GALAXY CLUSTER MERGERS ARE THE MOST ENERGETIC EVENTS IN THE UNIVERSE SINCE THE BIG BANG. IN THESE MERGERS A SIGNIFICANT FRACTION OF THIS KINETIC ENERGY IS TRANSFERRED INTO HEATING THE INTRACLUSTER MEDIUM (ICM) THROUGH SHOCKS AND TURBULENCE. IN ONLY A HANDFUL OF MERGING CLUSTERS HAVE CLEAR HIGH MACH NUMBER SHOCKS (M&GT;2.0) BEEN IDENTIFIED AND FINDING THEM IS VERY RARE. THIS HANDFUL OF SYSTEMS THEREFORE PROVIDES A POWERFUL AND UNIQUE INSIGHT INTO THE WAY THE ICM IS HEATED AND HOW THE ELECTRONS AND IONS IN THE ICM EQUILIBRATE AFTER HEATING WHICH CANNOT BE OBTAINED THROUGH ANY OTHER METHOD. RECENTLY A NEW HIGH MACH NUMBER SHOCK (M2.5) HAS BEEN IDENTIFIED IN A NEWLY DISCOVERED MERGING CLUSTER (SPT-CLJ2031) IDENTIFIED BY THE SOUTH POLE TELESCOPE AND FOLLOWED UP BY CHANDRA AND XMM. THE SHOCK HEATED GAS HOWEVER IS TOO HOT FOR AN ACCURATE TEMPERATURE MEASUREMENT TO BE MADE WITH CHANDRA AND XMM WITH THE BEST MEASUREMENT BEING 17 (+10 -5) KEV. ONLY WITH THE BROAD BAND PASS OF NUSTAR CAN THE TEMPERATURE OF THE SHOCK HEATED GAS BE ACCURATELY MEASURED AND MODELS FOR ICM HEATING BE CONSTRAINED. SINCE ACCURATE MEASUREMENTS OF HIGH MACH NUMBER SHOCKS ARE ONLY POSSIBLE FOR A SMALL NUMBER OF SYSTEMS THESE NUSTAR OBSERVATIONS ARE CRUCIAL FOR CONSTRAINING AND DEVELOPING OUR THEORETICAL UNDERSTANDING OF HOW GALAXY CLUSTERS ARE HEATED AS THEY GROW.