The radio-frequency (RF) field mapping and its analysis inside a space vehicle cabin, although of immense importance, represent a complex problem due to their inherent concavity. Further hybrid surface modeling required for such concave enclosures leads to ray proliferation, thereby making the problem computationally intractable. In this paper, space vehicle is modeled as a double-curvatured general paraboloid of revolution (GPOR) frustum, whose aft section is matched to an end-capped right circular cylinder. A 3D ray-tracing package is developed which involves a uniform ray-launching scheme, an intelligent scheme for ray bunching, and an adaptive reception algorithm for obtaining ray-path details inside the concave space vehicle. Due to nonavailability of image method for concave curvatured surfaces, the proposed ray-tracing method is validated with respect to the RF field build-up inside a closed lossy cuboid using image method. The RF field build-up within the space vehicle is determined using the details of ray paths and the material parameters. The results for RF field build-up inside a metal-backed dielectric space vehicle are compared with those of highly metallic one for parallel and perpendicular polarizations. The convergence of RF field within the vehicle is analyzed with respect to the propagation time and the number of bounces a ray undergoes before reaching the receiving point. 1. Introduction In the fore section of any space vehicle, astronauts work in the presence of multiple radiating sources. This makes the astronaut cabin of space vehicle an important indoor environment which necessitates RF field mapping. The space vehicle cabin is essentially a concave structure. Over the last decades, ray tracing has been employed for site-specific indoor propagation models [1–3], and it has been shown that multiple reflections are dominant for the RF field build-up within the cavity compared to the phenomenon of diffraction [4]. Although ray tracing has been used earlier for electromagnetic (EM) analysis of aircraft cabin-like enclosures, a closer scrutiny reveals that these predominantly employ measurements to merely fit their predictions or to validate their empirical models [5–7]. For EM environment analysis within the space shuttle interior (payload bay area), attempts have been made earlier to overcome the computational complexity by approximating the curved surfaces with large planar faceted plates [8]. However, this leads to a completely different ray solution set, which may not necessarily approximate to the case of curvatured surfaces
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