Performance of space durable polymeric nano composite under electromagnetic radiation at Low Earth Orbit

Abstract

It is well known that during long mission at low Earth orbit (LEO) as well as geosynchronous Earth orbit (GEO), electromagnetic radiation such as proton, gamma rays, alpha particles etc. creates severe damages to space electronics equipment as well as structural materials of spacecraft. In this context, present study investigates the rationale to developing space materials which could be useful as shielding material for spacecraft when spacecraft is subject to intense radiation at low Earth orbit (LEO). It is noted that several international space agencies such as National Aeronautics and Space Administration (NASA), European Space Agency (ESA) have launched several programs to investigating materials and techniques for shielding of spacecraft structure as well as electronic equipments involved in long-term missions. Usually high-mass density materials of high atomic number, are not good choices for shielding the spacecraft because, when struck by the primary positive ions, the nuclei of these materials fragment and produce a shower of secondary radiation that includes more charged particles, photons, and neutrons, and the thicknesses of heavy shielding material necessary to stop these becomes excessive from a weight standpoint. Therefore, new shielding materials that not only block and/or fragment more radiation than aluminium - the material currently used to build most spacecraft structures but also lighter than aluminium is polyethylene which is a good shielding material because it has high hydrogen content and hydrogen atoms are good at absorbing and dispersing radiation. However, longer mission under electromagnetic radiation, mechanical properties of the polymer deteriorate. Therefore, one of several novel material developments that are currently being researched is nano reinforced polyethylene and proper selection of nano particles in terms of physicothermal and theromechanical properties are of priorities. It is proved that at longer mission at LEO, polyethylene based shielding materials are not so useful in terms of physicothermal and thermomechanical properties. Therefore, attention is given to find better shielding materials and one such material is space durable polymer such as polybenzimidazole (PBI) having higher service temperature and also having excellent properties to resist high energy radiation. Therefore, this paper highlights future of polymeric nano composite based on these polymers with dispersion of appropriate nano particles such as carbon nano fibre and calcium and that could be a solution for materials of space radiation shielding for long mission at LEO.