Pulsed plasma thrusters with conductive liquid sacrificial electrode(s)

A spacecraft propulsion system comprising:

• a conductive liquid-fed pulsed plasma thruster comprising:
• a first electrode having a conductive solid portion, having a rear end and a front end, and a conductive liquid portion wherein the conductive liquid portion is formed by a an electrically-conductive liquid propellent;
• a second electrode separated to define an ignition space therebetween;
• at least one electric insulator separating the first electrode and the second electrode
• wherein at least one wall of the at least one electric insulator surround the first electrode and are adjacent to a front end of the conductive solid portion such that a portion of the front end extends from the at least one wall;
• a conductive-liquid passage extending within the conductive solid portion through which the electrically-conductive liquid propellent flows from an inlet to an outlet, wherein the outlet is located at the ignition space;
• and wherein the first electrode and the second electrode are configured so that repeatedly a drop of the conductive liquid portion forms at the outlet and grows toward the second electrode when the electrically-conductive liquid propellent flows through the conductive liquid passage until-the drop of the electrically-conductive liquid grows enough to be close enough to the second electrode to cause an arc discharge to form between the drop and the second electrode that vaporizes the drop to produce a superheated high-density plasma cloud that generates a thrust pulse when expanded and exhausted and after the thrust pulse is generated, additional drops are repeatedly formed and grown at the outlet of the first electrode to generate additional thrust pulses;
• a power source operatively connected to the first electrode and the second electrode so that one of the first electrode and the second electrode operates as an anode and the other of the first electrode and the second electrode operates as a cathode;
• a conductive-liquid reservoir for holding the electrically-conductive liquid propellent;
• a pump connected in fluidic communication with the conductive-liquid reservoir and the inlet of the first electrode to supply the electrically-conductive liquid propellent to the first electrode;
• and
• wherein the electrically-conductive liquid propellent is the only propellent utilized by the at least one conductive liquid-fed pulsed plasma thruster to generate the thrust pulses.

A method for propelling a spacecraft comprising a conductive liquid-fed pulsed plasma thruster comprising a first electrode having a conductive solid portion with a rear end and a front end, and a conductive liquid portion, wherein the conductive liquid portion is formed of a an electrically-conductive liquid propellent, and a second electrode separated from the first electrode to define an ignition space therebetween, at least one electric insulator separating the first electrode and the second-electrode wherein at least one wall of the at least one electric insulator surround the first electrode and are adjacent to a front end of the conductive solid portion such that a portion of the front end extends from the at least one wall, and a conductive-liquid passage extending within the conductive solid portion through which the electrically-conductive liquid propellent flows from an inlet to an outlet, wherein the outlet is located at the ignition space, the method comprising the steps of:

• forming a drop of the electrically-conductive liquid propellent outside the outlet of the first electrode by supplying the electrically-conductive liquid propellent into the inlet of the first electrode;
• growing the drop of the electrically-conductive liquid propellent outside the outlet of the first electrode toward the second electrode by continuing to supply the electrically-conductive liquid propellent into the inlet of the first electrode until the drop of the electrically-conductive liquid propellent grows enough to be close enough to the second electrode to cause an arc discharge to form between the drop of the electrically-conductive liquid propellent and the second electrode that vaporizes the drop of the electrically-conductive liquid propellent to produce a superheated high-density plasma cloud that generates a thrust pulse when expanded and exhausted, wherein the electrically-conductive liquid propellent is the only propellent utilized by the conductive liquid-fed pulsed plasma thruster to generate the thrust pulses;
• and
• after generating the thrust pulse, repeating the steps of forming the drop and growing the drop to generate a pulsing thrust.