Selection of the optimal thrust-to-weight ratio of the first stages of small-lift launch vehicles

Ultralight launch vehicles are among the most efficient means of inserting small satellites in the target orbits. Particular ballistic design problems being solved at the early stages in the ultralight launch vehicles development include rather actual selection of the most advantageous combination of the so-called design-ballistic parameters. They are usually understood as a set of the minimum possible number of parameters that, for a given payload mass, uniquely determine the rocket trajectory and its mass-energy characteristics. The paper considers issues related to selection of the thrust-to-weight ratio (launch load on thrust) of the first stages of disposable ultralight launch vehicles. This parameter is not included in the K. Tsiolkovsky formula; it determines the loss in the characteristic velocity for gravity, aerodynamics and backpressure. In this regard, its influence on the final rocket velocity is not that significant in comparison with such parameters as the specific void impulse or the relative final mass of the first stage. Selection of the optimal launch load on the rocket thrust is a responsible task, since it is determined by the thrust-to-weight ratio. Not only the mass, but also the cost of the designed product depends on its value. In addition to the specific void pulse, the relative final mass and the launch thrust load, the first stage design and ballistic parameters include the specific thrust pulse at the Earth surface (or the propulsion system altitude coefficient) and the load on the midsection.