Fecal Simulant Delivery Systems for Parabolic Flight Testing of the Flexible Membrane Commode

The Flexible Membrane Commode (FMC) is an alternative waste management system designed to address the severe mass restrictions on the Orion vehicle. The concept includes a deployable seat and single use, three layer bags that employ air flow to draw solids away from the body and safely contain them in disposable bags.¹ Simulated microgravity testing of the system was performed during two separate parabolic flight campaigns in July and August of 2008. Experimental objectives included verifying the waste fill procedures in reduced gravity, characterizing waste behavior during the filling process, and comparison of the results with model predictions. In addition the operational procedure for bag installation, removal, and sealing were assessed. ² A difficult operational requirement concerns the delivery of the fecal waste simulant into the upper area of the bag in a manner that faithfully simulates human defecation. The material must not receive excessive downward or rotational forces, and separation of the material from the delivery system must be complete. Therefore, given the complex and unpredictable effects of microgravity environment, four separate simulant delivery systems were developed and tested using two fecal waste simulants and two separate FMC test rigs. The first test rig was fixed to the aircraft, while the second was a self-powered “free floating” system that minimized the effects of residual gravity and “G-jitter” during parabolas.² This paper focuses on the development and testing of the waste stimulant delivery systems, and provides recommendations for future systems/operations for microgravity testing of commode systems.