In today’s world, a stealthy design alone isn’t enough to prevent detection, aircraft also have to incorporate the use of a variety of radar aborbent materials (RAM). In technical terms, radar absorbent materials or coatings are a special class of polymer-based materials that literally absorb electromagnetic energy, rather than reflecting it back at its source. In other words, this advanced (and often troublesome) material literally eats radar for breakfast.
Even with an advanced stealth design meant to deflect radar waves, the leading edge of an aircraft’s wings, its jet inlets, parts of vertical tail surfaces, and other parts of a fighter all tend to produce radar returns. These facets of an aircraft’s shape can’t be eliminated through advanced designs. As a result, you’ll often see a radar absorbent edge treatment over these portions of the aircraft. More radar absorbent material is often incorporated into a honeycomb or similar structure inside the turbofan intakes.
“RAM works on the principle of the aircraft absorbing the electromagnetic wave energy to minimize the intensity of the reflected signal,” wrote Adrian Mouritz in the academic textbook “Introduction to Aerospace Materials.”
“It is possible to reduce the radar cross-section of a fighter aircraft to the size of a mid-sized bird through the optimum design and application of stealth technologies.”
The RAM used by modern American fighters is incredibly important, as it’s been rated to absorb upwards of 70-80% of inbound electromagnetic energy. But it’s also expensive and time-consuming to maintain (part of the immense expense associated with maintaining the F-22 and F-35). Low Observable, or LO, maintainers are tasked with removing and applying these materials.
“No one touches the aircraft and gets into the systems without LO having a part in that job,” Senior Master Sgt. Angela Stovall, 325th MXS Fabrication flight chief, said.
“LO is the first one to touch the aircraft because they have to remove the coatings so [maintainers] can take panels and parts off. LO is the last one to touch the aircraft because they restore the coatings.”
Its inability to manage high heat is also an issue, and has even been known to limit some stealth fighters’ ability to sustain supersonic speeds without getting damaged.