A Fecal Processing Technology Trade Study for Water Recovery in Various Mission Duration Scenarios

Date

7/12/2021

Authors

Powell, Camilah
Waguespack, Glenn
Ewert, Michael

Journal Title

Journal ISSN

Volume Title

Publisher

50th International Conference on Environmental Systems

Abstract

To achieve long endurance human space missions such as a trip to Mars, a fully recycled or "closed loop" water system is almost essential. Even for shorter duration missions in Earth orbit, lunar orbit or on the surface of the moon, recovering and recycling water from as many sources as possible may pay off. One source of water that has not been exploited to date is human solid waste. Herein, a trade study is performed to evaluate the ability of several fecal processing technologies to recover >80% of the water content within the waste. Human solid waste (feces) contains approximately 75% water by mass, which upon quantification, translates to ~170 g of recoverable water per crew member per day and can scale to values of ~680 kg for a crew of 4 persons on a 1,000-day long exploration mission. Several fecal processing technologies (i.e., steam reforming, vacuum drying, freeze drying, pyrolysis, ultrasonic drying, etc.) are analyzed using an equivalent system mass (ESM) approach to assess and compare the estimated cost for recovering fecal water -- in terms of mass, power, and volume equivalents -- against the water recovery mass savings for each technology. Post-use volume, too, is used as a secondary metric for comparison to quantify the benefits of volume reduction resulting from the fecal drying process. From said analysis, clear patterns and benefits emerge that may prove helpful for future fecal processing technology development.

Description

Camilah Powell, ERC. Inc.
Glenn Waguespack, Geocontrol Systems Inc.
Michael Ewert, NASA Johnson Space Center
ICES304: Physio-Chemical Life Support- Waste Management Systems- Technology and Process Development
The 50th International Conference on Environmental Systems was held virtually on 12 July 2021 through 14 July 2021.

Keywords

Fecal Waste Management, Fecal Processing and Storage, Long duration space missions

Citation