Refrigerant-Based Propulsion System for Small Spacecraft

Abstract

The MR SAT spacecraft under development at UMR requires a propulsion system that can be utilized to perform orbital maneuvers and three-axis attitude control to complete its mission objective of conducting spacecraft formation flight. This thesis documents the research, analysis design and development of the cold gas propulsion system that was integrated in the MR SAT spacecraft. The basis of design and safety requirements stemmed from the AFRL University Nanosat Program competition, in which the UMR SAT project placed third out of eleven schools from across the nation. The MR SAT propulsion system was a primary feature as it implements a refrigerant (R-134a) propellant that has never been flown in space. As detailed in this thesis, through engineering modeling and laboratory testing R-134a is demonstrated to be a feasible propellant for small spacecraft. As the R-134a is stored as a saturated liquid in the tank, it was necessary to analyze the thermodynamic properties of the refrigerant and investigate phase changes for its use as a propellant. Also documented is the hardware selected and the integration into the MR SAT spacecraft, along with the laboratory testing that has been conducted. R-134a offers good performance characteristics and this thesis can be used as a design template by other small spacecraft developers who require a safe and inexpensive propulsion system. v

First and second law analysis of an ejector expansion Joule-Thomson cryogenic refrigeration cycle

“…Another study of geothermal energy system thermodynamics for two-phase horizontal pipe flow was conducted by Zhao et al [27]. Seubert [28] employed EES to compute thermodynamic properties of R-134a using a real fluid, highaccuracy for refrigerant-based spacecraft propulsion systems. Ghajar and Darabi [29] have also employed EES to investigate novel micro loop heat pipes under steadystate conditions, with applications in electronics.…”