The plasma dynamics of hypersonic spacecraft: Applications of laboratory simulations and active in situ experiments

Attempts to gain an understanding of spacecraft plasma dynamics via experimental investigation of the interaction between artificially synthesized, collisionless, flowing plasmas and laboratory test bodies date back to the early 1960's. In the past 25 years, a number of researchers have succeeded in simulating certain limited aspects of the complex spacecraft-space plasma interaction reasonably well. Theoretical treatments have also provided limited models of the phenomena. Several active experiments were recently conducted from the space shuttle that specifically attempted to observe the Orbiter-ionospheric interaction. These experiments have contributed greatly to an appreciation for the complexity of spacecraft-space plasma interaction but, so far, have answered few questions. Therefore, even though the plasma dynamics of hypersonic spacecraft is fundamental to space technology, it remains largely an open issue. A brief overview is provided of the primary results from previous ground-based experimental investigations and the preliminary results of investigations conducted on the STS-3 and Spacelab 2 missions. In addition, several, as yet unexplained, aspects of the spacecraft-space plasma interaction are suggested for future research

The interaction of small and large spacecraft with their environment

The most significant results from small scientific satellites and from the space shuttle mission STS-3 regarding body-plasma interactions are presented and discussed. The causes for the above information being meager and fragmentary are given. The research avenues to be followed in the future in order to correct this situation are mentioned, including practical ways to achieve this goal

Bodies in flowing plasmas: Spacecraft measurements

Results from in-situ measurements relevant to the interaction of bodies in flowing plasmas are reviewed. A brief discussion of the interaction in the general context of SPACE PLASMA PHYSICS, including possible applications to solar-system plasmas is given. The mode of experimentation in the Shuttle/Spacelab era is also mentioned.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/24558/1/0000838.pd

Slow ions in plasma wind tunnels

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/76134/1/AIAA-7205-171.pd

Shuttle-era experiments in the area of plasma flow interactions with bodies in space

A new experimental approach is discussed in general terms, that can be adopted in the Shuttle/Spacelab era starting in the 1980s for studies in the area of plasma flow interactions with bodies in space. The potential use of the Space Shuttle/Orbiter as a near Earth plasma laboratory for studies in the area of Space Plasma Physics and particularly in the area of Solar-System Plasmas is discussed. This new experimental approach holds great promise for studies in the Supersonic and sub-Alfvenic flow regime which has applications to the motion of natural satellites around their mother planets in the Solar-system (e.g. the satellite Io around the planet Jupiter). A well conceived experimental and theoretical program, can lead to a better physical understanding regarding the validity and range of applicability of using gas-dynamic, kinetic and fluid approaches in describing collisionless plasma flow interactions with bodies in a variety of flow regimes.In addition to the above scientific aspects of the program, significant technological advances can be achieved regarding the interaction of space probes in planetary atmospheres/ionospheres and the reliability of using various plasma diagnostic devices on board spacecraft and large space platforms.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/23141/1/0000065.pd

Electron depletion in the wake of ionospheric spacecraft--A comparison between results from Langmuir probes and antennas

In situ observations of the electron depletion in the wakes of satellites and rockets in the ionosphere using Langmuir type probes and antennas are analyzed and compared. The quantitative degree of agreement between the results is demonstrated and discussed. One consequence is an improved interpretation of results previously presented for the OGO II Satellite wake.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/33876/1/0000137.pd

Experimental evidence of an electron temperature enhancement in the wake of an ionospheric satellite

A study of electron temperature (Te) measurements made by a Langmuir probe mounted on the skin of the Explorer 31 satellite indicates that electron temperature in the very near wake exceeds that of the ambient electron gas. Potential causes of such an enhancement are mentioned but the possibility that the wake `temperatures' reflect the existence of non-Maxwellian energy distributions cannot be discounted. The results are compared with observations from the Gemini/Agena wake experiment and are found to be in reasonable agreement.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/34096/1/0000378.pd

Collisionless plasma flow over a conducting sphere

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/34034/1/0000311.pd

Parametric study of near-wake structure of spherical and cylindrical bodies in the laboratory

Some aspects of the interaction between metal bodies and streaming rarefied plasmas were studied in a newly constructed Plasma Wind Tunnel as part of an attempt to investigate (via simulation) phenomena relevant to the spacecraft/space plasma interaction. Detailed near-wake ion current profiles for both spherical and cylindrical bodies at different body potentials ([phi]S) and at different plasma flow parameters are presented. Various features of the profiles can be correlated, at least qualitatively, with both plasma and body characteristics. For example, the width of the wake zone appears proportional to the Debye length ([lambda]D) and depends on the potential of the target body although it appears to be relatively insensitive to the ratio S = Vflow/(2kTe/M+)1/2. The amplitude of the ion current peak(s) also appears proportional to [lambda]D while, for fixed [phi]S, the location of the peak is directly related to S and possibly dependent upon body geometry. The general importance of body geometry is qualitatively demonstrated. In addition, a discussion of the relevance of the above studies to previous in situ data obtained from the Ariel I and Gemini/Agena missions is given.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/22401/1/0000851.pd

Comparison of theory and in situ observations for electron and ion distributions in the near wake of the explorer 31 and AE-C satellites

Measurements of electron density, plasma potential, and mean ion mass from the Explorer 31 satellite and measurements of ion current, plasma potential, and ion composition from the Atmosphere Explorer C (AE-C) satellite were used in a comparative study with theory regarding the charged particle distribution in the near wake of an ionospheric satellite. The theoretical wake model of Parker (1976) has been used in the study. It is shown that theory and experiment agree fairly well in the angle-of-attack range between 90 and 135[deg]. In that angular range even the neutral approximation (which treats ions as if they were neutral particles thus ignoring the influence of the electric field) gives fair agreement with the measurements. In the maximum rarefaction zone (145 < [theta] < 180[deg]), however, the theoretical model overestimates the measured ion depletion (AE-C measurements) by several orders of magnitude. A similar conclusion is drawn from the comparison between theory and the Explorer 31 electron measurements where the theory also significantly overestimates the electron depletion. The study indicates that the discrepancies are mainly due to the use of a steady-state theory and of a single ion equation (using a mean ion mass). It is recommended that improved agreement between theory and experiment be obtained by the use of the timedependent Vlasov-Poisson equations with separate equations for the various ion species.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/24274/1/0000540.pd