Lessons Learned for the International Space Station Potable Water Dispenser

The International Space Station (ISS) Potable Water Dispenser (PWD) currently provides potable water for United States On-orbit Segment crew consumption in food and drink packages. The first PWD unit commenced on-orbit operation in early 2009 and is certified for 10 years of operation. A second PWD unit began development 3 years after the certification of the first PWD unit to extend support of the ISS beyond 2018. A number of design changes were incorporated into the second PWD unit based upon the on-orbit experience with the first PWD unit over those 3 years. Operational changes were developed in response to on-orbit issues, including the certification of a shock kit to address unacceptable microbial growth prior to PWD activation. A major redesign of the primary crew interface was developed to increase the ease of use and robustness of the system. This redesign was incorporated into the base design of the second PWD unit and also retrofitted into the first PWD unit on-orbit. Other observations over the years of sustaining the PWD have generated knowledge that can help direct the development of future potable water dispensers, such as updates to key design assumptions regarding crew and payloads usage of the PWD system. This paper will detail the lessons learned from the PWD systems to inform development of future potable water dispensing hardware for other vehicles.