MIRI Cooler System Design Update
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NASA, under the Cryogenic Fluid Management (CFM) Project, in partnership with Ball Aerospace Technologies Corporation (BATC), conducted a reduced boil-off demonstration employing an actively cooled thermal radiation shield. The shield, designed and fabricated by NASA, consisted of overlapping panels of 1100 aluminum foil, and three parallel 1/8 inch cooling lines attached to the foil with adhesive and communicating with 1/4 inch inlet and outlet manifolds. The shield and gas distribution network were instrumented and integrated with BATC's 500 L liquid nitrogen (LN2) cryogenic propellant tank simulator, high-performance multi-layer insulation (MLI), and a cryocooler and pressurized helium circulator. Two test conditions were run to evaluate the thermal performance of the system. An initial test was performed to measure the baseline or passive steady state heat leak into the LN2 tank. In the second test, the cryocooler/circulator was driven at maximum power until the system again reached steady state. By removing heat from both the shield and the tank support structure via the circulating helium stream, the average shield temperature dropped from ~228 K to ~132 K and the total heat leak into the tank was reduced by 82 %. This was despite the fact that the flow rate in the distribution network was unexpectedly low due to a partial blockage in one of the recuperators.