## 4 Results and Discussion  
The main propulsion module storage tank empty volume is 420 cm\({}^{3}\) and after considering the PMD and utlage volume of 15% of this value, the allowable propellant volume becomes 357 cm\({}^{3}\), refer to Figure 7. The allowable propellant volume for the extension tank is 474.16 cm\({}^{3}\), Figures A4-A6 (Appendix A), considering 20% PMD and utlage. Furthermore, the mass of each propellant along with the total impulse is calculated and presented in Table 9 using the fundamental equations of ideal rocket theory explained in Section 3.1. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Total Tank Empty Volume = 420 cm\({}^{3}\)** & & \\
**PMD and Utilage = 15\%** & & \\
**Allowable Propellant Volume = 357 cm\({}^{3}\)** & & \\ \hline \hline \multicolumn{4}{c}{**Propellants**} \\ \hline \multicolumn{4}{c}{**AF-M315E**} & **HNP225** & **LMP-1035** \\ \(\rho\) (g cm\({}^{-3}\)) & 1.4699 & 1.15023 & 1.2420 \\ \(m_{prop}\) (g) & 524.75 & 410.632 & 443.394 \\ \(I_{tot}\) (N s) & 1369.310 & 858.027 & 1096.123 \\ \multicolumn{4}{c}{**Extension Tank Allowable Prop. Volume = 474.1 cm\({}^{3}\)**} \\ \(I_{tot}\) (N s) & 1818.721 & 1139.627 & 1455.859 \\ \hline \hline \end{tabular}
\end{table} 
Table 9: MIMPS-G total impulse \(I_{tot}\) with the selected green monopropellants. The propulsion system mass budget of dry components is presented in Table 10. COTS components data were collected from the data sheets according to the design requirements. The propellant storage tank was sized to operate at approximately 0.7 MPa nominal pressure, and a 1.2 MPa MEOP was considered, moreover, a pressure burst of 2.0 MPa was calculated by imposing approximately 2.8 factor of safety. Furthermore, a design margin was considered for manufacturability, thus having at least 1 mm thickness titanium wetted part and an outer carbon fiber composite reinforcement plies of 2 mm thickness. The tank also accommodates polyimide Thermofoil(tm) heaters, a pressure sensor, and a temperature sensor, while a mass flow sensor of Out-of-Liquid type should be attached to the tank outlet pipe at least in the testing phase. The micro three-way flow control valve is made of the state-of-the-art acetal homopolymer Delrin(r) that possesses great anti-corrosion properties and is lightweight. The PMD consists of a combination of vanes and a sponge structure at the outlet considering Delrin(r) and Titanium alloy for these parts, respectively. The mass of the storage tank and the feed system was calculated using the CAD modeling software while considering a conservative error margin. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Part** & **Materials/Comments** & **Mass (g)** \\ \hline Cover & Carbon Fiber Reinforce Composites & 65 \\  & \(\rho\) = 1.430 g cm\({}^{-3}\) & \\  & Aluminum 6061-AHC \(\rho\) = 2.79 g cm\({}^{-3}\) & \\ Base & Carbon–Carbon Laminate \(\rho\) = 1.7 g cm\({}^{-3}\) & 101 \\ Micro e-Pump & COTS micro gear pump (7 W–12 VDC) & 75 \\
3-way solenoid & COTS Acetal polymer (Delrin®) \({}^{*}\) Material Compatibility & \\ micro FCV & A-Excellent with Alcohols and aqueous Ammonium nitrate & 45 \\  & [46–48] (2 W) & \\ Piezo Microvalve–Thruster FCV & Piezo tech/ Titanium-wet (200 mW) & 67 \\  & Niobium/ Titanium & \\ Thruster 0.5 N & (Heaters 7–12 W; 12 VDC) without FCV & 80 \\  & CFRP 2 mm thick. \(\rho\) = 1.430 g cm\({}^{-3}\) & 148 \\ Storage Tank & Ti64 1 mm thick. \(\rho\) = 4.43 g cm\({}^{-3}\) & 228 \\ Tank 1/O ports & 5 ports \(\times\) 20 g \"_Rough estimate_\" & \(\sim\)100 \\ \hline \hline \end{tabular}
\end{table} 
Table 10: Inert mass budget of MIMPS-G500 mN propulsion system. Figure 7: MIMPS-G500 mN main module showing the tank shape and different system components. A control and computing unit was considered in the MIMPS-G design although the propulsion system control can be handled by the spacecraft main computer unit. The preliminary design considered extra free volume to allow for further tuning and tweaking of internal components.