Application of Wave Propagation to Pyroshock Analysis

M Gherlone,D Lomario,M Mattone,R Ruotolo

doi:10.1155/2004/278676

Abstract

Pyroshocks are high frequency transients due to pyrotechnic devices used in aerospace engineering in order to deploy solar arrays and antennae, separate subsystems from the spacecraft or separate the spacecraft itself from the base stage booster; their prediction is usually complex and very time consuming.The aim of this article is to investigate on the application of the analysis of transmission of waves in elastic media in order to predict the dynamic response to pyroshocks. The work is completed by numerical examples, related to components of common use in the aerospace engineering field, showing the comparison between results obtained by using both MSC-NASTRAN and this novel application of wave propagation analysis.

Highlights

Launch vehicles make use of explosive charges to separate structural subsystems from the launcher, deploy appendices, activate or deactivate subsystems
The evaluation of the dynamic response to pyroshocks is a hard task: in this case classical techniques based on the Finite Element Method (FEM) are not efficient, since at high frequency a huge number of elements is required to match the smallest characteristic wavelength of the problem
A technique that usually is employed is that one suggested by NASA in [2]: it allows to determine the acceleration at the mounting points of most critical components by using empirical Transmissibilities that depend basically on the type of structure under analysis, on the distance between source and the receiver locations and on the presence of junctions

Summary

Introduction

Launch vehicles make use of explosive charges to separate structural subsystems (such as a satellite) from the launcher, deploy appendices, activate or deactivate subsystems (such as valves of the propulsion subsystem). A technique that usually is employed is that one suggested by NASA in [2]: it allows to determine the acceleration at the mounting points of most critical components by using empirical Transmissibilities that depend basically on the type of structure under analysis (e.g., honeycomb, skin-frame, monocoque, etc.), on the distance between source and the receiver locations and on the presence of junctions These data have been collected mainly during an experimental activity performed several years ago [3]. Gherlone et al / Application of wave propagation to pyroshock analysis determining the best choice for materials, thickness etc., so that a very fast computational method is needed while a reduced accuracy of results can be accepted It follows that SEM is the best method to be used during the following phases, when structure properties have been already fixed, while during the preliminary design a faster tool is required. Firstly the analysis of waves propagating through a structure is reviewed and, subsequently, comparisons between results related to a simplified structure of a satellite and obtained by using MSC-NASTRAN and this novel application of wave propagation analysis are described and discussed

Wave propagation analysis

Wave transmission at junctions

Damping effect

Numerical results

Conclusions