Research On Eliminating Carbon Dioxide In Spacecraft Cabins

Controlling the density of carbon dioxide in manned spacecraft cabins is an important task of the environmental control and life support system. Although the carbon dioxide eliminating equipment is important and already installed in the spacecraft, the theoretical analysis of its characteristic is rarely reported. The gas adsorption characteristic of the zeolite 5A molecular sieve was studied by means of the adsorption theory, so that the control arrangement for cabin carbon dioxide was designed and calculated in the thesis. The adsorption technology and representative theories are collected and analyzed. The isotherm adsorption formulas for the process of adsorbing nitrogen, oxygen and carbon dioxide on the zeolite 5A molecular sieve at 25 centigrade are obtained by using the Langmuir, Freundlich and BET models with the experimental data, respectively. Based on the above formulas and adsorption theory, the characteristic of the zeolite 5A molecular sieve in adsorbing air, especially carbon dioxide, has been gained, and the construction of adsorbing bed was therefore calculated for a three crewmember cabin. The results show that the zeolite 5A molecular sieve adsorbs the components of air competitively. Due to the fraction of nitrogen is much higher than that of carbon dioxide, the former adsorbed amount would be much greater than the latter. However, as the zeolite 5A molecular sieve had been modified with some technique, its adsorption to nitrogen might be ignored. The desorption process can be speeded at heating condition. The transition or breakthrough time and the volume of the adsorbing bed will be longer or larger with the increase of the bed length. The determination of the parameters of the adsorbing beds should be on the basis of their working condition, cabin space and etc.