ESA GNC Conference Papers Repository

During the flight, the satellite launch vehicle is subjected to disturbances that carry it to a flight condition different from the nominal. If the vehicle continues to suffer these disturbances and no compensation is applied, the mission of the vehicle can be impaired. In order to reduce the effects of the disturbances on the vehicle flight, and consequently the dispersion on the final orbit parameters, a strategy called Guidance Algorithm – GA was developed. This algorithm is based on the instantaneous conditions of flight and on the final objective to be reached. It produces the pitch angle profile during the third stage flight to the attitude control system, so that the vehicle reaches a transfer orbit with previously specified parameters. The purpose of this work is to present a particular study about the GA, analyzing its performance. In order to carry out this particular analysis, the Monte Carlo Simulation was performed, and the results were compared with the nominal trajectory without disturbances. For the simulations using Monte Carlo, dispersions were taken into account on the thrust and solid propellant mass of all launch vehicle´s engines, on the structural mass of the vehicle, aerodynamic drag, ignition time of the last stage, and on the attitude of the vehicle when the last engine starts. The results showed that the guidance strategy is an important tool to reduce the dispersion of the orbit parameters when the disturbances occur during the flight of the first and second stages. However, when the disturbances occur during the guidance strategy execution, the mission of the Brazilian Satellite Launch Vehicle (VLS, acronym in Portuguese) can be impaired, increasing the dispersion around the final orbit.