In late 1993, the Space Shuttle will cany aloft the Wake
Shield Facility, WSF. The prime experiment on WSF is
provided by the Space Vacuum Epitaxy Center at the Univ. of
Houston, and will explore the utility of the space vacuum for
ultra clean epitaxial film growth. WSF will also carry other
experiments to measure the contamination limits of a practical
wake vacuum facility. One such experiment is the Charge
Hazard And Wake Studies experiment, CHAWS, provided by
Phillips Lab. CWAWS will measure the plasma environment
on both the ram and wake sides of the WSF. On the wake side,
the monitor is a hybrid Langmuir probe in the shape of a
cylinder 4" in diameter by 18" in length. Both the ram side
monitor and wake side probe contain novel new multi-channel
array based retarding potential analyzers with entrance angle
imaging capability. In addition, the wake side probe will be
swept from zero to -5 KiloVolts to explore the nature of ion
collection by a high voltage surface in the wake of a larger
body.
to many problems in space science and engineering. The
current - voltage characteristic for a biased wake side surface
is difficult to predict from both theoretical considerations or
extrapolation of experimental measurements. This difficulty
arises from the interplay between the wake void and the space
charge shielding process. In support of the flight experiment,
numerous computational studies have been conducted, as well
as one laboratory simulation. The numerical calculations
include steady state models from the POLAR and MACH
codes, and a particle in cell simulation.
This talk will outline the challenges in relating laboratory
to space experiment using numerical simulation, review the
workings of the various codes, and make specific predictions
for the anticipated CHAWS current-voltage characteristic.
High voltage - ion collection in a wake is an issue relevant