Wave plasma sources (WPSs) were first proposed in the 1970s for electric propulsion (EP), and these research and development processes culminated in the flight test in 2021 of the WPS-based thruster REGULUS. Recently, new approaches to WPS use have emerged—multiple schemes of EPs that can generate propelling forces in multiple directions within a single thruster head, regarded as a breakthrough technology for in-space propulsion systems (PSs). One of the concepts is the bi-directional wave plasma thruster that is based on the open-ended gas discharge chamber—the symmetrical system. Up to now, the WPSs based on the open-ended chambers have not been widely studied. In this paper, the plasma flow formed by the WPS based on the open-ended chamber was axially characterized using a retarding potential analyzer (RPA), Langmuir probe (LP), and optical emission spectroscopy (OES). The presence of the double-layer (DL) was confirmed by a drastic change in the plasma potential along the axis, and a specific impulse of 1100 s was indirectly measured. The measurement results show the potential of the WPS based on the open-ended chamber for efficient operations.