Performance and control of a 30-cm-diam, low-impulse, Kaufman thruster

Abstract

An experimental investigation was conducted to develop a 30-cm-diam, mercury bombardment thruster for potential space applications. Thruster operating efficiencies were improved by variation of the discharge-chamber geometry and magnetic field shape. A single, glass-coated system was used to achieve efficient thruster operation at lower specific impulse than previous bombardment thrusters. Propellant utilization efficiencies greater than 90% and discharge losses less than 200 ev/ion were attained. Estimated over-all thruster efficiency was about 58% at a specific impulse of 2200 sec. The investigation included a control system that afforded enough flexibility to throttle the ion beam current over a range of 2 to 1. This was accomplished without compromising expected lifetime of thruster components. NomenclatureA 0 -annular open area between distribution pole piece and baffle, cm 2 d = diameter, cm / sp = specific impulse, sec J = neutral propellant flow, equivalent amp L/D = thruster-length/anode-diameter ratio I = length, cm AV = potential voltage, v 7] = efficiency e = energy loss per beam ion, ev/ion Subscripts B = baffle / = discharge chamber OK,OM,OT = cathode, main, and total (flow), respectively P = distributor pole piece p = power (efficiency) SC = screen collar T = total U -propellant utilization

Performance of 30-cm ion thrusters with dished accelerator grids

“…For all of the grids tested, when the FQS and FQ^ were increased the minimum EJ decreased as well as the nu-With a greater effective F 0 s the ions in the discharge chamber were more efficiently extracted, but the larger FQA also allowed a greater number of neutral atoms to be lost. 4. When the FQ^ was decreased while FQS was held constant the nu always increased for all EJ.…”

Component testing of a 30-centimeter diameter electron bombardment thruster

“…High accelerator drain currents and electron backstreaming currents accompanied these arcs. The cause of the arcs 3 and their long range effect on performance has not been determined. Fig.…”

“…( 1 9 2 ) The results of an initial optimization of a 30 centimeter diameter mercury thruster of this type have been detailed in references 3 and 4. The thruster typically operates at a discharge chamber loss of 200 electron volts per beam ion produced at a propellant utilization efficiency of greater than 90 percent.…”

Investigation of hollow cathode performance for 30-cm thrusters

“…Both the keeper and collector voltages rose between one and two volts over the test period but remained constant over the last half of the test. After testing in a bell jar cathode 8 was also run in a 30 cm thrusterl 5 ) as a neutralizer with a beam current of 2 amps. In the thruster test both the keeper and coupling voltages were 19 volts, for a keeper current of 500 ma and an equivalent flow of 84 ma.…”