The microplasma thruster ͑MPT͒ concept is a simple extension of a cold gas micronozzle propulsion device, where a direct-current microdischarge is used to preheat the gas stream to improve the specific impulse of the device. Here we study a prototypical MPT device using a detailed, self-consistently coupled plasma and flow computational model. The model describes the microdischarge power deposition, plasma dynamics, gas-phase chemical kinetics, coupling of the plasma phenomena with high-speed

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... ow, and overall propulsion system performance. Compared to a cold gas micronozzle, a significant increase in specific impulse is obtained from the power deposition in the diverging section of the MPT nozzle. For a discharge voltage of 750 V, a power input of 650 mW, and an argon mass flow rate of 5 SCCM ͑SCCM denotes cubic centimeter per minute at STP͒, the specific impulse of the device is increased by a factor of ϳ1.5 to about 74 s. The microdischarge remains mostly confined inside the micronozzle and operates in an abnormal glow discharge regime. Gas heating, primarily due to ion Joule heating, is found to have a strong influence on the overall discharge behavior. The study provides a validation of the MPT concept as a simple and effective approach to improve the performance of micronozzle cold gas propulsion devices. Physics 106, 063305-1 063305-2 Deconinck, Mahadevan, and Raja J. Appl. Phys. 106, 063305 ͑2009͒ 063305-3 Deconinck, Mahadevan, and Raja J. Appl. Phys. 106, 063305 ͑2009͒ 063305-6 Deconinck, Mahadevan, and Raja J. Appl. Phys. 106, 063305 ͑2009͒ 063305-7 Deconinck, Mahadevan, and Raja J. Appl. Phys. 106, 063305 ͑2009͒ FIG. 4. ͑Color online͒ Flow properties in the MPT. The operating conditions are indicated in Fig. 2 caption. 063305-8 Deconinck, Mahadevan, and Raja J. Appl. Phys. 106, 063305 ͑2009͒ FIG. 6. ͑Color online͒ Electron and dominant ion ͑Ar + ͒ number density contours for different values of the power input. The inlet total pressure is 100 Torr ͑13.3 kPa͒ and the flow rate is 5.2 SCCM for both cases. 063305-9 Deconinck, Mahadevan, and Raja J. Appl. Phys. 106, 063305 ͑2009͒ 063305-10 Deconinck, Mahadevan, and Raja J. Appl. Phys. 106, 063305 ͑2009͒ 063305-12 Deconinck, Mahadevan, and Raja J. Appl. Phys. 106, 063305 ͑2009͒ FIG. 11. ͑Color online͒ Dominant ion ͑Ar + ͒ number density and gas temperature contours for different values of the secondary electron emission coefficient. The flow rate is 5.2 SCCM and the applied potential difference between the electrodes is 750 V. 063305-13 Deconinck, Mahadevan, and Raja J. Appl. Phys. 106, 063305 ͑2009͒