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Porous media matric potential and water content measurements during parabolic flightControl of water and air in the root zone of plants remains a challenge in the microgravity environment of space. Due to limited flight opportunities, research aimed at resolving microgravity porous media fluid dynamics must often be conducted on Earth. The NASA KC-135 reduced gravity flight program offers an opportunity for Earth-based researchers to study physical processes in a variable gravity environment. The objectives of this study were to obtain measurements of water content and matric potential during the parabolic profile flown by the KC-135 aircraft. The flight profile provided 20-25 s of microgravity at the top of the parabola, while pulling 1.8 g at the bottom. The soil moisture sensors (Temperature and Moisture Acquisition System: Orbital Technologies, Madison, WI) used a heat-pulse method to indirectly estimate water content from heat dissipation. Tensiometers were constructed using a stainless steel porous cup with a pressure transducer and were used to measure the matric potential of the medium. The two types of sensors were placed at different depths in a substrate compartment filled with 1-2 mm Turface (calcined clay). The ability of the heat-pulse sensors to monitor overall changes in water content in the substrate compartment decreased with water content. Differences in measured water content data recorded at 0, 1, and 1.8 g were not significant. Tensiometer readings tracked pressure differences due to the hydrostatic force changes with variable gravity. The readings may have been affected by changes in cabin air pressure that occurred during each parabola. Tensiometer porous membrane conductivity (function of pore size) and fluid volume both influence response time. Porous media sample height and water content influence time-to-equilibrium, where shorter samples and higher water content achieve faster equilibrium. Further testing is needed to develop these sensors for space flight applications.
Document ID
20050164204
Acquisition Source
Kennedy Space Center
Document Type
Reprint (Version printed in journal)
Authors
Norikane, Joey H.
(University of Kentucky Lexington, KY 40546-0276, United States)
Jones, Scott B.
Steinberg, Susan L.
Levine, Howard G.
Or, Dani
Date Acquired
August 23, 2013
Publication Date
January 1, 2005
Publication Information
Publication: Habitation (Elmsford, N.Y.)
Volume: 10
Issue: 2
ISSN: 1542-9660
Subject Category
Aerospace Medicine
Funding Number(s)
CONTRACT_GRANT: NCC10-52
CONTRACT_GRANT: NAG9-1399
CONTRACT_GRANT: NAG10-291
Distribution Limits
Public
Copyright
Other
Keywords
Parabolic Flight
NASA Center JSC
NASA Discipline Life Support Systems
manned
NASA Center KSC
NASA Program Advanced Life Support
short duration
Flight Experiment

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