在轨冷气推进系统泄漏估计

Estimation for Cold Gas Propellant Leakage on Orbit

关键词:  冷气推进系统  姿态控制  泄漏  估计  预测  遥测

Key words:  Cold gas propulsion system  Attitude control  Leakage  Estimation  Prediction  Telemetry

摘要:

针对近地卫星长期管理与测控中冷气推进系统的泄漏问题，在轨道动力学数据基础上分析光照角漂移与半长轴衰减变化，利用气态方程对推进剂的泄漏率进行估计，进而对剩余推进剂进行预测，并对冷气泄漏造成的姿态扰动进行估计，同时在公式推导基础上对泄漏率估计进行计算误差分析，结合实际在轨的压力、温度等遥测数据进行检验。结果表明，在压力接近13MPa的初始条件之下，冷气推进系统的工质泄漏率在入轨的约前5y的时间里大致在150～450Pa·cm3·s-1之间振荡变化，在之后的时间里渐趋于275Pa·cm3·s-1稳定，与之对应的稳定的氮气质量泄漏率约为3.4μg/s；在轨10y时，推进剂质量的剩余率大于85%，预测入轨30y后的剩余率仍然优于60%；姿态角、磁力矩器电流、动量轮转速等数据表明冷气泄漏对卫星姿态扰动很小，可忽略不计。估计与预测结果可应用于在轨航天器长期管理与遥测诊断辅助、器件健康状态评估。

Abstract:

With respect to long-term management of satellites on orbit in TTC (Tracking， Telemetry and Command)， cold gas propellant leakage is a key performance parameter for LEO (Low Earth Orbit) satellite propulsion system. Based on the orbital dynamics data， details on solar incidence shift and semi major axis degradation are discussed. After analyzing pressure and temperature parameters from satellite history telemetry data， an estimation has presented to model propellant leakage with gaseous equation. This estimation has calculation error analysis based on formula derivation， and satellite attitude change caused by propellant leakage has been considered， too. In the following stage， a prediction has made to calculate the remaining propellant to work for attitude control. Validated by cold gas pressure and temperature data from satellite telemetry， the result has illustrated that cold gas propellant of nitrogen has a leakage between 150Pa·cm3·s-1 and 450Pa·cm3·s-1 from the original pressure about 13MPa in the early 5 years， and has a gradual convergence of 275Pa·cm3·s-1 that is approximately about 3.4μg/s for nitrogen gas in subsequent years. At the same time， the result has implied that the remaining propellant mass is more than 85% of the original mass in the early 10 years and will be more than 60% of that after the following 20 years. By calculating precision of satellite attitude control system data such as attitude angle， magnetic torque current and momentum wheel revolution， cold gas leakage has nearly zero effect to satellite attitude. Finally， estimation and prediction result is applicable to telemetry diagnosis assistant for long-term management of satellite on orbit， and to evaluation of device SOH (State of Health) for longevity satellite.