Having variable thrust during the operation of a rocket provides tremendous advantages while chasing down a target. For ducted rockets, the key factor to obtain variable thrust is the precise pressure control inside the gas generator, which is one of the main elements of a throttleable ducted rocket and utilized to generate the fuel in gaseous form for combustion. However, the inherent nature of the system makes the control problem di cult due to time varying parameters, nonlinearities and time delays. Furthermore, disturbances and uncertainties exist due to challenging operation conditions. All these challenges make it necessary to design an advanced control approach. Therefore, a delay resistant closed loop reference model adaptive control is proposed in this thesis to address the control problem. The proposed controller combines delay compensation and adaptation with improved transient response. The controller is successfully implemented using an industrial grade cold air test setup, which is a milestone towards obtaining a fully developed throttleable rocket gas generator controller. Simulation and experimental comparisons with alternative adaptive approaches and a xed controller demonstrate improved performance and e ective handling of time delays and uncertainties. A step by step design methodology, covering robustfying schemes, selection of adaptation rates and initial controller parameters, is also provided to facilitate implementations.