International Space Station Waste Collector Subsystem Risk Mitigation Experiment Design Improvements 2002-01-2304

The International Space Station Waste Collector Subsystem Risk Mitigation Experiment (ISS WCS RME) was flown as the primary (Shuttle) WCS on Space Shuttle flight STS-104 (ISS-7A) in July 2001, to validate new design enhancements. In general, the WCS is utilized for collecting, storing, and compacting fecal & associated personal hygiene waste, in a zero gravity environment. In addition, the WCS collects and transfers urine to the Shuttle waste storage tank. All functions are executed while controlling odors and providing crew comfort.

The ISS WCS previously flew on three Shuttle flights as the Extended Duration Orbiter (EDO) WCS, as it was originally designed to support extended duration Space Shuttle flights up to 30 days in length. Soon after its third flight, the Space Shuttle Program decided to no longer require 30 day extended mission duration capability and provided the EDO WCS to the ISS Program. Based on lessons learned from the three previous flights and crew comments, the EDO WCS was upgraded as the ISS WCS RME. Modifications covered both major subsystems, urinal and commode. Urinal subassembly modifications included elimination of urine carryover & condensation within the urine separator, and increased airflow to maximize urine entrainment. Commode subassembly modifications included decreasing fecal collection airflow for crew comfort and increasing solid waste compaction efficiency.

This paper provides a brief history of the ISS WCS program, with a short comparison to the nominal Shuttle WCS, and a detailed explanation of each hardware modification. Discussion will include what necessitated these modifications, the applied solutions, flight certification method, and in-flight results based on a successful Space Shuttle mission.