Fluids have a higher heat capacity than gases and are much more efficient at conduction-based heat transfer in many military operational environments. Thermal-management systems leveraging active liquid cooling, with COTS conduction cards in a rugged liquid flow through enclosure, represent a low-risk evolutionary solution for current and future military platforms
MCHALE REPORT: What are the current challenges and requirements you are seeing regarding thermal management in aircraft systems?
JANICKI: Military aircraft requirements focus on flight envelope, SWaP, dynamic loads, operating temperatures, storage temperatures, reliability, maintainability, and cost. Air density is also important, as it changes with altitude, which affects the thermal-management formula and the performance of equipment like fans.
MCHALE REPORT: The same for ground systems?
JANICKI: Military ground-vehicle requirements focus on SWaP, shock and vibration loads, operational and storage temperatures, reliability, maintainability, and cost.
Ground vehicles are additionally challenged because they have to have their vapor system on all the time, like an air conditioner running all the time in a car. The electronics need to have their own power sources.
MCHALE REPORT: What about naval platforms?
JANICKI: For naval systems, thermal management is not as big an issue, as these platforms have access to large heat sinks called oceans.
MCHALE REPORT: What types of thermal-management challenges do high-energy laser weapons present and how far along is the industry toward solving them?
JANICKI: The most challenging application and the majority of applications are driven by upgrades to legacy platforms and the introductions of high-energy weapons such as high-energy lasers and rail guns.
There are multiple advanced laser weapon programs trying to field a 100-200 kW weapon. We are supporting some of this and also the electromagnet rail gun being developed for the Navy. Many of these systems still have a way to go to be called a product.
MCHALE REPORT: What new types of cooling methods are being explored today that we may see in future military systems?
JANICKI: There are many efficient ways to directly cool electronics, and every few years a recycled technology or technology du jour from a laboratory, university, or company grabs the attention of designers. Some of these include liquid immersion, impingement cooling, direct refrigeration, and nanoparticle liquid conduction cooling, none of which are ready for prime time on military platforms because after you remove the heat from the chip/board/line-replaceable unit, that heat has to go somewhere using a platform subsystem.
MCHALE REPORT: Many military ground-platform upgrades have had tough power-management challenges when adding new electronics and capability because the vehicles were designed from the ground up to meet today’s SWaP requirements. Do you see next-gen platforms taking this into account or will we face the same power-management problems with the newer platforms?
JANICKI: The greatest constraint in ground-vehicle upgrade programs – such as on the HWMMV (commonly called the Humvee) or Bradley Fighting Vechicle – is power. On next-generation platforms such as the Joint Light Tactical Vehicle (JLTV), the designers are taking that into consideration, using larger generators on the engines from the get-go, while most existing platforms try to force-fit larger generators that are still not enough for current and projected loads. Even with the new systems’ additional power, that number has to evolve every two to three years as you add high-performance radars and other processing-intensive equipment and communications electronics. These improvements impact all subsystems and total system thermal management. These platforms need to not only prepare for it today, but need to think ahead, for example, with a separate auxiliary-power unit to adapt to changing additional electric loads in the future.
MCHALE REPORT: Where will additional power resources come from in aircraft systems?
JANICKI: In modern aircraft, the engines being developed today provide about four times the amount of power compared to legacy platforms, but they produce a lot less or no bleed air as in the past. Now, engine-based generators, ram air-turbine-driven generators, and even batteries are being added to aid in electrical support and storage, as well as thermal batteries to combat extreme thermal requirements for next-generation high-energy weapons. Even if these generators are approaching 95 percent efficiencies, you still have an additional 50 kW of heat to deal with on a 1 mW generator. This situation gets much worse with the very inefficient high-energy weapons projected to be used on these platforms: Adding a 150-kW inefficient laser to the platform heat load can add more than double the generators’ wasted heat energy – all of this also needs to be managed. Much more work has to be done to improve efficiencies with high-energy weapons.
It’s not just the high-energy weapons that are creating challenges, increases in commercial processor clock speeds will as well. According to a new report from IPC.org on the printed circuit board (PCB) industry clock speeds will be hitting 25 GHz and higher by 2019.
MCHALE REPORT: Designers are using high-performance commercial processors to drive performance while saving costs, but then they see those costs go back up as they have to innovate to overcome the thermal challenges in military platforms. How do you balance that?
JANICKI: It comes down to managing the total life cycle costs. SWaP-C (SWaP plus cost), myopically applied, can significantly drive a solution in the wrong direction. Electronics obsolescence and support need to be balanced against system reliability and what the cost of the program will be down the road if something goes wrong, as opposed to saving money on the front end to meet a reduced cost need.
Any thermal-management system may add additional thermal loads, power draw, space claim, added weight, thermal inertia, and operational-based thermal impacts. It all comes down to what balance works best for your program and how you can best reduce the total life cycle costs while still meeting thermal and performance requirements.
For a more technical overview on thermal management from Janicki, view his presentation in the webinar titled, “Keeping it cool: solving military electronics thermal management challenges.” To register and view, .