Abstract: An ultra-low, long-range flight trajectory with themaximum altitude of about 100km is investigated. Such an ultra-lowtrajectory employs the satellite mode against the gravitation by thecentrifugal force. Different from a running satellite, the rarefied gaseffects on the ultra-low trajectory are essentially important. It is shownthat under the same payload and range, the power requirements of theultra-low trajectory and classic minimum energy trajectory are almostthe same. For anaxial symmetric configuration with the nose radius of 5cm, its stagnationheat flux along an ultra-low trajectory arrives at a maximum value of50MW/m2 around altitude 25km, which is about half of the maximumstagnation heat flux along a minimum energy trajectory. The aerodynamicheating along an ultra-low trajectory can be solved using conventionalmature techniques such as ablation, because it does not require lift. Ingeneral, the power and aerodynamic requirements of ultra-low flighttrajectories can be satisfied based on existing technologies, and thereforeit is realistic to promote the anti-defense ability of long-range missilesby taking the ultra-low flight trajectory.