Gas exchange between humans and multibiological life support system

To establish a Bioregenerative Life Support System (BLSS) in lunar or Mars bases in the future, manned stimulation experiments including several kinds of creatures are needed to be conducted first. Gas exchange relation, element transfer and transformation principles, etc. between humans and the multibiological system composed of plants, animals, microalgae and so on must be investigated in order to place different organisms with appropriate numbers and proportions in the BLSS. This research cultivated lettuce (Lactuca sativa L.) and silkworm (Bombyx mori L.) in the CICS (Closed Integrative Cultivating System) of the IES (Integrative Experimental System) with Chlorella vulgaris cultivated in the PPB (Plate Photo Bioreactor) of the IES. Conveyor-type cultivation method was implemented for harvesting the largest batch of lettuce and silkworms through the mass exchange chamber of the IES every four days and transferring the smallest batch of lettuce and silkworms into the system; carrying certain amounts of alga liquid out with nutrient liquid replenished every day. Gas exchange between testers and the IES including three phases was conducted periodically. Phase I involved one person participating in gas exchange with lettuce in plant chamber as primary means of air revitalization for 3 months. Phase II was gas exchange between one person and autotrophic creatures, which were lettuce and microalgae, for 1 month. In the Phase III test, silkworms were introduced into the animal chamber for 2 months. Mathematical modeling and experimental simulation for this system was done to study its gas robustness. Results show that CO2/O2 concentration fluctuated around normal levels, the system possessed relatively good gas robustness and there were no trace gas (CH4, NH3 and C2H4) contaminant problems in the system.