LIGHTING EQUIPMENT FOR A CROP GROWING SYSTEM IN MICROGRAVITY CONDITIONS FOR SPACE MISSION

The international scientific community has been making efforts towards developing technologies to realise a sustainable spaceflight Bioregenerative Life Support System for food production, water purification, air revitalisation, and waste recovery in the International Space Station. Space environment, characterized by the absence of the Earth’s gravitational and magnetic fields, of tidal forces, and of the influence of the cyclical events of celestial mechanics, complicates the realization of this kind of system. A critical analysis of the lighting equipment requirements for a crop growing system is presented on the basis of the data and information collected on several Bioregenerative Life Support Systems developed or under development for spaceflight. Aim of the research is to compare different lighting equipment for Bioregenerative Life Support System. Traditional lighting regimes and innovative ones, such as light emitting diode module providing photons in the red and blue regions of the spectrum, has been analysed in order to assess the lighting engineering solutions for a crop growing system on-board the International Space Station supported by Italian Space Agency. The lighting system must maximise photon flux in the spectral range to satisfy plant photosynthesis needs, spatial uniformity and energy efficiency while the thermal load must be minimised because natural convection does not exist in microgravity to transfer heat away from the lights. Plants need photosynthetically active radiation in the wavelengths range between 400 and 700 nm for photosynthesis. Besides it is necessary to control radiation level at 670 and 735 nm which drives the phytochrome response, that is related to plant morphogenesis. Radiation over 750 nm seems not having direct effect on the plant growth and thus needs to be removed as heat via circulation of the chamber air by means of air ventilation.