The F-117’s elaborate stealth-enabling innovations gave it one significant drawback: it had the aerodynamics of a brick.
Known internally as “Project Have Blue,” and later “Senior Trend,” the development of the F-117 Nighthawk was one of the most secretive and groundbreaking projects in the history of military aviation. The first operational stealth aircraft ever built, the F-117 was developed against the backdrop of the Cold War, as the Soviet Union was developing increasingly sophisticated air defense systems. Led by designer Ben Rich, the F-117 was developed in absolute secret at the legendary “Skunk Works” experimental division of Lockheed. The finished product would set a new benchmark for aviation technology—thanks to a slew of novel features.
The F-117 Nighthawk Was Nearly Invisible to Ground Radar
The F-117 was jam-packed with innovative features. The most obvious innovation, jarringly apparent to anyone looking at the plane, were its strange faceted surfaces. Rather than the smooth, sleek surfaces that had come to dominate most fuselage designs, the F-117 was constructed with angular, faceted surfaces—a collection of flat panels stuck together. The resulting aircraft seemed quite bizarre to onlookers. Yet the plane’s unique faceted design scattered radar waves instead of reflecting them directly back to radar receivers, making the plane nearly invisible to the air defense systems of the era.
In addition to the faceted surfaces, the F-117 also incorporated “planform alignment,” which is the alignment of all the aircraft’s edges along a few specific directions—allowing for controlled and minimized radar return. All of the aircraft’s sharp edges and grooves were carefully modeled to reduce radar returns in all directions.
The F-117 further introduced radar absorbent materials (RAM) to help absorb radar energy and enhance the F-117’s ability to operate undetected. The F-117 used iron ball paint, a polymer-based coating that is embedded with tiny iron or ferrite spheres that serve to absorb radar energy and convert it into small amounts of heat. As one might imagine for a paint embedded with iron, the paint was very heavy—and required intensive maintenance due to its tendency to degrade quickly. Maintenance crews were required to touch-up the RAM coatings after nearly every flight, as the RAM was sensitive to rain, heat, and sunlight. The RAM application had to occur in secret, and required precise environmental conditions.
The F-117 also featured carbon-based RAM—carbonyl or carbon-loaded materials that were used in layered composites to absorb electromagnetic radiation across a wider frequency range than just the iron ball paint alone.
Disguising the F-117’s Heat Signature
Radar is not the only way to track a plane. Indeed, many surface-to-air missiles also use heat signatures to track and destroy aircraft; one of the most easy to detect features of any plane is its engine exhaust.
Accordingly, the F-117’s engine intake was buried and covered in radar-absorbing screens, which served to reduce the return from the highly reflective fan blades. The exhaust plume was also designed to be flattened and shielded, reducing both only radar returns and infrared heat signatures.
The F-117’s elaborate stealth-enabling innovations gave it one significant drawback: it had the aerodynamics of a brick. Without thousands of automatic microcorrections per second from an advanced fly-by-wire system, the plane would have simply fallen from the sky. In fact, engineers referred to the F-117 as “the Hopeless Diamond.”
Hopeless or not, though, the F-117 became the world’s first operational stealth aircraft, laying the groundwork for the stealth features that are still in use today.
About the Author: Harrison Kass
Harrison Kass is a defense and national security writer with over 1,000 total pieces on issues involving global affairs. An attorney, pilot, guitarist, and minor pro hockey player, Harrison joined the US Air Force as a Pilot Trainee but was medically discharged. Harrison holds a BA from Lake Forest College, a JD from the University of Oregon, and an MA from New York University. Harrison listens to Dokken.
Image: Shutterstock / VanderWolf Images.
