Air gap influence on the vibro-acoustic response of Solar Arrays during launch

One of the primary elements on the space missions is the electrical power subsystem, for which the critical component is the solar array. The behaviour of these elements during the ascent phase of the launch is critical for avoiding damages on the solar panels, which are the primary source of energy for the satellite in its final configuration. The vibro-acoustic response to the sound pressure depends on the solar array size, mass, stiffness and gap thickness. The stowed configuration of the solar array consists of a multiple system composed of structural elements and the air layers between panels. The effect of the air between panels on the behaviour of the system affects the frequency response of the system not only modifying the natural frequencies of the wings but also as interaction path between the wings of the array. The usual methods to analyze the vibro-acoustic response of structures are the FE and BE methods for the low frequency range and the SEA formulation for the high frequency range. The main issue in the latter method is, on one hand, selecting the appropriate subsystems, and, on the other, identifying the parameters of the energetic system: the internal and coupling loss factors. From the experimental point of view, the subsystems parameters can be identified by exciting each subsystem and measuring the energy of all the subsystems composing the Solar Array. Although theoretically possible, in practice it is difficult to apply loads on the air gaps. To analyse this situation, two different approaches can be studied depending on whether the air gaps between the panels are included explicitly in the problem or not. For a particular case of a solar array of three wings in stowed configuration both modelling philosophies are compared. This stowed configuration of a three wing solar arrays in stowed configuration has been tested in an acoustic chamber. The measured data on the solar wings allows, in general, determining the loss factors of the configuration. The paper presents a test description and measurements on the structure, in terms of the acceleration power spectral density. Finally, the performance of each modelling technique has been evaluated by comparison between simulations with experimental results on a spacecraft solar array and the influence on the apparent properties of the system in terms of the SEA loss factors has been analyse

Vehicle-induced loads on traffic sign panels

The determination of the loads on traffic sign panels in the current standards does not, in general, take into account the vehicle-induced loads, as explained by Quinn, Baker and Wright (QBW in what follows) (J. Wind Eng. Ind. Aerodyn. 89 (2001) 831). On the other hand, a report from Cali and Covert (CC) (J. Wind Eng. Ind. Aerodyn. 84 (2000) 87) indicates that in highway sign support structures, vehicle-induced loads have led to premature failures in some cases. The aim of this paper is to present a mathematical model for the vehicle-induced load on a flat sign panel, simple enough to give analytical results, but able to explain the main characteristics of the phenomenon. The results of the theoretical model help to explain the behaviour observed in the experiments performed in previous studies

A Small Platform for Astrophysical Research Based on the UPM-Sat 1 Satellite of the Universidad Politécnica de Madrid

UPM-Sat 1 is a small scientific, in-orbit demonstration, educational satellite which has been designed, built, tested, integrated, launched and operated by a team of professors, students, and auxiliary personnel belonging to the Universidad Politécnica de Madrid (UPM). After completion of UPM-Sat 1 Mission a new small satellite, UPM-Sat 2, oriented to low-Earth-orbit scientific mission has been designed. In this paper the different subsystems of UPM-Sat 1 are described and the main characteristics of the second small satellite UPM-Sat 2 are outlined

Modular deployable structures

Large aperture antennas and telescopes, long baselines and long focal lengths in space have important applications for Telecommunications, Earth Observation and Science missions. Within this context, an ESA TRP activity is currently under development, carried out by COMET Ingeniería, PROSIX Engineering and Airbus DS (CASA Espacio), with the aim of designing overall structural assemblies based on unit cells developing representative parts of deployable masts (linear structures) and rings (antenna or radiotelescope aperture). This paper presents the current status of this project and the results obtained until the date of presentation of this paper. The results of these paper will be confirmed during next PDR to be celebrated at ESA-ESTEC

Structural Characterization and Modeling of Metallic Mesh Material for Large Deployable Reflectors

Metallic mesh is a key component of Large Deployable Reflectors for telecommunication and Earth observation spacecraft antennas. Deep knowledge of mesh structural characteristics and the possibility to numerically simulate its behaviour are mandatory steps for its correct use in the reflectors. The mesh is strongly compliant and anisotropic; hence, a specific testing machine has been designed and built, able to stretch the specimen along two directions, with uncoupled motion laws, controlled both in force and displacement. The mechanical characterization is driven so that a numerical simulation of the mesh is derived requiring only common finite element formulations