Victoria Lapuerta

Weakly dissipative Faraday waves in 2D large aspect ratio annuli

Weakly dissipative parametrically excited (by vertical vibration) surface gravity-capillary waves in a two-dimensional, horizontally periodic container are considered. A set of equations is derived for the coupled evolution of the left- and right-traveling surface waves and the associated mean flow, in the case when the container depth is small compared to its length but large compared to the wavelength of the excited waves. The stability of the spatially uniform standing waves (SWs) is first analyzed and then the large time spatio-temporal behavior of the system beyond threshold is numerically studied. The viscous mean flow is found to drastically affect the dynamics of the system and the resulting surface wave patterns.

Fuzzy attitude control for a nanosatellite in low Earth orbit

We design a PID and an adaptive fuzzy controller for the same satellite mission.This is the first time the performances and cost of operation of a PID and an adaptive fuzzy controllers are compared.The fuzzy controller is more efficient than the PID for single manoeuvres with similar accuracy. In order to develop and introduce intelligent systems in the space field, an adaptive fuzzy logic controller is designed for a nanosatellite. Attitude determination and control subsystem (ADCS) and its performance and efficiency are compared with a traditional proportional integrative derivative (PID) controller. Fuzzy controllers have already been studied for satellite attitude control; however their performance has not been compared with the classical PID controllers typically being implemented on board spacecrafts currently. Both controllers have been designed and implemented in order to be tested on board a nanosatellite (QBITO) in a nearby mission (QB50), a constellation of 50 nanosatellites. Due to the requirements imposed by the mission, the orbit, and the significant limitations in the power available in these small spacecrafts, an efficient ADCS is required in order to fulfill the mission objectives. The comparison between the classical PID and the fuzzy controllers shows that the fuzzy controller is much more efficient in single maneuver (up to 65% less power required), achieving better precision in general than the PID. This shows that the use of this type of intelligent control systems is a great advantage over conventional control systems currently being used in satellite attitude control, and open new possibilities of application of intelligent controllers in the field of space technologies.

Components of a Wind Tunnel Balance: Design and Calibration

The aim of wind tunnel tests is the simulation of the flow around bodies or their scaled models. In aeronautical applications, the measurement of aerodynamic loads in a wind tunnel, forces and momentums, is a very difficult task due to the required accuracy. The wind tunnel balances, comprised by several hardware and software components, provides directly the pursued measurements, with high accuracy and reliability. For these reasons, among others, wind tunnel balances have become a common tool in testing facilities. This chapter starts with a general description of wind tunnel balances. The number of measuring components and the position of the balance with relation to the model and wind tunnel chamber determine the wind tunnel balances designs. The most flexible ones, in terms of usability, are the six components external balances, so these will be referenced for introducing the calibration process, which is one of the key points to achieve the required aerodynamic tests results accuracy and reliability. Because of its influence on the drag measurement accuracy, the coupling effect between lift and drag measurements is analysed very deeply as well. The analysis of the non-stationary effects are finally done taking into account the wind tunnel balance requirements and constraints, with special attention on an issue not commonly mentioned, the inertia forces generated on the balance by the model vibrations, and their influence on the aerodynamic forces to be measured. Several mentions to signal processing and acquisition are done, as this is the other key point on the measurements accuracy. However, it is easy to extrapolate these procedures to other types of balances, as the main intention is to show which are the critical points that make wind tunnel balances such a special and complex hardware. We do not intend here to describe the design and calibration procedures of the industrial manufacturers. This is the result of a work done in the Universidad Politecnica de Madrid (UPM), and the Instituto Tecnologico y de Energias Renovables (ITER, Tenerife, Canary Island, Spain, www.iter.es). Nevertheless, we do consider that is a good guide for developers of wind tunnel balances in institutions like UPM and ITER, where research and education are very important points.

ULISSE Access to Data

This section describes the whole life cycle of space data, from the initial design of the experiment to the storage of data once the experiment has been performed. The need to subsequently preserve and exploit these data is also discussed; the relevant information required for data exploitation in the future is described with the main legal issues and possible data dissemination constraints. Then, the Topic Maps technology and the main features of the ULISSE knowledge base are described. The section ends with a description of the ULISSE data exploitation services, illustrated with an example of access to data through ULISSE.

GeoFlow - Outcomes from E-USOC's First Mission On-Board Columbus

-USOC is the Spanish User Support and Operations Centre, one of the ten similar centres distributed at different locations in Europe. These centres perform the operations of experiments on board the Columbus Module, the main contribution from the European Space Agency (ESA) to the International Space Station (ISS). The first mission for E-USOC on the Columbus laboratory consisted of executing the GeoFlow experiment, inside the Fluid Science Laboratory (FSL). This experiment studied the movement and behaviour of a fluid contained in between two concentric spheres, representing the geophysical fluid inside the Earth. This fluid motion was observed by means of Interferometry images. The GeoFlow Experiment Container was launched on Space Shuttle Atlantis with the Columbus Module and was installed inside the FSL by a member of the ISS crew. Once placed in the facility, E-USOC operators used telescience to operate the experiment from their control room: Telecommands were sent to control the different GeoFlow subsystems, and telemetry and scientific images from the experiment were received. Achieving successful results from the experiment was a challenging mission, starting in March 2008 and continuing until January 2009, when a malfunction in the GeoFlow Experiment Container forced its return to ground and the interruption of the experiment. The paper will present a general description of the project, address the preparation and execution of such a complex mission and provide an overview of the activities and responsibilities of E-USOC. Furthermore, it will present the outcomes and lessons learned from this project.

Weakly-nonlinear analysis of the Rayleigh–Taylor instability in a vertically vibrated, large aspect ratio container

We consider a horizontal liquid layer supported by air in a wide (as compared to depth) container, which is vertically vibrated with an appropriately large frequency, intending to counterbalance the Rayleigh-Taylor instability of the fiat, rigid-body vibrating state. We apply a long-wave, weakly-nonlinear analysis that yields a generalized Cahn-Hilliard equation for the evolution of the fluid interface, with appropriate boundary conditions obtained by a boundary layer analysis. This equation shows that the stabilizing effect of vibration is like that of surface tension, and is used to analyze the linear stability of the fiat state, and the local bifurcation at the instability threshold.