The objective of the research is to analyze the external ballistic characteristics of middle-range rocket target with a constant thrust and varying rocket motor operating time. The main requirement is to achieve the rocket target with horizontal distance (range) of 20 km and vertical distance (altitude) of 10 km. The rocket motor to be used should be RM-12K designed and built by the Kaunas University of Technology, Institute of Defence technology. This motor can produce up to 12 kN thrust for 3.2 seconds. To achieve the goal, a computational model is designed and numerical modelling for ballistic analysis is carried out. In this research, two different configurations are used to achieve the requirement. In the first test, all four motors are ignited together for 3.2 seconds which produce 48 kN thrust force. In third configuration two motors are used for 3.2 seconds to produce 24 kN and after the burnout, the second two motor is ignited for 3.2 seconds. Comparative analysis of two different configuration shows that the requirement of 20 km range and 10 km altitude was realised by using two plus two motors for 6.4 seconds of operational time.