Cooling the Next Generation of Defence Computing

As computing performance accelerates, so too does the challenge of keeping systems cool and running optimally. In the world of ruggedised defence electronics, where high power processing and environmental extremes are the norm, thermal management becomes mission critical. In this insight piece, we look at the next generation of Air Flow Cooling and how it’s enabling Concurrent’s customers to extract more performance on the frontline.

As anyone who has built a PC at home will know, ensuring adequate cooling is one of the significant challenges of any system build. Thermal management becomes even greater as the computer’s performance increases, with parts generating more heat. For PCs, a user can add a heat sink, a myriad of fans to cool down the PC with air flow or even add water-cooling – but it’s not so simple for ruggedised systems.

The traditional approach – conduction cooling

To ensure they are compliant with military ruggedisation standards, manufacturers such as Concurrent have traditionally used conduction cooling for embedded computers, a reliable design approach used to manage heat in sealed systems.

But what is conduction cooling? In a conduction-cooled design, heat from the electronic components transfers through a thermal interface into a metal plate – typically aluminium or copper – and from there into the chassis via mechanical wedge locks. The wedge locks are tightened in and expand to press the board against the chassis, forming a thermal path with many ‘junctions’ that remove heat without the need for airflow.

This method remains widely used and has a secondary effect of protecting from shock and vibration, but it has inherent limits.

In the compact 3U VPX form factor, conduction cooling can typically dissipate around 80 watts of heat under ideal conditions. That is sufficient for many legacy processors and low-power cards, but the latest generation of compute-intensive processors – and the workloads they enable – is requiring significantly more cooling.

As the laws of physics begin to limit conduction cooling capabilities, new cooling methods are required.

Kratos – pushing the boundaries of performance and cooling

Concurrent’s latest, high-performance Kratos board demonstrates exactly what modern 3U VPX boards are capable of. Kratos leverages the latest Intel® Xeon® 6 SOC (formerly known as Granite Rapids-D HCC) processors rated at 145 watts, and it can consume up to 160 watts in total once memory and supporting components are considered. Boards such as Kratos enable considerable consolidation of applications within rugged systems, using fewer, but higher performance boards, enables SWaP (Size Weight and Power) reduction.

To unlock the board’s full performance without compromising reliability, it needs a cooling solution capable of removing twice the heat energy that a conventional conduction-cooled design can handle. Customers purchasing high-performance boards expect to use every watt of available power, and thermal limits should not stand in the way.

This is where Air Flow Through (AFT) cooling becomes critical.

What is Air Flow Through (AFT) cooling?

Instead of relying on solid metal conduction paths, AFT uses a heat exchanger mounted directly above the board’s heat-generating components. When the board is inserted into the chassis, seals at the top and bottom mate with the heat exchanger, creating an enclosed channel where air cannot leak out, but instead it can flow through (hence the name).

That airflow removes heat from intricately designed exchanger fins, which, in, turn draws heat away from the components.

The AFT design provides a dramatic increase in cooling capacity, capable of managing up to 160 watts or more in a 3U card while maintaining rugged reliability. It effectively doubles the thermal performance of conduction cooling, allowing the most demanding processors, FPGAs, and GPGPUs, often used for AI-based applications, to operate at full capability.

The benefits of advanced cooling technologies are particularly relevant to software-defined and AI-based systems, including advanced intelligence, surveillance, and reconnaissance (ISR) and communications in the defence sector.

These applications are demanding ever greater processing performance to manage high-resolution sensors, real-time analytics, and secure data links. Whether supporting airborne ISR platforms, vehicle-mounted command systems, or private 5G networks, the ability to remove heat efficiently translates directly into greater compute capability and faster data throughput at the edge of the battlefield.

Air Flow Through cooling also provides flexibility for a range of environmental conditions. For example, at high altitudes, where air density is low and cooling might seem problematic, the extremely cold ambient temperatures can make airflow cooling surprisingly effective.

Compliance with VITA standards

It is critical for Concurrent that our technology adheres to the latest industry standards. Our current AFT boards, for example, comply with VITA 48.8, which defines the mechanical interfaces, seals, and tolerances necessary for rugged AFT embedded VPX systems, both in 3U and 6U module form factors.

The seals themselves are crucial: they ensure an airtight fit between the card and chassis so that airflow is directed through the heat exchanger rather than leaking into the enclosure. The boards are tapered slightly to engage these seals smoothly during insertion, maintaining both performance and serviceability.

While AFT brings major gains in cooling efficiency, it also introduces new design challenges.

Traditional conduction-cooled cards achieve high rigidity through continuous wedge locks that secure the entire edge of the board. The VITA 48.8 AFT standard, by contrast, uses a four-point front-panel mounting system and a backplane connector instead of wedge locks. This has advantages, including reducing plug-in module weight, but can leave the central section of the board more susceptible to vibration.

Concurrent has addressed this through careful mechanical design and testing, ensuring that its embedded AFT boards meet the same shock and vibration standards as their conduction-cooled counterparts.

VITA 48.5, the original standard that combined airflow cooling with mechanical wedge locks for added stiffness, is now being updated. Until recently, that standard applied only to 6U form factors, but is now being extended to include 3U VPX boards, which will have additional benefits for customers.

The future of cooling – hybrid and liquid-cooled

Concurrent has already validated AFT designs in products beyond Kratos, and the company sees airflow cooling as an essential capability for next-generation embedded computing.

There is also work on potential hybrid solutions that provide greater flexibility for system integrators and OEMs, allowing them to optimise cooling configurations depending on the type of board in the system.

In the not-too-distant future, liquid flow through (LFT) cooling will also offer further performance enhancements beyond AFT. The VITA 48.4 standard defines this approach; however, this is still only for 6U modules and few rugged LFT products exist today. For Concurrent, LFT is part of our cooling roadmap and will once again provide significant flexibility to customers.

Behind these innovations lies significant engineering refinement. The heat exchanger designed for the Kratos board, for example, is a compact but highly sophisticated structure, with extremely fine, densely packed fins that maximise surface area and heat transfer efficiency.

Designed and manufactured in the UK using precision techniques, it represents a balance of thermal, mechanical, and manufacturability requirements, an example of the kind of detailed mechanical engineering that underpins the company’s thermal strategy.

Looking ahead, the shift to higher power densities shows no sign of slowing. As processors, FPGAs, and GPUs continue to evolve, system designers will require more advanced cooling architectures capable of managing hundreds of watts within compact footprints.  Enabling higher performance, across fewer PICs, pushes capability to the far-edge, which previously was only considered for less mobile installations.

In response, Concurrent’s roadmap is focused on building flexibility - supporting air, conduction, and liquid cooling within modular, standards-based chassis architectures that can evolve and keep pace with the rapid developments in computing technology.

Conclusion

As defence systems become more software-defined and AI-enabled, processing density will continue to increase. Cooling technologies like Air Flow Through are therefore not just incremental upgrades; they are enablers of capability. By overcoming thermal limits within compact VPX architectures, they ensure that the latest processors and accelerators can operate at their full rated performance, allowing customers to exploit every watt of available compute power.

For Concurrent, this represents a logical progression. From conduction cooling to airflow and ultimately to liquid-cooled systems, each step extends the company’s ability to deliver high-performance, rugged embedded computing in the most demanding environments.