AQUARIUS (AQUA ResIstojet propUlsion System), a water resistojet propulsion system installed on a 6U CubeSat EQUULEUS (EQUilibriUm Lunar–Earth point 6U Spacecraft), successfully conducted multiple orbital transfers including the world’s first water-fueled propulsion system operation in deep space. We present the on-orbit performance analysis of AQUARIUS with a focus on reaction control thrusters responsible for the spacecraft’s angular momentum management. The reaction control thrusters were capable of producing torques about all axes for angular momentum management as intended. Additionally, they provided fine translational delta-V, demonstrating the thrusters’ dual functionality and reliability in critical maneuvers. The impulse vector of each reaction control thruster was estimated by considering the thrust vector direction. The calculated impulse in the translational axis was about 0.10 N⋅s per shot, which was validated by comparing the impulse obtained from the Doppler shift of the communication waves. The estimated on-orbit specific impulse of the reaction control thrusters was approximately 78 s, 1.3 times larger than the measured value in the ground test. This improvement on orbit could be due to the degradation of thrust coefficient efficiency in the ground test caused by low Reynolds number flows and high background pressure lowering the apparent pressure thrust. The consumed propellant mass on orbit was estimated but deviated from the expected value under high-temperature conditions, possibly due to temperature measurement uncertainties or the influence of the on-orbit environment.

中文翻译：

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6U CubeSat EQUULEUS 上的水阻喷推进系统：深空反应控制演示


AQUARIUS （AQUA ResIstojet propUlsion System） 是安装在 6U CubeSat EQUULEUS（EQUilibriUm Lunar-Earth point 6U 航天器）上的防水喷气推进系统，成功进行了多次轨道转移，包括世界上第一个在深空运行水燃料推进系统。我们介绍了 AQUARIUS 的在轨性能分析，重点是负责航天器角动量管理的反应控制推进器。反作用力控制推进器能够产生绕所有轴的扭矩，以按预期进行角动量管理。此外，它们还提供了精细的平移 delta-V，展示了推进器在关键机动中的双重功能和可靠性。通过考虑推力矢量方向来估计每个反应控制推进器的脉冲矢量。在平移轴上计算出的脉冲约为每次发射 0.10 N⋅s，通过比较从通信波的多普勒频移获得的脉冲来验证这一点。反应控制推进器的估计在轨比冲约为 78 秒，比地面测试中的测量值大 1.3 倍。轨道上的这种改进可能是由于低雷诺数流和高背景压力降低视在压力推力导致地面测试中推力系数效率的下降。在轨消耗的推进剂质量是估计的，但在高温条件下偏离预期值，可能是由于温度测量的不确定性或在轨环境的影响。