Date of Completion


Document Type

Honors College Thesis


Mechanical Engineering

Thesis Type

Honors College

First Advisor

Dr. William Louisos

Second Advisor

Dr. Yves Dubief


Microgravity, Volume of Fluid, Monopropellant, Satellite Propulsion System, Computational Fluid Dynamics, ANSYS Fluent


High Test Peroxide (HTP) is a non-toxic propellant used in satellite missions. The auto-decomposition of HTP produces oxygen gas, increasing pressure within the propellant tank and the risk of tank rupture. Benchmark Space Systems has developed a solution utilizing a Polytetrafluoroethylene (PTFE) breather tube within the tank to evacuate the oxygen gas bubbles; the simple polymeric structure of PTFE allows oxygen molecules to permeate through the tube and be drawn out of the propellant tank, reducing pressure and mitigating the risk of tank rupture.

It is known from physical, 1g experiments conducted at Benchmark Space Systems, that upon contact with the breather tube, the oxygen gas is immediately evacuated from the tank and the tank pressure decreases. However, the behavior and distribution of oxygen bubbles in microgravity, where buoyancy is absent and satellite maneuvers induce fluid sloshing, is unknown.

This study aims to evaluate the breather tube’s effectiveness under microgravity conditions by analyzing the behavior and location in time of the oxygen bubbles within the propellant tank, as well as the approximate deformation and movement of the breather tube (via 1D beam-bending) in response to satellite maneuvers using Computational Fluid Dynamics. The project utilizes the Volume of Fluid (VOF) Multiphase Model and Tecplot 360 analysis tools in determining a method of quantifying the locations of the oxygen bubbles within the liquid HTP of the propellant tank.

The study explored a range of total oxygen volume fractions and the effects of different initial sloshing accelerations. The results indicated that higher oxygen concentrations and greater sloshing accelerations led to greater breather tube deflection. The effectiveness of the breather tube in microgravity conditions, in removing oxygen gas from the propellant tank, is determined by a combination of factors, including the deflection of the tube and its location relative to the location of the oxygen bubbles. Maximum deflection coincided with instances of the most complex sloshing behavior, as is shown by qualitative and graphical representations of the percentage of oxygen occupying the breather tube region, which would result in more frequent contact between the gas and breather tube under such conditions.

Creative Commons License

Creative Commons Attribution-Noncommercial-No Derivative Works 3.0 License
This work is licensed under a Creative Commons Attribution-Noncommercial-No Derivative Works 3.0 License.