On May 22, 2024, the US Air Force (USAF) unveiled the first official photos of the B-21 Raider stealth bomber in flight, following its inaugural flight last year. Northrop Grumman, the manufacturer, released additional images showcasing the bomber's takeoff, flight, and presence at Edwards Air Force Base. The B-21 Raider joins the B-2 Spirit as the only active stealth bombers, with China's Xi’an H-20 expected by 2025 and Russia's Tupolev PAK DA by 2027. These aircraft represent the forefront of heavy stealth technology.
Stealth Technology Overview Stealth technology involves integrating various low-observable (LO) technologies to significantly reduce an aircraft's detectability. This includes minimizing radar cross-section (RCS), acoustic signature, thermal imprint, and other detectable attributes. The term "stealth" became widely known in the late 1980s with the F-117 stealth fighter's deployment during the 1991 Gulf War.
Key techniques include tilting or removing vertical stabilizers, applying radar-absorbing materials (RAM) to leading edges, and internalizing weapons and fuel tanks. Advanced materials and coatings, such as dielectric composites and transparent conductors for cockpit canopies, further reduce radar reflections. Placing engines within the wing or fuselage reduces infrared signatures, and passive infrared and low-light TV sensors help maintain stealth by avoiding active emissions.
Operational Use of Stealth Technology Stealth technology saw its first operational use with the F-117 in the Gulf War, later deployed in Yugoslavia, Iraq, Afghanistan, and Libya. Stealth helicopters, like the modified Sikorsky UH-60 Black Hawk used in the 2011 Osama bin Laden raid, also utilized stealth features. More recent combat applications include the F-22 over Syria and the Israeli F-35I in Syrian and Iranian airspace.
Limitations and Countermeasures Despite its advantages, stealth technology has limitations. Low-frequency radars can detect stealth aircraft, though with reduced accuracy. Infrared search and track (IRST) systems can detect aircraft heat signatures. Stealth design involves trade-offs in aerodynamics, development time, and cost, often requiring larger internal bays and specific maintenance procedures. Additionally, counters to stealth technology continue to evolve.
Stealth Aircraft Developments The B-2 Spirit, produced from 1987 to 2000, remains the only operational stealth bomber, with a wingspan of 172 feet and a maximum takeoff weight of 170,600 kg. The new B-21 Raider, smaller and estimated at $700 million per unit, aims to replace the aging B-2 fleet. The USAF plans to invest $203 billion over 30 years to develop and operate at least 100 B-21s. China's H-20 and Russia's PAK DA are still in development, with limited details available.
Future of Stealth Technology The USAF's plans include stealthy flight refueling aircraft (FRAs) to support closer refueling of stealth fighters and bombers in contested environments. Lockheed Martin's Skunk Works has proposed concepts for stealth tankers, and Boeing's MQ-25 Stingray is in development as a stealth refueling drone.
Stealth AEW&C aircraft, such as the Boeing E-7 Wedgetail, aim to reduce detectability through design modifications. Future stealth initiatives may also encompass cargo and special operations aircraft, with flying wing designs offering potential solutions for stealth transport.
Innovative Stealth Concepts Emerging technologies, such as metasurfaces and plasma stealth, promise further advancements in RCS reduction. Adaptive aero-elastic wings and fluidic controls are also under exploration, though these remain costly and in developmental stages.
Overall, the USAF's investment in stealth technology for various aircraft ensures continued global dominance and operational effectiveness in increasingly contested environments.
