THE MAGNETO-ACTIVE SLOSH CONTROL (MASC) PROJECT BRINGS TOGETHER TWO EXISTING EFFORTS IN ACTIVE SLOSH SUPPRESSION AND IN-SPACE PROPELLANT GAUGING TO BOTH REDUCE GAUGING ERRORS IN SPACECRAFT AND LAUNCH VEHICLES AND ELIMINATE DESTABILIZING LIQUID SLOSH DURING VEHICLE MANEUVERS. THE MODAL PROPELLANT GAUGING (MPG) EFFORT IS A NONINVASIVE APPROACH TO PROPELLANT GAUGING THAT HAS DEMONSTRATED SUB-1% GAUGING RESOLUTION IN SETTLED LIQUIDS AND 2-4% RESOLUTION IN UNSETTLED (SLOSHING) LIQUIDS ABOARD PARABOLIC FLIGHTS. MPG IS CURRENTLY BEING DEVELOPED FOR INFUSION INTO THE SLS/ORION EM3 ARCHITECTURE. THE CURRENT PROJECT IS AN EFFORT TO FURTHER ENHANCE THE GAUGING RESOLUTION OF MPG IN SLOSHING PROPELLANT THROUGH THE INCLUSION OF A FREE-FLOATING DIAPHRAGM THAT CAN BE POSITIONED AUTONOMOUSLY WITHIN THE LIQUID USING SMALL MAGNETIC FIELD GRADIENTS AND WHICH CAN BE STIFFENED BY ORDERS OF MAGNITUDE OVER ITS UN-ACTIVATED STATE USING STATIC MAGNETIC FIELDS. WHEN INTEGRATED WITH THE MPG FLIGHT RIG THE DIAPHRAGM A MAGNETO-ACTIVE PROPELLANT MANAGEMENT DEVICE (MAPMD) CAN BE AUTONOMOUSLY CONTROLLED SUCH THAT IT REMAINS NEAR THE LIQUID SURFACE OF THE CYLINDRICAL TANK AT ALL FILL LEVELS AND CAN STIFFEN IN RESPONSE TO SLOSH SURGES. THE MAPMD IS A PATENTED TECHNOLOGY DEVELOPED BY EMBRY RIDDLE AERONAUTICAL UNIVERSITY AND HAS DEMONSTRATED EFFECTIVE SLOSH SUPPRESSION IN 1-G LABORATORY TESTING. THE DIAPHRAGM CONSISTS OF A METALLIC ALLOY MESH EMBEDDED IN A FLEXIBLE POLYMER MATRIX. THE PARTICULAR METALLIC ALLOY BELONGS TO A CLASS OF MATERIALS THAT EXHIBIT UNUSUALLY LARGE MAGNETOSTRICTION ELONGATION UNDER APPLIED MAGNETIC FIELDS. WHEN THE MESH IS EXPOSED TO AN EXTERNAL STATIC MAGNETIC FIELD THE FIBERS OF THE MESH EXPAND CAUSING THE MESH TO STIFFEN. THE ACTIVATED (RIGID) MESH SUPPRESSES SLOSH WAVES IN AN UNDERLYING LIQUID. UNDER A GRAVITATIONAL FIELD THE MAPMD FLOATS ON THE SURFACE OF THE LIQUID. IN MICROGRAVITY THE POSITION AND MOTION OF THE DIAPHRAGM CAN BE CONTROLLED AUTONOMOUSLY BY A SET OF FIELD COILS EXTERNAL TO THE TANK THAT BOTH SENSE THE POSITION OF THE DIAPHRAGM AND PROVIDE FIELD GRADIENTS TO DRIVE THE DIAPHRAGM INTO POSITION AT THE SURFACE OF THE LIQUID. IN COMPUTER SIMULATIONS THE FIELD GRADIENT CONTROL (FGC) METHOD OF POSITIONING THE MAPMD HAS BEEN DEMONSTRATED TO EFFECTIVELY CONTROL THE DIAPHRAGM BUT REQUIRES PARABOLIC FLIGHTS TO ESTABLISH OPERATIONAL VALUES OF KEY PARAMETERS. MPG IS A WELL-TESTED TRL6 TECHNOLOGY PREVIOUSLY SUPPORTED BY THE FLIGHT OPPORTUNITIES PROGRAM TO DEMONSTRATE THE NON-INVASIVE MEASUREMENT OF PROPELLANT IN ZERO-G USING SURFACE ACOUSTIC WAVES PROPAGATING ON THE EXTERIOR OF A PROPELLANT TANK. THE PRESENCE OF LIQUID ADHERED TO THE INNER TANK WALL MASS-LOADS THE TANK AND THEREBY MODIFIES ITS RESONANT MODE FREQUENCIES. USING A REALTIME MODAL ANALYSIS IMPLEMENTATION THE MPG TECHNOLOGY CAN TRANSLATE THESE MODAL SHIFTS INTO ESTIMATES OF CONTAINED LIQUID MASS PROVIDING A FUEL GAUGE THAT REQUIRES NO INTERNAL HARDWARE OR TANK MODIFICATIONS OPERATES IN REAL-TIME AND ADDS LITTLE MASS TO TANK SYSTEMS. THE INTEGRATION OF ACTIVE SLOSH SUPPRESSION INTO THE MPG ARCHITECTURES PROMISES TO ADDRESS A KEY NASA TECHNOLOGY ROADMAP GOAL OF INSPACE PROPELLANT GAUGING OF UNSETTLED (SLOSHING) PROPELLANT WITH AN ACCURACY OF AT LEAST 2%. WITH CURRENT PROPELLANT MARGINS OF 10% OR MORE REQUIRE TO ACCOMMODATE UNCERTAINTIES IN GAUGING THE MASC EFFORT REPRESENTS A SUBSTANTIAL ECONOMIC BENEFIT ACROSS COMMERCIAL SPACE INDUSTRIES WHILE PROVIDING ENHANCED MISSION FLEXIBILITY. IF MASC CAN BE DEMONSTRATED TO SCALE WELL TO LAUNCH VEHICLES THE INCREASED SAFETY MARGINS AFFORDED BY REDUCED PROBABILITY OF SLOSH-INDUCED INSTABILITIES WILL BE OF SUBSTANTIAL BENEFIT TO COMMERCIAL LAUNCH PROVIDERS AND TO THE SLS/ORION PROGRAM.