Accurately controlling the mass flow rate of a compressible fluid over a large dynamic range is of practical importance for a variety of industrial and engineering applications.  The sonic nozzle is a potential control device applicable to such a broad range of flow rates that is finding wide spread acceptance for gases.  To determine the feasibility of such a control device, two-dimensional, axisymmetric computational fluid dynamics simulations are coupled with one-dimensional isentropic, compressible flow models to develop a new, variable-area, sonic nozzle capable of dynamically controlling the volumetric flow rate of a gas through almost five orders of magnitude, from 0.5 sccm to 30 slm.  This achievement is in sharp contrast to adjustable sonic nozzles currently available having dynamic flow rate ranges on the order of 10:1 to 20:1, depending on the orifice diameter.  The volumetric flow rate of air through the theoretical nozzle is calculated by varying two independent variables, the inlet pressure and the cross-sectional area of the nozzle throat.  The energy losses predicted by the computational fluid dynamics simulations, which will be discussed in detail, are also taken into consideration and incorporated into the isentropic flow model in terms of a discharge coefficient, C_D.  The cross-sectional area of the throat is varied by incremental motion of a rod centered in the nozzle.  The distance from the surface of the rod to the orifice wall is calculated and compared to typical fabrication tolerances.  It has been determined that, for higher flow rates, machining tolerances do not preclude device fabrication.  At low flow rates, however, extremely stringent control of the manufacturing process is required to ensure that the rod surface does not contact the inner wall of the nozzle.