Spacecraft with modulated thrust electrostatic ion thruster and associated method

A dual-spin stabilized spacecraft comprising:

• a nominally despun platform;
• a nominally spun rotor which rotates relative to said platform about a rotational axis;
• an electrostatic ion thruster positioned on said rotor off the rotational axis of said rotor for providing axial thrust by generating a charged ion beam;
• means for modulating the thrust of said ion thruster between an upper thrust value and a lower thrust value;
• and
• means for maintaining the ion beam current from said thruster substantially constant for all thrust values.

A method of operating an electrostatic ion thruster including an ion extraction assembly having a screen electrode and an accel electrode, said method comprising the steps of:

• providing a relatively constant flow of a gaseous propellant to an ionization chamber;
• ionizing said gaseous propellant to generate a plasma of positively charged ions and negatively charged electrons;
• extracting a beam of positively charged ions from said plasma with said ion extraction assembly by maintaining a positive voltage on said screen electrode and a negative voltage on said accel electrode;
• and
• modulating the voltage on said screen and accel electrodes between predetermined bounds while maintaining a substantially constant potential difference between said electrodes;
• whereby thrust modulation is achieved while maintaining substantially constant ion beam current.