Gary W. Stutte

Concept for Sustained Plant Production on ISS Using VEGGIE Capillary Mat Rooting System

Plant growth in microgravity presents unique challenges associated with maintaining appropriate conditions for seed germination, seedling establishment, maturation and harvest. They include maintaining appropriate soil moisture content, nutrient balance, atmospheric mixing and containment. Sustained production imposes additional challenges of harvesting, replanting, and safety. The VEGGIE is a deployable (collapsible) plant growth chamber developed as part of a NASA SBIR Phase II by ORBITEC, Madison, WI. The intent of VEGGIE is to provide a low-resource system to produce fresh vegetables for the crew on long duration missions. The VEGGIE uses a LED array for lighting, an expandable bellows for containment, and a capillary matting system for nutrient and water delivery. The project evaluated a number of approaches to achieve sustained production, and repeated plantings, using the capillary rooting system. A number of different root media, seed containment, and nutrient delivery systems were evaluated and effects on seed germination and growth were evaluated. A number of issues limiting sustained production, such as accumulation of nutrients, uniform water, elevated vapor pressure deficit, and media containment were identified. A concept using pre-planted rooting packs shown to effectively address a number of those issues and is a promising approach for future development as a planting system for microgravity conditions. (Supported by NASA IPP Grant).

Characterization of Nutrient Solution Changes During Flow through Media

A research project has begun to identify the best cultivar for strawberry production as part of an advanced life support system for space. For the cultivar trials, hydroponic systems will be used, so the plants can be grown optimally under controlled environmental conditions and without water stress. The objectives of this project were to determine changes in nutrient solution characteristics, specifically dissolved oxygen (DO), electrical conductivity (EC), hydrogen ion concentration (pH), and temperature, versus four different flow rates (0.5, 1.0, 2.0, and 3.6 L·min -1 ) at fixed distances in the hydroponic channel with and without media. Three media treatments were used: 1) no media, 2) arcillite, and 3) perlite. The results showed that the highest flow rate (i.e., 3.6 L min -1 ) exhibited the most uniform conditions of all nutrient solution characteristics and for each of the media treatments over the 7.92 m length of channel. Additional system testing is required to determine how the nutrient solution characteristics are affected by the inclusion of plants.