Title: Electromagnetic Pulses from Hypervelocity Meteoroid Particle Impacts (HMPI) on Spacecraft

The smoothed particle hydrodynamics (SPH) method has been used to simulate several cases of hypervelocity impact in an exploratory study to determine the suitability of the method for such problems. The calculations compare favorably with experimental results and with other numerical simulations. We discuss the requirements that must be satisfied for SPH to produce accurate simulations of such problems. 18 refs., 9 figs.

A one-dimensional numerical model for the expansion of impact-produced vapor clouds is used to investigate magnetic field generation mechanisms in events such as meteor collisions with the moon. The resulting cloud properties, such as ionization fraction, electrical conductivity, radial expansion velocity, mass density, and energy density are estimated. The model is initiated with the peak shock states and pressure thresholds for incipient and complete vaporization of anorthosite lunar surface materials by iron and GA composition meteorites. The expansion of the spherical gas cloud into a vacuum was traced with a one-dimensional explicit lagrangian hydrodynamic code. The hypervelocity impact plasmas producedmore » are found to be significant in the amplitudes and orientations of the magnetic fields generated. An ambient magnetic field could have been provided by the core dynamo, which would have interacted with the expanding plasmas and formed induced paleomagnetic fields. Several other field-contribution mechanisms are discussed and discarded as potential remanent magnetism contributors.« less

Hypervelocity micro particles (mass < 1 ng), including meteoroids and space debris, routinely impact spacecraft and produce plasmas that are initially dense (∼10{sup 28} m{sup −3}), but rapidly expand into the surrounding vacuum. We report the detection of radio frequency (RF) emission associated with electromagnetic pulses (EMPs) from hypervelocity impacts of micro particles in ground-based experiments using micro particles that are 15 orders of magnitude less massive than previously observed. The EMP production is a stochastic process that is influenced by plasma turbulence such that the EMP detection rate that is strongly dependent on impact speed and on the electricalmore » charge conditions at the impact surface. In particular, impacts of the fastest micro particles occurring under spacecraft charging conditions representative of high geomagnetic activity are the most likely to produce RF emission. This new phenomenon may provide a source for unexplained RF measurements on spacecraft charged to high potentials.« less

Wave forms of the electromagnetic pulse received from low-yield detonations were recorded for use in improving methods of estimating yields of such devices. Also, display components of the det onation locator central AN/GSS-5(XE-1) were evaluated. The wave forms were measured over frequency bands of 1 kc to 10 Mc and 0 to 250 kc, at a regge of about 100 miles. In each of the three detection and recording systems, the means of detection was a probe antenna coupled to oscilloscope inputs. Photographic records were made of the oscilloscope displays. Recordings were obtained from three above-ground, kiloton range nuclear detonations.more » Electromagnetic pulses from very-low-yield shots were not observed because of locally generated noise (sferics). Signals from subsurface detonations were not detected. The equipment proved to be adequate for the recording of known friendly fire detonations in the kiloton range.« less