The research studies the accelerating and decelerating behavior of liquid fuel stored in the fuel tank of a spacecraft in the absence of gravity. When the tank is not completely filled with fuel and part of its volume is fuel vapor, a sudden change in the spacecraft motion will cause liquid motion inside the tank. This will compress and/or expand the vapor, assumed to be an ideal gas, altering the vapor properties according to Boyle’s Law.
Two processes of liquid motion are taken into consideration in this research: isothermal and adiabatic processes. Taking a cylindrical tank moving along its axis, both result in a periodic motion of the liquid slug between two bases of the fuel tank. Evaporation is then added into the calculation.