| Summary: | <p>The article describes a ballistic software kit to calculate a moving vehicle trajectory in atmosphere and space. Such software gives an opportunity to accelerate the acquisition of flying vehicle’s ballistic parameters at the stage of draft design. It contributes to improving collaboration efficiency between adjacent departments involved in the project. The developed software kit includes three different programs: Trajectory-LAND© (motion in atmosphere with possible correction of a trajectory), Trajectory-SPACE© (motion in the non-central gravity field with possible simulation of maneuvers), Trajectory-LAUNCH© (launch-vehicle’s insertion into the orbit with possible defining the impact points of separated stages). Each of the software concedes the addition of computational modules to use the solution results of the basic task. Implemented mathematical models permit to take into account the influence of main perturbations on the flying vehicle during the flight. For illustration purposes, the article gives some examples of using each of the programs and their block-diagrams.</p><p>The developed software implements some algorithms, which allow attaining the convergence of numerical simulation of differential equations of motion. This problem arises, for example, while determining an attitude in case the stages have already separated from the launch vehicle. The mathematical conversion from Rodriguez-Hamilton parameters into Euler’s angles disables us to obtain reliable values of attitude angles due to the limitations for existing area of inverse trigonometric functions being used. Incorrect values of pitch lead to raw and roll channels divergences. Moreover, the mistakes in attitude determination lead to mistakes in obtained values of attack angle, which is included into the forms for aerodynamic forces and torques. As a result, the solution of system of differential equations is a failure when a flying vehicle enters the height of 30-35 km. The similar situations happen also when using other software of the kit. So there are special logical and mathematical tricks to overcome these difficulties.</p><p>The free accessible software available for the trajectory calculation is either inappropriate for solving the regarded tasks, in principle, or is functionally limited. The real analogues are available either at the rocket and space enterprises, or in research institutes, and a high cost disables their licensing use, especially, in state educational institutions. Besides, such software often falls within the restrictions on double-purpose technology circulation. In spite of the existing non-commercial analogues the developed software kit allows the transformation of the program while dealing with various tasks in new projects. This kit holds an intermediate niche between approximate estimations of vehicle’s ballistic properties at the stage of technical proposal and accurate calculations to be performed, usually, only for final version of the flying vehicle.</p>
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