Development and testing of the $$\text{DESTINY}^{+}$$ microwave discharge ion engine system

The Demonstration and Experiment of Space Technology for INterplanetary voYage with Phaethon fLyby and dUst Science ( $$\\text{DESTINY}^+$$ ) mission will demonstrate technologies for future deep space exploration at lower cost and higher frequency developed by the Japan Aerospace Exploration Agency (JAXA). The $$\\text{DESTINY}^+$$ spacecraft also demonstrates a high-speed flyby at 36 km/s and the observation will elucidate the characteristics of the Geminids meteor shower parent body, the asteroid (3200) Phaethon. The spacecraft is proceeding toward a rideshare launch with RAMSES by European Space Agency (ESA) on a Japanese H3 launch vehicle in 2028 and will first fly by the asteroid (99942) Apophis, while the spacecraft was originally planned to be launched by the Japanese Epsilon-S rocket with a kick stage and reach interplanetary space via spiral orbit ascent using solar electric propulsion. The ion engine system (IES), inherited from the Hayabusa2 spacecraft, is installed on the $$\\text{DESTINY}^+$$ spacecraft and is capable of providing delta-V as high as 4 km/s. The $$\\text{DESTINY}^+$$ ion thruster $$\\mu10$$ can produce total thrust of 40 mN through the simultaneous operation of four thrusters, exceeding the 30 mN of Hayabusa2. Furthermore, by incorporating recent design updates, a single ion thruster’s thrust is increased from 10 mN of Hayabusa2 to 12 mN. The thrust and specific impulse have been further improved via waveguide design and gas injector optimization described in results of this study. This paper reports not only the IES design but also experimentally obtained results on the latest design improvements and performance verification test results of the $$\\text{DESTINY}^+$$ flight model.