Cold gas thrusters are generally used for performing precise attitude control operations, station keeping, manned maneuvering, formation flying, de-orbiting of launch vehicle stages and spacecrafts. They operate in continuous and pulse mode for thrust generation, offering a simple and reliable system. Cold gas thruster consists of an upstream solenoid valve (SV) assembled to a downstream nozzle. This work presents the design, numerical study and developmental testing of a helium cold gas thruster with rated nominal thrust of 1 N in vacuum. In-house designed fast acting SV qualified for 1 million cyclic actuations was selected. Nozzle was designed analytically and verified by numerical analysis using ANSYS Fluent 2022. Parametric studies were conducted by varying nozzle throat dimension to understand its sensitivity on thrust. Analysis for estimating sea-level thrust was carried out; reduction in thrust by 30% was observed due to flow separation from the nozzle divergent portion. The estimated sea-level thrust for the final nozzle configuration compares well with the measured value and the design has been experimentally validated.