PBR@LSR: A Hybrid Life Support System Experiment at the ISS

Space Agencies' human spaceflight plans include as possible future destinations the Moon, asteroids and Mars. The long duration of these missions and its further distance to Earth will require reducing the dependence on Earth's resources as much as possible. A potential solution is the use of a hybrid Life Support System (LSS), combining physico-chemical and biological technologies. The experiment PBR@LSR (Photobioreactor at the Life Support Rack) will be launched to the International Space Station in November 2018 to demonstrate the functionality of such a hybrid life support system. A second objective is to prove the feasibility of non-axenic long-term cultivation of microalgae (Chlorella vulgaris) for up to 180 days under space conditions. The experiment and development of the μg adapted photobioreactor was initiated in 2014 by DLR and the Institute of Space Systems (IRS) of the University of Stuttgart with Airbus Defence and Space as prime for the flight hardware. The hybrid approach will be demonstrated by the connection of the photobioreactor to the European Life Support Rack (LSR, also known as ACLS - Advanced Closed Loop System). The LSR uses physico-chemical technologies to collect and process the carbon dioxide produced by the astronauts into oxygen, by using a solid-amine absorber, a Sabatier reactor and water electrolysis. A highly concentrated CO _{2} surplus from the LSR will be fed to the biological component, the PBR, which will produce oxygen and biomass. Every two weeks a partial liquid exchange will allow harvesting biomass and providing fresh nutrients. Relevant sensors (CO _{2}, O _{2}, pH, cell density, etc.) will allow evaluating the performance and stability of the experiment and several algae suspension samples will be taken at different intervals and returned to Earth to evaluate the radiation and μg influence on the algal cells. Various experiments were carried out in three breadboards on ground to investigate both biological and technical aspects, in order to design the flight experiment. This presentation gives an overview of the knowledge gained in ground experiments, the design and construction of the flight experiment and the planned operations.