This paper deals with the control problem of obtaining desired gas pressure inside a control volume with constant inlet mass flow rate of cold air. Cold air flow system dynamics is similar to that of a gas generator of a throttleable ducted rocket, which sends fuel in gaseous form, with metal additives, to ram combuster with desired amount of mass flow rate to obtain variable thrust. Being able to control gas pressure in cold air flow system is a milestone towards obtaining a fully developed throttleable ducted rocket gas generator controller. In this study, a detailed modeling of the cold air test plant together with a delay resistant closed-loop reference model adaptive controller design is presented. The proposed controller is compared with several other alternatives including a classical proportional-integral controller, model reference adaptive controller and a closed- loop reference model adaptive controller that does not have explicit delay compensation. Simulation results verifying the performance improvement of the delay resistant controller over the alternatives are presented.