Rocket booster effect on RKX-200TJ flight stability

Started in 2013, research development on RKX-200TJ had given promising results. As the research was conducted, the rocket needed some improvement so that it could be used as a spinoff of defense system by Indonesian National Armed Force (TNI). The improvement needed was increasing potential weight in its payload, so RKX-200TJ had at least payload weight 25 kilogram. Thus, a rocket booster launcher was needed to replace the existing pneumatic launcher. However, the safety of the rocket booster had to be confirmed by calculating the stability of the vehicle at the switch of Cg location in Z axis at the time of booster launch and release. This research was done by using Integrated Simulation System (ISS) and the result was compared directly with the data from flight test RKX-200TJ Dummy Booster. The vehicle was designed to cruise at a speed of 250 km/hour, auto pilot by way points, using turbine jet as the main launcher (thrust max 20 kgf) and rocket booster as the initial launcher (average thrust 120 kgf). The crucial thing in this discussion was the one second when the booster was burning. Before flying, the vehicle had ZCg minus 6 cm, but when it was burning out, the booster was released and ZCg went back to 0. Such condition needed to be anticipated by locating the booster in the right angle. The right angle could be found by a simulation using XPlane repeatedly with different variations of angles. The result was later compared to the real flying data. The simulation result showed more details on the vehicle´s pitch tendency with different angles of booster location. The significant result was separated within 0.1 deg of booster location, which might produce unsafe pitch up and pitch down if had not been recognized properly in the real flight test. The comparison between simulation result and flight test data showed that the simulation was quite reliable for different condition of ZCg for each vehicle fabrication which was done manually.