# Hybrid Shielding for Hypervelocity Impact of Orbital Debris on Unmanned Spacecraft
## 3 Results and Discussion  
This section discusses the results of further analyses done with the models described and validated in the previous sections. These include a number of critical design parameters of the Whipple shield, such as (i) the density of the honeycomb core (i.e., the number of honeycomb cells along the width of the core); (ii) the thickness of the honeycomb shell, both of which will directly impact the weight (areal density) of the final shield; (iii) the honeycomb base material; and (iv) the exact location of the impact relative to the honeycomb. The capacity for the shield to dissipate the kinetic energy of the impact was used as the main design parameter in these studies. The labels and specifications of the developed models are listed in Table 2, along with the key results from each parameter study to analyse the effectiveness of the honeycomb core shield. As an example, Figure 11 shows a 3-dimensional view of the T-50 model, with a core cell density of 6 and a shell thickness \(t_{\text{h}}=0.5\) mm. Table 3 and Figure 12 summarise the main results from all the tests. In order to record the energy dissipated before particles bounce back off the back plate, some results are captured at different times, \(t=17.5\) us for the honeycomb shell thickness simulations and \(t=20\) us for all remaining ones. \begin{table}
\begin{tabular}{l l c c c c} \hline \hline
**Test** & **Model Label** & **Material** & **Cells** & \
\begin{tabular}{c} **Thickness** \\ **\(\mathbf{f_{h}}\) (mm)** \\ \end{tabular} &
\begin{tabular}{c} **Impact** \\ **Location** \\ \end{tabular} \\ \hline Standard shield & C-0 & – & 0 & – & – \\ \hline \multirow{4}{*}{Cell density} & C-2 & & 2 & 0.5 & \multirow{4}{*}{Single edge} \\  & C-4 & & 4 & 0.5 & \\ \cline{1-1}  & C-6 & & 6 & 0.5 & \\ \cline{1-1}  & C-8 & & 8 & 0.5 & \\ \cline{1-1}  & C-10 & & 10 & 0.5 & \\ \hline \multirow{4}{*}{Shell thickness} & T-01 & & 6 & 0.01 & \multirow{4}{*}{Single edge} \\  & T-05 & & 6 & 0.05 & \\ \cline{1-1}  & T-10 & & 6 & 0.1 & \\ \cline{1-1}  & T-15 & AL2024-T3 & 6 & 0.15 & \\ \cline{1-1}  & T-20 & & 6 & 0.2 & \\ \cline{1-1}  & T-30 & & 6 & 0.3 & \\ \cline{1-1}  & T-50 & & 6 & 0.5 & \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Characteristics and labels of the developed Whipple shield numerical models. Figure 10: Computational run time (CPU) against finite element mesh element size of the honeycomb core structure. \begin{table}
\begin{tabular}{l l l l l l} \hline \hline
**Test** & **Model Label** & **Material** & **Cells** & \begin{tabular}{l} **Thickness** \\ **\(t_{\text{h}}\) (mm)** \\ \end{tabular} & \begin{tabular}{l} **Impact** \\ **Location** \\ \end{tabular} \\ \hline Material & \begin{tabular}{l} M-AL \\ M-TI \\ \end{tabular} & \begin{tabular}{l} AL2024-T3 \\ Ti-6 Al-4V \\ \end{tabular} & \begin{tabular}{l} 6 \\ 6 \\ \end{tabular} & \begin{tabular}{l} 0.3 \\ 0.3 \\ 0.3 \\ 0.3 \\ 0.3 \\ \end{tabular} & Single edge \\ \hline Impact location & \begin{tabular}{l} L-SE \\ L-MP \\ \end{tabular} & \begin{tabular}{l} 6 \\ \end{tabular} & \
\begin{tabular}{l} 0.3 \\ 0.3 \\ 0.3 \\ 0.3 \\ 0.3 \\ 0.3 \\ \end{tabular} &
\begin{tabular}{l} Single edge \\ Mid point \\ Double point \\ \end{tabular} \\ \hline \hline \end{tabular}
\end{table} 
Table 2: _Cont._  
Figure 11: 3-dimensional view of model T-50, with a core cell density of 6 and a shell thickness \(t_{\text{h}}=0.5\) mm (see Table 2).