Thermodynamic Properties of Hydroxylammonium Nitrate-Based Electric Solid Propellant Plasma

Abstract

Electric solid propellants are advanced solid chemical rocket propellants controlled by electric current. An electric solid propellant may also be used in an electric propulsion system: specifically, an ablative pulsed plasma thruster. Previous experiments with the electric solid propellant known as high-performance electric propellant, or HIPEP, suggest its ablation processes are similar to the traditional propellant polytetrafluoroethylene (). Better understanding of the ablation and the resulting propulsion performance of HIPEP requires a model of its vapor composition, bulk plasma quantities, and thermodynamic properties. Such a model was developed and favorably compared with previous analogous model predictions found in the literature for . The electric solid propellant vapor composition was predicted in the temperature range of 500–40,000 K at 1 bar pressure. Low temperatures (less than 2000 K) were dominated by water (), carbon dioxide (), and molecular nitrogen (), with results at 700 K matching to within 10% of the previous combustion model predictions. At high temperatures (greater than 25,000 K), the vapor was strongly ionized and dominated by carbon (), oxygen (), nitrogen (), and hydrogen () ions. The calculated enthalpy and specific heat were higher for high performance electric propellant (HIPEP) vapor than , suggesting increased thermal losses could be inherent to ablation-controlled HIPEP discharges.