Tethered rocket experiment (Charge 2): Initial results on electrodynamics

The tethered mother‐daughter rocket experiment (Charge 2) was carried out by a NASA sounding rocket, Black Brant 9, at White Sands Missile Range in New Mexico in December 1985. It was intended to perform a new type of active experiment in space by applying a high voltage between the two payloads, as well as by injecting an electron beam from the tethered rocket system. An insulated conductive wire connecting the two payloads was deployed up to its maximum length of 426 m during the flight. An electron beam from 0.5 to 48 mA at 1 keV was injected from the mother payload. A voltage up to 500 V was applied between the two payloads with and without the beam injection. This paper describes the initial results on the electrodynamic effects induced by the potential difference between the two payloads. Measurements of the v×B electromotive force and the voltage/current characteristics up to 500 V have been explained by a model in which the ion current to the negatively biased payload effectively limited the tether current. Two kinds of VLF waves were observed when the bias voltage was applied between the two payloads; narrow‐band emission at 2–4 kHz and broadband emission up to 15 kHz, depending on the applied voltage. The characteristic features of these emissions suggest that the lower hybrid instability (modified two‐stream instability) driven by the potential difference between the rocket and the ambient plasma was responsible for the wave generation.