During FY03, NASA GRC began investigating two approaches to achieve Hall thruster specific impulses greater than 4000 s at a 50 kW power level by utilizing lower molecular weight propellants and increasing the applied discharge voltage of xenon Hall thrusters. The feasibility of using krypton propellant to achieve the performance goals was demonstrated using the existing NASA-457M V1 Hall thruster. A discharge specific impulse of 4500 seconds was demonstrated at a discharge voltage of 1000 Volts and discharge efficiencies up to 64% were measured. During FY04, a new high-power Hall thruster, designated the NASA-400M was designed to investigate high-specific impulse operation. The NASA-400M was developed to investigate high-power, high specific impulse Hall thruster operation.The design evolved from the NASA-457M V1, and incorporated improved electrical isolation, single piece inner and outer discharge rings (not segmented), an improved thermal design and refined hollow cathode. Following thruster assembly in November 2003, functional and performance testing was performed using both xenon and krypton propellant. The performance testing of the NASA-400M operating on krypton propellant was investigated at discharge voltages up to 1100 Volts and stable operation was demonstrated up to 64 kW. A discharge specific impulse (calculated without cathode flow) of 4700 seconds was demonstrated at 1050 Volts, which was the highest specific impulse achieved with a NASA developed Hall thruster. This data point was collected at a discharge power of 43 kW and corresponded to a discharge efficiency (calculated without cathode flow and magnet power) of 0.65.
Electrical Input Power: 43.00 kW.
Thrust: 1.02 N (0.23 lbf).
Specific impulse: 4,000 s.
First Launch: 2003-on.