Design approach of Closed Loop Food Systems in Space

Interest on food production systems based on the cultivation of vegetables for future planetary exploration missions is increasing as these units can help overcome difficult and costly re-supply logistics. In addition to producing edible biomass by growing vegetable species, these systems can be used in closed loop configuration with bioregenerative life support subsystems for water and CO\d2 recycling and O\d2 production. Aiming at this objective, the European Space Agency (ESA) undertook a feasibility study on Closed Loop Food Systems (CLFS) for Low Earth Orbit (LEO), Transit to Mars and Mars Surface scenarios. This paper describes the study's results. Firstly, candidate crops are selected based on nutritional characteristics and aspects like yield, cultivation surface and volume, and generated inedible biomass. A culture plan for these crops is then established. The design process of a Food Production Unit (FPU) begins with the definition of an On Ground Experimental Growth Unit (OGEGU), a ground reference system that is later adapted to the proposed Space scenarios. For Low Earth Orbit (LEO), two secondary structures options (racks and spiral), fitting a Columbus-sized module, are presented and their food production capabilities are analyzed. Similarly, design options for Transit to Mars and Mars Surface are described. Mass, power and volume budgets are determined and the Equivalent System Mass (ESM) methodology is used for trade-off study. For the LEO options process modelling and preliminary mechanical, thermal, safety and logistics analysis are done. Impacts on the International Space Station (ISS) due to potential FPU implementation are also studied. For the Mars surface scenario, an adapted FPU architecture is presented. Interface issues between FPU and bioregenerative life support systems are also addressed. The study shows that FPU systems for LEO application could deliver ca. 12% of the food requirements, which makes them a very interesting platform for both space agriculture research and complementing nutritional requirements. For the Mars Surface application provision of up to 40 % food requirements is shown possible. Finally, relevant technological gaps identified throughout the study are outlined