Design and Qualification of a High Temperature Multi-Layer Insulation Blanket for the Europa Clipper Mission

The Europa Clipper mission and environment imposes several constraints on the design of multi-layer insulation (MLI) blankets that insulate the thruster engine brackets. The driving environmental constraints are material compatibility with ionizing radiation, low or no electrostatic discharge, low outgassing rates in vacuum and in the presence of ionizing radiation, not a generator of foreign object debris, magnetic cleanliness to not interfere with instrument science data, and compatibility with monomethyl hydrazine and mixed oxides of nitrogen propellants. The combination of these constraints limits the number of materials acceptable for the flight blanket design. These requirements are most driving for materials on the space-viewing side of the blanket that would experience the worst case space environment effects. Furthermore, the MLI must simultaneously survive a 0.82 AU solar load as well as infrared and plume impingement heat loads generated by the nearby thruster engines during trajectory maneuvers. Development testing was performed with constituent materials to identify materials that fully address these constraints or minimize negative impacts to the mission. Coupons of several prospective MLI layups were then fabricated for qualification to the high temperatures and a separate thermal balance test for heat loss characterization. These tests were designed to demonstrate capability to the worst case thermal environment and provide inputs for the Europa Clipper system thermal model. This paper will describe the driving requirements, the materials considered and tested for this application, the candidate high temperature MLI blanket designs, the qualification test efforts, test observations, and lessons learned.