MELiSSA Pilot Plant: Progressing in the MELiSSA Loop Closure

The MELiSSA project is developing regenerative Life Support technologies to enable long-term human Space missions. The MELiSSA Pilot Plant serves as a testing ground facility for demonstrating the MELiSSA loop, a system composed of several interconnected compartments to provide the essential life support functions: producing food, recycling water and revitalizing atmosphere. To support those functions in a sustainable way, wastes generated by the crew are considered as resources. The facility uses rats as a crew mimicking the respiration of humans, operates under terrestrial conditions, adheres to industry standards and supports long-term experimental studies. The Pilot Plant aims to achieve the complete integration of the MELiSSA loop through a stepwise approach, progressively integrating the different streams of the five compartments. The most recent integration work including the interconnection of up to four compartments of the Pilot Plant will be discussed. This includes the connection of the liquid phase of three compartments: Compartment 3 (ureolysis and nitrifying packed-bed bioreactor), Compartment 4a (photobioreactor for the culture of the edible cyanobacteria Limnospira indica) and Compartment 4b (higher plant growth chamber, capturing CO2, producing O2, drinking water and food). In this set-up, the effluent of Compartment 3, containing nitrified urine, is feeding the photosynthetic compartments (C4a and C4b). Additionally, the complete gas closure of the four compartments has been prepared, with the photosynthetic compartments (C4a and C4b) providing the necessary O2 to support the respiration of the rat’s mock-up crew in Compartment 5 (C5) and the ureolysis, nitrification and Chemical Oxygen Demand removal of urine (C3). This paper describes the preparatory work at the MELiSSA Pilot Plant, including configuration, hardware improvements, and functional test, for the first time connection of four compartments in liquid and gas phases. Furthermore, the experimental conditions to be explored in the integration test campaign are also discussed.