Avaliação do desempenho propulsivo utilizando dois agentes oxidantes na forma de propelente sólido em minifoguetes

Abstract

The mini rockets use a mixture of potassium nitrate and sucrose known as propellant grain, which, when ignited, produces an energy burn that has the function of moving the vehicle upwards through the principle of action and reaction. For this study, two types of oxidizing salts were considered: potassium nitrate and sodium nitrate in order to establish comparisons between which of these two components and in which oxidant/fuel ratio would have a better result. Five small rocket engines were analyzed for each percentage of propellant grain mix-ture, totaling 30 tests on a static bench in order to fulfill the objectives of this work. The tested formulations contained 55/45, 65/35 and 75/25 percentages by mass of propellant made with KNO3 and sucrose (C12H22O11) respectively, keeping the same prepared compositions, using another type of oxidant, NaNO3. The methodology followed in the preparation of the propellant grain was the same for both oxidizing agents. Performance characteristics such as burn time, total thrust, maximum thrust, average thrust, specific thrust, and characteristic speed are basic design parameters that will determine solid fuel performance. These parameters were evaluated by a software whose results for the propellant made with potassium nitrate (65/35), showed better performance in all items, confirming in the literature that it is the best proportion to be used. With the smallest residual mass (4.28%), also obtained in relation to all other samples. The results obtained for NaNO3 compared to KNO3 were much lower, but the proportion of (55/45) of oxidizing/fuel mixture was the one that presented slightly better results, except for the average thrust and the mixture (75/25) did not was able to ignite and the residual mass for the other propellants made with this salt had an average above 94%. [resumo fornecido pelo autor]