LSR in-orbit: A Summary of Achievements, Challenges and Lessons Learnt

The Life Support Rack (LSR), previously known as the Advanced Closed Loop System (ACLS), is a European regenerative life support system for air revitalization in closed habitats. It is classified as a technology demonstrator with the purpose to test three air revitalization functions combined in only one rack: carbon dioxide removal from cabin air, oxygen generation, and carbon dioxide reprocessing with hydrogen to water and methane. Subject to preventive maintenance on Life Limited Items, the LSR flight model is qualified for an in-orbit operational lifetime of ten years. Being launched in 2018 with JAXA’s HTV 7, the system has come to an early end-of-life after six years on-board the International Space Station. The paper presents an overview over the successful operation of the LSR during the commissioning phase: - Stand-alone utilization of the different subsystems and operation modes -- Carbon dioxide removal -- Oxygen generation -- Water generation by carbon dioxide reprocessing - Combined operations of the above listed functions Additionally, a summary of technical and operational challenges, implemented solutions, as well as lessons learnt accumulated within these 6 years are presented in this paper: - Filter clogging and water membrane pump failure in the water loop - Hydrogen sensor cross sensitivity with water - Water separation issues in the carbon dioxide reprocessing system - Power trips - S/W issues experienced after an upgrade of the LSR’s operating system. Finally, the H/W failures, which led to an early decommissioning of LSR are described.