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A common question for students to ask educators is “When am I ever going to use this?” An excellent way to answer that question is to demonstrate how interrelated many subjects are. At ORBITEC in Madison, WI, we are developing systems to help teachers demonstrate the exciting interrelationships of science, math and technology using activities related to growing plants in space. We are developing two portable plant growth systems that integrate multiple disciplines, enriching students’ classroom experiences. Each portable growth unit is based on similar principles. The Space Garden and Biomass Production Education System (BPES) are growth units for indoor use that utilize a bellows technology to create a greenhouse-like environment. The Space Garden is a personal growth unit that a student can use individually while the BPES will be 0.25 m2, allowing larger-scale experimentation. The Space Garden will be best used in classrooms of grades four through seven.

The Biomass Production System (BPS) is a double middeck locker payload designed to fly on the Orbiter or Space Station. The BPS contains four plant growth chambers (PGCs) with independent control of temperature, humidity, lighting, CO2, and nutrient solution delivery, allowing for multiple experimental treatments. The BPS provides several features to support on-orbit science activities including the ability to downlink system and science data, video cameras with framegrab capability to collect images for recording plant development, access to plants to perform activities such as pollination or tissue sampling, and gas and fluid sampling ports for sampling of the plant environment. Other capabilities include the ability to conduct CO2 drawdowns, allowing photosynthetic measurements, and the ability to meter plant CO2 and water use. Several technology developments have been evaluated for possible implementation during future upgrades to enhance science capabilities.

The Plant Research Unit development effort will provide a high-performance and highly versatile, controlled environment plant growth chamber for space-based variable gravity science and biotechnology investigations on the International Space Station. Temperature, humidity, atmospheric composition, lighting, and nutrient delivery are the critical parameters to control in an automated and reliable way. Access to plant material on-orbit and maintenance of the unit with minimal crew effort are other major requirements, as is a modular design allowing easy subsystem/technology change-outs so that science capability and maintainability are maximized. The Plant Research Unit (PRU) development program is based on the results of the Biomass Production System (BPS) and many other technical developments, and uses the BPS as a risk mitigation prototype for the PRU.

The Plant Research Unit (PRU) is the Space Station Biological Research Program plant growth facility being developed for the International Space Station. The plant habitat is designed for experiments in near-zero gravity or it can be rotated by the ISS Centrifuge for experiments at any gravity level from microgravity to twice Earth's gravity. Plant experimentation will be possible in multiple Plant Research Units at one time, isolating the effect of gravity on the biological specimens. The PRU will provide and control all aspects of a plant's needs in a nearly closed system. In other words, the shoot and root environments will not be open to the astronaut's environment except for experiment maintenance such as planting, harvesting and plant sampling. This also means that all lighting, temperature and humidity control, nutrient delivery, and air filtering and cleaning must be done in a very small volume, with very little mass and power usage and with minimal crew time.

Based upon the development experience and flight heritage of the Biomass Production System, the Plant Research Unit embodies the next generation in the evolution of on-orbit plant research systems. The design focuses on providing the finest scientific instrument possible, as well as providing a sound platform to support future capabilities and enhancements. Performance advancements, modularity and robustness characterize the design. This new system will provide a field ready, highly reliable research tool.

The ORZS flight experiment is designed to measure gas diffusion through plant growth substrates at varying water content levels in microgravity. This information is critical for proper water management and the prevention of root zone hypoxia during plant growth and advanced life support (ALS) biomass production experiments. Microgravity data that suggest enhanced hysteresis in water retention may alter the gas diffusion process, changing the optimum root zone moisture control set point in μg plant growth systems. Small gas diffusion cells are being evaluated as measurement systems for coarse-textured plant growth media at 1g and 0g. Design guidelines aim to minimize gravitational force while maintaining a representative porous medium. Substrate physical properties (e.g., water retention) pose additional complications for diffusion coefficient determination.

The ASTROCULTURE™ (ASC) middeck flight experiment series was developed to test subsystems required to grow plants in reduced gravity, with the goal of developing a plant growth unit suitable for conducting quality biological research in microgravity. Previous Space Shuttle flights (STS-50 and STS-57) have successfully demonstrated the ability to control water movement through a particulate rooting matrix in microgravity and the ability of LED lighting systems to provide high levels of irradiance without excessive heat build-up in microgravity. The humidity and temperature control system used in the middeck flight unit is described in this paper. The system controls air flow and provides dehumidification, humidification, and condensate recovery for a plant growth chamber volume of 1450 cm3.

The ASTROCULTURE™ (ASC) middeck flight experiment series was developed to test and integrate subsystems required to grow plants in reduced gravity, with the goal of developing a plant growth unit suitable for conducting quality biological research in microgravity. Flights on the Space Shuttle have demonstrated control of water movement through a particulate rooting material, growth chamber temperature and humidity control, LED lighting systems and control, recycling of recovered condensate, ethylene scrubbing, and carbon dioxide control. A complete plant growth unit was tested on STS-63 in February 1995, the first ASC flight in which plant biology experiments were conducted in microgravity. The methods and objectives used for control of environmental conditions in the ASC unit are described in this paper.

The PESTO (Photosynthetic Experiment System Testing and Operation) experiment flew in the Biomass Production System (BPS) to International Space Station (ISS) on STS-110 (Atlantis) April 8, 2002, and returned on STS-111 (Endeavour) June 19, 2002, after 73 days in space. The ground control was conducted on a two-week delay at Kennedy Space Center in a BPS unit under environmental conditions comparable to ISS. Wheat (Triticum aestivum cv Apogee) and Brassica rapa cv Astroplant were independently grown in root modules for multiple grow-outs. On-orbit harvests, root modules exchanges and primings, seeds imbibitions, and gas and water samplings occurred at periodic intervals; all were replicated in ground controls. Many operations required crew handling and open access to individual chambers, allowing the exchange of microorganisms between the crew environment and the BPS modules.

The Biomass Production System (BPS) was flown on the ISS for 73 days as part of the Increment 4 mission. To obtain maximum benefit from the long mission duration, numerous manual crew procedures were incorporated into the BPS experiments. These procedures included gas sampling, root module priming, harvesting, pollination, filter cleaning, water refill, and water sampling. On-orbit crew assessments were filled out for each of these procedures to evaluate the ability of BPS to accommodate them. The assessment asked questions about each phase of an activity and solicited recommendations for improvements. Further analysis of most procedures was provided by detailed video made on-orbit and multiple post-flight crew debriefs. Most assessments indicated no need for improvements, but a number of crew suggestions will be incorporated into hardware and procedure updates.

The Deployable Vegetable Production System (VEGGIE) was originally developed as a way to produce fresh vegetables on the ISS with minimal resources. We are reassessing this system for use in lunar habitats to produce palatable, nutritious, and safe fresh food, provide a recreational tool, and provide a platform to support biological life support development by allowing in situ study of crop productivity and air and water revitalization. The VEGGIE system consists of plant growth chambers that can be stowed in a volume less than 10% of their deployed volume, while still providing the light output and root zone capabilities necessary to support high plant productivity rates. The system has significantly reduced logistical and operational requirements compared to other plant growth systems, and is of a modular design to allow logistical flexibility in terms of transport options and placement in a habitat structure.