3M en pantalla (mitos y mentiras sobre metales en pantalla)

Los metales han formado parte de la evolución de la humanidad desde la antigüedad. Han sido objeto de culto, por escasos y exclusivos, y han sido la clave del desarrollo de armas, para, progresivamente, formar parte de los elementos cotidianos. En la actualidad los metales suponen un 30% de los materiales de aplicación industrial [1] y son temas de estudio básicos en contenidos de ciencia y tecnología. Sin embargo, este conocimiento general, por parte de la sociedad, es muy superficial y suele limitarse a su aspecto brillante, o su capacidad de deformarse ante un esfuerzo, o a su facilidad para oxidarse,conducir calor o conducir electricidad. Pero no se conocen en detalle, por lo cual a menudo se muestran en pantalla con propiedades desafortunadas, en ocasiones imposibles. Se recogen aquí algunos tópicos tratados erróneamente en el celuloide, sin que se perciba esta inexactitud, en general, por parte del gran públicoPostprint (published version

On the exploitation of differential aerodynamic lift and drag as a means to control satellite formation flight

For a satellite formation to maintain its intended design despite present perturbations (formation keeping), to change the formation design (reconfiguration) or to perform a rendezvous maneuver, control forces need to be generated. To do so, chemical and/or electric thrusters are currently the methods of choice. However, their utilization has detrimental effects on small satellites’ limited mass, volume and power budgets. Since the mid-80s, the potential of using differential drag as a means of propellant-less source of control for satellite formation flight is actively researched. This method consists of varying the aerodynamic drag experienced by different spacecraft, thus generating differential accelerations between them. Its main disadvantage, that its controllability is mainly limited to the in-plain relative motion, can be overcome using differential lift as a means to control the out-of-plane motion. Due to its promising benefits, a variety of studies from researchers around the world have enhanced the state-of-the-art over the past decades which results in a multitude of available literature. In this paper, an extensive literature review of the efforts which led to the current state-of-the-art of different lift and drag-based satellite formation control is presented. Based on the insights gained during the review process, key knowledge gaps that need to be addressed in the field of differential lift to enhance the current state-of-the-art are revealed and discussed. In closer detail, the interdependence between the feasibility domain/the maneuver time and increased differential lift forces achieved using advanced satellite surface materials promoting quasi-specular or specular reflection, as currently being developed in the course of the DISCOVERER project, is discussed.Peer ReviewedPostprint (author's final draft

A Review and Gap Analysis of Exploiting Aerodynamic Forces as a Means to Control Satellite Formation Flight

Using several small, unconnected satellites flying in formation rather than a single monolithic satellite has many advantages. As an example, separate optical systems can be combined to function as a single larger (synthetic) aperture. When the aperture is synthesized, the independent optical systems are phased to form a common image field with its resolution determined by the maximum dimension of the array. Hence, a formation is capable of much finer resolution than it could be accomplished by any single element. In order for the formation to maintain its intended design despite present perturbations (formation keeping), to perform rendezvous maneuvers or to change the formation design (reconfiguration) control forces need to be generated. To this day, using chemical and/or electric thrusters are the methods of choice. However, their utilization has detrimental effects on small satellites’ limited mass, volume and power budgets. In the mid-eighties, Caroline Lee Leonard published her pioneering work [1] proving the potential of using differential drag as a means of propellant-less source of control for satellite formation flight. This method consists of varying the aerodynamic drag experienced by different spacecraft, thus generating differential accelerations between them. Since its control authority is limited to the in-plane motion, Horsley [2] proposed to use differential lift as a means to control the out-of-plane motion. Due to its promising benefits, a variety of studies from researches around the world have enhanced Leonard’s work over past decades which results in a multitude of available literature. Besides giving an introduction into the method the major contributions of this paper is twofold: first, an extensive literature review of the major contributions which led to the current state-of-the-art of different lift and drag based satellite formation control is presented. Second, based on these insights key knowledge gaps that need to be addressed in order to enhance the current state-of-the-art are revealed and discussed. In closer detail, the interdependence between the feasibility domain and advanced satellite surface materials as well as the necessity of robust control methods able to cope with the occurring uncertainties is assessed.Peer ReviewedPostprint (published version

Inductive Plasma Thruster (IPT) for an Atmosphere-Breathing Electric Propulsion System: design and set in operation

Challenging space missions include those at very low orbits, where the atmosphere is source of significant drag on a satellite. Therefore, an efficient dragcompensation propulsion system is required to extend the mission lifetime. One solution is Atmosphere-Breathing Electric Propulsion (ABEP), a system that collects atmospheric particles and directly uses them as propellant for an electric thruster, therefore minimizing the requirement of limited propellant availability. The system is theoretically applicable to any celestial body with atmosphere. This would enable new mission types due to the new altitude ranges available for continuous orbiting. Challenging is also the presence of reactive chemical species, such as atomic oxygen in Earth orbit, erosion source of (not only) the propulsion system components, i.e. acceleration grids, electrodes and discharge channels of conventional EP systems such as RIT and HET. IRS is developing within the DISCOVERER project an intake and a thruster for an ABEP system. This paper, deals with the design of novel contact-less RF thruster, the inductive plasma thruster (IPT) based on a novel antenna design.The DISCOVERER project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No.737183Postprint (published version

Advances on the Inductive Plasma Thruster Design for an Atmosphere-Breathing EP System

Challenging space mission scenarios include those in very low Earth orbits, where the atmosphere creates significant drag to the S/C and forces their orbit to an early decay. For drag compensation, propulsion systems are needed, requiring propellant to be carried on-board. An atmosphere-breathing electric propulsion system (ABEP) ingests the residual atmosphere through an intake and uses it as propellant for an electric thruster. Theoretically applicable to any planet with atmosphere, the system might allow drag compensation for an unlimited time without carrying propellant. A new range of altitudes for continuous operation would become accessible, enabling new scientific missions while reducing the required effort for the launcher by achieving these low orbits. Preliminary studies have shown that the collectible propellant flow for an ion thruster in low Earth orbit (LEO) might not be enough, and that electrode erosion due to aggressive gases, such as atomic oxygen, will limit the thruster’s lifetime. In this paper we present the advances on the design of an inductive plasma thruster (IPT) for the ABEP. The IPT is based on a small-scale inductively heated plasma generator IPG6-S. IPG have the advantage of being electrodeless, and have already shown high electric-tothermal coupling efficiencies using O2 and CO2 as propellant. IPG6-S requires a scaling of the discharge channel to meet with power requirement and expected collected mass flows, as well as optimisation of the accelerating stage, to provide the required thrust to the spacecraft. Tests have been performed to verify some of the parameters and are as well presented within this paper.Peer ReviewedPostprint (published version

The benefits of very low earth orbit for earth observation missions

Very low Earth orbits (VLEO), typically classified as orbits below approximately 450 km in altitude, have the potential to provide significant benefits to spacecraft over those that operate in higher altitude orbits. This paper provides a comprehensive review and analysis of these benefits to spacecraft operations in VLEO, with para-metric investigation of those which apply specifically to Earth observation missions. The most significant benefit for optical imaging systems is that a reduction in orbital altitude improves spatial resolution for a similar payload specification. Alternatively mass and volume savings can be made whilst maintaining a given performance. Similarly, for radar and lidar systems, the signal-to-noise ratio can be improved. Additional benefits include improved geospatial position accuracy, improvements in communications link-budgets, and greater launch vehicle insertion capability. The collision risk with orbital debris and radiation environment can be shown to be improved in lower altitude orbits, whilst compliance with IADC guidelines for spacecraft post-mission lifetime and deorbit is also assisted. Finally, VLEO offers opportunities to exploit novel atmosphere-breathing electric propulsion systems and aerodynamic attitude and orbit control methods. However, key challenges associated with our understanding of the lower thermosphere, aerodynamic drag, the requirement to provide a meaningful orbital lifetime whilst minimising spacecraft mass and complexity, and atomic oxygen erosion still require further research. Given the scope for significant commercial, societal, and environmental impact which can be realised with higher performing Earth observation platforms, renewed research efforts to address the challenges associated with VLEO operations are requiredThis project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 737183Peer ReviewedPostprint (author's final draft

Mission analysis of nanosatellite constellations with OpenSatKit

CubeSat reliability is still considered an obstacle due to the sizeable fail rates generally attributed to the dead-on-arrival cases and early subsystem malfunctions. Thus, as CubeSats' primary purpose moves from technological demonstrations and university projects to missions where a significant risk of failure is not acceptable, an inexpensive method to emulate low Earth orbit constellations is being researched. The results presented have been developed in the framework of the PLATHON research project, which intends to develop a hardware-in-the-loop emulation platform for nanosatellite constellations with optical inter-satellite communication and ground-to-satellite links. Consequently, a crucial aspect of this project is to have a sufficiently precise orbital propagator with real-time manoeuvring control and graphical representation. NASA's OpenSatKit, a multi-faceted open-source platform with an inbuilt propagator known as 42, has been chosen to analyse the programme's feasibility in order to create a constellation testing bench. As an initial development of a software-in-the-loop application, the pre- processing of files has been automated; enhanced Attitude Determination and Control System manoeuvres have been added and configured through bidirectional socket interfaces, and the results format has been modified to be easily post-processed with MATLAB and Simulin

Integració curricular d'assignatures per al disseny del nou màster d'enginyeria aeronàutica

Aquest projecte ha implementat una prova pilot d’un pla transversal de coordinació de diferents assignatures (Projectes d’Enginyeria Aeronàutica (UPC-enginyeria aeronàutica), Direcció Estratègica (UPC-enginyeria industrial) i Creativitat en Comunicació (UAB-facultat de comunicació)) superposat a un pla de coordinació seqüencial d’assignatures (Projectes d’Enginyeria Aeronàutica (UPC-enginyeria aeronàutica), Disseny d’Avions (UPC-enginyeria aeronàutica)) que es vé desenvolupant des del 2009. Des del 2009 que s’ha estat treballant amb èxit en la seqüenciació coordinada d’assignatures dins l’àmbit de l’Enginyeria Aeronàutica i aquest projecte ha ampliat la coordinació d’assignatures de forma transversal dins el mateix Centre (ETSEIAT) i fora del Centre (UAB-Facultat de Comunicació). L’eix vertebrador dels treballs ha estat l’assignatura Projectes d’Enginyeria Aeronàutica que s’imparteix a l’ETSEIAT, amb l’objectiu d’assolir un esquema de coordinació de continguts globals que afavoreixi l’adequat desenvolupament de competències per part de l’estudiantat. Ha estat un objectiu molt ambiciós que entronca amb models de Màster que ja s’estan impartint a les escoles de referència en el camp de l’enginyeria Aeronàutica com són el Master Course in Aircraft Design, que s’imparteix a la University of Cranfield.Els resultats s’han presentat per part del PDI del projecte a tres Universitats estrangeres (Universitat de Lyon, University of Cranfield i Instituto Politecnico de Setubal) en el marc d’accions de mobilitat Erasmus i també a dos Congressos Internacionals a Brussel·les i Varsòvia, a més de servir d’element aglutinador d’un grup de treball d’estudiants que s’ha presentat el 2012 a la competició Fly Your Ideas, patrocinat per Airbus i que ha arribat a la penúltima ronda del concurs aquest 2013.Peer Reviewe

Deployment mechanism for an L-Band Helix antenna on-board the 3Cat-4 1U CubeSat

Earth Observation (EO) is key for climate and environmental monitoring at global level, and in specific regions where the effects of global warming are more noticeable, such as in polar regions, where ice melt is also opening new commercial maritime routes. Soil moisture is also useful for agriculture and monitoring the advance of desertification, as well as biomass and carbon storage. Global Navigation Satellite System - Reflectometry (GNSS-R) and L-band microwave Radiometry are passive microwave remote sensing techniques that can be used to perform these types of measurements regardless of the illumination and cloud conditions, and -since they are passive- they are well suited for small satellites, where power availability is a limiting factor. GNSS-R was tested from space onboard the UK-DMC and the UK TechDemoSat-1, and several missions have been launched using GNSS-R as main instrument, as CyGNSS, BuFeng-1, or the FSSCAT [1] mission. These missions aim at providing soil moisture [2], ocean wind speed [3], and flooding mapping of the Earth. L-band microwave radiometry data has also been retrieved from space with SMOS and SMAP missions, obtaining sea ice thickness, soil moisture, and ocean salinity data [4]. The 3Cat-4 mission was selected by the ESA Academy "Fly your Satellite" program in 2017. It aims at combining both GNSS-R and L-band Microwave Radiometry at in a low-power and cost-effective 1-Unit (1U) satellite. Moreover, the 3Cat-4 can also detect Automatic Identification System (AIS) signals from vessels. The single payload is the Flexible Microwave Payload 1 (FMPL-1) [5] that performs the signal conditioning and signal processing for GNSS-R, L-Band microwave radiometry and AIS experiments. The spacecraft has three payload antennas: (1) a VHF monopole for AIS signals; (2) an uplooking antenna for the direct GPS signals; (3) a downlooking antenna that captures reflected GPS signals, and for the Microwave Radiometer. The downlooking antenna is a deployable helix antenna called the Nadir Antenna and Deployment Subsystem (NADS) which has a volume of less than 0,3U when stowed, achieving an axial length of more than 500 mm when deployed. As part of this mission, the design of the NADS antenna, its RF performance, as well as the environmental tests performed in terms of structural and thermal space conditions will be presented