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The Magnetic Field Apparatus (MFA) was developed specifically to test whether high gradient magnetic fields (HGMFs) can simulate gravity by providing a directional stimulus for plants grown in space. This space shuttle middeck-locker experiment was designed to imbibe dry flax (Linum usitatissimum L.) seeds on orbit, capture time-lapsed images of the emerging roots as they are exposed to HGMFs, and, at the appropriate time, chemically fix the biological material. One of the major obstacles in the development of this payload system was to determine exactly when was the ‘appropriate’ time for fixation. Ideally the emerging roots were to be fixed after they have passed the area of highest magnetic gradient (∼8mm), but before they have grown so long as to physically touch the sides of the chamber (∼12mm). Initiating the fixative delivery sub-system within this relatively narrow window of acceptability was obtained with a unique iterative control methodology.

We report here on a series of KC-135 parabolic flight studies investigating various aspects of water distribution in plant nutrient delivery systems being developed for spaceflight applications. Several types of porous tubes were evaluated. Under microgravity conditions, fluid was observed to creep up the end walls of polycarbonate substrate compartments. Capillary mats wrapped around the porous tubes wetted up in a uniform fashion regardless of the level of gravity to which they were being exposed, and they were found to eliminate the end-wall creep wetting-up pattern. Results from observations using 1-2 mm glass beads and 1-2 mm Turface substrates are presented. The Turface’s absorption of water effectively minimized fluid redistribution as the compartment alternated between microgravity and 1-1.8g conditions.

A plant cultivation material known as the Fibrous Ion Exchange Resin Substrate (FIERS) was assessed for its ability to provide nutrients to wheat plants growing hydroponically on a porous tube nutrient delivery system. Seeds were imbibed and grown on six porous tubes; three at different wetness levels utilizing only the FIERS (as a source of nutrients) and three at comparable wetness levels but with Hoagland’s solution used as the source of nutrients. Although there were significant differences between wetness levels and methods of nutrient provision treatments, the FIERS demonstrated the capability to support plant growth through seed production.

Installation of a ‘salad machine’; in the International Space Station (ISS) will be the first step toward long-term biological regeneration of food during space missions. Salad crops have demonstrated promise for providing dietary supplements and psychosocial benefits. A cylindrical conveyer-type design (called the Phytoconveyer) under development exhibits high productivity and low energy and crew time demands. The overall dimensions are 54 × 59 × 40 cm. Power consumption is 0.25 kW and the volume of the plant growth chamber is 0.09 m3. The Phytoconveyer includes a cylindrical planting surface area comprised of six root modules. Each root module contains a porous tube wrapped in a fibrous ion-exchange resin substrate (BIONA V-3) enclosed within a black plastic cover with an open slot on the top for seed insertion. The total outer diameter of the root module is 5 cm.

The WONDER space flight experiment will compare the operation of both substrate-based and porous tube nutrient delivery systems (NDS) under microgravity conditions. Each NDS will be evaluated with three moisture availability regimes, and moisture sensing will be critical for the operation and evaluation of the systems. Orbital Technologies (Madison, WI) has developed a space flight-rated temperature and moisture acquisition system (TMAS) for measuring water content of plant growth medium. The sensors were evaluated in 0.25-1 mm and 1-2 mm baked ceramic aggregate (Profile and Turface, respectively). The sensors' pooled standard deviations ranged from approximately 2% to 5% relative water content (RWC), and root mean square error between sensor RWC and measured RWC was greater than 3% using linear calibration.

The Magnetic Field Apparatus (MFA) is a newly developed hardware system for space flight experimentation. The main goal of the MFA is to provide a platform to conduct experiments exposing plant tissues to a high gradient magnetic field (HGMF) in a microgravity environment. The MFA is being developed as a Space Shuttle middeck facility, and once completed will be classified as generic Life Science Laboratory Equipment (LSLE) and available to all NASA-sponsored investigators. The first flight of the MFA will be on STS-107 (currently scheduled for mid-2001). It will be configured to carry dry flax (Linum usitatissimum L.) seeds into space, imbibe the seeds on-orbit, and expose the emerging roots to a high-gradient magnetic field. Time-lapse digital imagery will document root development, and the hardware will support chemical fixation at the appropriate time to preserve the specimens and terminate the experiment.