Electric propulsion systems, such as ion thrusters and Hall thrusters, are widely utilized in aerospace. The target indirect measurement method (TIMM) is a simple and robust way to measure its thrust. In general, one can obtain the thrust by scaling up the force exerted on the target surface immersed in the plume flow. However, the charge exchange (CEX) allows ions to become neutral particles, increasing the scaling coefficient. Meanwhile, the sputtered atoms and reflected incident particles exert force on the target surface and enlarge the measured thrust. In this study, the effects of the CEX, the sputtering, and the reflection on the TIMM are mathematically quantified, and then a modified model of the TIMM is proposed. Besides, the thrusts of the LIPS-200 and LIPS-300 ion thrusters were separately measured using the TIMM with the modified model, and the measured thrusts are in good agreement with the rated thrusts. Under the test conditions, the results of the LIPS-300 ion thruster show that the fast neutral atoms produced by the CEX account for more than 20% of all fast particles impacting on the target, and the force caused by the sputtered atoms is about 3.4% of the total force exerted on the target. We discuss how test conditions affect the CEX, sputtering, and reflection, thereby influencing the TIMM. The modified model was also validated through the simulation results, by showing that the measured thrust cannot be influenced by the test conditions.

电力推进系统，如离子推进器和霍尔推进器，在航空航天领域得到广泛应用。目标间接测量法（TIMM）是一种简单而稳健的推力测量方法。通常，可以通过放大施加在浸没在羽流中的目标表面上的力来获得推力。然而，电荷交换 (CEX) 允许离子变成中性粒子，从而增加了比例系数。同时，溅射的原子和反射的入射粒子对靶表面施加作用力，增大了测得的推力。在这项研究中，CEX、溅射和反射对 TIMM 的影响在数学上量化，然后提出了 TIMM 的修正模型。此外，LIPS-200 和 LIPS-300 离子推进器的推力是使用 TIMM 和修改后的模型分别测量的，实测推力与额定推力吻合良好。在测试条件下，LIPS-300离子推进器的结果表明，CEX产生的快中性原子占所有撞击目标的快粒子的20%以上，溅射原子产生的力约为3.4施加在目标上的总力的百分比。我们讨论测试条件如何影响 CEX、溅射和反射，从而影响 TIMM。修改后的模型也通过仿真结果得到验证，表明测得的推力不受测试条件的影响。LIPS-300离子推进器的结果表明，CEX产生的快中性原子占所有撞击目标的快粒子的20%以上，溅射原子产生的力约为总力的3.4%施加在目标上。我们讨论测试条件如何影响 CEX、溅射和反射，从而影响 TIMM。修改后的模型也通过仿真结果得到验证，表明测得的推力不受测试条件的影响。LIPS-300离子推进器的结果表明，CEX产生的快中性原子占所有撞击目标的快粒子的20%以上，溅射原子产生的力约为总力的3.4%施加在目标上。我们讨论测试条件如何影响 CEX、溅射和反射，从而影响 TIMM。修改后的模型也通过仿真结果得到验证，表明测得的推力不受测试条件的影响。