Summary and

This report presents a preliminary study of a ramjet that would use the chemical energy of dissociated molecules in the ionosphere for pro-pulsion. A review of the physical properties and chemical composition of the upper atmosphere shows that the available energy is not sufficient for flight requiring aerodynamic lift. Above 300,000 feet, dissociation energy might be useful for satellite-sustaining. Ccnrparison of maximum thrustandexternal dragfor an orbitingrsmjetfrcm300,OOOto 700,OO~ feet shows that a positive net-thrust margin might be obtained over the entire region for SCXKE of the engine sizes considered. However, the re-gion between 325,000 and 400,OCO feet is the most favorable, because high gas densities produce high recc&Fnation rates. Two thermodynsmic engine cycles are considered for a ramjet orbit-at 328,080 feet: (1) all-supersonic flow with frozen composition in the diffuser and chemical equilibrium Fn the nozzle; (2) normal-shock inlet with equilibrium expansion. Only the all-supersonic cycle shows promis