Field-Effect Modulated Electro-Osmotic Pumps for High Precision Colloid Thrusters

The ability to precisely control the position of satellites is a critical enabling technology for space missions involving interferometric arrays. One proposed mission, LISA (Laser Interferometer Space Antenna), would use an array of 3 satellites whose relative position is monitored and controlled to an accuracy of 10 nm. Precise station-keeping such as this demands precise, high stability thrusters supplied with propellant flows on the order of microliters/min and producing micro-newtons of thrust. These requirements are difficult or impossible to meet with traditional thrusters and feed systems such as cold-gas thrusters or monopropellants. The proposed program will evaluate the use of electro-osmosis to supply and control the flow of ionic liquid propellants to micronewton colloid thrusters. In addition, the use of a gate electrode to control the surface charge and therefore the magnitude and direction of flow will be examined as will the use of AC fields to limit electrolysis effects. Phase I will provide basic information on the electro-osmotic behavior of ionic liquids using simple test devices and electrospray emitters. Phase II will involve detailed design work to fabricate a practical propellant feed system using electro-osmotic pumps.