In order to evaluate whether the space lubricant can meet longlife requirements of space scanning mechanism under boundary lubrication conditions,the friction and wear and longlife lubrication performance of the lubricating oil in the space environment were analyzed.Taking the space synthetic hydrocarbon lubricant RP4751 as the research object,the vacuum lubrication test system(SOT) and the sliding friction test system(SRV) were used to test the nominal lubrication life(the cycles of steel ball rotation when consuming 1 μg lubricating oil),wear spot diameter and sliding friction coefficient of the lubricating oil,and microscopic analysis of the wear spot was carried out by combining scanning electron microscope with an Xray energy dispersive spectrometer.The results show that the RP4751 lubricating oil has a small sliding friction coefficient and a long wear life in a vacuum environment,and has good vacuum boundary lubrication performance and high nominal life.The infrared transmittance analysis results show that there is no qualitative change of lubricating oil before and after SRV test.The 1∶1 vacuum life test of RP4751 lubricating oil was carried out with two scanning motors.The motor operational life meets the 8year onorbit operational life requirements of the infrared earth sensor motion mechanism when lubricated by RP4751 lubricating oil.The lubrication life of steel ball in motor bearing is more than 2 943 r/μg,which is in good agreement with the nominal life of lubricating oil 3 598 r/μg in SOT test,it provides an important experimental basis for the selection of lubricants for other space motion mechanisms and longlife lubrication design.