## 2 Research Status on Anhydrous Hydrazine Fuel
### Research Status on MMH Fuel
\begin{table}
\begin{tabular}{c c} \hline
**Study** & **Description and Findings** \\ \hline [PERSON] et al. [33] & Investigated primary reaction rate constants for uniform bond \\  & breaking of N-N bonds in N2H4 and MMH \\ \hline [PERSON] and [PERSON] [25] & Studied decomposition reactions of N2H4, MMH, and UDMH \\  & in adiabatic flowers at atmospheric pressure 750–1000 K \\ \hline  & Conducted a pyrolysis study of 1–3\% MMH/argon mixtures in \\  & 38.4 mm excitation tubes in the temperature range of 1040 to \\ [PERSON] et al. [9] & 1370 K and pressure range of 1.4 to 4.5 atm. MMH can \\  & decompose ecothermally at 70–80 mol\% argon dilution. Pure \\  & gaseous MMH is much less sensitive to explosive bombardment \\  & than hydrazine \\ \hline  & Investigated the kinetics of the thermal decomposition reaction \\  & of MMH using quantum Rice–Ramsperger–Kassel (QRRK) \\ Sun and Law [62] & theory and pressure drop master equation analysis. N-N and \\  & C-N bond-breaking reactions are the main reaction pathways \\  & simulating the homogeneous decomposition of MMH under \\  & atmospheric pressure conditions \\ \hline  & Using laser absorption techniques, measured the time histories \\  & of NH2 and NH3 during MMH pyrolysis after reflecting \\  & excitation waves in an excitation tube. N-N bond splitting is the \\  & most sensitive reaction pathway to simulate the homogeneous \\  & decomposition of MMH at high pressures. Overall MMH \\  & decomposition rate is consistent with first-order kinetics \\ \hline \end{tabular}
\end{table} 
Table 3: Some MMH studies and findings. implications would help researchers and practitioners optimize MMH fuel utilization, safety protocols, and performance in specific applications. Other areas for analysis are discussed next. Understanding MMH Decomposition at Different Pressure Ranges: While the reviewed studies have shed light on MMH decomposition at atmospheric pressure, there is a lack of research on its behavior under different pressure conditions. Further studies could explore the kinetics and mechanisms of MMH decomposition at low and high pressures, providing a comprehensive understanding of its behavior across various operating conditions. Investigating MMH Combustion in Combination with Various Oxidizers: Most reviewed studies focused on MMH decomposition and reaction kinetics in isolation. Future research could explore the behavior of MMH in combination with different oxidizers, such as nitrogen tetroxide (NTO) or nitrous oxide (N2O), to better understand the combustion characteristics and combustion efficiency of MMH-based propellants. This would facilitate the optimization of propellant formulations for specific applications. Studying MMH Stability and Aging: Understanding MMH fuel's stability and aging characteristics is crucial for safe handling and storage. Further research could focus on investigating the long-term stability of MMH under various storage conditions, such as temperature, pressure, and exposure to contaminants. This would contribute to developing guidelines for the safe storage and transportation of MMH fuel. Exploring Alternative MMH Decomposition Pathways: While the reviewed studies have provided insights into the primary decomposition pathways of MMH, there may be alternative or secondary pathways that have not been extensively explored. Further investigation could focus on identifying and characterizing these alternative pathways, which could impact the overall reaction kinetics and product formation during MMH decomposition. Modeling and Simulation of MMH Combustion and Ignition: The development of accurate and reliable numerical models for simulating MMH combustion and ignition is essential for predicting and optimizing the performance of propulsion systems. Future research could refine existing kinetic models and reaction mechanisms to improve their predictive capabilities. Additionally, experimental data from different operating conditions can validate and calibrate these models, ensuring their accuracy and applicability.