  Hypersonic flight regime is conventionally defined for Mach larger than 5; in
these conditions, the flying object becomes enveloped in a plasma. This plasma
is densest in thin surface layers, but in typical situations of interest it
impacts electromagnetic wave propagation in an electrically large volume. We
address this problem with a hybrid approach. We employ Equivalence Theorem to
separate the inhomogeneous plasma region from the surrounding free space via an
equivalent (Huygens) surface, and the Eikonal approximation to Maxwell
equations in the large inhomogeneous region for obtaining equivalent currents
on the separating surface. Then, we obtain the scattered field via (exact) free
space radiation of these surface equivalent currents. The method is extensively
tested against reference results and then applied to a real-life re-entry
vehicle with full 3D plasma computed via Computational Fluid Dynamic (CFD)
simulations. We address both scattering (RCS) from the entire vehicle and
radiation from the on-board antennas. From our results, significant radio link
path losses can be associated with plasma spatial variations (gradients) and
collisional losses, to an extent that matches well the usually perceived
blackout in crossing layers in cutoff. Furthermore, we find good agreement with
existing literature concerning significant alterations of the radar response
(RCS) due to the plasma envelope.
