Engineering and Operational Validation of a Closed-Loop ECLSS Test Platform for the Mars Gravity Biosatellite

We present details of the design, implementation, test and operation with live mice of a closed-loop integrated ECLSS ground test apparatus for the Mars Gravity Biosatellite. The sealed system includes accommodations for two flight-design habitat modules, which can be deployed in either a rotational or a non-rotational configuration. Installed within the apparatus are scaled-down versions of a subset of flight-equivalent atmospheric reconditioning subassemblies together with sensors, actuators and a computer to perform autonomous feedbackdriven supervisory control. We present data that validates an integrated closed-loop system which includes oxygen replenishment, carbon dioxide scrubbing via reaction with lithium hydroxide, ammonia removal using acid-treated activated charcoal, and humidity control with a custom-designed condensing heat exchanger. An atmospheric monitoring suite incorporates commercially available off-the-shelf low-mass, low-power sensors to perform continuous environmental monitoring. The entire system is enclosed within a zero pressure gradient barrier membrane with sealed ports for power, data and contingency air sampling. Results of a 25- day experiment represent a proof-of-concept for certain key elements of the Mars Gravity Biosatellite's ECLSS strategy. Not all elements were investigated – notably, control of total pressure and temperature were outside the scope of this study. In addition, no attempt was made to model the expected on-orbit atmospheric leakage.