Current human spaceflight requirements limit the number of hours a crewmember can be outside of the habitation unit to 8 hours in a 48-hour period, and 24 hours in a seven-day period. This time must be appropriately balanced to complete science, exploration, and maintenance tasks. Off-days can be used for site transit (traverse), crew rest, or intra-vehicular activities (IVA). The “building blocks” approach to mission design organizes crewmember activities for extra-vehicular activities (EVA) at each investigation site based on the types of tasks that must be completed and the tools required to complete each task. Building blocks colocate payload and crewmember information for timeline construction. Similar tasks or tasks that accomplish similar goals are grouped into blocks and distributed according to EVA requirements for a specified number of days, including allocations for site arrival activities and departure preparations.
Designing building blocks and surface mission timelines becomes a time-consuming and tedious process when done by hand. Timeline Builder Assistant (TBA) was designed to reduce the time required for this process. The EVA Builder is a combination of Microsoft Excel worksheets and a data manipulation system written in Visual Basic for Applications that is built on a database of all building blocks, elements, and activities. The activities database allows the user to create a new building block from selected activities.
The result of the timeline builder should not be considered a “final product,” and does not represent the only feasible approach to mission success. TBA makes no attempt to optimize the solution; for example, if the set currently requires 6.5 hours but the next block in the set requires 1.75 hours, it will create another day of EVA without searching for a different block that may be able to fill that gap. In this version, the user specifies the number of sites visited; the number of days required to complete an investigation at each site becomes a dependent variable. This allows for quick analysis of multiple surface scenarios with a consistent set of building blocks. The resulting timeline can easily be updated or replaced as capabilities, goals, or constraints change.