After the invention of metasurfaces, the conventional techniques of reducing RCS have significantly been improved.
As mentioned earlier, the primary objective in purpose shaping is to redirect scattered waves away from the backscattered direction (or the source). However, it compromises the performance in terms of aerodynamics. One feasible solution, which has extensively been explored in recent time, is to utilize metasurfaces which can redirect scattered waves without altering the geometry of the target.
Such metasurfaces can primarily be classified in two categories: (i) Checkerboard metasurfaces, (ii) Gradient index metasurfaces. Similarly, Negative index metamaterials are artificial structures for which refractive index has a negative value for some frequency range, such as in microwave, infrared, or possibly optical.
These offer another way to reduce detectability, and may provide electromagnetic near-invisibility in designed wavelengths.
Plasma stealth is a phenomenon proposed to use ionized gas (plasma) to reduce RCS of vehicles. Interactions between electromagnetic radiation and ionized gas have been studied extensively for many purposes, including concealing vehicles from radar. Various methods might form a layer or cloud of plasma around a vehicle to deflect or absorb radar, from simpler electrostatic to RF more complex laser discharges, but these may be difficult in practice.
Several technology research and development efforts exist to integrate the functions of aircraft flight control systems such as ailerons, elevators, elevons, flaps, and flaperons into wings to perform the aerodynamic purpose with the advantages of lower RCS for stealth via simpler geometries and lower complexity (mechanically simpler, fewer or no moving parts or surfaces, less maintenance), and lower mass, cost (up to 50% less), drag (up to 15% less during use) and, inertia (for faster, stronger control response to change vehicle orientation to reduce detection). Two promising approaches are flexible wings, and fluidics.
In flexible wings, much or all of a wing surface can change shape in flight to deflect air flow. Adaptive compliant wings are a military and commercial effort.The X-53 Active Aeroelastic Wing was a US Air Force, Boeing, and NASA effort.
In fluidics, fluid injection is being researched for use in aircraft to control direction, in two ways: circulation control and thrust vectoring. In both, larger more complex mechanical parts are replaced by smaller, simpler fluidic systems, in which larger forces in fluids are diverted by smaller jets or flows of fluid intermittently, to change the direction of vehicles.
In circulation control, near the trailing edges of wings, aircraft flight control systems are replaced by slots which emit fluid flows.