Arestie Steven M, Marrese-Reading Colleen M, Shaik Saba Z
NASA Jet Propulsion Laboratory, California Institute of Technology, Pasadena, 91109 CA USA.
Department of Aeronautics and Astronautics, Massachusetts Institute of Technology, Cambridge, 02139 MA USA.
J Elect Propuls. 2025;4(1):22. doi: 10.1007/s44205-025-00121-5. Epub 2025 Apr 1.
Electrospray thruster ground testing, with well understood facility effects, is of critical importance to qualify the technology for long duration flight missions. While there has been substantial work to understand the beam physics and plume dynamics of electrospray thrusters and the implications thereof on performance and lifetime, work to understand the impact of facility effects has been neglected until recently. Interactions between an electrospray plume and the vacuum chamber test facility have implications on both performance and lifetime. Therefore, any effort to characterize electrospray thruster performance and lifetime must be done so with an understanding of facility effects. In some ways, this is no different than the significant investment that has been made to understand the facility effects for plasma thruster testing. However, there are different challenges with the management of positively charged, negatively charged, and neutral propellant particles across a distribution of particle charge and mass when testing electrospray thrusters in a vacuum chamber. The focus of this paper is to characterize the significance of secondary particles from the impact of ionic liquid electrosprays with a beam target, and the influence of a novel beam target design and biasing. Results on secondary current and mass flux measurements are presented with some initial results on secondary time-of-flight measurements from the beam target. Additionally, beam target modeling results are presented to support the experiments and interpretation of the results. The results revealed secondary particles with an average charge-to-mass ratio as low as 31 C/kg, and that an improperly biased beam target, or no beam target, can artificially inflate emitted current due to electron back streaming by as much as 20%. The experimental and modeling results suggest an optimized beam target and screen voltage of -100 V and -200 V, respectively. If no consideration of facility effects is included in testing electrospray thrusters, performance, reliability, and lifetime can be adversely affected, and premature thruster failure may result. The work presented here improves our understanding of facility effects and our capabilities to mitigate them to successfully qualify and acceptance test electrospray thrusters for flight.
在充分了解设施影响的情况下进行电喷雾推进器地面测试，对于使该技术具备执行长时间飞行任务的资格至关重要。虽然在理解电喷雾推进器的束流物理和羽流动力学及其对性能和寿命的影响方面已经开展了大量工作，但直到最近，对设施影响的研究工作仍被忽视。电喷雾羽流与真空室测试设施之间的相互作用对性能和寿命都有影响。因此，在表征电喷雾推进器性能和寿命时，必须在了解设施影响的情况下进行。在某些方面，这与为理解等离子体推进器测试的设施影响所做的大量投入并无不同。然而，在真空室中测试电喷雾推进器时，在处理跨越粒子电荷和质量分布的带正电、带负电和中性推进剂粒子时会面临不同的挑战。本文的重点是表征离子液体电喷雾与束流靶碰撞产生的二次粒子的重要性，以及一种新型束流靶设计和偏置的影响。给出了二次电流和质量通量测量结果以及来自束流靶的二次飞行时间测量的一些初步结果。此外，还给出了束流靶建模结果以支持实验和结果解释。结果显示二次粒子的平均荷质比低至31 C/kg，并且偏置不当的束流靶或没有束流靶会因电子回流而使发射电流人为地增大多达20%。实验和建模结果表明，优化后的束流靶和屏蔽电压分别为-100 V和-200 V。如果在测试电喷雾推进器时不考虑设施影响，性能、可靠性和寿命可能会受到不利影响，可能导致推进器过早失效。本文所开展的工作增进了我们对设施影响的理解，以及我们减轻这些影响以便成功使电喷雾推进器通过飞行鉴定和验收测试的能力。
