In order to fully characterize the performance of the colloid thruster system the electrospray (ES) beam must itself be fully characterized. This may be achieved by measuring various properties such as flow rate, current, droplet/ion charge to mass ratio and current profile. Beam properties of both standard electrospray mass spectrometry (ESMS) emitters and arrays of custom made micro-fabricated emitters have been determined. By varying the geometries of the micro-fabricated emitters two basic modes of thruster operation have been identified a high Isp with lower thrust density and a lower Isp with higher thrust density. The versatility of this system allows for a thruster design that has a thrust range spanning two orders of magnitude from ~ 5 to 500μN with highly competitive power requirements ~ 0.05W/μN. The proposed thruster system is designed to meet the needs of future formation flying missions.