Analysis of the expansion of a plasma thruster plume into vacuum

Mención Internacional en el título de doctorThe analysis of the interaction between a plasma plume and a satellite is gradually becoming a very demanded task in the space industry, given the increasing use of electric propulsion. In fact, the plasma plumes generated by the electric thrusters can damage sensitive spacecraft components, such as the solar arrays or onboard optical sensors. Moreover, plasma plumes can be used to one's benefit in the context of the ion beam shepherd technique for space debris removal, in which a shepherd spacecraft relocates a debris object to a different orbit, by directing towards it a plasma plume, at an operational distance of several meters. This thesis focuses on the numerical study of the expansion of a plasma thruster plume into vacuum and its interaction with the satellite and any downstream object. Two simulation codes have been developed. The first code, named EASYPLUME, is based on an axisymmetric two-fluid plasma plume model and allows to quickly estimate the plasma plume properties farther downstream. With this code the physics of the plume expansion has been investigated, understanding its dependence on the most important plume parameters, such as the divergence angle, the ion Mach number, and the electron cooling rate. Moreover, the code has been used in the context of the ion beam shepherd technique to estimate the force transmission to a space debris object, and optimize the overall electric propulsion subsystem of the shepherd spacecraft. The second code, named EP2PLUS, is a three-dimensional hybrid particle-incell/fluid code that simulates the complex interaction between a plasma plume, the spacecraft and other objects. The most relevant modeling novelties regard the electron model, which enables the computation of the electric currents in the plume, and the treatment of quasineutral and non-neutral plasma regions. This code has been applied to study both the satellite-plume interaction and a reference ion beam shepherd scenario. In the latter, several operational problems have been evaluated: the ion backscattering towards the shepherd satellite, the sputtering of the debris object (due to the impingement of hypersonic ions), the backsputtering contamination of the spacecraft, and the electric charging of both the satellite and the target debris. Finally, the report of an experimental campaign, carried out during my PhD visit at the “Laboratoire de Physique des Plasmas" (Paris) and aiming at characterizing the plasma plume of the PEGASES plasma thruster, completes this work.El estudio de la interacción entre el satélite y un chorro de plasma producido por un propulsor eléctrico se está convirtiendo en un análisis muy demandado en la industria espacial, debido al uso cada vez más extenso de la propulsión eléctrica. Dicho chorro puede dañar seriamente componentes sensibles del satélite, como los paneles solares o los sensores ópticos. Por otra parte, puede utilizarse activamente en el contexto de la técnica de eliminación de desechos espaciales conocida como “ion beam shepherd". Esta técnica se basa en trasladar dichos objetos a una órbita diferente, por medio de la presión producida por el impacto de los iones de un chorro de plasma dirigido hacia ellos, desde una distancia de varios metros. Esta tesis se centra en el estudio numérico de la expansión de un chorro de plasma generado por un propulsor eléctrico en el vacío, y de su interacción con otros objetos. Con este propósito, se han desarrollado dos códigos de simulación. El primero, llamado EASYPLUME, se basa sobre un modelo axial simétrico con dos fluidos (iones y electrones) y permite estimar rápidamente las propiedades del chorro de plasma a grandes distancias aguas abajo. Con este código, se ha estudiado la física de la expansión del plasma en detalle, comprendiendo la influencia de parámetros como el ángulo de divergencia, el número de Mach y la tasa de enfriamiento electrónico. Además, el código ha sido utilizado en el contexto del “ion beam shepherd" para estimar la fuerza transmitida al objeto y optimizar el sistema de propulsión eléctrica del satélite. El segundo, llamado EP2PLUS, es un código tridimensional híbrido PIC-fluido que simula la interacción compleja entre un chorro de plasma, el satélite y otros objetos. Entre las novedades más relevantes destacan el nuevo modelo electrónico, que permite estudiar las corrientes eléctricas en el plasma, y el tratamiento de regiones quasi-neutras y no neutras. Este código se ha empleado en el estudio de la interacción chorro-satélite y en el análisis de la interacción chorro-satélite-objeto en el contexto del “ion beam shepherd" para una misión de referencia. En este último estudio, diferentes problemas operacionales han sido evaluados numéricamente: el retorno de los iones lentos hacia el satélite, la emisión de partículas erosionadas desde la superficie del desecho espacial (debido al impacto de los iones hipersónicos), la contaminación por difusión de dichas partículas hacia el satélite, y la acumulación de carga eléctrica de _este y del objeto espacial. Finalmente, el informe de una campaña de caracterización experimental del chorro del motor de plasma PEGASES completa este trabajo. Dicha campaña se realizó durante mi estancia de visita al “Laboratoire de Physique des Plasmas" en París.Programa Oficial de Doctorado en Plasmas y Fusión NuclearPresidente: Victoria Lapuerta González.- Secretario: Luis Raúl Sánchez Fernández.- Vocal: Francesco Taccogn

Emissive Langmuir Probe Theory with Application to Low Work Function Electrodynamic Tethers

Mención Internacional en el título de doctorMotivated by the need of mitigating the increase in the debris population that has been accumulating in the Low Earth Orbit (LEO) in more than 60 years of intense human activity in space, Electrodynamic Tethers (EDTs) have been proposed as efficient devices to deorbit satellites at the end of life. Consisting in long conductors that are deployed from the satellite at the end of its mission, EDTs exploit the interaction with the ionospheric plasma to create a current that, flowing along the device, interacts with the geomagnetic field giving rise to a magnetic drag that deorbits the satellite. Low Work-function tethers (LWTs) are particularly attractive because no expellant is needed for their operations. Once deployed, the LWT exchanges electrons with the ionospheric plasma, collecting them at one segment and, upon being coated with a material of low-enough work function, emitting them back at the complementary segment. Accurate models of the plasma-LWT interaction are necessary to quantify the performances of the device with software for mission analysis. Since the characteristic length of a space tether is several orders of magnitude larger than the Debye length in LEO, the current distribution along the tether can be computed from the current-voltage characteristic of a two-dimensional probe of same cross-section. This dissertation presents a numerical investigation of the interaction between twodimensional (electron-emitting) objects and Maxwellian plasmas representative of the LEO environment. A kinetic approach is adopted to study the features of the plasma sheath. In particular, a model based on the Orbital Motion Theory (OMT) is applied to study geometries that, although favourable for LWTs applications, received little attention in past works. To this extent, a novel stationary Eulerian Vlasov-Poisson solver based on a backward Liouville method is presented in detail. After a thorough verification procedure versus more mature numerical tools, a discussion of the physical and numerical limitations of stationary Vlasov-Poisson solvers is presented. Its results are used to provide a list of guidelines for their practical use in plasma-material interaction problems. Using the same code, an analysis was carried out in order to characterise deeply the sheath around electron-emitting objects with elliptic cross sections. By varying the size, eccentricity and emission level of the probe, the study assessed the parameter domains for which Orbital-Motion-Limited (OML) current collection and Space-Charge-Limited (SCL) current emission hold. The local curvature of the probe revealed to have an important impact on its operational regime and, as compared with cylindrical ones, elliptic bodies were found to be more likely to meet non-OML and SCL conditions. Electron emission was also shown to be favourable for OML current collection. Regarding LWTs applications, an interesting equivalence between the emitted current in SCL conditions by ellipses and cylinders was found. In the last part of the dissertation the hypothesis about the steady-state of the system is relaxed and a novel semi-Lagrangian Vlasov-Poisson solver developed as an extension of the stationary one is introduced. The impact of the population of trapped particles on the macroscopic magnitudes of the sheath is discussed. The results of a comparison between Eulerian solvers and a Particle-In-Cell (PIC) code for emissive probes are also presented to investigate the importance of the numerical noise of the PIC code. Particle trapping is shown to depend on both the history of the system and on the emission level. For high electron-emission, the trapped population reduces SCL effects.Ante el reto de mitigar el aumento de la población de basura espacial que se ha ido acumulando en la órbita terrestre baja (Low Earth Orbit - LEO) en los más de 60 años de intensa actividad humana en el espacio, las amarras electrodinámicas (Electrodynamic Tether - EDT) surgen como dispositivos eficientes para el desorbitado de satélites al final de su vida útil. Los EDTs, largos cables conductores, aprovechan su interacción con el plasma ionosférico para crear una corriente que, al fluir a los largo del cable, interactúa con el campo geomagnético y generan una fuerza de frenado que desorbita el satélite. Las llamadas amarras con baja función de trabajo (Low Work-function tethers - LWTs) son especialmente atractivas porque no involucran ningún consumible ni elemento activo para su funcionamiento. Una vez desplegado, el LWT intercambia electrones con el plasma ionosférico de manera totalmente pasiva. Los electrones son recogidos en un segmento llamado anódico y se emiten de vuelta al plasma en el segmento complementario catódico gracias a los efectos termoiónico y fotoeléctrico que facilitan el recubrimiento con baja función de trabajo de la propia amarra. Para poder evaluar las prestaciones del dispositivo, se necesitan modelos precisos de la interacción entre el plasma y el LWT. Dado que la longitud de una amarra espacial es varios ´ordenes de magnitud mayor que la longitud de Debye en LEO, los perfiles de corriente y voltaje se pueden calcular a partir de las curvas características de una sonda bi-dimensional con la misma sección transversal. La tesis presenta un análisis numérico de la interacción entre objetos bidimensional que emiten electrones y plasmas representativos del entorno espacial en LEO. Se adopta un enfoque cinético para estudiar las características de la vaina del plasma. En particular, se aplica un modelo basado en la Orbital Motion Theory (OMT) para el estudio de geometrías que, pese a ser ventajosas para aplicaciones de LWTs, recibieron poca atención en el pasado. Para ello se ha desarrollado un nuevo código Vlasov-Poisson euleriano y estacionario basado en el método de backward Liouville. Tras un extenso proceso de verificación frente a resultados obtenidos con código más maduros, se discuten las limitaciones de tipo físico y numérico intrínsecas a los códigos Vlasov-Poisson estacionarios. Los resultados se han utilizado para preparar una lista de recomendaciones prácticas sobre el uso de estos códigos en problemas de interacción plasma-material. El código se ha utilizado para caracterizar en profundidad las vainas que se forman alrededor de objetos con sección transversal elíptica y que emiten electrones. En el análisis se ha variado el tamaño, la excentricidad y el nivel de emisión del objeto, lo cual ha permitido determinar los dominios paramétricos en donde la captura de corriente esta dada por la llamada teoría Orbital Motion Limited (OML) y la emisión ocurre bajo condiciones de Space Charge Limited (SCL). Se ha observado que la curvatura local de la elipse juega un papel importante en determinar el régimen de operación y se encontró que los cuerpos elípticos son más propensos a cumplir con las condiciones de no-OML y SCL que los cilíndricos. También ha permitido concluir que la emisión de electrones favorece la captura de corriente en condiciones OML. Con respecto a los LWTs, se ha encontrado que existe un radio equivalente para calcular la corriente emitida por un cuerpo elíptico bajo condiciones SCL a partir de los resultados de un cuerpo cilíndrico. La última parte de la tesis estudia los transitorios que ocurren entre una condición iniciales dada y el estado estacionario que se alcanza en el equilibrio. Para ello se ha desarrollado un código semilagrangiano para resolver el sistema Vlasov-Poisson no estacionario, el cual constituye una extensión del código estacionario usado en la primera parte de la tesis. El nuevo código ha permitido discutir el impacto de la población de partículas atrapadas en el transitorio sobre las magnitudes macroscópicas de la vaina del plasma en el equilibrio. Se presentan también los resultados de una comparación entre el código euleriano y un código Particle-In-Cell (PIC) para sondas emisivas con el fin de investigar la importancia del ruido numérico del código PIC. Se demuestra que la cantidad de atrapados depende tanto de la historia del sistema como del nivel de emisión. Para una alta emisión de electrones, la población de atrapados reduce los efectos SCL.This work was supported by PIPF Scholarship awarded on a competitive basis by Universidad Carlos III de Madrid. During the thesis I had the opportunity to participate in the European Union’s Horizon 2020 Research and Innovation Programme under grant agreement No 828902 (E.T.PACK project) and the FET Innovation Launchpad project No 101034874 (BMOM).Programa de Doctorado en Ingeniería Aeroespacial por la Universidad Carlos III de MadridPresidente: Eduardo Antonio Ahedo Galilea.- Secretario: Fernando García Rubio.- Vocal: Richard Marchan

Pilot Perception of Cockpit Organizational Framework’s Impact on Flight Safety and Subordinate Pilot Behavior

Past accidents have indicated that first officers (FO) are less likely to identify and correct captain errors than captains are to correct FO errors. Crew resource management (CRM) training was introduced in the late 1970s to improve captain teamwork skills to utilize the FO more effectively and to increase FO willingness to interject to preserve safety. Despite the effectiveness of CRM training programs, there continue to be incidences where subordinate pilots make weak or ineffective attempts to preserve safety. This research investigated commercial and airline transport pilots’ perception of the impact cockpit organizational framework (COF) has on both flight safety and subordinate pilot behavior. Six research questions asked if the COF used in determining pilot positional assignments is perceived as having an impact on flight safety and subordinate pilot behavior. It was hypothesized that COF had an impact, and that pilots would perceive a flight deck where both crewmembers were qualified as captains, referred to as a captain-captain (CAPT-CAPT) COF, as improving both. This quantitative research employed an online survey and non-probability sampling techniques that targeted commercial and airline transport-rated pilots. The survey was posted on the SurveyMonkey website, which administered the survey and screened participants for suitability. To increase participation, participants were provided the opportunity to enter a random drawing for one of three participation rewards. An a priori analysis estimated a minimum of 251 respondents were needed. Four-hundred fifty respondents participated in the study; 261 respondents provided data that were used in the analysis. Cockpit organizational framework, the independent variable, was introduced to describe the combination of choices made by an aircraft operator regarding how pilot positional assignments are made. It was operationalized at two levels: a CAPT-CAPT and captain-first officer (CAPT-FO) COF. Pilot perceptions were the dependent variable. The survey utilized 27 structured close-ended questions, 24 of which measured pilot perceptions of COF on an 11-point Likert scale, and three of which measured perceptions of COF via four categorical choices. Statistical analysis utilized multiple techniques, including (a) t-test, (b) ANOVA, (c) ANCOVA, and (d) Chi-square tests of independence. The results indicated that pilots perceived COF’s impact on the three markers of safety, the first three research questions, as being statistically non-significant. However, results were statistically significant and with small to medium effect sizes for subordinate pilot behaviors, the second three research questions. Experience, as measured by total flight hours, was determined to have a statistically significant impact on pilot perceptions of COF. An additional and unplanned finding was that pilot perceptions of COF were strongly influenced by industry sector, with airline pilots favoring the CAPT-FO COF and business/corporate pilots the CAPT-CAPT COF. Airline pilot preference for the CAPT-FO COF was lower when asked about subordinate pilot behaviors, but business/corporate pilot preferences for the CAPT-CAPT COF increased for these questions. Based upon these results, it is recommended that pilot behavior in each of these two COFs be measured under experimental conditions to determine whether pilot perceptions of COF is consistent with actual subordinate pilot behaviors

Novel Discretization Schemes for the Numerical Simulation of Membrane Dynamics

Motivated by the demands of simulating flapping wings of Micro Air Vehicles, novel numerical methods were developed and evaluated for the dynamic simulation of membranes. For linear membranes, a mixed-form time-continuous Galerkin method was employed using trilinear space-time elements, and the entire space-time domain was discretized and solved simultaneously. For geometrically nonlinear membranes, the model incorporated two new schemes that were independently developed and evaluated. Time marching was performed using quintic Hermite polynomials uniquely determined by end-point jerk constraints. The single-step, implicit scheme was significantly more accurate than the most common Newmark schemes. For a simple harmonic oscillator, the scheme was found to be symplectic, frequency-preserving, and conditionally stable. Time step size was limited by accuracy requirements rather than stability. The spatial discretization scheme employed a staggered grid, grouping of nonlinear terms, and polygon shape functions in a strong-form point collocation formulation. Validation against existing experimental data showed the method to be accurate until hyperelastic effects dominate

Development and applications of the Finite Point Method to compressible aerodynamics problems

This work deals with the development and application of the Finite Point Method (FPM) to compressible aerodynamics problems. The research focuses mainly on investigating the capabilities of the meshless technique to address practical problems, one of the most outstanding issues in meshless methods. The FPM spatial approximation is studied firstly, with emphasis on aspects of the methodology that can be improved to increase its robustness and accuracy. Suitable ranges for setting the relevant approximation parameters and the performance likely to be attained in practice are determined. An automatic procedure to adjust the approximation parameters is also proposed to simplify the application of the method, reducing problem- and user-dependence without affecting the flexibility of the meshless technique. The discretization of the flow equations is carried out following wellestablished approaches, but drawing on the meshless character of the methodology. In order to meet the requirements of practical applications, the procedures are designed and implemented placing emphasis on robustness and efficiency (a simplification of the basic FPM technique is proposed to this end). The flow solver is based on an upwind spatial discretization of the convective fluxes (using the approximate Riemann solver of Roe) and an explicit time integration scheme. Two additional artificial diffusion schemes are also proposed to suit those cases of study in which computational cost is a major concern. The performance of the flow solver is evaluated in order to determine the potential of the meshless approach. The accuracy, computational cost and parallel scalability of the method are studied in comparison with a conventional FEM-based technique. Finally, practical applications and extensions of the flow solution scheme are presented. The examples provided are intended not only to show the capabilities of the FPM, but also to exploit meshless advantages. Automatic hadaptive procedures, moving domain and fluid-structure interaction problems, as well as a preliminary approach to solve high-Reynolds viscous flows, are a sample of the topics explored. All in all, the results obtained are satisfactorily accurate and competitive in terms of computational cost (if compared with a similar mesh-based implementation). This indicates that meshless advantages can be exploited with efficiency and constitutes a good starting point towards more challenging applications.En este trabajo se aborda el desarrollo del Método de Puntos Finitos (MPF) y su aplicación a problemas de aerodinámica de flujos compresibles. El objetivo principal es investigar el potencial de la técnica sin malla para la solución de problemas prácticos, lo cual constituye una de las limitaciones más importantes de los métodos sin malla. En primer lugar se estudia la aproximación espacial en el MPF, haciendo hincapié en aquéllos aspectos que pueden ser mejorados para incrementar la robustez y exactitud de la metodología. Se determinan rangos adecuados para el ajuste de los parámetros de la aproximación y su comportamiento en situaciones prácticas. Se propone además un procedimiento de ajuste automático de estos parámetros a fin de simplificar la aplicación del método y reducir la dependencia de factores como el tipo de problema y la intervención del usuario, sin afectar la flexibilidad de la técnica sin malla. A continuación se aborda el esquema de solución de las ecuaciones del flujo. La discretización de las mismas se lleva a cabo siguiendo métodos estándar, pero aprovechando las características de la técnica sin malla. Con el objetivo de abordar problemas prácticos, se pone énfasis en la robustez y eficiencia de la implementación numérica (se propone además una simplificación del procedimiento de solución). El comportamiento del esquema se estudia en detalle para evaluar su potencial y se analiza su exactitud, coste computacional y escalabilidad, todo ello en comparación con un método convencional basado en Elementos Finitos. Finalmente se presentan distintas aplicaciones y extensiones de la metodología desarrollada. Los ejemplos numéricos pretenden demostrar las capacidades del método y también aprovechar las ventajas de la metodología sin malla en áreas en que la misma puede ser de especial interés. Los problemas tratados incluyen, entre otras características, el refinamiento automático de la discretización, la presencia de fronteras móviles e interacción fluido-estructura, como así también una aplicación preliminar a flujos compresibles de alto número de Reynolds. Los resultados obtenidos muestran una exactitud satisfactoria. Además, en comparación con una técnica similar basada en Elementos Finitos, demuestran ser competitivos en términos del coste computacional. Esto indica que las ventajas de la metodología sin malla pueden ser explotadas con eficiencia, lo cual constituye un buen punto de partida para el desarrollo de ulteriores aplicaciones.Postprint (published version

Development and applications of the finite point method to compressible aerodynamics problems

This work deals with the development and application of the Finite Point Method (FPM) to compressible aerodynamics problems. The research focuses mainly on investigating the capabilities of the meshless technique to address practical problems, one of the most outstanding issues in meshless methods. The FPM spatial approximation is studied firstly, with emphasis on aspects of the methodology that can be improved to increase its robustness and accuracy. Suitable ranges for setting the relevant approximation parameters and the performance likely to be attained in practice are determined. An automatic procedure to adjust the approximation parameters is also proposed to simplify the application of the method, reducing problem- and user-dependence without affecting the flexibility of the meshless technique. The discretization of the flow equations is carried out following wellestablished approaches, but drawing on the meshless character of the methodology. In order to meet the requirements of practical applications, the procedures are designed and implemented placing emphasis on robustness and efficiency (a simplification of the basic FPM technique is proposed to this end). The flow solver is based on an upwind spatial discretization of the convective fluxes (using the approximate Riemann solver of Roe) and an explicit time integration scheme. Two additional artificial diffusion schemes are also proposed to suit those cases of study in which computational cost is a major concern. The performance of the flow solver is evaluated in order to determine the potential of the meshless approach. The accuracy, computational cost and parallel scalability of the method are studied in comparison with a conventional FEM-based technique. Finally, practical applications and extensions of the flow solution scheme are presented. The examples provided are intended not only to show the capabilities of the FPM, but also to exploit meshless advantages. Automatic hadaptive procedures, moving domain and fluid-structure interaction problems, as well as a preliminary approach to solve high-Reynolds viscous flows, are a sample of the topics explored. All in all, the results obtained are satisfactorily accurate and competitive in terms of computational cost (if compared with a similar mesh-based implementation). This indicates that meshless advantages can be exploited with efficiency and constitutes a good starting point towards more challenging applications

Hydrology

In this book, an attempt is made to highlight the recent advances in Hydrology. The several topics examined in this book form the underpinnings of larger-scale considerations, including but not limited to topics such as large-scale hydrologic processes and the evolving field of Critical Zone Hydrology. Computational modeling, data collection, and visualization are additional subjects, among others, examined in the set of topics presented

Cyber Infrastructure Protection: Vol. III

Despite leaps in technological advancements made in computing system hardware and software areas, we still hear about massive cyberattacks that result in enormous data losses. Cyberattacks in 2015 included: sophisticated attacks that targeted Ashley Madison, the U.S. Office of Personnel Management (OPM), the White House, and Anthem; and in 2014, cyberattacks were directed at Sony Pictures Entertainment, Home Depot, J.P. Morgan Chase, a German steel factory, a South Korean nuclear plant, eBay, and others. These attacks and many others highlight the continued vulnerability of various cyber infrastructures and the critical need for strong cyber infrastructure protection (CIP). This book addresses critical issues in cybersecurity. Topics discussed include: a cooperative international deterrence capability as an essential tool in cybersecurity; an estimation of the costs of cybercrime; the impact of prosecuting spammers on fraud and malware contained in email spam; cybersecurity and privacy in smart cities; smart cities demand smart security; and, a smart grid vulnerability assessment using national testbed networks.https://press.armywarcollege.edu/monographs/1412/thumbnail.jp

Elasto-plastic deformations within a material point framework on modern GPU architectures

Plastic strain localization is an important process on Earth. It strongly influ- ences the mechanical behaviour of natural processes, such as fault mechanics, earthquakes or orogeny. At a smaller scale, a landslide is a fantastic example of elasto-plastic deformations. Such behaviour spans from pre-failure mech- anisms to post-failure propagation of the unstable material. To fully resolve the landslide mechanics, the selected numerical methods should be able to efficiently address a wide range of deformation magnitudes. Accurate and performant numerical modelling requires important compu- tational resources. Mesh-free numerical methods such as the material point method (MPM) or the smoothed-particle hydrodynamics (SPH) are particu- larly computationally expensive, when compared with mesh-based methods, such as the finite element method (FEM) or the finite difference method (FDM). Still, mesh-free methods are particularly well-suited to numerical problems involving large elasto-plastic deformations. But, the computational efficiency of these methods should be first improved in order to tackle complex three-dimensional problems, i.e., landslides. As such, this research work attempts to alleviate the computational cost of the material point method by using the most recent graphics processing unit (GPU) architectures available. GPUs are many-core processors originally designed to refresh screen pixels (e.g., for computer games) independently. This allows GPUs to delivers a massive parallelism when compared to central processing units (CPUs). To do so, this research work first investigates code prototyping in a high- level language, e.g., MATLAB. This allows to implement vectorized algorithms and benchmark numerical results of two-dimensional analysis with analytical solutions and/or experimental results in an affordable amount of time. After- wards, low-level language such as CUDA C is used to efficiently implement a GPU-based solver, i.e., ep2-3De v1.0, can resolve three-dimensional prob- lems in a decent amount of time. This part takes advantages of the massive parallelism of modern GPU architectures. In addition, a first attempt of GPU parallel computing, i.e., multi-GPU codes, is performed to increase even more the performance and to address the on-chip memory limitation. Finally, this GPU-based solver is used to investigate three-dimensional granular collapses and is compared with experimental evidences obtained in the laboratory. This research work demonstrates that the material point method is well suited to resolve small to large elasto-plastic deformations. Moreover, the computational efficiency of the method can be dramatically increased using modern GPU architectures. These allow fast, performant and accurate three- dimensional modelling of landslides, provided that the on-chip memory limi- tation is alleviated with an appropriate parallel strategy