THIS PROJECT IS TARGETED AT TOPIC 1: DEMONSTRATION OF SPACE TECHNOLOGY PAYLOADS. THE NEED THAT WILL BE ADDRESSED IS WITHIN TA 2.4.2.3: IN-SPACE TANK-TO-TANK PROPELLANT TRANSFER [1]. HUMAN MARS MISSIONS WILL REQUIRE EFFICIENT DELIVERY OF CRYOGENS FROM A SUPPLY TANK TO A RECEIVER TANK IN MICROGRAVITY. AS NOTED IN THE NASA SSTIP STORAGE AND TRANSFER OF CRYOGENS IN SPACE IS CRITICAL FOR DEEP SPACE HUMAN EXPLORATION MAKING IT ONE OF THE SIX NRC HIGH PRIORITIES WITHIN THE LAUNCH AND IN-SPACE PROPULSION CORE TECHNOLOGY INVESTMENT. THE HIGH PERFORMANCE OFFERED BY THE CRYOGENIC PROPULSION WILL PERMIT LONGER RANGE MISSIONS LARGER PAYLOAD MASSES AND REDUCE HUMAN EXPOSURE TIME TO SPACE ENVIRONMENTAL HAZARDS. IN-SPACE TANK-TO-TANK TRANSFER IS COMPOSED OF THREE OPERATIONAL ELEMENTS 1) HIGH EFFICIENCY LINE CHILLDOWN 2) HIGH EFFICIENCY TANK CHILLDOWN AND 3) NO-VENT FILL OF THE RECEIVER TANK. WHEN TRANSFERRING CRYOGEN FROM A SUPPLY TANK TO A RECEIVER TANK THE TRANSFER LINE (I.E. PIPE AND VALVES) AND RECEIVER TANK ARE AT HIGH TEMPERATURES COMPARED TO THAT OF THE LIQUID PROPELLANT. CHILLDOWN IS THE PROCESS OF INTRODUCING THE CRYOGEN INTO THE SYSTEM TO COOL THE HARDWARE DOWN TO THE LIQUID TEMPERATURE. THE FLOWING PROPELLANT BOILS OFF AS IT COOLS THE LINE AND TANK. SINCE THE PROPELLANT IS ONLY STORABLE AND USEFUL TO THE ENGINE IN PURE LIQUID FORM THIS VAPORIZED PROPELLANT IS VENTED OVERBOARD AND CONSIDERED LOST . SINCE EACH OF THE THREE ELEMENTS IS A TWO-PHASE FLOW PROCESS THEY ARE ALL HIGHLY INFLUENCED BY THE GRAVITY LEVEL. THE PI S GROUP HAS PREVIOUSLY PERFORMED MANY TERRESTRIAL CHILLDOWN AND MICROGRAVITY PARABOLIC FLIGHT CHILLDOWN EXPERIMENTS FOR PIPES. MORE DIFFICULT TO MODEL AND IN MOST CASES MORE IMPORTANT FOR THE PROPELLANT THERMAL MANAGEMENT IS THE CHILLDOWN OF THE RECEIVER TANK. THE RECEIVER TANK IS THE MOST MASSIVE COMPONENT OF THE SYSTEM TO BE CHILLED DOWN AND THEREFORE TAKES MUCH MORE TIME TO CHILL DOWN AND THUS MORE CRYOGEN CONSUMPTION. AS A RESULT THE TIME AND PROPELLANT SPENT DURING CHILLDOWN WILL MOSTLY BE DICTATED BY HOW FAST THE TANK CAN BE CHILLED DOWN. BUT AT THIS TIME THERE HAVE BEEN NO STUDIES ON TANK CHILLDOWN IN ZERO GRAVITY. PREVIOUS TANK CHILLDOWN STUDIES HAVE BEEN LIMITED TO JUST 1G CONDITIONS AND WERE VERY SCARCE WITH ONLY TWO DATA SETS AVAILABLE AND THE EXPERIMENTS WERE POORLY EXECUTED [2]. THE PROPOSED PROJECT SEEKS TO FILL THIS VOID AND CLOSE THIS GAP BY CONDUCTING REDUCED GRAVITY EXPERIMENT FOR CRYOGENIC CHILLDOWN OF A RECEIVER TANK IN REDUCED GRAVITY ANALYZING DATA DEVELOPING MODELS AND THEN SUGGEST OPTIMAL TANK CHILLDOWN METHODS. [1]. NASA TECHNOLOGY ROADMAPS. TA 2 IN-SPACE PROPULSION TECHNOLOGIES (2015). [2] K. A. KEEFER AND J. W. HARTWIG DEVELOPMENT AND VALIDATION OF AN ANALYTICAL CHARGE-HOLD-VENT MODEL FOR CRYOGENIC TANK CHILLDOWN INT. J. HEAT AND MASS TRANSFER VOL. 101 PP. 175-189 (2016).