SAWE Report - Cal Poly San Luis Obispo

Another area of concern is that of visual observability. This is not a very big problem as the
aircraft cruises so high that visually detecting the Vendetta would be near impossible. The only
threat here is the contrails left by the engines. The contrails can be minimized by contrail
avoidance techniques and don’t pose a large problem.
To quantitatively analyze the radar cross section of the Vendetta, Radbase2 software by Surface
Optics was utilized. First, a faceted model was generated from the 3D model. Faceting was
limited to only those necessary because of the demanding processing requirements. Facets were
limited to 10 degree tolerances at roughly 0.017 feet minimums. The facetted model is presented
as Figure 4.2.
Figure 4.2 - RCS Model Faceting
It can be seen that heavy facet optimization was needed to make sure that all facets followed
tangency requirements to leave smoothly curved and splined surfaces. The spline arc on the top
of the fuselage is modeled with facets every 10°. For the flat surfaces like the wings and
empennage 10° is more than adequate.
The Radbase2 RCS code calculates the radar returns based on Physical Optics and Chu-Stratton
integral methods. These are highly computationally intensive. Because of this, bounces off of
surfaces were limited to 2 after the initial bounce off the surface. This was deemed adequate for
this level of analysis. The vertical-vertical polarization of the return and transmission was
analyzed as it is the most relevant to how radar stations operate. Monostatic radars which both
broadcast and receive were used in the analysis as there would be too many possibilities to
calculate for bistatic radars.
The code was allowed to iterate on the model with 1° azimuth increments and for 0° and 15°
lookup angles. It was also run for 1, 5, 10, and 12 GHz radar frequencies. Most fast track and
search radar runs at the higher frequencies while long range threat radars utilize the lower
frequencies. The 1 to 10 GHz range covers most of the radars that are expected for the role of
this aircraft. A table of common ground and surface radars with their respective frequencies is
presented as Table 4.I.
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