Unfortunately, this situation can o

Unfortunately, this situation can only occur at one specific atmospheric pressure on a fixed-geometry nozzle. As we have seen previously, pressure decreases as altitude increases. Nozzle designers typically must select a shape that is optimum at only one altitude but minimizes the losses that occur at lower or higher altitudes. These losses result from the fact that the atmospheric pressure will either be higher than the exit pressure of the exhaust gases, i.e. at low altitudes, or lower than the exit pressure, i.e. at high altitudes.