Electromagnetic stealth

Stealth refers to all the technical characteristics of an aircraft (or military vehicle in general) designed to reduce its signature to enemy detection systems. We typically talk about radar stealth, but it can also apply to infrared, acoustic, and visual detection (camouflage, shapes, specific paints). It is a technological and structural property. In contrast, discretion is a tactical or behavioral approach. It involves a set of practices and strategies aimed at minimizing the chances of detection, regardless of the level of technological stealth. Some examples include flying at low altitude to avoid radar (nap-of-the-earth flying), radio silence, using radar blind spots, and choosing a time to attack when defenses are weakened. This article addresses the issue of stealth, mainly in relation to radar.

Electromagnetic stealth, often referred to by the English term "stealth," is therefore a technology aimed at reducing the detectability of aircraft by radar detection systems. It is based on several fundamental principles, including the deflection and absorption of radar waves. Stealth aircraft are detected later by enemy radars, allowing them to carry out penetration missions. The idea of electromagnetic stealth emerged during the Cold War, when the United States and the Soviet Union sought to develop aircraft capable of penetrating enemy air defenses without being detected. Early work on stealth began in the 1950s and 1960s, but it was with the development of the Lockheed F117 Nighthawk in the 1980s that the technology really took off. The F117, with its angular shapes and absorbent materials, demonstrated the viability of stealth in real operations, notably during the Gulf War in 1991. However, it was only shot down once in operational service, in 1999, in Serbia during the Kosovo War.

Since then, technology has evolved significantly. Modern aircraft such as the F-22 Raptor and F-35 Lightning II, and the B2 Spirit and B21 Raider bombers, incorporate more sophisticated designs and advanced materials. These aircraft not only reduce their radar signature, but also seek to minimize their infrared and acoustic signatures, making them even more difficult to detect. However, designing a stealth aircraft is extremely complex. Designers must balance stealth requirements with those of aeronautical performance, maneuverability, and load capacity. Angular shapes and absorbent materials can increase weight and reduce aerodynamic efficiency. In addition, stealth aircraft are generally very expensive to develop and maintain. Advanced materials, cutting-edge technologies, and specific maintenance requirements significantly increase costs.

Simulating and calculating radar cross section (RCS) is a crucial issue in the development of stealth aircraft. RCS...