Demonstration of electric micropropulsion multimodality.

Electric propulsion has become popular nowadays owing to the trend of miniaturizing the size and mass of satellites. However, the main drawback of the most popular approach-Hall thrusters-is that their efficiency and thrust-to-power ratio (TPR) markedly deteriorate when its size and power level are reduced. Here, we demonstrate an alternative approach-a minute low-power (<50 W), lightweight (~100 g), two-stage propulsion system. The system is based on a micro-cathode vacuum arc thruster with magnetoplasmadynamic second stage (μCAT-MPD), which achieves the following parameters: a thrust of up to 1.7 mN at a TPR of 37 μN/W and an efficiency of ~50%. A μCAT-MPD system, in addition to "traditional" inverse, displays the anomalous direct (growing) "TPR versus specific impulse I sp " trend at high I sp values and allows multimodality at high efficiency.