The project deals with the experimental study of the velocity decay characteristics of Single Expansion Ramp Nozzle (SERN) flows at low supersonic speeds. The preliminary design is carried out for the SERN with an 18° ramp angle without cowl and the model is fabricated. The experiment has carried out at low Nozzle Pressure Ratios (NPRs) ranging from 3 to 6. The readings for total pressure is taken along the mutually perpendicular transverse axes of the nozzle. A Pitot tube fitted with three dimensional traverse mechanisms is used to take the total pressure reading at different X/h locations of the nozzle. A pressure scanner and pressure indicator connected to the Pitot tube is used to measure the total pressure. The result is compared with a converging-diverging (C-D) nozzle at NPRs 3 & 6 & graph is plotted.