Sputter-Resistant Materials for Electric Propulsion, Phase II

This SBIR Phase 2 project shall develop sputter-resistant materials for use in electric propulsion test facilities and for plume shields on spacecraft using electric thrusters. A critical need arises because NASA is developing higher impulse, higher power thrusters for deep space science missions. Such thrusters will erode chamber walls ten-times more aggressively than before and create unacceptably high levels of contamination in the life test facilities. Without new materials that are ten-times more resistant than graphite, the only alternative may be installation of larger vacuum test chambers at huge facility cost. The proposed sputter-resistant materials are based on carbon fibers in a highly textured configuration that allows deep penetration of incident ions and trapping of sputtered secondary atoms. Phase 1 testing has demonstrated a 5x reduction in sputter backflow toward the ion source, consistent with modeling predictions. It appears feasible to extend the use of existing test facilities at least into planned near term testing of next generation ion engines. Phase 2 will develop thicker low-contamination chamber liners intended for long duration exposure, and modeling tools will be developed to aid in the design of baffled chamber liners. Lightweight rigid plume shields for spacecraft using EP will be demonstrated and offered for testing. Removable, cleanable, liner configurations will be demonstrated for use with condensable liquid metal propellants. Sputter testing will be performed by CSU using hemispherical witness plates to rapidly acquire directional yield data. Low-contamination chamber liner materials designed for use in testing high current, high voltage ion sources will be delivered under the contract for evaluation by NASA. More »