## 4 Structural Analysis of Unit Structure of Deployable Reflector Antenna  
For the unit structure of the main reflector with the stacking sequence in Figure 2c, the modal, quasi-static structural, and thermal-elastic analyses were conducted. To compare \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Property** & **2.1 (High Density)** & **2.2 (Low Density)** & **2.3 (Various Densities)** & **2.4 (Various Thickness)** \\ \hline Mass (kg) & 2.73 & 2.49 & 2.51 & 2.71 \\
1 st mode (\(\mathrm{Hz}\)) & 3.66 & 3.86 & 3.89 & 3.59 \\
2 nd mode [\(\mathrm{Hz}\)] & 11.29 & 11.95 & 11.97 & 10.96 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Modal analysis of the unit structure in the main reflector with respect to each stacking sequence defined in Figure 2.  
Figure 2: Stacking sequence of the main reflector consisting of the facesheet with a laminated pattern of Case 1.1 and the material distribution of the honeycomb core of (**a**) Case 2.1, (**b**) Case 2.2, (**c**) Case 2.3, and (**d**) Case 2.4.  
relative performance, numerical analyses were performed based on the high-density core of Case 2.1 and the low-density core of Case 2.2. The modal analysis of unit structure in the main reflector is conducted for the stowed and deployed conditions, respectively. For both cases, the clamped boundary condition is applied to the connection point such as a hinge point connected with the antenna system. However, for the stowed condition, the clamped boundary condition is also imposed at the top and middle of the main reflector to account for the hold-and-release mechanism devices as shown in Figure 3a. For the deployed condition, the fixed boundary condition is imposed at only the bottom of the hinge. First, the quasi-static analysis of the unit structure in the DR-A was conducted under the 0 g condition for the orbital environment and the 1 g condition for the ground environment. The effect of gravity acceleration change on the deformation of the antenna was quantitatively analyzed using quasi-static analysis. The clamped boundary condition was applied at the hinged mechanism to simulate the deployed condition in Figure 3b. Figure 4 shows that the maximum displacement in the z-direction of the reflector was compared to that of the honeycomb core model of Case 2.1 (high-density core) and Case 2.2 (low-density core). As shown in Figure 4, the z-directional maximum displacement of the low-density core structure was \(1.74\times 10^{-2}\) m lower than that of the high-density structure. In this viewpoint, the structural stability of gravitational environments of the low-density core model is higher than that of high-density core ones. Figure 4: Quasi-static analysis result with a 1 g gravitational acceleration field; the displacement field of the honeycomb core distribution with (**a**) high-density and (**b**) low-density material; (**c**) contour of displacement. Figure 3: Boundary Condition of Unit Structure in Deployable Reflector Antenna under (**a**) the stowed and (**b**) deployed condition. Figure 5 shows the structural-thermal coupled analysis of the unit structure in the DR-A. During mission operation, the satellite is subjected to severe thermal load from low to high temperature, depending on the relative position of the satellite with respect to Earth and Sun. In this study, the worst hot condition where a satellite is located between Earth and Sun is applied to simulate the significant temperature gradient. In order to determine temperature distribution, the orbital thermal analysis for the DR-A is implemented. The temperature distribution for the worst hot case is shown in Figure 5a. The unit structure (blue dotted line) with the highest temperature is applied to the input load for the structural-thermal coupled analysis where the range of the temperature load is from 0 to 110 \({}^{\circ}\)C. Stress distributions for high- and low-density models are shown in Figure 5c,d, respectively.