Electromagnetic Properties of Impact-Generated Plasma, Vapor and Debris
Plasma, vapor and debris associated with an impact or explosive event have been demonstrated in the laboratory to produce radiofrequency and optical electromagnetic emissions that can be diagnostic of the event. Such effects could potentially interfere with communications or remote sensing equipment if an impact occurred, for example, on a satellite. More seriously, impact generated plasma could end the life of a satellite by mechanisms that are not well understood and not normally taken into account in satellite design. For example, arc/discharge phenomena resulting from highly conductive plasma acting as a current path across normally shielded circuits may have contributed to the loss of the Olympus experimental communications satellite on August 11, 1993. The possibility of significant storm activity during the Leonid meteor showers of November 1998, 1999 and 2000 (impact velocity, 72 km/s) has heightened awareness of potential vulnerabilities from hypervelocity electromagnetic effects to orbital assets. The concern is justified. The amount of plasma, electrostatic charge and the magnitude of the resulting currents and electric fields scale nearly as the cube of the impact velocity. Even for microscopic Leonid impacts, the amount of plasma approaches levels that could be dangerous to spacecraft electronics. The degree of charge separation that occurs during hypervelocity impacts scales linearly with impactor mass. The resulting magnetic fields increase linearly with impactor radius and could play a significant role in our understanding of the paleomagnetism of planetary surfaces. The electromagnetic properties of plasma produced by hypervelocity impact have been exploited by researchers as a diagnostic tool, invoked to potentially explain the magnetically jumbled state of the lunar surface and blamed for the loss of the Olympus experimental communications satellite. The production of plasma in and around an impact event can lead to several effects: (1) the plasma provides a significant perturbation to the ambient magnetic field via the electromagnetic pulse; (2) it supports the production of transient radiofrequency electromagnetic fields; (3) it charges ejected debris which, because of inertial separation, leads to significant electrostatic and magnetostatic field production; and (4) its high electrical conductivity provides a convenient path for discharge of the resulting high electrostatic fields. Effects (1) and (2) have been discussed by the authors elsewhere. Effects (3) and (4) will be discussed here. Typical studies of kinetic energy warheads focus on lethality as a function of impactor momentum or energy as they couple mechanically to the target. At high enough energies, however, additional physical processes come into play. Vaporization plays an important role and a partially ionized plasma can form. Impact-generated plasma, charged debris and magnetic fields have been characterized by laboratory hypervelocity impact experiments and are shown to be more abundant when certain easily ionized materials (such as alkali metals) are used in either projectile or target.
- Research Organization:
- Sandia National Laboratories (SNL), Albuquerque, NM, and Livermore, CA (United States)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- AC04-94AL85000
- OSTI ID:
- 1544
- Report Number(s):
- SAND98-2463C; ON: DE00001544
- Resource Relation:
- Conference: Hypervelocity Impact Symposium; Huntsville, AL; 11/16-19/1998
- Country of Publication:
- United States
- Language:
- English
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