For a radar transmitter and receiver at (almost) the same location — "monostatic" radar, the normal case for search and fire-control radar — a flat conducting panel reflects strongest straight back at the radar when the panel's surface normal points directly at it. This model uses the physical-optics estimate for a flat facet at boresight:
σ_facet(θ) = (4π A² / λ²) · cosⁿ(θ), θ = angle(facet normal, radar direction)
n ∝ √A / λ (larger facets, relative to wavelength, have a narrower specular lobe)
σ_total ≈ Σ σ_facet (incoherent sum over sunlit facets, θ < 90°)
RCS[dBsm] = 10·log₁₀(σ_total / 1 m²)
- Faceted stealth — every panel is tilted to a different, oblique angle (the F-117 design philosophy), so no facet's normal lines up with common threat directions; the strong "glint" is scattered into a few narrow, predictable, low-priority slivers instead of a broad reflective lobe.
- Conventional (boxy) — panels sit parallel/perpendicular to the body axes, so as the radar sweeps in azimuth its line of sight repeatedly lines up square with a flat side, producing frequent strong "corner-reflector"-style spikes.
- Depression angle — a ground radar looking up at a flying aircraft; most low-observable shaping is optimized for this lower forward hemisphere, where a threat radar is statistically most likely to be.
- Band selector — RCS scales as 1/λ²; a longer-wavelength radar (L-band and below) also starts to see facets that are no longer "electrically large," where diffraction and traveling-wave effects this simplified specular-only model omits become significant — one real reason low-frequency radar is a harder threat for faceted stealth shapes.
Simplification note: real RCS prediction sums facet returns coherently (with phase, causing constructive/destructive interference) and includes edge diffraction, cavity effects (inlets, cockpit) and traveling waves. This simulator sums facet power incoherently for a clean, real-time visualization of the shaping principle — it is a teaching model, not a certified RCS prediction code.