SDIO space insulation technologies

During the last five years the Strategic Defense Initiative Organization (SDIO) has performed a number of experiments, in a program called Space Power Experiments Aboard Rockets (SPEAR), to understand the interaction of directed energy and kinetic energy systems with the low-earth-orbit (LEO) environment. The SPEAR experiments are described. The conditions prevalent in the LEO environment and the problems related to operation of power systems in the ambient plasma are briefly presented. SPEAR I, launched in December 1987, was designed to understand the formation of the plasma sheath around the spacecraft at high potentials up to 12 kV. The SPEAR II program was designed to validate the space vacuum insulation technology by exposing two separate systems to the LEO environment. In SPEAR III, four grounding schemes will be tested for spacecraft charging levels up to about 4 kV as a function of altitude and geomagnetic field orientation