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The BIO-Plex facility will need to support a variety of life support system designs and operational strategies. These systems will be tested and evaluated in the BIO-Plex facility. An important goal of the life support program is to identify designs that best meet all size and performance constraints for a variety of possible future missions. Integrated human testing is a necessary step in reaching this goal. System modeling and analysis will also play an important role in this endeavor. Currently, simulation studies are being used to estimate air revitalization buffer and storage requirements in order to develop infrastructure requirements of the BIO-Plex facility. Simulation studies are also being used to verify that the envisioned operation strategy will be able to meet all performance criteria. In this paper, a simulation study is presented for a nominal BIO-Plex scenario with a high-level of crop growth.

This paper builds on a steady-state investigation of waste heat reuse in an Advanced Life Support System (ALSS) for a Mars mission with a low degree of crop growth. In past studies, such a system has been defined in terms of technology types, hot and cold stream identification and stream energy content. The maximum steady-state potential for power and cooling savings within the system was computed via the Pinch Method. In this paper, the next step is taken toward achieving a pragmatic estimate of costs and savings associated with waste heat reuse in terms of equivalent system mass (ESM). In this paper, the assumption of steady-state flows are discarded, and a proposed schedule is developed for activities that are of interest in terms of waste heat reuse. The advanced life support system for the Mars Dual Lander Transit Vehicle is the system of interest.

Reduction in power requirements for long-term space travel remains a critical technological challenge, since power provision for an advanced life support system determines a significant portion of the system's equivalent system mass (ESM). Optimization of individual processors alone is not sufficient to minimize power needs; system studies must be performed in order to maximize power savings. It is important to develop system designs that are more efficiently integrated from an energy standpoint, so that the equivalent system mass of future life support systems can be reduced. In a procedure referred to as the ‘pinch technique’, hot and cold streams within the system are matched and their energy exchanged in order to lower the external cooling and heating requirements. This paper describes an investigation of power savings by application of the pinch technique to a closed life support system under steady-state conditions.

As a part of the systems modeling research at NASA Ames Research Center, the use of a market-based control strategy to actively manage power for a model of a regenerative life support system (LSS) is examined. Individual subsystem control agents determine power demands and develop bids to ‘buy’ or to ‘sell’ power. A higher level controller collects the bids and power requests from the individual agents, monitors overall power usage, and manages surges or spikes. The higher level controller conducts an ‘auction’ to set a trading price and then allocates power to qualified subsystems. The auction occurs every twelve minutes within the simulated LSS. This market-based power reallocation cannot come at the expense of life support function. Therefore, participation in the auction is restricted to those processes that meet certain tolerance constraints. These tolerances represent acceptable limits within which system processes can be operated.

Dynamic system models are being developed which track the flow of material through a regenerative life support system over time periods of months to years. These models, written in MATLAB/SIMULINK©, are designed to help perform system trade studies and to evaluate system operations issues. They include atmosphere regeneration, water recovery, crop growth, food processing, and waste processing. The overall system simulation is being used to quantify variations in stream flow rates and subsystem processing rates and to estimate buffer requirements for various system configurations and design options. It will also be used to investigate scheduling, operations, and control issues and to evaluate the sensitivity of system-level dynamics to model inaccuracies and off-nominal operation. Results will be presented on sharing or separating the atmospheres of the crew, crops, and waste chambers.

This paper offers a concept for a regenerable, low-power system for purifying exhaust from a solid waste processor. The innovations in the concept include the use of a closed-loop regeneration cycle for the adsorber, which prevents contaminants from reaching the breathable air before they are destroyed, and the use of a humidity-swing desorption cycle, which uses less power than a thermal desorption cycle and requires no venting of air and water to space vacuum or planetary atmosphere. The process would also serve well as a trace contaminant control system for the air in the closed environment. A systems-level design is presented that shows how both the exhaust and air purification tasks could be performed by one processor. Data measured with a fixed-bed apparatus demonstrate the effects of the humidity swing on regeneration of the adsorbent.

A steady-state system mass balance calculation was performed to investigate design issues regarding the storage and/or processing of solid waste. In the initial stages of BIO-Plex, only a certain percentage of the food requirement will be satisfied through crop growth. Since some food will be supplied to the system, an equivalent amount of waste will accumulate somewhere in the system. It is a system design choice as to where the mass should accumulate in the system. Here we consider two approaches. One is to let solid waste accumulate in order to reduce the amount of material processing that is needed. The second is to process all of the solid waste to reduce solid waste storage and then either resupply oxygen or add physical/chemical (P/C) processors to recover oxygen from the excess carbon dioxide and water that is produced by the solid waste processor.

A Laboratory-Scale Controlled Ecological Life Support System (Lab-Scale CELSS) is being developed in order to provide the insight, knowledge, and experience needed to design a human-rated CELSS facility. This multi-phase project will integrate pre-existing processors into a closed loop regenerative life support system testbed. Phase I of the Lab-Scale CELSS Project involves the integration of a crop growth chamber with a solid waste processor. Tests to date have shown that carbon and water can be recovered from inedible biomass for recycling to the plant chamber. This paper will describe the requirements, design, and some experimental results from Phase I of the Lab-Scale CELSS project and provide an overview of future phases.

A preliminary design of a Life Support System (LSS) has been developed as part of an ongoing comprehensive trade study of advanced processor technologies and system architectures for an Initial Lunar Outpost. The design is based on a mission scenario requiring intermittent occupation of a lunar surface habitat by a crew of four. It incorporates physiochemical process technologies that were considered for Space Station Freedom. A system-level simulation model of the design was developed to obtain steady-state material balances for each LSS processor. The mass flow rate predictions were used to obtain estimates of the LSS mass, volume, and power consumption by means of processor sizing correlations that were extrapolated from Space Station Freedom processor designs.