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Plant Water Management (PWM)

PWM Quad Chart

This project fundamentally explores the microgravity design space for a fully autonomous passive farming system in space. The technology demonstration is expected to further develop our fundamental understanding and physical models characterizing the interaction of microgravity passive water and nutrient delivery to various plant configurations. The phase change between water delivery, plant evaporation, and environmental condensation parameters will be investigated visually and used to model the complete passive processes involved. This project will leverage current on-orbit techniques for active water and nutrient delivery and condensation techniques.

Research Overview

Food is a critical element for human survival.  The time to effect may be shorter for oxygen, shelter, or water, but the consequences are just as serious.  Stored food is a significant logistics burden for initial human missions to Mars.  Scientific experiments have demonstrated that plant growth in space is feasible. Crew response to food and voluntary time spent tending plants also provide evidence for the benefit plants can have for future missions.  Past experiments have shown difficulty with sufficient hydration and aeration to the plant root zone.  The plant requires water for nutrient transport, biochemical processes, and thermal management.  Aeration is required for the root zone to exhaling carbon dioxide and inhaling oxygen at a minimal but necessary level.

The plan is to utilize an evolutionary approach to examine capillary forces to control the watering but examine various hydration methods such as soil-based, hydroponics, aeroponics, or some other technique. Furthermore, the approach is amenable towards satisfying requirements ranging from plant science studies to a deep space food production system. This project is a collaborative effort between the Fluid Physics researchers and NASA’s Glenn and the plant biologists at NASA’s Kennedy Space Center. ZIN Technologies, Inc is providing engineering support, manufacturing of the hardware, and ISS operations. The Principle Investigator (PI) for the technology demonstration is Dr. Mark Weislogel of Portland State University, who has decades of experience with microgravity capillary fluids research.

The Lunar Orbiting Module – Gateway is planning to have a garden system that would provide farming in space for several reasons, including nutrient delivery to the astronauts, mass savings on multiple launches, food logistics, and science benefits comparing to the earth gravity. The “Earth-independent” leg of the NASA Strategic Plan is supported by the potential for pure passive support systems for these farming outposts. There are researchers at Kennedy Space Center, under the Space Life and Physical Sciences Research and Application (SLPSRA) Program, who are experimenting with all other parameters of the microgravity biologic life cycles. There does not currently exist an alternative for earth’s gravity as a passive means of controlling plant watering and aeration in NASA’s toolbox.

The NASA Glenn Research Center Fluid Physics research team has decades of microgravity passive fluid experiments, and significant experience with design and operation of both active and passive two-phase fluid systems in both earth bound and microgravity environments. The knowledge and expertise developed over the past several decades of fluids research should be able to uniquely define the necessary parameters for a specific semi-closed loop system that allows for energy input and outputs edible plants of various types.

The International Space Station as a microgravity research facility has the facility capability to provide detailed, unique fluids experiments that are designed to provide engineering parameters for the follow-on lunar and earth-independent environments.

Portland State University has unique capabilities including their own 2.1 second drop tower, development of the Surface Evolver-Fluid Interface Tool, and  the engineering coursework that has the potential to redefine the engineering of passive fluid support systems for not only plant water delivery and recovery, but entire thermal processes involving water that are vital to long term un-resupplied space habitats.

Science Objectives


The strategic goals of this project including using the science capabilities of the ISS for long duration microgravity fluids research, as well as being the primary research center for a passive fluid management garden concept in the Garden Gateway mission set, managed by Kennedy Space Center project managers under the Space Life and Physical Sciences Research and Application (SLPSRA) Program. The passive fluids requirements and active transition points are planned to give the Garden Gateway program a minimum set of fluids parameters and capillary-based design criteria to define an integrated system.

This will be accomplished by providing fundamental capillary transport fluid physics data for water-based solutions. A series of experiments are in planning to justify capillary flow design integrations into the future garden concepts. The flow rates, aeration types, soil configurations, and evaporation / condensation parameters will be able to be adjusted for each type of experiment.

Cameras will collect visual records, and all parameters are able to be recorded through the camera link from MWA to the Telescience Support Center (TSC).

The technology to be developed are specific manufacturing techniques for visually clear root ball uptake devices, along with improvements in clear capillary flow devices for a range of flow rates. All other devices within the system will be spaceflight certified reuse items, integrated into a single design for flight.

Development Approach

This technology demonstration will utilize the Maintenance Work Area, the light sources, video and still cameras that are available on the ISS.

To simulate the capillary demands of a typical plant, rayon felt and nylon string will be used to simulate the evaporative characteristics of the foliage and to simulate the water uptake of the root zone and the transport function of the stem. Six test concepts are envisioned.

Current Status

The first two demonstrations for PWM, Soil and Hydroponics experiments, are scheduled for ISS operations in late 2019 with several more iterations still in development.

Project Management

Project Manager: Kelly Bailey, NASA Glenn Research Center

Project Scientist: Dr. David Chao, NASA Glenn Research Center

Deputy Project Scientist: Tyler Hatch, NASA Glenn Research Center

Principal Investigator: Dr. Mark Weislogel, Portland State University

Engineering Team: ZIN Technologies, Inc.

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