The European Space Agency MELiSSA project: Food Production and Preparation - The state of the art

The project MELiSSA aims to conceive a closed-loop artificial ecosystem, based on recovering fresh food, water and oxygen through the complete recycling of organic waste (carbon dioxide, urine and faeces). The MELiSSA loop was originally conceived without higher plants and utilized a photosynthetic microorganism, the cyanobacterium Arthrospira platensis (also known as Spirulina), as source of food. However, this strategy entailed low rate of air regeneration and limitations in the diet nutritional value and composition. Higher plants were introduced as bioregenerative component in 1997, and research on a plant chamber to be integrated in the loop started. The MELiSSA Pilot Plant (MPP), a sealed chamber with gas, liquid, and solid connections from/to the other compartments, was built and the study of its interface with the system, in terms of quantity and quality of fluxes, was introduced as a research topic. Three crops, wheat, beet and lettuce, were selected for initial hydroponic cultivation tests, in a staggered plantation system, with the target of an edible biomass production of 20% of the crew needs. Results on crop yield and carbon exchange modeling, even in response to variable CO2 concentration and light intensity, demonstrated the potential of plant research in closed environment systems. Based on these results, more challenging goals were introduced in Food Characterization Phase 1 (years 2009 - 2010), which aimed to the characterization of 4 crops, potato, soybean, bread wheat and durum wheat (4 cultivars each) in hydroponics under controlled environment, and to the design of a next generation chamber. On the same crops, in Phase 2 Cultivar Selection - CulSel (2013 - 2015), further objectives were to improve the criteria of cultivar selection for Space cultivation and to assess the impact of beneficial microbes in the rhizosphere on plant performance. Beside, within the project HYdroponic SubSystem Engineering - HYSSE, studies to model and develop, with engineering approach, a modified hydroponic system to address critical modeling requirements in closed chamber were carried out. The lecture will present an overview on fundamentals of the food production and preparation chain in MELiSSA. Focus will be on the relevant achievements in controlled environment technologies for higher plants and crop productivity, and the related current technical and scientific issues. The contribution of fresh food to preserve the physiological and psychological wellbeing of the astronauts during long distance flights will be also considered. Finally, future directions, including prospective terrestrial exploitation of developed technologies and missing space application will be summarized.