Evolution of Space-Based Plant Growth Technologies for Hybrid Life Support Systems
Hybrid Life Support Systems (HLSS) integrate biological components and physical-chemical components with a goal to increase system closure while reducing power and mass in space habitats. Our efforts are directed toward developing precursor plant growth systems for HLSS, with a plan to evolve the technology from smaller ISS systems to large standalone systems that can provide significant levels of supplemental food production. This phased approach transitions plant growth technologies from ground-based development, to component, subsystem and system testing, to sortie mission testing of subsystem and subscale system technologies. This provides a point of departure for transitioning these technologies into larger integrated ground and flight testbeds to allow validation of system function and reliability prior to demonstration in a long-duration LEO or cis-lunar environment as being capable of meeting deep space/transit mission life support requirements. Plant growth systems were first flown in space in the 1960s and plant chambers flown since then have been used not only to conduct fundamental gravitational biology research but also to understand the capability of plants to play a role in human life support in space. As part of this process, component technologies for plant growth in space have been developed and refined, and testing of subsystems and systems on a small scale conducted on the ISS. A renewed emphasis has been placed on flight testing early precursors to plant based life-support through the development of small scale crop production systems such as the Veggie unit currently being used to grow edible crop plants on-orbit. As need for long duration spaceflight increases, these precursor crop production units will evolve to larger growing systems that may become components of HLSS for deep space use. One example is the Greenwall modular plant growth system developed to meet the growing-area requirements for NASA’s Exploration Life Support salad crop architecture.