A study of methods of measurement of the electric charge on a rocket and of ambient electric fields using probe techniques

Abstract

A summary is given of literature on causes of rocket charge, ambient fields, and on probe techniques. A variety of techniques are available for determining rocket charge, represented by a potential relative to space of 0 to 10 volts. A cylindrical probe characteristic, analysed by the older Engel and Steenback methods, was obtained for a pulse discharge with a low electron concentration of 2 x 10(^7) electrons/c.c, in the author’s experiments. The probe sheath was collision free, and conditions for such sheaths in the upper atmosphere are given. The predicted ambient field is about .02 mV/cm, fields measured being .60 mV/cm. (by a probe technique) and 200 V/m (by field meters). The author’s tentative opinion is that the ambient field might be measured by a simultaneous determination of potential at two points using probes. Laboratory simulation seems to require a low voltage gradient discharge, (preferably with ions and electrons in thermal equilibrium,) because two probes cannot be placed as close as a Debye length. The contract specifically excluded development of circuitry so a precise answer cannot be given, but definite proposals are made. In the experiment, the measured voltage gradient was about 30 V/cm, which seems abnormally high at a discharge current of about 10(^-4) amps when compared with recent results for steady glow discharges. The explanation may reside in the existence of striations. From the work recently reported in a Czechoslovakian journal it might be argued that the probe is responsible foe the striations. No material is included oh re-entry physics, nor on the time and space variations of electric fields. A study of the latter should be related to a precise knowledge of the rocket motion. Tine research represents a branch of Atmospheric Electricity which had not previously been studied at Durham.