An Integrated Approach to Analyzing Ascent Abort Ground Track Sea Conditions for Crewed Space Vehicles

This paper provides a methodology to support day-of-launch (DOL) sea condition assessments for space vehicles through the assessment of both climatological variables and vehicle capabilities. Crewed vehicles launching from Kennedy Space Center (KSC) need to ensure that vehicles with abort-to-water capabilities can safely land in the ocean and that recovery personnel can reach and extract the crew in a timely manner if an abort occurs along the ascent abort ground track. As such, the programs impose limits to sea conditions, such as wave height and wind speed, to both vehicle and recovery capabilities. The Marshall Space Flight Center Natural Environments Branch (EV44) determines the likelihood of violating the specified constraints along the ground track not only for mission planning, but also for potential flight rule development. However, gaps arise when only assessing geographical areas without regard to abort potential. These gaps include the need to mitigate over-conservatism stemming from the implied requirement to meet all criteria along the entire ground track, and effectively applying EV44 analysis techniques to flight rule development. To bridge these gaps, EV44 recently worked with colleagues at KSC and Johnson Space Center to develop a methodology that combines sea condition climatology with the probability of a given vehicle landing in specific areas along a ground track. This methodology produces the percent of the ground track that violates constraints at each timestamp in the climatology, with appropriate weighting given to areas that the vehicle would more likely land given an abort. Combining these results with program’s acceptance threshold for the percent of the ground track that contains conditions that violate specified constraints, the potential exists to translate analysis results to DOL flight rules. This paper describes the methodology and provides some examples using hypothetical vehicle capability inputs and sea condition output from the Interim European Centre for Medium-Range Weather Forecast Re-Analysis.