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Technical Paper

Plant Research Unit Lighting System Development

As part of the PRU project a new plant lighting system has been developed. System design focused on light source development, chamber optical performance improvements and electronics optimization. Central to the lighting system performance is a high density LED Light Engine, enabling increased spectral diversity, higher irradiance levels, enhanced uniformity and improved efficiency. Chamber wall surface materials were tested to minimize the vertical irradiance gradient and improve planar uniformity. Total lighting system efficiency was improved through the use of switching converter LED drive circuitry. As an alternative to the LED light source, an advanced planar fluorescent lighting source has also been developed.
Technical Paper

PRU, The Next Generation of Space Station Plant Research Systems

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.
Technical Paper

Plant Research Unit - Program Overview and Update

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.
Technical Paper

Fluid Handling and Maintenance Experiment Capabilities

The objective of the Fluid Handling and Maintenance Experiment (FHAME) is to research, test, and demonstrate liquid/gas phase control in fluid handling subsystems in microgravity. FHAME is currently being developed as a risk mitigation experiment for the upcoming verification and science investigations in plant growth systems, especially the Biomass Production System (BPS) and the Plant Research Unit (PRU). Because FHAME contains controlled fluid handling systems, a large suite of sensors, data acquisition, and visual observation capability, it is well suited for empirical research and testing of movement and to assessing the liquid/gas characteristics for a wide variety of applications. Its first application is to assess fluid priming and gas/liquid characteristics in a particulate bed. FHAME can play a major role in the development of future new nutrient delivery systems for plant growth application in addition to many fluid and gas/liquid empirical research investigations.
Technical Paper

Science Accommodations in the Biomass Production System

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.
Technical Paper

Plant Research Unit – Program Overview

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.
Technical Paper

Humidity and Temperature Control in the ASTROCULTURE™ Flight Experiment

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.