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This paper describes the need and solution for minimizing EVA airlock time and depress gas losses using a new method that minimizes EVA out-the-door time for a suited astronaut and reclaims most of the airlock depress gas. This method consists of one or more related concepts that use an evacuated reservoir tank to store and reclaim the airlock depress gas. The evacuated tank can be an inflatable tank, a spent fuel tank from a lunar lander descent stage, or a backup airlock. During EVA airlock operations, the airlock and reservoir would be equalized at some low pressure, and through proper selection of reservoir size, most of the depress gas would be stored in the reservoir for later reclamation. The benefit of this method is directly applicable to long duration lunar and Mars missions that require multiple EVA missions (up to 100, two-person lunar EVAs) and conservation of consumables, including depress pump power and depress gas.

A generalized computer program for analysis of pressure and composition in multiple volume systems has been under development by the National Aeronautics and Space Administration (NASA) since 1976. This paper describes the most recent developments in the program. These improvements include the expansion of the program to nine volumes, improvements to the model of the International Space Station (ISS) carbon dioxide removal system, and addition of a detailed Sabatier carbon dioxide reduction mode. An evaluation of the feasibility of adding of trace contaminant tracking was also performed. This paper will also present the results of an analysis that compares model predictions with ISS flight data for carbon dioxide (CO2) maintenance.

A generalized computer program for analysis of pressure and composition in multiple volume systems has been under development by the National Aeronautics and Space Administration (NASA) since 1976. This paper describes the most recent developments in the program. These improvements include the addition of an X-windows style graphical user interface (GUI), the inclusion of simulations of International Space Station (ISS) Environmental Control and Life Support System (ECLSS) components, the addition of simulation of Shuttle space suits, the addition of an event processor, and the addition of an option for the user to select the volume configuration. The ARPCS2AT2_STATION computer program was developed by NASA as a tool for analyzing the changes in partial pressures of four gasses (nitrogen, oxygen, carbon dioxide, and water vapor) in interconnected volumes.

A pre-prototype expert system called SLMES (Shuttle Leak Management Expert System) has been developed that enables an ECLSS (Environmental Control and Life Support System) subsystem manager to analyze subsystem anomalies and formulate flight procedures based on flight data. SLMES combines rule-based expert system technology with traditional FORTRAN-based software into an integrated system. SLMES uses rules to ask the user for configuration information and to prompt for flight data. SLMES analyzes the data using rules and when it detects a problem that requires a simulation it sets up the input for the FORTRAN-based simulation program ARPCS2AT2. This program predicts the cabin total pressure and composition as a function of time. The program simulates the pressure control system, crew O2 masks, airlock repress/depress valves, and leakage, etc. When the simulation has completed, other SLMES rules are triggered to examine the results for simulation contrary to flight data.

A generalized computer program for analysis of pressure and composition in a multiple-volume system has been developed by the National Aeronautics and Space Administration (NASA). This paper describes the development of the program, outlines the program's capabilities, and illustrates the application of the program to Space Shuttle-related atmospheric pressure and composition control analyses. The program's features include the calculation of transient partial pressures of four gases in four volumes, an option for either isothermal or temperature-transient analyses, simulation of pressure and composition control hardware, and simulation involving 0-10 crewmembers. This computer program has been used successfully for a variety of Shuttle-related analyses to support hardware design, develop operating procedures, and provide real-time Shuttle mission support. Due to the versatility of this computer program, it will be utilized for Space Station program analyses.