Impact of Crewmember Schedule on System Performance

A simple simulation model is built to determine the oxygen, carbon dioxide, and water supplies needed from Earth, as well as their respective storage tank sizes required to sustain crewmembers activities in different scenarios. The scenarios investigated include full supply of oxygen, carbon dioxide, and water from Earth without regenerative technologies, constant re-supply and removal rates from regenerative technologies, and variable re-supply and removal rates from crops. Hourly crewmember schedule is implemented to determine its effect on the storage cost. No specific regenerative technologies are assumed, hence giving the freedom to minimize the storage tank size without technical constraints. Equivalent system mass (ESM) analysis on storage tanks is conducted to investigate the storage cost in all scenarios. ESM is a cost metric used to perform trade study analysis. The components considered in ESM are mass, volume, power, cooling and crew time. In this paper, a 15-year Mars surface mission is selected. Results indicate that crewmember schedule affects the storage tank capacity significantly when the re-supply/removal rate is constant. Crop effect is greater than crewmember schedule when it is introduced into the model. It becomes the driving force on the storage cost. However, when contingency, leakage and technology inefficiency levels are considered, the leakage and technology inefficiency rates of more than 1% have a larger impact on the storage ESM than crops do.