Latest developments in artificial lighting technologies for bioregenerative space life support

Reducing the electrical power demand of a bioregenerative life support system (BLSS) is a critical factor that will help decide the feasibility of any longduration manned space mission leaving low-Earth orbit, including that for Mars. NASA is currently exploring two strategies for reducing the high power demand of a BLSS. First is the development of Hybrid Solar and Artificial Lighting (HYSAL) systems, and second is the use of specialized electric lighting systems. Two experimental HYSAL systems have been developed: one employing xenon-metal halide (XMH) lamps and the other adopting light-emitting diodes (LEDs) as the electric-lighting components, both systems using a mirror-based, fiberoptic-based solar collection system. The results showed that both HYSAL systems provided acceptable spectral quality and lighting uniformity. The apparent electrical conversion efficiency of the HYSAL system with LEDs, however, exceeded that of the HYSAL system with XMH by five-fold. Preliminary simulations of a Martian BLSS indicated that the lighting power required for plant production could be supplemented by the available extraterrestrial solar irradiance by as much as 50%. Also, NASA is looking at specialized lamps that can break through the current range of electrical conversion efficiencies of 10%-35%. The prime candidate is the microwave lamp, with an expected improved electrical conversion efficiency of 50%. The thermal analyses and the spatial power output distributions of standard and water-cooled HPS lamps as well as LEDs are also currently being conducted.