In future, advanced propulsion system integrated with different features like reusable single stage to orbit (SSTO) and rocket engines, light weight and high performance propulsion system from low altitude to high altitude were essential. Aerospike nozzles with different possible surface contoured nozzles were used for propulsion system in space vehicle. Complex flow field develops on nozzles, the potential thrust and structural gains are interested parameters to the propulsive flow adapt in the external stream. The commercial software Ansys-Fluent 6.3.26 was used for the numerical simulation with Mach number of 3. Ideal state analysis with implicit formulation is carried out. Mass, Momentum and energy equations with Spalart -Almaras turbulence model were solved. In this project a study on different types of aero spike nozzles and characteristics of its flow field were analyzed. Numerical analysis carried out for flow characteristic of typical aero spike nozzle, comparison on full spike and truncated spike with 50% modification of spike length configuration for different pressure ratios. The flow characteristics such as shock waves and wake formation were discussed with contour plots. Numerical simulation found that modification of Aerospikes nozzle increases the flow velocity and optimize expansion waves.