Maintaining continuous low orbit flight by using in-situ atmospheric gases for propellant

An analysis is performed to determine the requirements for spacecraft propulsion systems operating in free-molecule flow and employing ambient atmospheric neutral gas as a propellant. It is concluded that some form of electric propulsion is required and the requirements for an electrostatic thruster system to be applied for this purpose are also discussed. An example thruster system based on an orbitron electrostatic electron trap is evaluated in several modes of operation. The selected configurations are shown to be unable to provide in any obvious way the required ionization fractions. The technological and physical limits that require solutions for this type of device are discussed.