PROPOSAL SUMMARY

PROGRAM ELEMENT: NRA 00-OSS-06 Gossamer Spacecraft Exploratory Research and Technology

TITLE OF INVESTIGATION: Dynamic and Optical Characterization of Dusty Plasmas for Use as Solar Sails

PRINCIPAL INVESTIGATOR/INSTITUTION: Robert Sheldon, The University of Alabama in Huntsville

SUMMARY OF PROPOSED INVESTIGATION:

Solar sails presently have mass loadings about 5 gm/m$^2$, which when including the support structure and payload, could easily average to $>$ 10 gm/m$^2$. For realizable spacecraft, the critical parameter is the total mass / total area, which when combined with the reflectivity, directly give the true acceleration. We propose that dusty plasmas trapped in a ``mini-magnetosphere'' (Winglee et al. JGR 2000) can produce a solar sail with a total mass loading $<$ 0.01 gm/m$^2$, and reflectivities of $\sim$1%. This configuration provides an acceleration equivalent to a standard sail of 95% reflectivity with $<$ 1gm/m$^2$. Thus, dusty plasma sails represent a potential replacement for thin film technology.

However, the physics of dusty plasma sails is not mature. Several important questions need to be resolved in the laboratory before a large scale effort is warranted. Foremost among these questions are, what is the largest force a dusty plasma can sustain before it demagnetizes and separates from the binding magnetic field? What are the charging properties of dust under solar UV conditions? What is the light scattering cross section for the dust? What is the optimum dust grain size for magnetization and scattering? What are the optimum dust grain materials?

We propose to augment two existing dusty plasma experiments at MSFC and at Auburn University to study candidate dusty plasma sail material, by adding an artificial sun light source, tuneable laser light sources, a spectrometer, and combination Paul trap-DC field-magnetic field confinement device. Possible dust sources include: calibrated latex/styrene spheres for studying size effects; CuS and FeO needles for studying the effects of shape on dust properties; ErO or DyO for studying the effect of composition on light scattering; Au spheres for studying the effect of size/composition on UV charging.