Infrared radiation is given off by heat, either body heat on the ground or jet engines in the air—making IR-seeking technology deadly.

Infrared radiation, or IR, is the electromagnetic radiation from heat. Everything emits IR—engines, electronics, even the human body. And on the battlefield, many sensors are designed to detect IR in order to improve situational awareness. Increasingly, warfare revolves around managing heat—both the reduction of one’s own, and the detection of the enemy’s.

IR Signatures Matter—on Land, in the Air, and on Sea

In the battlefield context, there are a few main contributors to IR.

In the air, the most obvious source of infrared radiation are aircraft engines—burning jet fuel in order to propel the plane at supersonic or near-supersonic speeds. Exhaust plumes offer another high IR contrast. Even if the plane’s jet engines could somehow be muffled, the airframe itself is a major source of IR; airframes propelled forward at high speed heat up from friction with the air they push out of the way. The aircraft’s electronics are smaller, but still a persistent heat source.

An important concept to understand is that contrast matters. The heat of a target relative to its background determines visibility; detection depends upon how much hotter something is than its surroundings. 

To reduce IR signature, and thereby reduce detection, aircraft and vehicles engage in a variety of tactics. One of the most effective of these is exhaust management, by mixing hot exhaust with cool air, flattening the exhaust plume, and reducing the exhaust temperature before release. Similarly, engine placement can be tailored to reduce IR. For example, the engines can be buried inside the airframe or shielded from direct line of sight. This is the case with the B-2 Spirit, whose jet engines are set inside the airframe and whose exhausts are shielded in order to better dissipate heat.

Thermal coatings are used to absorb or dissipate heat, reducing the surface temperature of a vehicle, and reducing the likelihood of IR detection. Heat can also be distributed across larger surfaces, resulting in lower peak IR intensity. Finally, operational tactics can be adjusted to reduce the likelihood of IR detection. Flying at high altitudes, avoiding high-thrust regimes, and using terrain masking all serve to reduce IR detection. In sum, IR reduction is about lowering peak heat and breaking the line-of-sight between a vehicle and sensors. 

Ground troops engage in IR reduction, too. Soldiers on the ground use thermal camouflage, IR-suppressing overgarments, and insulating materials that trap body heat. Ground vehicles often have their engines shielded or their exhaust rerouted. Of course, one cannot eliminate heat fully—only mitigate it and hope to delay detection.

Spotting IR Is a Critical Attack Advantage

To detect IR, a variety of tools are available.

• FLIR (Forward-Looking Infrared) is a passive system that detects heat differences. FLIR is widely used in aircraft, drones, and vehicles.
• Infrared Search and Track (IRST) detects aircraft without radar through long-range passive tracking. Missile seekers can be equipped with heat-seeking guidance that lock onto engine exhaust, like the MANPADS used against US forces in Operation Epic Fury.
• IR can even be detected from space, where sensors detect missile launches and track the heat plume globally. Because IR detection is passive, it is harder to counter than radar. 

Recent developments in IR, on the detection side, include higher resolution sensors, multi-spectral IR, and AI-enhanced tracking. On the reduction side, improvements include adaptive camouflage, experimental metamaterials, and better heat dissipation systems. And on the battlefield, drones with thermal cameras are being deployed at scale to offer persistent surveillance.

It seems that detection is improving faster than concealment; as time goes by, it will become increasingly difficult for soldiers and aircraft to stay hidden on the battlefield. Heat is becoming one of the hardest signals to hide, and future efforts will likely revolve around a battle between cooling systems and sensor resolution. 

About the Author: Harrison Kass

Harrison Kass is a writer and attorney focused on national security, technology, and political culture. His work has appeared in City Journal, The Hill, Quillette, The Spectator, and The Cipher Brief. He holds a JD from the University of Oregon and a master’s in Global & Joint Program Studies from NYU. More at harrisonkass.com.

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