The ground testing of DoD high speed and hypersonic (HS/H) propulsion systems requires supporting utility supply systems that can provide various fluids and gases to the test article at conditions similar to or in excess of those expected to be experienced while the system is in flight. Because of the extreme temperatures and pressures experienced during hypersonic flight, the fuel that is used by the propulsion system will also be used to provide cooling to flight vehicle hardware and propulsion system components before injection into and burned in the combustor. At the Aerodynamic and Propulsion Test Unit (APTU) of the Arnold Engineering Development Complex at Arnold Air Force Base in Tennessee, a Heated Fuel System (HFS) has been installed to support HS/H propulsion system testing using kerosene-based fuels. It is designed to provide fuel to the propulsion system under test at high pressures and temperatures. Once the fuel is heated to the desired test temperature the fuel may be in a supercritical thermodynamic state and endothermic reactions may have broken long-chain hydrocarbon molecules into shorter molecules. This in turn results in a large uncertainty in the density of the fuel since the actual composition of the fuel mixture after heating is unknown. A new measurement method is needed to determine the fuel mass flow rate downstream of the fuel heating system. It is desired that the measurement uncertainties of this method are on the order of the methods used to measure low temperature flows. A direct measurement of mass flow rate is preferred since requiring the conversion of a volume flow rate to mass flow rate using the fluid density is not conducive to maintaining a low measurement uncertainty.