| Summary: | In this thesis the energy loads and equivalent mass loads of three life support systems for human space flight have been studied. The physico-chemical system on International Space Station, ISS, has been compared to two concepts for biological life support: the Russian BIOS-3 system and the European MELiSSA system. BIOS-3 is a system where vegetables and wheat are grown hydroponically and waste is burnt. MELiSSA is a system where waste is decomposed by microorganisms in biological reactors. The products of decomposition are used as nutritient for edible Spirulina algae and hydroponically grown plants. The conceptual layouts of the three systems were found in the literature. They were complemented with assumptions when needed. Data on masses and power consumptions were found in the literature and in fact sheets on commercial equipment from different companies. The study shows that MELiSSA uses about four times the average power of BIOS-3. ISS and BIOS-3 use approximately the same amount of average power. Regarding equivalent mass, BIOS-3 breaks even with ISS after 2 years. MELiSSA breaks even with ISS after 7.5 years. MELiSSA and BIOS-3 never break even because BIOS-3 has lower startup mass and needs less supply mass than MELiSSA. The MELiSSA system is more controllable than the BIOS-3 system, due to its biological reactors. It can be discussed whether the reactors also make MELiSSA a more reliable system than BIOS-3. If the BIOS-3 system uses the self-restoring capabilities of plants its reliability might increase. In conclusion: this study has shown that for a long-term mission a biological life support system might be an economically viable alternative to a physico-chemical one. More empirical research is needed in order to find out how much energy and mass resources biological life support systems need, and whether they can be as reliable as physico-chemical ones.
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