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Aeroponics is the process of growing plants in an air/mist environment without the use of soil or an aggregate media. Aeroponics has contributed to advances in several areas of study including root morphology, nutrient uptake, drought and flood stress, and responses to variations in oxygen and/or carbon dioxide root zone concentrations. The adaptability of the aeroponic process that has benefited researchers makes its application to spaceflight plant growth systems appealing. Greater control of growth parameters permits a greater range of crop performance throttling and the elimination of aggregates or common growth substrates lowers system mass, lessens disease propagation between plants, and can decrease the required crew time for both planting and harvesting.

The Autonomous Garden Pod (AG-Pod) is a modular crop production system that can lower the equivalent system mass (ESM) for bioregenerative life support systems. AG-Pod combines existing technologies, many of which are at the technology readiness level (“TRL”) 8 or 9, into a flight-ready system adaptable to many needs from Space Station microgravity plant research to interplanetary transit and planetary surface food production systems. The plant-rated module resides external to the spacecraft pressurized volume and can use natural direct solar illumination. This reduces the ESM of crop production systems by eliminating the use of spacecraft internal pressurized volume and by reducing power and heat rejection resources that would be needed for full artificial lighting. However, lowering of the crop production ESM is also achieved from the use of lightweight structures including composite and inflatable technology.

Through the development of 35 spaceflight payloads during the last ten years, BioServe Space Technologies has gained valuable practical experience in developing thermal control systems for the microgravity environment. Design constraints imposed by NASA, such as limited power availability, limited material selections, and limited acoustic emissions, coupled with the design constraints imposed by the functional requirements of each payload, impact spaceflight designs in a manner that requires a high degree of optimization. BioServe payloads typically employ thermoelectric coolers (TEC's), air and liquid heat exchangers, a variety of insulation materials, several types of fans and blowers, and various control strategies in order to achieve the desired thermal environment. In the present work methods of selecting thermal system components are discussed.

PGBA, a plant growth facility developed for commercial space biotechnology research, successfully grew a total of 50 plants (6 species) during 10 days aboard the Space Shuttle Endeavor (STS-77), and has reflown aboard the Space Shuttle Columbia (STS-83 for 4 days and STS-94 for 16 days) with 55 plants and 10 species. The PGBA life support system provides atmospheric, thermal, and humidity control as well as lighting and nutrient supply in a 33 liter microgravity plant growth chamber. The atmosphere treatment system removes ethylene and other hydrocarbons, actively controls CO2 replenishment, and provides passive O2 control. Temperature and humidity are actively controlled.

The Plant Generic BioProcessing Apparatus (PGBA), a plant growth facility developed for commercial space biotechnology research, has flown successfully on 3 spaceflight missions for 4, 10 and 16 days. The environmental control systems of this plant growth chamber (28 liter/0.075 m2) provide atmospheric, thermal, and humidity control, as well as lighting and nutrient supply. Typical performance profiles of water transpiration and dehumidification, carbon dioxide absorption (photosynthesis) and respiration rates in the PGBA unit (on orbit and ground) are presented. Data were collected on single and mixed crops. Design options and considerations for the different sub-systems are compared with those of similar hardware.

LoTEC© is a passive thermal carrier designed to maintain the temperature of biological samples for ten days or more for transport to and from the International Space Station (ISS) without the need of external power. LoTEC© relies on a combination of high thermal resistance insulation and high energy density storage phase change materials. The initial capability of LoTEC© encompasses several temperature ranges (e.g. 36 to 40C, 18 to 22C, 0 to 4C, and - 16 to -20C). LoTEC© fits into a standard mid-deck locker or an Express Rack locker; this facilitates easy transfer between the shuttle and the ISS. Thermal analysis modeling and laboratory test results are presented that characterize the performance of LoTEC© and the planned PCM materials.

Spaceflight life sciences research typically requires accurately controlled thermal environments to help isolate the effects of gravity on the development of living organisms or biochemical reactions. Given the power, mass and volume constraints of spaceflight experimental hardware, highly efficient temperature control is necessary to provide scientists with adequate tools for their research. The main focus is on 3 incubators, designed by the authors, for commercial space biotechnology research. While the simplest incubator allows for highly accurate temperature control above ambient only, the more sophisticated units use temperature-controlled liquid circulation systems for above and below ambient temperature control. The latest design variation provides eight individually controlled sample containers, where temperatures can be maintained constant or profiled for automated experiment initiation and termination, or preservation of samples on orbit.

P-MASS, the Plant-Module for Autonomous Space Support, is designed to support and provide life support for a variety of plants, algae and bacteria in low earth orbit during the maiden flight of COMET-1. The first launch is scheduled for early 1993. With a nominal mission duration of 30 days in microgravity, P-MASS will bridge the gap between the shorter duration experiments possible onboard the NSTS Space Shuttle (approximately 14 days) and the future Space Station Freedom for space biology applications. Environmental data and video images are collected, stored onboard and downlinked daily. In addition, the payload and all specimens will be returned for ground analysis with the recovery system (reentry capsule). P-MASS is designed within a payload envelope of 0.28 x 0.22 x 0.32 m (19.71) and a mass of approximately 20 kg. A total of 115 Watt electric power is available continuously for the Plant-Module (60 W lighting, 40 Watt cooling, 15 W housekeeping).

Technology for microgravity plant growth has matured to a level which allows detailed gravitational plant biology and commercial plant biotechnology studies. Consequently, plants have been shown to adapt to the space flight environment, which validates their use in advanced life support applications. However, the volume available for plant growth inside pressurized modules is severely constrained, both in present and future spacecraft. Furthermore, the required power and heat rejection associated with the artificial lighting on existing systems, and the resulting weight and volume increases, affect the viability of these systems for life support. The Autonomous Garden Pod (AG-Pod), an inflatable module specifically for plants, resides outside the habitable modules and uses passive solar illumination. It’s based on existing technologies including flight-proven plant growth subsystems, commercial satellite thermal systems, and off-the-shelf inflatable technology.