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NASA's Centrifuge Facility is a multi-purpose life sciences research facility to be flown on Space Station Freedom. It will provide the capability for conducting experiments with living plants and animals in the microgravity environment of space. One component of the Facility is a plant habitat which is capable of supporting a wide variety of plant species under highly controlled environmental conditions. The conditions to be controlled include temperature, humidity, lighting (photosynthetically active radiation or PAR), air velocity, trace contaminant concentrations, nutrient element concentrations, and atmospheric composition. Lockheed conducted a “rapid prototyping” exercise to develop and test a preliminary design for such a plant habitat. Concurrent with an analytical effort, breadboard fabrication and testing was performed to support the acquisition of detailed performance data for both design analysis and validation of the simulation models used in the analysis.

A successful CELSS (Controlled Ecological Life Support System) design must accommodate the potential mismatch between the crew's relatively constant CO2 production and the widely varying crop CO2 consumption over the plant growth cycle. Any additional changes in material flows, processor characteristics or other system characteristics may have deleterious effects which propagate throughout the CELSS. Important transient conditions which the system design and planting regimen must allow for are described, including: Crop startup. Crop failures. Changes in number of humans supported. A general-purpose life support system simulator was used to evaluate several CELSS design and operation approaches. The simulator was used to investigate CO2 generation and removal interactions occurring between the CELSS food production subsystem and the rest of the system. These interactions were selected because they are major drivers of the system design and operation.

One of the most frequently encountered problems in the design and development of life support systems concerns system integration and evaluation. Lockheed Missiles & Space Co. has developed a simulation modelling toolkit to assist life support system designers in conducting system design, integration and performance assessment. This work arose from a recognized need for a flexible, easily-visualized simulation tool to support aerospace life support system design. The simulator supports performance analysis and “what if” studies based on the construction of block diagrams of the systems to be simulated. Libraries of physicochemical, bioregenerative and hybrid technologies have been developed. These subroutines can be accessed for use in developing system block diagrams. The blocks specified in a particular model can be easily interchanged with other blocks which perform similar functions to assess changes in system performance.