Evaluation of EVA Egress Concepts for a Dual-Orion NEA Mission

Abstract

Among the various missions being considered for future human space exploration beyond low Earth orbit, a number of near Earth asteroids (NEAs) are emerging as candidate destinations. Lockheed Martin’s Plymouth Rock NEA mission proposal, which utilizes a baseline dual-Orion/Multi-Purpose Crew Vehicle (MPCV) configuration, appears to be among the most viable near-term options for such a mission. The baseline extra-vehicular activity (EVA) scenario for Plymouth Rock calls for egress via the MPCV hatch. This study presents and evaluates alternative egress approaches that could facilitate EVA operations and also improve the overall mission design. Among the secondary benefits are a potential reduction in atmosphere mass purged per EVA and an increase in crew habitable volume. The latter is particularly significant given that potential mission durations, which are target dependent, are expected to range from 150 to 210 days. As a result, the focus of this study is to propose and evaluate a number of potential changes to the Plymouth Rock baseline spacecraft configuration versus anticipated high level mission trade criteria. By way of a decision matrix, which applies weighting factors to both mission trade criteria and egress concepts, a numerical analysis is undertaken to identify the most favorable egress concepts for further evaluation. The ultimate goal of this study is to thoroughly characterize the various concepts by identifying the most sensitive mission trade criteria and how they would impact design choices. This will provide mission planners with generic, quantitative trade values and analysis tools to aid in the evaluation of potential EVA egress concepts.