ОПРЕДЕЛЕНИЕ НАГРУЗОК ДЛЯ ПРОЧНОСТНЫХ РАСЧЕТОВ УЗЛОВ КРЕПЛЕНИЯ ПРИБОРОВ И АГРЕГАТОВ КОСМИЧЕСКОГО АППАРАТА НА АКТИВНОМ УЧАСТКЕ ПОЛЕТА © 2019 А.А. Попков, магистрант кафедры космического машиностроения В.А. Филатов, кандидат технических наук, доцент кафедры космического машиностроения А.Г. Филипов, аспирант кафедры автоматических систем энергетических установок Самарский национальный исследовательский университет имени академика С.П. Королева, Самара (Россия) Ключевые слова: космический аппарат; расчетный случай нагружения; вибропрочность; конечно-элементная модель; динамический анализ; анализ переходного процесса; коэффициент демпфирования. Аннотация: В статье приведена методика исследования нагрузок на установки гироскопов системы управления движением космического аппарата на участке полета в составе ракеты космического назначения. Задача относится к типу вибропрочностных и решается в основном для навесного оборудования, которое крепится к корпусу изделия. У космических аппаратов это могут быть механизмы, антенны, замки, пирозаряды, электроприводы, передатчики телеметрии, приборы и агрегаты. Помимо вышеперечисленного, объектом рассмотрения также могут выступать элементы крепления оборудования: фитинги, посадочные плоскости, кронштейны, фланцы. Цель работы-описание расчета нагрузок (динамический анализ) для бортовой аппаратуры космического аппарата на участке полета в составе ракеты космического назначения. Значения нагрузок необходимы для прочностных расчетов, результаты которых учитываются при проектировании креплений приборов и агрегатов, а также при составлении конструкции и компоновки изделий ракетно-космической техники. В качестве примера расчета выбраны гироскопы системы управления движением малого космического аппарата «АИСТ-2Д», случай нагружения-«максимальный скоростной напор». Для определения значений нагрузок на основе исходных данных построена конечно-элементная модель установок. Построение модели проводится в программе интерактивного создания и сопровождения Femap. Решателем является NX Nastran, с помощью которого выполняется динамический анализ конструкции-анализ переходного процесса. В результате решения на основе полученных данных показано изменение по времени характерных параметров нагружения-ускорений. Эксплуатационные перегрузки, действующие на установки гироскопов в каждом из направлений прямоугольной системы координат, получены из графиков ускорений путем деления на ускорение свободного падения. Проведено сравнение расчетных и экспериментальных данных. Для удобства оценки характеристик, значения показаны для одного из четырех гироскопов, установленных в модуле служебных систем космического аппарата.

The article presents a solution to the problem of dynamic loading of a perforated partition located in the fuel tank of a launch vehicle. A technique for calculating the dynamic loading of the partition is described. Its equation of motion was decomposed into components and the loads at harmonic oscillations of the launch vehicle were calculated. The acceleration of the attachment points and the acceleration of the oscillators simulating the oscillations of the fuel tank, obtained from the solution of the general dynamic problem for assessing the hydrodynamic force for the launch vehicle, were given as the initial data for the dynamic calculation of loads. At this stage, the load on the partition was calculated, taking into account the added mass of the liquid in the event of an emergency shutdown of the propulsion system, as one of the most heavily loaded for the system under discussion. Non-linear dynamic analysis was used to calculate the loads on the perforated partition. As a result of the calculation, forces were obtained in the attachment points of the element in question.

This article considers the solution of the problem of dynamic loading of the pipeline [1], which is necessary to supply fuel to the booster engine. The method of calculating the dynamic loading [2] of the pipeline is described. Its equation of motion is decomposed into components and loads are calculated for harmonic vibrations of the launch vehicle. The accelerations of the propulsion system and pipeline attachment points obtained from solving a general dynamic problem for estimating the hydrodynamic force for a launch vehicle were set as initial data for dynamic load calculation. At this stage, the load on the pipeline was calculated taking into account the hydraulic shock of the liquid mass in the event of the launch vehicle flight, as one of the most loaded for this system. Nonlinear dynamic analysis was used to calculate pipeline loads [3]. As a result of the calculation, the forces in the attachment points of the structure under consideration, as well as the forces distributed along the length of the pipeline, were obtained. The method of calculating the dynamic loading of the pipeline is described. Pipeline loads consist of quasi-static components, which usually include trajectory overloads and low-frequency dynamic components [4] from transient processes such as start-up, as well as additional loads from vibration and acoustic influences. Quasi-static and low-frequency dynamic components in loads [5] usually have a fairly high degree of certainty and, as a rule, are estimated by calculation using appropriate RCN models and attachments. The loads obtained in this way cover the low-frequency part of the spectrum up to 20-30 Hz. Spatial beam models[6] with elastic supports and kinematic connections with tank bottoms and propulsion system are usually used for pipelines. When calculating the force factors in the sections of pipelines (longitudinal and shearing forces, bending and torques, forces in the support nodes), the fuel is allowed to be considered frozen (without taking into account the speed of movement). The fluid velocity should be taken into account when assessing the pressure of hydraulic shocks in pipelines to calculate the stress-strain state of pipelines from internal pressure.

The article describes a methodology of experimental determination of dynamic behavior of rocket and space equipment, using the example of AIST-2D small spacecraft. Experimentally obtained modal characteristics (natural modes and frequencies) are compared with modal characteristics calculated for the said spacecraft using a finite element model (FEM). The natural modes and frequencies of the spacecraft were experimentally obtained using scanning laser vibrometry; the modal analysis was performed using finite elements and the MSC. Patran / Nastran FEM package. The objectives and tasks are formulated; the main stages of modal analysis are described. It is necessary to update the finite-element models of spacecraft parts to obtain precise loads applied to such parts. During the tests target resonance frequencies of the test object were obtained for the 5-130 Hz range, as this range contains the first modes of the structure. Since the spacecraft is characterized by many uncertainties in stiffness parameters, the error of determining own frequencies was as high as 45.75% at the first stage of the research, which confirms the necessity of carrying out modal analysis. Dynamic characteristics of spacecraft structural elements obtained during the research will allow creating more precise and reliable spacecraft dynamic models at the design stage; this, in its turn, will improve precision of load calculations and reliability of the spacecraft in general.

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