Microfluidic electrospray thruster

An indium-fueled electrospray thruster comprising:

• a porous substrate having a plurality of emitters formed on a substantially planar surface thereof and extending perpendicularly thereto wherein the planar surface of the substrate has a roughness;
• each of said emitters having at least one groove extending axially along the length of said emitter from the proximal to the distal end thereof;
• each of said porous substrate and said emitters being formed of silicon and further having a metalized coating comprising at least a first titanium layer and a further layer of indium disposed thereon;
• a titanium coated borosilicate glass heater disposed in thermal relation to said porous substrate such that the substrate may be heated substantially uniformly at a rate of about 1 to 2° C./s such that the viscosity of an indium propellant may be reduced such that said propellant flows through and/or across said substrate and upward along said emitter during operation;
• an extractor electrode grid disposed substantially parallel to said planar substrate, said extractor electrode grid having an aperture aligned above the longitudinal axis of each said emitter such that when a voltage is applied across said extractor grid ions of said indium propellant are formed and pass through the apertures of said grid to produce thrust, and where the grid is formed of a titanium coated silicon material, and where surface of the extractor electrode grid is grooved, and wherein the grid is in thermal communication with a heating element capable of uniformly heating said extractor electrode grid to a temperature a temperature of between about 171 and 200° C. to reduce the viscosity of the indium propellant to a level such that said indium propellant is able to flow across said extractor grid and along said grooves;
• a reservoir for an indium propellant, the reservoir being formed of a porous material and being in fluid communication with the porous substrate;
• and
• wherein dimensions of the pores of said reservoir, the roughness of said substrate and the grooves of said emitters decrease in size from reservoir to substrate to emitter such that the indium propellant is at least partially drawn from the reservoir through and/or across the substrate and upward along the emitter via a passive capillary action.

A method of forming an electrospray emitter array comprising:

• providing a porous substrate having at least one substantially planar surface;
• said planar surface having a roughness;
• forming on said surface a plurality of emitters extending perpendicularly thereto, wherein each of said emitters have at least one groove extending axially along the length of said emitter from the proximal to the distal end thereof;
• and
• metalizing said porous substrate and said emitters by disposing a first titanium layer under vacuum and then without breaking said vacuum disposing a second layer of a propellant material thereon;
• and
• providing a reservoir for an indium propellant, the reservoir being formed of a porous material and being in fluid communication with the porous substrate;
• and
• wherein dimensions of the pores of said reservoir, the roughness of said substrate and the grooves of said emitters decrease in size from reservoir to substrate to emitter such that the indium propellant is at least partially drawn from the reservoir through and/or across the substrate and upward along the emitter via a passive capillary action.