Impacts of the spill hole in the stability of a model rocket parachute

Rocketry is a practice that has been growing in Brazil, especially within universities. One of the major challenges in this activity is the recovery system, responsible for ensuring a safe descent of the rocket. This study aimed to analyze the efficiency of a scale parachute, using a wind tunnel to compare the obtained data with that found in the literature. The influence of the spill hole diameter was examined by utilizing a device with 5% and 10% diameter relative to the total parachute diameter, assessing its impact on stability during descent. Based on this, the experiments were conducted using scale models in a wind tunnel at the Federal University of Minas Gerais, maintaining ambient conditions for both models. The results of the tests indicated that the parachute with a larger spill hole had significantly better stability, with less variation in drag force. The 5% parachute exhibited a standard deviation in drag force values 3.9 times greater than the 10% parachute (at a flow velocity of 25 m/s). The findings suggest an increase in the parachute's drag coefficient with a smaller canopy opening, resulting in higher drag force.