Preliminary Plume Characterization of a Low-Power Hall Thruster Cluster

Abstract

Public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing this collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden to Department of Defense, Washington Headquarters Services, Directorate for Information Operations and Reports (0704-0188), 1215 Jefferson Davis Highway, Suite 1204, Arlington, VA 22202-4302. Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to any penalty for falling to comply with a collection of information if it does not display a currently valid OMB control number. PLEASE DO NOT RETURN YOUR FORM TO THE ABOVE ADDRESS. REPORT DATE (DD-MM-YYYY) REPORT TYPE Technical Papers DATES COVERED ABSTRACTIn an effort to understand the technical issues related to running multiple Hall effect thrusters in close proximity to each other, testing of a cluster of four Busek BHT-200-X3 devices has begun in Chamber 6 at the Air Force Research Laboratory. Preliminary measurements have shown that the variations in the discharge currents of the four thrusters are synchronized, possibly due to cross talk through the thruster plumes. Measurements of plasma density, electron temperature, and plasma potential in the thruster plumes obtained using a triple Langmuir probe are presented. Anomalously high electron temperatures were recorded along the centerline of each thruster. Collisionless, magnetosonic shock waves induced by the ion-ion two-stream instability are proposed as a possible cause of the high temperatures. The unperturbed ion velocity distribution along the centerline of a Hall thruster is shown to be unstable and a simple geometric model is presented to illustrate the qualitative changes in plasma properties expected across the proposed shock. Estimates using this model show that relatively large changes in electron temperature are consistent with small changes in electron number density across a shock. Qualitative arguments are presented indicating that collisionless shocks are unlikely to form as a result of clustering multiple thrusters.

Plasma Properties in the Plume of a Hall Thruster Cluster

“…6 Typical operating conditions for the BHT-200 are given in Table 1. 3 Figure 1 shows the cluster during operation.…”

Studying of Atomic and Molecular Interaction Processes in Rarified Hypervelocity Expanding Flows by Methods of Emissive Spectroscopy

“…Possibility for such amplification and synchronization of oscillations in the thrusters integrated in a cluster was demonstrated in Ref. 86 . This is of fundamental importance for further examination of the cluster electromagnetic compatibility via taking measurements of an individual thruster performances.…”

The Air Force Clustered Hall Thruster Program

“…During this time, a number of measurements have been performed including a series of preliminary measurements which explore issues, such as plume interactions and plasma cross-talk, related to clustering Hall thrusters. Several of the more detailed measurements are presented in greater depth in companion papers [9,10].…”

“…A paper will be presented detailing plume interactions [9]. Another paper will detail a thruster start-up transient that can also affect cluster operations [10].…”