Testing of Greenhouse Cladding Materials for Space Environments, Part 2: Laminates

Plants grown in greenhouse-type structures are potential sources of food, oxygen, clean water, fiber, and other resources needed for bioregenerative life support systems during long-term space missions. Identification of cladding materials with appropriate optical and physical properties that can withstand the high ultraviolet radiation, low pressure, and low temperature Martian environment is necessary for greenhouse design. The objective of this study was to evaluate the effects of simulated Mars environmental conditions on yield strength and light transmissivity of composites composed of a layer of 0.15 mm polyimide film (LaRC™CP1) attached to acrylic, polyvinyl chloride (PVC), or polycarbonate cladding materials. The University of Florida’s Mars Simulation Chamber (MSC) at Kennedy Space Center was utilized to expose material samples to simulated Mars environmental conditions. Changes in control versus exposed material sample transmissivities were measured using a spectroradiometer over the PAR range of wavelengths from 400 to 700 nm and material peak yield strengths were determined using an Instron universal testing machine. Keywords: LaRC™CP1, Mars greenhouse, PAR transmission, Plastics, Strength of materials, UV damage. The overall results comparing pre- and post-exposure of samples to simulated Martian conditions in the MSC showed that the addition of a layer of polyimide did not benefit either the transmissivity or strength of polycarbonate cladding materials, but did show benefits in retaining transmissivity for PVC and in maintaining strength for acrylics exposed to Mars simulated environment. However, transmissivities of the plastics were reduced by the addition of protective layers of polyimide. Keywords: LaRC™CP1, Mars greenhouse, PAR transmission, Plastics, Strength of materials, UV damage.