Annotation: The main solid rocket motors of surface-to-air missiles and some short-range missiles have, as a rule, two operation modes – starting (augmented rating) and cruise (with decreased propellant consumption level). The methods to calculate intraballistic characteristics of such motors have a number of peculiarities, which set them apart from the methods of determining the characteristics of motors with constant propellant consumption level. The purpose of this article is to analyze such peculiarities, design methods, to find interrelation between the parameters of propellant consumption diagram, to determine the impact on the latter of motor design features and propellant characteristics. To achieve this goal, the method of analytical dependencies was developed. The equations obtained show that the required parameters of diagrams (including consumption-thrust characteristics difference between the starting and cruise modes) can be ensured due to varying either case diameter or propellant combustion rate or due to combined variation of these values. In practice, the cases are possible when for some reasons it does not seem possible to vary the case diameter or propellant combustion rate and the requirements to consumption diagram cannot be satisfied to the full extent. The task of motor developer in that case consists in determination of acceptable (alternative) propellant consumption diagrams that would be closest to required. The proposed method is based on calculation and construction of nomograms of dependencies of relative propellant consumption in cruse mode on relative time of starting leg at different propellant combustion rates and constant (required) case diameter and vice versa, at different values of case diameter and constant (available) propellant combustion rate. Using these nomograms, the rocket developer can determine the propellant consumption diagram acceptable for the rocket. In a number of cases, design limitations for separate main motor assemblies are imposed on consumption characteristic diagram that have an impact on its required parameters. The presented materials allow evaluating that impact and contain the proposals to remove it. The presented method allows quickly determining the conditions needed to fulfill required propellant combustion products consumption diagrams and in case of nonfulfillment of these conditions – allow presenting alternative options for selection of most acceptable one.

Annotation: Service life (resource) of the device (system, structure, material) is one of the major factors, which defines the reliable performance of the device or necessity of its replacement. The purpose of this paper is to develop the engineering methodology to estimate the service life of the device to support the well-founded design decision-making. The methodology of estimation of the service life of material or structure is based on the generalization of great amount of Yuzhnoye SDO experimental data and theoretical research on the impact of various factors (properties of materials, loads, storage and operation conditions) on their service life on the ground of strength analysis. At the same time, service life definition is based on the results of stress and deformation analyses and their comparison with strength properties of the applied material (tensile strength and deformation properties). Strength properties of the material should be reduced to test conditions in terms of temperature, pressure, rate of loading, degrees of material aging etc. Methodology provides the estimation of safety margins in all phases of storage and operation of the device, consideration of the impact of the active factors (mass, temperature, loading, process of material aging), performance of calculations for the chosen specific zones of the device. It is shown that the service life estimation is in general case a probabilistic observation because of the random combination of the influencing factors (strength properties, storage and operation conditions, loads). Analysis of experimental and computation data as applied to solid-propellant rocket engine shows that the most dangerous zones, which define the service life, are the fuel charge channel (deformations at launch), a fuel-body coupling zone (breakaway coupling stress) and a “lock” zone of the release collar (concentration of shear and breakaway stresses and deformations). Developed methodological guidelines of the engineering estimate of the service life can be used as the computational basis for the service life of materials and structures in the phase of system design and updating of the assumed design solutions.

Annotation: A comparative assessment of effectiveness of usage of hybrid rocket motors and solid rocket motors for meteorological rocket with propellant mass of 540 kg is made. Different combinations of oxidizer and fuel are considered based on which the power characteristics of hybrid rocket motors were determined. Based on the results of investigation, an assessment is given of ballistic effectiveness of hybrid rocket motors, the peculiarities of combustion process and of selection and designing of solid propellant charge shape are analyzed.

Annotation: The factors are considered that have an impact on the value and behavior of SRM flow rate and thrust characteristics after stage separation (in the leg of deep decay). It is shown that thrust behavior in the leg of deep decay is determined by two main processes: afterburning of solid propellant charge residues within the first 3-5 s and mass input of internal thermal protection coating destruction products within the following several tenths of second. The dependences are proposed for design evaluation of SRM intra-ballistic and flow rate/thrust characteristics.