# Review of Adaptive Shock Control Systems
## 3 Discussion
### Concept 1--Perforated Skin/Porosity (Passive Approach)
#### 3.1.1 Advantages  
The passive design and consequent low complexity are key advantageous features of this approach. Furthermore, this concept requires very little installation space, thus, it could be applied on almost any region of the wing.  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline \# & **Concepts** & \multicolumn{2}{c}{**Advantages**} & \multicolumn{2}{c}{**Challenges**} \\ \hline \multirow{3}{*}{3} & \multirow{3}{*}{SMA 3 wire bundle actuators} & \(\bullet\) & Accurate bump shape control & \(\bullet\) & SMAs need constant heat supply, sufficient isolation and/or locking device \\  & & \(\bullet\) & Height \& position variable & device \\  & & \(\bullet\) & Not limited to spoiler & \(\bullet\) & Reduce complexity of controlling several actuators \\ \hline \multirow{3}{*}{4} & \multirow{3}{*}{SMA plate} & \multirow{3}{*}{SMA plate} & \multirow{3}{*}{\(\bullet\)} & \multirow{3}{*}{Little installation space required} & \(\bullet\) & Since only 3D bumps are possible, SCBs must be designed accurately to perform as good as 2D SCBs \\  & & \(\bullet\) & Not limited to spoiler & \(\bullet\) & Not position variable \(\rightarrow\) VC is needed \\  & & & & \(\bullet\) & SMAs need constant heat supply, sufficient isolation and/or locking device \\ \hline \multirow{3}{*}{5} & \multirow{3}{*}{Pressure-actuated concepts} & \(\bullet\) & Accurate bump shape control & \(\bullet\) & Sealing for pressure system \\  & & \(\bullet\) & Height \& position variable & Reduce weight increase due to pressure system \\  & & \(\bullet\) & Not limited to spoiler & \(\bullet\) & Reduce complex of control (depending on number of elements) \\ \hline \multirow{3}{*}{6} & \multirow{3}{*}{Thin flexible plate deformation by airflow pressure differences} & \(\bullet\) & Simple (especially the passive approach) & \(\bullet\) & Strong dependency on cavity pressure \\  & & \(\bullet\) & Small weight impact & \(\rightarrow\) Accurate control and sealing needed \\  & & \(\bullet\) & Little installation space & \(\bullet\) & Passive: No active shape control \\  & & \(\bullet\) & Height and (limited) position variation & \(\bullet\) & Possible \\ \hline \multirow{3}{*}{7} & \multirow{3}{*}{Compliant structures} & \(\bullet\) & Not limited to spoiler & \(\bullet\) & Multidisciplinary design framework \\  & & \(\bullet\) & Could be combined with several other concepts & \(\bullet\) & Reduce actuator forces \\  & & \(\bullet\) & Potentially reduced wear & \(\bullet\) & Simplify manufacturing and assemblies \\ \hline \multirow{3}{*}{8} & \multirow{3}{*}{Shock mitigation with plasma} & \(\bullet\) & Fast control & \(\bullet\) & Limit high energy amount for plasma \\  & & \(\bullet\) & Small weight impact & \(\bullet\) & Strong insolation of fuel tanks against \\ \cline{1-1}  & & \(\bullet\) & Little installation space & \(\bullet\) & electrical currents and plasma needed \\ \cline{1-1}  & & & & \(\bullet\) & Early technology stage for shock control \\ \hline \hline \end{tabular}  
* The flexible hinge technology is innovative but challenging, however, this technology is not mandatory for these concepts and it could be applied to any other spoiler concept as well; 2 VC: Variable Camber; 3 SMA: Shape memory alloy.  
\end{table}
Table 1: _Cont._