Anticipated Extravehicular Activity Time on the Lunar Surface Based on ISS Operations

Abstract

Extravehicular activities (EVA) on the lunar surface will be frequent and of extended duration to provide the most efficient use of time for exploration activities. This goal of maximizing crew time for exploration activities is analogous to the International Space Station’s (ISS) goal of maximizing time for science activities. On ISS, however, science activities were less than expected due in part to additional time being taken up by habitat maintenance needs. To avoid a similar occurrence on the lunar missions, realistic estimates were determined for maintenance and other non-exploration activities, so that alternative design approaches could be examined. The two main categories of non-exploration activities are habitat maintenance and personal activi ties (e.g., sleep and exercise); these activities are estimated to use 17.2 hours per crew me mber per day (hr/CM/d). The third category is standard operations (e.g., communications, medical operations) that are anticipated to take approximately 2.6 hr/d/CM. Therefore , on an average day, only 4.3 hr/CM/d are left for EVA, which is further reduced by pre- and post-EVA operations. Therefore, assuming a crew size of four and two-person EVA sorties, the average daily total time for EVA surface excursions is less than 2.2 hours. Given the potential for this likely unacceptably low EVA time, different approaches were evaluated to reduce the daily need for vehicle maintenance and personal activities and to increase time available for lunar exploration. After modifying the mission design with respect to human performance, schedule and technology factors, it is shown that productive EVA time could be increased to up to 5.0 hr/d.