## 7 Discussion of the Results
### Examination of the New Design Performance  
The soft iron laminated yoke launcher is an innovative design that reduces the magnetic circuit reluctance by shortening the air gap path for the lines of magnetic flux through the iron yoke. And due to the low reluctance of the iron yoke, the overall reluctance drops as mentioned in Equation (5). Consequently, the inductance of the coil is significantly changed between the initial and plugged positions of the projectile which develops higher force than usual as in Equation (1). Two launchers of the same dimensions are built. These two launchers are identical, but one has an iron yoke and the other does not. A comparison has been carried out between them as they have the same design aspects for a controlled experiment, and this illustrates the superiority of adding an iron yoke. According to the experimental results shown in Table 6 and Figure 15, a significant improvement in the velocity of the projectile reaches 17% compared to the launcher without an iron yoke. Moreover, the efficiency in Table 6 is calculated using Equation (11) in the case of with/without iron yoke to highlight the improvement that rises by 36% over the ordinary launcher's efficiency. In addition, it is proven through Figures 15 and 16 that higher velocities can be achieved by the same voltages by adding an iron yoke. To check the device's eligibility for voltage increase, the ratio between the change in velocity and the voltage change was calculated, as shown in Table 7, and is plotted in Figure 16 in the case of a 6.6 mm iron yoke. This table shows that at high voltages the ratio drops due to the suck-back effect, the saturation of the projectile, and the eddy current effect. when a massive number of magnetic flux lines flow inside the ferromagnetic slug. Figure 14: Magnetic dipole domain direction before and after exposure to launcher magnetic field. Figure 15: Comparison between the projectile velocities with/without iron yoke. To investigate the influence of the iron yoke on the magnetic flux lines, FEMM 4.2 software was used to plot the magnetic flux lines of the launcher coil in the presence and absence of the iron yoke as shown in Figure 17. Figure 17 shows four cases for the launcher, two of them when the projectile is at the start with/without an iron yoke while the other two are when the projectile is plugged into the launcher with/without an iron yoke. To achieve fair judgment, the four cases are simulated at the same time and, consequently, the legend is valid for all of them. Figure 17b,d show the distribution of the magnetic flux lines in the case of the iron yoke where the magnetic flux density is approximately three times higher than in the case of the absence of the iron yoke as is the case in Figure 17a,c. In general, Figure 18 shows the superiority of the proposed design as it boosts the magnetic flux line number without consuming excess energy. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Capacitor Voltage** & **Velocity (\(\frac{\text{m}}{\text{s}}\))** & \(\frac{\text{Av}}{\text{AV}}\) (\(\frac{\text{m}}{\text{volt}\cdot\text{s}}\)) \\ \hline
60 v & 4.7 & - \\ \hline
80 v & 8.75 & 0.2025 \\ \hline
100 v & 11.59 & 0.142 \\ \hline
120 v & 13.18 & 0.0795 \\ \hline
140 v & 14.39 & 0.0605 \\ \hline \hline \end{tabular}
\end{table} 
Table 7: Ratio Between the Change in Velocity and the Change in Supply Voltage. Figure 16: Comparison between velocity difference percentage for each reading. There are many design aspects considered in this work. To compare between the different design aspects of launchers, the efficiency must be calculated for each.