The state of art on lubrication methods in space environment

Space tribology is a very big aspect of space exploration, despite of this fact, there is a dearth of coherent and concise literature available in the field of space tribology. It becomes difficult to understand the tribological behaviour of mating bodies under the extreme environmental circumstances in space due to their potential chemical and physical interactions. The radiation, vacuum, environmental conditions and temperature, are the factors which affects the friction and wear behaviour of mating surfaces and may alter the chemical structure of solid or liquid lubricant. The combination of tribo-physical and tribo-chemical interactions makes the tribological analysis very difficult to understand. The lack of understanding and ignorance might be the reason for not addressing this issue in the past. This review contains the qualitative and quantitative information on the tribological behaviour of different types of liquid lubricants, greases, soft and hard coatings, combined lubrication systems, testing equipment, composites, solid lubricants and alloys developed for space applications.