The charge neutralization of an electrically-isolated rocket payload emitting an energetic electron beam has been studied in experiments in the large vacuum chamber at Johnson Space Center. The introduction of an RF-discharge-produced ambient plasma density (104-5¿104 cm-3) reduces the payload potential to <200 V for low current (1 and 10 ma) beams. The ignition of the beam-plasma discharge provides an efficient neutralization process for higher current beams.