Fluid Testing of the Gateway MMH Refueling System

Lunar Gateway, as part of NASA’s Artemis program, is intended to support long-term human exploration of the moon. To allow for a longer vehicle life span, it is designed for on-orbit refueling (similar to the International Space Station). The bipropellant refueling system will have the capability to transfer propellants, monomethylhydrazine (MMH) and mixed oxides of nitrogen-3 (MON-3), under controlled conditions and will span across three modules: the European System Providing Refueling Infrastructure and Telecommunication Refueling Module (ESPRIT-RM or ERM), the Habitation and Logistics Outpost (HALO), and the Power and Propulsion Element (PPE). Because these propellant transfers are complex operations with known hazards, a test stand has been developed at White Sands Test Facility (WSTF) to test these operations on a fluid emulator of the MMH refueling flight system. The fluid emulator has many complex tubing sections with hundreds of welds and bends that mimic the flight configuration. Since water is a common simulant for MMH, water testing was performed on this test stand first to vet out the procedures and provide initial performance data before the fuel campaign. Different variables including starting supply tank pressure, helium saturation, and temperatures were tested with both water and MMH to assess impacts on pressure transients and flow behavior of priming and transfer sequences. The data is also being used to anchor analytical fluid models. These campaigns were the first milestones to a multi-year program that will eventually provide final test verifications for the bipropellant refueling system.