A hollow cathode-based plasma contactor will be own on the international space station to control the station's potential to within 40 V of the local ionosphere. Extensive testing of the plasma contactor has been conducted in vacuum facilities at the NASA Lewis Research Center. Signi cant performance differences were observed between tests of the same plasma contactor in different facilities. Why measured plasma contactor performance differs in the laboratory in different tank environments and how the plasma contactor performance measured in the laboratory relates to expected performance in space is addressed. Presented are models of plasma contactor plasma generation and interaction in a laboratory environment, including anode area limiting. These models were integrated using the Space Station Environment Work Bench to predict plasma contactor operation, and the results are compared with the laboratory measurements.
Nomenclature
F= gas ow rate, standard cubic centimeter per minute I D = total ori ce electron current, A I emission = ori ce current emitted, A I keeper = keeper electrode current, A I loss = ion loss rate, A I max = maximum possible electron current, A I prod = total ion production rate, A J e = electron current density, A m 2 L = ori ce length, m m = neutral atom mass, kg m e = electron mass, kg m i = ion mass, kg N n = neutral density, m 3 r = ori ce radius, m W conv = power loss by electron convection, W W ion = power loss by ionization, W W rad = power loss by radiation, W e = ori ce electron temperature, eV i = ion temperature, eV in = insert region electron temperature, eV n = neutral gas temperature, eV = electrical conductivity, ohm m 1 ion = ionization cross section, m 3 rad = inelastic cross section, m 3 p = electron plasma frequency, rad s 1
