Clawson, J., Hoehn, A., Stodieck, L., Todd, P. et al., "Re-examining Aeroponics for Spaceflight Plant Growth," SAE Technical Paper 2000-01-2507, 2000, doi:10.4271/2000-01-2507.
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. However, because of the use of less reliable types of aeroponic techniques and concerns with open two-phase fluids within the root zone in microgravity, many advanced life support technology researchers opted for nutrient delivery concepts that offered more fluid control, containment and simpler subsystem designs. The resulting systems have been successful for on-orbit plant growth, but have yet to achieve high performance crop production equal to terrestrial standards. Re-examining historical concerns, along with an overview of recent work demonstrating hypogravity aeroponics, shows the promise that aeroponics still holds for spaceflight crop production.