The research studied optimal arrangement of rocket fuel tanks of minimum starting weight with preserving the stability. We paid the main attention to calculating the strength and stability of the tank shells, determining their thickness in the two layout options: oxidizer - fuel, fuel - oxidizer. First, we calculated the weight of the obtained structure in both cases, analyzed the extension of centre of pressure and centre of mass. Then, we made a comparison of the weight value obtained from the strength calculation, with the value adopted in the statistics design. Moreover, we proposed a solution to the problem of static rocket instability by installing lattice stabilizers and we showed the advantage of the obtained design in a weight ratio. Finally, we proved the benefits of placing the oxidizer tank behind the fuel tank, which makes it possible to create lighter rockets and increase the payload mass without increasing the general product weight.