Mass Spectrometric Study of Various Coated Targets Utilizing PUPR-MC Plasma Machine for NASA Solar Probe Space Mission

Abstract

The NASA Solar Probe Space Mission will be a historic operation, flying for the first time into one of the last unexplored regions of the solar system, the Sun's atmosphere or corona; hopefully revolutionizing our knowlege of physics regarding the origin and evolution of the solar wind phenomenom. One of the spacecraft's most prominent features is the Thermal Protection System (TPS), composed of a large carbon-carbon conical shield, desighned to withstand the Sun's violent temperatures. Thermal testing was performed on various coatings on the carbon-carbon targets in order to study mass loss components using mass spectrometry. Mass spectometry is an analytical technique used to measure the mass-to-charge ratio of ions. The composition of a gaseous sample is found by generating a mass spectrum where the masses of the elements present in the sample. Using a quadrupole mass spectrometer, the effects of the exposition to low density plasma on various coated targets were analyzed at PUPR Mirror/Cusp (PUPR-MC) plasma machine. A series of five tests were performed for this experiment. The first four tests consist in creating plasma with four different gases, and studying the effects of each gas on plasma using mass spectrometry, in order to decide which plasma resembles the Sun's atmosphere or corona; the gases utilized were: (1) residual gas, (2) argon, (3) nitrogen, and (4) hydrogen. The fifth test consists in the introduction of various coated targets, representing the spacecraft's shield, inside PUPR-MC plasma machine for approximately twelve hours, to study the reactionof the coatings to the plasma best resembling the Sun's atmosphere,. After studying the first four tests results, is is evident that each gas has a distinctive effect on the plasma. For the fifth test following the study of the mass spectrometry results, it is clear that the quadrupole mass spectrometer was able to detect mass loss components for the introduced targets, and the presence of the coatings were successfully identified inside PUPR-MC plasma machine, therefore assisting in the shield coating selection for the Solar probe aircraft.