Reentry Plasma Research Articles

Use of radio frequency bridge for re-entry plasma diagnostics.

The use of an rf bridge technique to determine the electrical conductivity of the plasma sheath surrounding a re-entry vehicle (R/V) is considered. The theory of bridge operation and an analytical prediction of the bridge sensitivity are presented and validated by metal foil calibration and shock tube experiments. The range of plasma properties over which the rf bridge technique is valid is discussed, and the demonstrated sensitivity is shown to be capable of measuring the plasma encountered during re-entry. The Hall effect and rf breakdown could cause difficulty; these are examined and found to be of negligible influence. Requirements for installation aboard the R/Fare discussed.

Effect of Using a D.C. Magnetic Field in a Re-entry Plasma Sheath†

Abstract The problem considers the effect of an angular d.c. magnetic field on the radiation of a uniform magnetic ring source (slot antenna) situated on the surface of an infinitely long metal cylinder covered by a plasma sheath. It is observed that, in a relatively high density plasma (ω p /ω>1), the application of a static magnetic field improves the transmission of electromagnetic waves. However, it is shown in this paper that, in a low density plasma for which ω/ p /ω 1. When a static magnetic field is present, the increas...

A discussion of factors affecting the performance of microwave systems in certain plasma channels

Principal factors affecting the performance of microwave systems in composite and transient plasma channels are reviewed. Only macroscopic aspects of the channel characterization are considered. These include such effects as absorption, refraction, dispersion and depolarization; also nonlinear and random effects. An effort is made to assess their importance to communication with and tracking of rocketborne systems. It is concluded that channels incorporating, for example, the re-entry plasma sheath or the rocket exhaust are inaccessible at the present time to a detailed characterization. Further research, especially of experimental nature and extending beyond the traditional study o absorption loss, is indicated

Performance of digital signals through re-entry plasmas

Summary form only. An abstract of the above-titled article, taken from the 1963 IEEE International Convention (held March 25-28, New York, NY, USA), is presented.

Effects of Electron Random Motion on Microwave Propagation through a Plasma Parallel to a Magnetic Field

Expressions for the propagation of a circularly polarized microwave through a plasma parallel to a uniform and static magnetic field are derived from the Boltzmann equation and, alternately, from the equation of motion of an individual electron. Both methods yield identically the same formulation in which effects of the random motion of the electrons are predicted to result from (i) the Doppler shift due to electron motion parallel to the direction of propagation, (ii) electron free paths extending over distances significant compared to the attenuation length, and (iii) variation of collision frequency with electron velocity. The results of a numerical study of the propagation of a right-handed wave indicate that the first two of these effects are important in the region of cyclotron resonance even at moderate temperatures (e.g., in re-entry plasmas) provided that the collision frequency is small compared to the signal radian frequency. Substantial reduction of the attenuation of a right-handed wave in a plasma may be achieved by means of a magnetic field aligned parallel to the direction of propagation. The cyclotron frequency must be of the order of the signal radian frequency or larger and such that the enhanced attenuation arising from the electron random motion is avoided. The effectiveness of a given magnetic field in reducing the attenuation increases with decreasing ratio of collision frequency to signal radian frequency.