Abstract: Air breathing electric propulsion is a very promising propulsion technology for ultra low orbit satellite, and one of the keys is to efficiently collect atmospheric molecules as propellant. Several representative air intake systems are compared and analyzed, which helps to summarize the basic principles to increase collection efficiency. The common physical problems in air intake systems are then investigated through theoretical analysis and numerical simulation, and the influence of key parameters such as non dimensional tube length and exit transmission probability on collection efficiency is obtained. It is found that when the non dimensional tube length increases the collection efficiency first increases and then decreases, and the highest collection efficiency shows a positive correlation with the exit transmission probability.Based on the analysis,a preliminary design of air intake system is provided for earth orbit at 150 km and the optimized collection efficiency is over 50%.

Key words: Air breathing electric propulsion, Gas collection, Free molecular flow, Turbomolecular pump