A variational treatment of hydrodynamic and magnetohydrodynamic flows

In order to describe stationary plasma flows in thrusters based on plasma propulsion, an ideal, axial symmetric, single-fluid motion is assumed. The conservation laws of conductive fluids and the Maxwell\u2019s equations lead to a second order differential equation for the magnetic flux function \u3c8, i.e. the generalized Grad Shafranov (GS) equation, and to two implicit constraints relating \u3c8 to the plasma density and the azimuthal velocity. This set of three equations, one differential and two algebraic, is then expressed using a variational approach and the solution is obtained in a straightforward manner from the extremum of the appropriate Lagrangian functional. The numerical approach is based on Ritz\u2019s method, which has the advantage of producing analytic (though approximate) solutions. Both non-conductive fluids, where the acceleration can only be obtained exploiting the internal energy of the flow (thermodynamic process), and conductive fluids, where the electromagnetic forces play a fundamental role, are considered. In order to apply this approach to the acceleration processes in nozzle-like configurations, an open-boundary geometry is investigated and specific attention is paid to a physical definition of boundary conditions. Hydrodynamic shocks are taken into account and it is shown that the appropriate jump conditions follow implicitly from a natural extension of the Lagrangian variational principle. A comparison test with an explicit solution permits an estimate of the approximate results

Reduced-order particle-in-cell simulations of a high-power magnetically shielded Hall thruster

High-power magnetically shielded Hall thrusters have recently emerged to meet the needs of the next-generation space missions. Even though a few such thrusters are currently undergoing their late-stage development campaigns, many unanswered questions yet exist concerning the behavior and evolution of the plasma in these large-size thrusters that feature an unconventional magnetic field topology. Noting the complex, multi-dimensional nature of plasma processes in Hall thrusters, high-fidelity particle-in-cell simulations are optimal tools to study the intricate plasma behavior. Nonetheless, the significant computational cost of traditional PIC schemes renders simulating high-power thrusters without any physics-altering speed-up factors unfeasible. Thus, in this article, we demonstrate the applicability of the novel reduced-order PIC scheme for a cost-efficient, self-consistent study of the high-power Hall thrusters by performing simulations of a 20 kW magnetically shielded Hall thruster along the axial-azimuthal and radial-azimuthal coordinates. The axial-azimuthal simulations are performed for three operating conditions in a rather simplified representation of the thruster's inherently 3D configuration. Nevertheless, we resolved self-consistently an unprecedented 650 us of the discharge evolution without any ad-hoc electron mobility model, capturing several breathing cycles and approximating the experimental performance parameters with an accuracy of 70 to 80 % across the operating conditions. The radial-azimuthal simulations casted further light on the evolution of the azimuthal instabilities and the resulting variations in the electrons' cross-field mobility and the plasma-wall interactions. Particularly, we observed the development of a long-wavelength, relatively low-frequency wave mode near the exit plane of the thruster's channel that induces a notable electron transport.Comment: 29 pages, 25 figure

Flow regimes in T-shaped micro-mixers

The different flow regimes occurring in T-mixers are investigated by means of direct numerical simulations. Three different values of the aspect ratio of the inlet channels, ki, that is their width to height ratio, are considered, namely ki= 0.75, 1 and 2. For the configurations with ki= 0.75 and 1, the same behavior as previously described in the literature, is found. In particular, as the Reynolds number is increased, the flow evolves from vortical to engulfment steady regimes, then to unsteady asymmetric and symmetric periodic regimes, until, finally, it becomes chaotic. All the critical values of the Reynolds number, at which the transitions between the different regimes occur, are found to be very similar for ki= 0.75 and 1, while some differences are highlighted in the vorticity dynamics and characteristic frequencies of the unsteady regimes. The observed scenario is completely different for ki= 2. Indeed, in this case, the flow evolves directly from the vortical regime to an unsteady symmetric behavior, with a vorticity dynamics that is significantly different from those observed for the other aspect ratios

Design for test and qualification through activity-based modelling in product architecture design

Test and qualification (T&Q) phases take a significant portion of the time to market for critical products in the space industry, especially when introducing new technologies. Since T&Q are treated as standard procedures, they tend to be independent of the architectural design phases and kept away from design decisions. However, when introducing new technologies, qualification procedures may differ from those established in regular design scenarios, and the estimation of qualification costs and duration is problematic. There is a lack of design for qualification methods capable of modelling these activities in early phases and use those models to support the architecture design of products with affordable test and qualification phases. In this article, a computer-assisted, model-based design method to model T&Q activities concerning early product architecture designs is proposed. Product architecture alternatives, test schedules and cost are connected through the quantification of T&Q drivers and driver rates. The design method is demonstrated using a case study about electric propulsion for satellites. The method is applicable for design situations where the choice of technology has a strong dependence on the qualification procedure

Non-Human + Human Deep Space Exploration: By The NEP INPPS Flagship

INPPS Flagship Structure & Subsystems, Ground Based Tests, Pure NEP, International Electric Thrusters, Humans Internationally To Mar

Mars- plus Europa-INPPS Flagship Missions with High Power Electric Thrusters and Heavy Science Payload

2020/2021 orbit calculations (DLR Bremen + MAI Moscow): 3 Orbits for one non-human MARS/EUROPA-INPPS flagship 1. Orbit Earth (11 Oct 2026) => Mars (28 Jan 2028); 2. Orbit Mars (22 Sept 2028) => Earth (29 Jul 2029); 3. Orbit Earth (12 Oct 2031) => Jupiter / Europa (6 Dec 2035) 22 ETs (for the INPPS flagship CET): example - gridded CET plate with combined ET

Humans to Mars: by MARS- plus EUROPA-INPPS Flagship Mission

The first non-human INPPS (International Nuclear Power and Propulsion System) flagship flight with orbits Earth-Mars-Earth-Jupiter/Europa (after 2025) is the most maximal space qualification test of INPPS flagship to carry out the second INPPS flagship flight to Mars with humans (in the 2030th). This high power space transportation tug is realistic because of A) the successful finalization of the European-Russian DEMOCRITOS and MEGAHIT projects with their three concepts of space, ground and nuclear demonstrators for INPPS realization (reached in 2017), B) the successful ground based test of the Russian nuclear reactor with 1MWel plus important heat dissipation solution via droplet radiators (confirmed in 2018), C) the space qualification of the Russian reactor by 2025 and D) the perfect celestial constellation for a Earth-Mars/Phobos-Earth-Jupiter/Europa trajectory between 2026 and 2035. Therefore the talk sketches the preparation status of INPPS flagship with its subsystems. Critical performance will be studied by parallel realizations of the ground and nuclear demonstrators of DEMOCRITOS (until 2025). The space qualification of INPPS with all subsystems including the nuclear reactor in the middle of the 2020th plus the INPPS tests for about one to two years - first in high Earth orbit robotic assembly phase of INPPS and later extended in nearby Earth space environment flight - means a complete concepts driven approval for all applied INPPS space subsystem technologies. It is also important to consider wider aspects for the overall mission implementation phase. Component like the nuclear reactor as the power source for the propulsion system will have to agree with the 1992 UN principles relevant to the use of nuclear power sources (NPS) in outer space. Therefore this talk will look into the legal and policy issues of nuclear space systems related to the international realization of mission design, requirements of associated safety regulations (including AI applications in the subsystems) and new aspects for INPPS flagship commercialization and new media communication on board

Hybrid-PIC Modeling of Hall Thruster Acceleration Channels

In order to study the physics of the acceleration process in Hall Thrusters, an innovative hybrid particle-in-cell (PIC) numerical model has been developed in this work. A set of two dimensional axisymmetric fluid equations are used for electrons, while heavy species such as ions and neutrals are modeled via a particle tracking approach. The two solutions are linked by charge neutrality. The computational domain covers all the acceleration channel, boundary conditions are imposed on sheath-plasma interface based on classical plasma physics assumptions. The code is able to perform a full simulation of the flow proceeding through neutral injection, ionization, ions acceleration and collision processes up to particles expulsion into the free space. Electrons are expected to reach stationary state in a very shorter time if compared with typical ions and neutrals time-step; consequently, electrons equations are solved every PIC time-step giving as output the electric field and the ionization rate, both consistently evaluated with heavy species instantaneous distributions. The aim of this work is to predict Hall Thruster performances and to provide a reliable mean for sensitivity analysis on main geometrical and system parameters. First results on simulations performed are in great accordance with experimental and numerical results reported by several authoritative publications. In order to reduce those discrepancies, future developments of the code could include extension of the simulation domain out of the channel and plume tracking in the region close to the exhaust of the thruster

Hamiltonian magnetohydrodynamics: Lagrangian, Eulerian, and dynamically accessible stability-Examples with translation symmetry

Because different constraints are imposed, stability conditions for dissipationless fluids and magnetofluids may take different forms when derived within the Lagrangian, Eulerian (energy-Casimir), or dynamically accessible frameworks. This is in particular the case when flows are present. These differences are explored explicitly by working out in detail two magnetohydrodynamic examples: convection against gravity in a stratified fluid and translationally invariant perturbations of a rotating magnetized plasma pinch. In this second example, we show in explicit form how to perform the time-dependent relabeling introduced in Andreussi et al. [Phys. Plasmas 20, 092104 (2013)] that makes it possible to reformulate Eulerian equilibria with flows as Lagrangian equilibria in the relabeled variables. The procedures detailed in the present article provide a paradigm that can be applied to more general plasma configurations and in addition extended to more general plasma descriptions where dissipation is absent

GEO telecommunication satellite: new opportunities enabled by a 20kW class Hall thruster

Nowadays, the telecommunication satellite market in geostationary orbit (GEO) is suffering of a plummeting in the order rate of new GEO satellites. Compared to the average rate of launch between 20 and 25 satellites per year of the last decade, only five orders for large communication satellites were placed in 2018. Apparently, no real solutions can be implemented in near terms to revitalize GEO market. According with the opinions of several large integrators, the new trend in the development of large constellations in lower orbits is the main cause of the customer’s uncertainties in the GEO market. At the same time, they are waiting for new, cutting-edge technologies in order to further increase GEO satellite capabilities in terms of payload size, satellite operational lifetime and performance. One of the technologies that may enhance the competitiveness of GEO telecom satellites is high power electric propulsion (HP-EP). This technology coupled with reusable platforms in the field of GEO telecom satellites can bring to two different mission concepts. The first one consists of a reusable space tug that performs GEO on-orbit services, such as orbit raising maneuvers, orbit refueling and orbit relocation. The second mission concept consists of an integrated reusable platform as GEO telecom satellite that utilizes HP-EP to perform the above mentioned on-orbit services, in addition to its nominal mission operations. The paper presents a comparison between these two concepts, in order to investigate the technical feasibility of GEO on-orbit services and to assess the corresponding new market opportunities. Among different thruster technologies, Hall thrusters appears to be the most promising, owing to their extended performance envelope, their intrinsic reliability as well as their operational flexibility. After selecting the propulsion subsystem architecture, both platforms are sized for different mission scenarios thanks to the software MultidisciplinAry desiGN Electric Tug tOol (GEOMAGNETO), an ad-hoc developed tool for mission and system design. Eventually, main conclusions about advantages and disadvantages of both mission concepts are drawn