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The interest in urban air mobility as a potential solution for urban congestion is steadily growing. Air operations in urban areas can present added complexity as compared with traditional air traffic management. As a result, it is necessary to test and develop novel airspace designs and rules. As airspace in urban areas is a scarce resource, creating structures and rules that effectively utilise the airspace is an important challenge. This work specifically focuses on layered airspace design in urban operations constrained to fly between the existing buildings. Two design parameters of airspace design are investigated with two sub-experiments. Sub-experiment 1 investigates layer function assignment by comparing concepts from previous research with different layer assignment distributions. Sub-experiment 2 investigates the flight rules of vertical distribution of traffic within the airspace, to determine whether this is best achieved in a static (pre-allocated) or dynamic manner. Both sub-experiments analyse the overall system safety, route duration, and route distance under increasing traffic demand. Results reveal that the importance of cruising airspace is apparent at high densities. Results also shows that the safest layer allocation flight rule depends on the traffic density. At lower densities dynamic rules help to spread traffic locally. However, when the airspace is saturated it is safer to pre-allocate flight heights if achieved uniformly., Control & Simulation

Unmanned Aircraft Systems (UAS) Traffic Management (UTM) is an active research subject as its proposed applications are increasing. UTM aims to enable a variety of UAS operations, including package delivery, infrastructure inspection, and emergency missions. That creates the need for extensive research on how to incorporate such traffic, as conventional methods and operations used in Air Traffic Management (ATM) are not suitable for constrained urban airspace. This paper proposes and compares several traffic capacity balancing methods developed for a UTM system designed to be used in highly dense, very low-level urban airspace. Three types of location-based dynamic traffic capacity management techniques are tested: street-based, grid-based, and cluster-based. The proposed systems are tested by simulating traffic within mixed (constrained and open) urban airspace based on the city of Vienna at five different traffic densities. Results show that using local, area-based clustering for capacity balancing within a UTM system improves safety, efficiency, and capacity metrics, especially when simulated or historical traffic data are used., Control & Simulation

The use of small aircraft for a wide range of missions in urban airspace is expected to increase in the future. In Europe, efforts have been invested into developing a unified system, called U-space, to manage aircraft in dense very-low-level urban airspace. The Metropolis II project aimed to research what degree of centralisation an air traffic management system should use in such airspace. The paper at hand is a follow-up, and investigates improvements that can be brought to the tactical conflict prevention, detection, and resolution module of such a system in order to harmonise these components with an organic high-density U-space environment. The proposed improvements are: the prioritisation of vertical conflict prevention in intersections, the use of intent in detecting and resolving conflicts, and the use of heading-based manoeuvres in open airspace. Results show that the use of intent information in the conflict detection process, as well as the implementation of suitable tactical prevention procedures, can greatly increase airspace safety. Furthermore, the experiments revealed that the effectiveness of conflict resolution algorithms is highly dependent on the airspace rules and structure. This reiterates the potential for increasing the safety and efficiency of operations within constrained airspace if the tactical separation modules are unified with the other components of air traffic management systems for U-space., Control & Simulation

The Metropolis II project aimed to study the impact of centralised separation management for urban aerial mobility. Three concepts were developed in this study: a fully centralised, strategically separated concept, a hybrid concept featuring centralised strategic separation and distributed tactical separation, and a fully distributed tactical concept. A comparative simulation study was performed, using traffic scenarios based on predicted demand in an urban airspace in the city of Vienna. Simulations were performed with varying traffic densities and situations. Results show that the purely strategic and purely tactical strategies perform comparably in terms of safety, and that further improvements can be achieved with a combination of those strategies.

Propulsion, path planning and control of satellite formations in Geostationary Earth Orbits (GEO) and other high Earth Orbits is a challenging problem. This paper presents the results of the analysis of two types of controllers for satellite formation flying; the first one linear, using classical Proportional-Derivative (PD) control, and the second one nonlinear, using Sliding Mode Control (SMC). The Artificial Potential Field (APF) method is used for collision-free path planning of the satellites in the formation. The satellites are propelled using Coulomb forces and conventional electric/ion thrusters. This hybrid propulsion is more efficient as it minimizes the use of on-board power. Simulation results show that for the formation flying scenario considered in this study, the sliding mode controller gives better performance over the PD controller. Simulation results prove that for the tetrahedron formation considered in this study, both the control effort and drift in the geometric center of the formation are less when a sliding mode controller is used. © 2009 EUCA., European Union Control Association (EUCA);IEEE CSS;IFAC;MTA SZTAKI;National Office for Research and Technology (NKTH)

The artificial potential field (APF) method provides simple and effective path planners for practical terrestrial robotics control. Sliding mode control (SMC) strategy together with artificial potential field has been used for control of multiagent systems or swarms. The aim of this work is to examine for the first time the applicability of APF and SMC for spacecraft swarm navigation and control. This paper demonstrates that spacecraft formation flying can be successfully achieved using SMC for closed loop feedback and APF method for path planning., The results in this paper are part of the project supported by the European Space Agency Advanced Concept Team under the Ariadna programme. This support is gratefully acknowledged., IEEE, IEEE Ind Elect Soc, European Space Agency Advanced Concept Team under the Ariadna programme

Propulsion, path planning and control of satellite formations in Geostationary Earth Orbits (GEO) and other high Earth Orbits is a challenging problem. This paper presents the results of the analysis of two types of controllers for satellite formation flying; the first one linear, using classical Proportional-Derivative (PD) control, and the second one nonlinear, using Sliding Mode Control (SMC). The Artificial Potential Field (APF) method is used for collision-free path planning of the satellites in the formation. The satellites are propelled using Coulomb forces and conventional electric/ion thrusters. This hybrid propulsion is more efficient as it minimizes the use of on-board power. Simulation results show that for the formation flying scenario considered in this study, the sliding mode controller gives better performance over the PD controller. Simulation results prove that for the tetrahedron formation considered in this study, both the control effort and drift in the geometric center of the formation are less when a sliding mode controller is used. © 2009 EUCA., European Union Control Association (EUCA);IEEE CSS;IFAC;MTA SZTAKI;National Office for Research and Technology (NKTH)

The artificial potential field (APF) method provides simple and effective path planners for practical terrestrial robotics control. Sliding mode control (SMC) strategy together with artificial potential field has been used for control of multiagent systems or swarms. The aim of this work is to examine for the first time the applicability of APF and SMC for spacecraft swarm navigation and control. This paper demonstrates that spacecraft formation flying can be successfully achieved using SMC for closed loop feedback and APF method for path planning., The results in this paper are part of the project supported by the European Space Agency Advanced Concept Team under the Ariadna programme. This support is gratefully acknowledged., IEEE, IEEE Ind Elect Soc, European Space Agency Advanced Concept Team under the Ariadna programme

The Daedalus mission has been proposed to the European Space Agency (ESA) in response to the call for ideas for the Earth Observation program's 10th Earth Explorer. It was selected in 2018 as one of three candidates for a phase-0 feasibility study. The goal of the mission is to quantify the key electrodynamic processes that determine the structure and composition of the upper atmosphere, the gateway between the Earth's atmosphere and space. An innovative preliminary mission design allows Daedalus to access electrodynamics processes down to altitudes of 150 km and below. Daedalus will perform in situ measurements of plasma density and temperature, ion drift, neutral density and wind, ion and neutral composition, electric and magnetic fields, and precipitating particles. These measurements will unambiguously quantify the amount of energy deposited in the upper atmosphere during active and quiet geomagnetic times via Joule heating and energetic particle precipitation, estimates of which currently vary by orders of magnitude between models and observation methods. An innovation of the Daedalus preliminary mission concept is that it includes the release of subsatellites at low altitudes: combined with the main spacecraft, these subsatellites will provide multipoint measurements throughout the lower thermosphereionosphere (LTI) region, down to altitudes below 120 km, in the heart of the most under-explored region in the Earth's atmosphere. This paper describes Daedalus as originally proposed to the ESA.

[ES] El trabajo consiste en modelado en Simulink del avión espacial Ascender diseñado por la compañía británica Bristol Spaceplanes. Una vez se ha creado el model a través de los datos proporcionados por la compañía y una serie de datos obtenidos de aviones semejantes, se procederá a la creación de un piloto automático para la fase turbojet del vuelo. En esta fase el piloto introduce una serie de waypoints, una altura de vuelo y una velocidad y el piloto automático se encarga de controlar el avión para conseguir dichos valores. En cuanto a la fase cohete, un sistema de control de vuelo (también creado en Simulink como el modelo del avión y el piloto automático) se encargar de controlar el ángulo de trepada y el numero de Mach. Por ultimo, un sistema de thrusters serán modelados y utilizados posteriormente para controlar la actitud del avión cuando no existe propulsion y el mismo se encuentra en su altura maxima (100 kilómetros). Todos los sistemas sera probado a través de una simulación de la misión completa que debe realizar el avión, la cual se encuentra detallada en la pagina web de la compañía., [EN] The spaceplanes have been a feasible option to cut prices on the space missions. Because of their capability to be totally reusable, they can perform even more than one flight per day, launching small satellites in LEO orbits or carrying space tourists, which has become a very profitable market. The goal of this thesis is to develop a mathematical model of Ascender, a spaceplane designed by Bristol Spaceplanes. The mode will be created in Simulink, which provides a set of very useful tools in the aerospace field to simulate and create the model. The geometric data of the aircraft will be obtained from a 3D view map provided by the company, which will also be the basis to estimate the inertia moments, weights and gravity center. Around the aircraft model, a set of controllers will be created, each one operating in a different phase according to the propulsion system used in them (turbojet, rocket or thrusters). In the case of the turbojet, a proper autopilot will be designed which will enable the pilot to command an altitude, a speed and a waypoint route for Ascender to follow. In the rocket phase, the flight path angle and the Mach number will be controlled to obtain a suitable climb a limit the demand over the aircraft structure. Finally, during the unpowered phase (climb and glide back to Earth), the thruster will control the spaceplane attitude to facilitate the launch of the payload and to improve the comfort of the passengers. Al the control systems will be checked through their response to the different commands sent to them, so the time history of the controlled variables will be plotted to assure a good performance. Finally, a simulation of the whole flight of Ascender from a trim state at 4000 meters to the point where the turbojet starts again to help in the landing, will be carried out and the system variables will be monitored to guarantee a good system behaviour.