Preliminary Design Definition of the C.R.O.P.® Filter Unit for Integration in a closed on-orbit Life Support System

Kurzfassung

Regarding the future of human spaceflight the development of bioregenerative life sup- port systems is of great importance. Long-term manned space missions will meet the challenge of a complete recycling capability to limit the consumption of resources and resupply. Gravitation biologists of the German Aerospace Center (DLR) have developed the Combined Regenerative Organic food Production (C.R.O.P.®) filter which degrades biowaste to a nutrient solution for plants. Aiming at a closed ecosystem this biofilter represents a key element connecting human and flora. In its current composition the filter operates only under gravity so that the general concept has to be changed for future use in space. An overall design condition is to fit into the on the International Space Station commonly used Middeck Locker and to comply with the respective interfaces. The motivation of this work is a preliminary design of the C.R.O.P.® filter unit for application in microgravity and the determination of the particular components. As a restriction merely the conversion of human urine is performed. The procedural method to develop the overall system complies with the guidelines of the European Cooperation for Space Standardization (ECSS). It includes the following steps: Once the existing filter device is illustrated a requirement specification for its on-orbit adaption can be generated. Subsequently feasible solution concepts are demonstrated, assessed and compared considering technical and biological conditions. Based on this a detailed system design for the preferred technology is established. The major challenge of the development process is to meet the demands of both the technical realization itself and the issue of its biocompatibility. The design development of the biofilter for weightlessness as presented below is performed at the Institute of Aerospace Medicine at DLR Cologne. The content of the thesis is structured as follows: In chapter 2 the filter performance under gravity is described and the problem of its on-orbit utilization is determined. The thereof derived requirements analysis forms the input for the development process. Having presented and evaluated general concept approaches in chapter 3 the concrete technical solution is settled. The detailed specification of the preliminary system design is then deduced in chapter 4: Properties of the subsystems and its components are analytically established. Schematics visualize their interaction and the arrangement within the overall system architecture. Decisive parameters for future integration and operation such as weight and power consumption of the entire unit are assessed. In chapter 5 this preliminary design is critically reflected. Chapter 6 summarizes the results and points out the next steps of the project proceeding.