A theoretical model of a life support system, composed of a cascade of well
-mixed continuous culture reactors, is investigated (e.g. photoautotroph, h
erbivore and carnivore). Simple one limiting nutrient reactor equations pro
vide a starting point for the analysis. Optimum surface illumination intens
ity for a given reactor depth and population density has been calculated. L
inking reactors in a cascade enables decoupling of equations, easier analys
is, control and optimisation. Greater stability is thereby also achieved. M
aximum sustainable yield for a given nutrient input is found in a general c
ascade. Needed nutrient input for desired output from each reactor has been
calculated as well. In contrast to a single reactor food chain, we found l
inear dependence of the highest trophic level in each reactor on the nutrie
nt input. Model provides a theoretical basis for acquiring desired yield fr
om each reactor, thus enabling formation of balanced diet for users (e.g. a
spaceship crew). Nutrient cycling is achieved with bacterial degradation.
A buffer, which acts as a low pass filter, is inserted in a cycle. (C) 2001
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