The science, history and future of stealth materials
Oct 28, 2016 Dan Katz | Aviation Week & Space Technology
This is the third article in a series. Stealth is traditionally associated with aircraft shaping, but as more nations field low-observable aircraft and counter-stealth sensors, radar-absorbing materials (RAM) may take on increasing importance.
Typically, shaping accounts for 90% of the radar cross-section (RCS) reduction of a stealth aircraft and RAM the remaining 10%. And where RAM might reduce RCS by an order of magnitude, shaping can shrink it by three or four orders. But RAM reduces radar returns from certain features more than these guidelines imply and, while progress in shaping may be plateauing, in materials it is advancing rapidly.
The ability of a substance to absorb electromagnetic (EM) waves depends on two material properties called permittivity and permeability, which are the capacity to store electrical or magnetic energy, respectively. The source of both is the existence of electric or magnetic dipoles at the atomic, molecular or crystal lattice level.