To propose an efficient illumination method of plant cultural system in a CELSS, net photosynthetic rates per plant (NPR) of lettuce and turnip were investigated under the conditions of 12 -24hr photoperiod, 400-3200 ppm CO₂ concentrations, and 140-320 μ mol/m²/s light intensities.
At 24hr photoperiod (continuous illumination), NPR of lettuce decreased remarkably as compared to that at 12hr photoperiod, whereas NPR of turnip did not change appreciably, with increasing the light intensity or the CO₂ concentration.
In order to avoid the decrease in light efficiency, the condition of a continuous illumination of low light intensity (less than 140 μ mol/m²/s) is effective in the case of plants with the small sink volume like letuce.

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A controlled ecological life support system composed of three subsystems, crew, plants, and waste processor system, is investigated by the use of system dynamics. In this system we used biochemical stoichiometry to express human and botanical metabolisms related toprotein, carbohydrate, fat, fiber, lignin, CO₂, H₂O, NH₃ and HNO₃. The simulation method used here can be expanded to analyze dynamics of more complex system.

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It is necessary for the design of Microalgae Culturing System which control CO₂/O₂ concentration in the closed air to study about the conditions of culturing microalgae. Microalgae culturing experiments were carried out on Chlorella ellipsoidea C-27. The photoenergy source used as an Xe lamp, from which light was transferred through optical fibers and diffused on the cultured medium. As a fundamentally study, photosynthetic rate under the various conditions which are changed lighting, supplying a culture medium in the culture system are investigated.

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To design closed ecological life support systems (CELSS), several methods to check whether the values of steady-state mass circulation fluxes are correctly assigned are considered. The method in which one examines whether steady-state mass balances are zero in simultaneous first-order differential equations promises easy understanding of the arrangement of incoming and outgoing fluxes but is disadvantageous to the storage of the steady-state flux data. To reduce this disadvantage, two similar types of methods that make possible more compact storage of the data are proposed. With respect to intuitive understanding of the flux arrangement, however, these may be somewhat inferior to the previous method. In conclusion, the authors recommend that one carries out appropriate selection according to the situation; thus, it is meaningful to develop a computer software that can satisfy this demand. In addition, the method in which one checks whether the determinant value of the dependent variable matrix generated as a result of tranformation of the differential mass balance equations to the power-law types is equal to zero is also useful. As an example of application, the proposed methods are used to check and modify the steady-state flux data for the water circulation system in the habitat module of Biosphere-J.

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System analysis of Biosphere-J is carried out within the framework of the systematic method for analyzing closed ecological life support systems (CELSS), named CELSS Theory. The present water circulation system in the habitat module, expressed by the first-rder kinetic model, is very stable and the dynamic behaviors of the amount of water in each pool reflect the characteristics of the kinetic model. Additionally, under the assumption of constant incoming and outgoing fluxes for a man, the water circulation system is little influenced by the variation in the amount of water in the plantation module and this variation can be succeeded to only the drinking water tank in the habitat module. As a result, one can conclude that the CELSS Theory is very useful to study the dynamic behaviors of large-scale CELSS.

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System analysis of Biosphere-J is carried out within the framework of the systematic method for analyzing closed ecologicallife support systems (CELSS), named CELSS Theory. A detailed investigation of the logarithmic gains (the percentage change in a dependent variable resulting from an 1% increase in an independent variable) of the water circulation system in the habitat module reveals that their larger values appear at the pools with small volume and/or with small numbers of incoming and outgoing fluxes. In the CELSS having nonlinear fluxes, the logarithmic gains becomes larger at the pools with higher degrees of flux fixation. It is concluded that the CELSS theory can characterize the closed ecological systems throughout the logarithmic gains more easily and accurately than do the conventional methods and is very useful.

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