• analytical model
• carbon dioxide
• experiment
• fluid transfer
• green propellants
• in-space refuelling
• nitrous oxide
• test bench

In-space refueling is essential for extending satellite operational life and enabling ambitious, long-duration space missions. With rising concerns over the environmental and health risks of traditional propellants, especially carcinogenic hydrazine, there is an increasing demand for green propellants. Nitrous oxide (N₂O) presents a promising, eco-friendly alternative due to its lower toxicity and self-pressurizing capabilities, which simplify propulsion system design while maintaining high performance.

This project focuses on developing a fluid transfer model for N₂O and constructing a test bench to simulate in-space fueling operations. Modeling N₂O fluid transfer poses unique challenges, particularly in accurately representing its complex thermodynamic behavior and two-phase flow during pressure changes. Reliable prediction of mass flow rates and thermodynamic properties is crucial for designing dependable refueling systems. After evaluating various discharge models—the Equilibrium Model, Zilliac and Karabeyoglu model, and Casalino and Pastore model—the Equilibrium Model was selected as a suitable first approximation for its simplicity and ability to yield comparable data.

To support model validation, a fluid transfer test bench was developed to simulate N₂O transfer dynamics. For practicality and safety, carbon dioxide (CO₂) is used as an analog fluid, given its similar thermodynamic characteristics. The test bench provides a controlled environment to examine fluid transfer behavior under conditions representative of in-space refueling.

Preliminary results from test bench experiments indicate that the model captures the core phenomena involved in the fluid transfer process reasonably well, though further analytical code improvement and limitation of the first iteration of the test bench is discussed in the thesis. This foundational work contributes to the advancement of safe, efficient in-space refueling technologies and supports the broader goal of sustainable, extended space missions.