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PLANT RESEARCH UNIT FUNCTIONALITY AND CAPABILITY.  M.C. Lee, R.C. Morrow, J.A Bernard, T.M. Crabb, Orbital Technologies Corporation, Madison, WI.

     The Plant Research Unit (PRU) is one of six life science habitats in the suite of experimental hardware 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 up to eight Plant Research Units at one time in multiple gravity environments, 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, “watering,” 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. The PRU will be about the size of a large bread box weighing around 150 pounds but will consume less power than five 100 watt light bulbs.  Within these strict limitations of volume, weight and power usage, the PRU must maintain “happy” plants in a very accurately controlled growth environment. The PRU will be modular and will allow scientists to select various lighting systems and nutrient delivery systems. The nutrient delivery systems may range from a soil-type matrix to hydroponics to aeroponic sprays. The PRU will also provide continuous data logging of the environment including video images of the plants. The system will be robust enough for 10 years of life and dozens of trips to and from orbit. The Plant Research Unit will provide a significant new science capability that could accelerate biotechnology and controlled agriculture applications on Earth. The paper will review the functions and capabilities for science accommodations.