###### Abstract  
Space-mission development introduced the problem of human isolation in extreme environments. The integration of architectural concepts such as windows, with their technical implications into human space missions, is necessary especially for long-duration space flights. Such solutions must be subjected to close certification testing in order to establish their compliance with severe space environment conditions. Moreover, projects of long-term missions involve a renewed concern about fire safety in manned space vehicles. The supposed occupancy time of the order of decades, in fact, makes unplanned fire ignition events virtually unavoidable. An experimental test-plan performed to qualify a commercial thermoplastic material for applications as transparent element in spacecraft is reported in the present work. A flame exposure test, as well as ultraviolet radiation and atomic oxygen erosion rate measurements, was carried out on a commercial poly-sulfone material, following ASTM standard procedures. The aim of the research was to develop and put forward flame retardant structures able to withstand the harsh space environment, preventing or mitigating the degradation of their physical and chemical integrity, with particular regard to the visible-light transparency. The results obtained show that the tested poly-sulfone may be considered as a promising material for the claimed application, even if further surface optimization treatments should be conceived in order to gain a full adaptability to the operative constraints.  
Keywords:spac environment; flame retardants; ultraviolet aging; atomic oxygen erosion; thermoplastic poly-sulfone +
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and flame resistance [12]. Such characteristics could make them competitive with respect to the glass-based materials so far employed for spacecraft optical components.  
In this work, the experimental testing activity carried out in order to qualify a commercial thermoplastic sulfone polymeric material is reported, including flammability test, as well as ultraviolet (UV) and atomic oxygen (AtOx) erosion analysis. The former evaluates the response to a well-defined laminar flame at the bottom of a test sample and is currently used to screen for flammability all materials intended for using inside manned spacecraft [8]. The latter evaluates the materials behavior in LEO working conditions, focusing in particular on the surfaces aging due to the combined effects induced by high vacuum and UV/AtOx irradiation [2; 13; 14; 15; 16; 17; 18; 19; 20]. The results reported in the paper show that applying the proposed solution in spacecraft design could provide overall architectural and functional advantages, as far as the LCC reduction is concerned. The materials used, in fact, are generally low-price and available, which does not translate into sharp increases in the price of the potential product. Such a feature is particularly suitable in the view of the currently adopted concepts driving aerospace industry development; nowadays space economy and commercialization demand for multi-functional structures, as well as time/cost-saving procedures, with particular emphasis on low-waste technological processing and components reusability and biocompatibility.