Two different types of electrostatic thrusters are used to propel spacecraft: ion thrusters and Hall-effect thrusters. Ion thrusters have the benefit of relatively high exhaust velocities with higher overall thrust efficiencies. Hall-effect thrusters typically offer higher thrust-to-power ratios, but they operate somewhat less efficiently than ion thrusters. To take advantage of both thrusters' strengths, innovators at NASA's Glenn Research Center have developed what is essentially a dual-thruster propulsion system. This patented electric propulsion device offers the ability to switch a spacecraft's propulsion system to ion-thruster mode or Hall-thruster mode, depending on whether the principal need is efficiency or thrust power. In addition, Glenn's novel technology allows the dual thruster to operate in burst mode, with one thruster acting as an ion thruster and one as a Hall thruster. This capability can be valuable to facilitate smooth transitions between operating modes or to raise total thrust level (for short periods) beyond what either mode can achieve on its own.
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