Imperial College London

MrJesús ManuelMunoz Tejeda

Faculty of EngineeringDepartment of Aeronautics

Research Postgraduate
 
 
 
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Contact

 

jesus.munoz.tejeda Website

 
 
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Location

 

308. Desk 25City and Guilds BuildingSouth Kensington Campus

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Summary

 

Publications

Publication Type
Year
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7 results found

Munoz Tejeda JM, Knoll A, 2023, A water vapour fuelled Hall Effect Thruster: characterization and comparison with oxygen, Acta Astronautica, Vol: 211, Pages: 702-715, ISSN: 0094-5765

A Hall Effect Thruster propelled by water vapour is investigated at the Imperial Plasma Propulsion Laboratory. For that purpose,a water vapour feed system is designed, optimised and tested, with the major objective of keeping water in vapour state at all times.This system primarily consists of a mass flow controller, a flow restrictor, and a heating and pressure monitor system capable ofidentifying under which conditions water condensation occurs. A hanging pendulum thrust balance is used to measure the thruston the power range of Pd = 600 − 1600 W. Different magnetic field strengths and mass flows are investigated to determine theconditions in which the highest efficiency can be achieved. Then, a comparison between water vapour and oxygen (intended tobe the propellant of a water electrolysis Hall Effect Thruster) is included. The results show that oxygen is approximately 20 %more efficient than water vapour under the same operating conditions. Overall, the highest thrust measurement recorded with watervapour was 20.0 ± 0.2 mN; with a specific impulse of 2039 ± 20 s and an anode efficiency of 12.5 ± 0.3 % at the largest dischargepower of investigation (Pd = 1600 ± 1 W).

Journal article

Tejeda JM, Knoll A, 2023, An oxygen-fuelled Hall Effect Thruster: Channel length, ceramic walls and anode material experimental analyses, Acta Astronautica, Vol: 203, Pages: 268-279, ISSN: 0094-5765

An oxygen-fuelled Hall Effect Thruster is investigated at the Imperial Plasma Propulsion Laboratory vacuum chamber facilities over a different range of discharge channel axial lengths, ceramic walls and anode materials. The purpose of using oxygen as a propellant is to better understand the principles of water electrolysis Hall Effect Thrusters, which are envisaged to use oxygen to propel the thruster. These studies aimed to answer whether if for molecular plasmas, a larger channel length would benefit the overall performance of the thruster by increasing the length of the ionization region, or if a shorter channel would be more beneficial due to a reduction in the energy losses associated with the plasma-wall interactions. Experimentally, it is found that channel lengths of 13.1 mm performed the best amongst the lengths tested in terms of thrust, specific impulse and thrust efficiency. Larger channels (59.8 mm, 44.8 mm and 34.8 mm) showed a reduction in thruster performance with increasing channel length. A very short channel length of 5.5 mm is found to be less efficient than the best performing case (13.1 mm), possibly indicating that the ions are being formed within or downstream of the peak acceleration region due to the constrained length of the channel. These behaviours appear to be more evident the higher the discharge power. The impact of the walls material is also investigated. In the past, changing the thruster walls from Alumina (Al2O3) to Boron Nitride (BN) made a significant improvement on the performance, generally because of the lower Secondary Electron Emission of the BN walls. In this study, two different grades of BN walls are used: 99% purity BN (grade AX05) and a BNSiO2 compound (grade M26). Although BNSiO2 walls are said to have slightly lower Secondary Electron Emission than BN, the thrust measurements obtained using these walls are very similar. Finally, anodes made out of different materials are also tested. The main goal is to identify a su

Journal article

Rosati Azevedo E, Jones-Tett K, Larsen H, Reeve S, Longhi EC, Munoz Tejeda JM, Moloney R, Schwertheim A, Knoll Aet al., 2022, Sizing and Preliminary Design of a 2-kW Water Propelled Hall Effect Thruster, The 37th International Electric Propulsion Conference

Conference paper

Abbi M, Munoz Tejeda JM, Reza M, Knoll A, Jones-Tett K, Rosati Azevedo Eet al., 2022, Investigation into the Wall Interactions of a Hall Effect Thruster Using Water Vapor as a Propellant, The 37th International Electric Propulsion Conference

Conference paper

Munoz Tejeda JM, Knoll A, 2022, A Water Electrolysis Hall Effect Thruster Computational Model with Radiofrequency Excitation, International Electric Propulsion Conference, no 313

A Hall Effect Thruster operating with the products of water electrolysis (oxygen for the anode and hydrogen for the cathode) is modelled using a pseudo 2-dimensional full Particle-In-Cell code capable of tracking five different species (diatomic neutrals, monoatomic neutrals, diaotomic ions, ions and electrons). The diatomic model developed for that purpose is verified against an analytical solution from the fluid governing equations of the system. Then, the complete code is validated against experimental data collected at the Imperial Plasma Propulsion Laboratory from a non-excited Hall Effect Thruster operating on oxygen. Once the code is verified and validated, electrostatic excitation is studied as a possible mechanism to enhance the performance of this technology, and its influence on the reactive model is analyzed. The proposed excitation mechanism is based on high frequency oscillations of the ground reference potential of the neutralizing hollow cathode. This radiofrequency excitation induces electromagnetic waves into the Hall Effect Thruster channel, whose electrostatic solution is known as the ’Bernstein Modes’. The resonance frequencies of these waves are chiefly found at the Electron Cyclotron Resonance and upper harmonics, which can be excited by setting the right power and oscillation frequency coming from that hollow cathode. Several spectral analyses confirm the presence of these waves at Electron Cyclotron Resonance within the channel. For an excited simulation, it is found that the ionizing and dissociating rates increase, together with the electron temperature and overall potential. In turn, this can potentially boost the thruster performance compared to a non-excited thruster, which can unlock an innovative satellite architecture where the microwave generator hardware is shared between the communications-payload and the propulsion subsystems.

Conference paper

Munoz Tejeda JM, Knoll A, 2022, Water as an Environmentally Friendly Propellant for a Multi-functional Spacecraft Architecture, Space Propulsion Conference, no 00272

We propose water can be utilized as spacecraft propellant to dramatically reduce the environmental impact of constructing and operating a satellite. We present a multi-mode chemical-electrical propulsion system where water acts as the propellant for both high thrust chemical manoeuvres, and high specific impulse electrical manoeuvres. Such a system would allow the community to divest from traditional propellants such as hydrazine and xenon, reducing the production of highly toxic chemicals and dramatically reducing the carbon footprint of the propulsion system. Water has the lowest toxicity, carbon footprint and price of any current or proposed propellant and has demonstrated both feasibility and competitiveness in laboratory testing. The unique role it can play across multiple spacecraft subsystems suggests that the commercial adoption of water as a propellant will reduce cost and mass while also reducing the environmental impact of the satellites of tomorrow. This technology has the ability to enable the development of a modular, multi-functional, competitive and environmentally friendly spacecraft architecture.

Conference paper

Munoz Tejeda JM, Reza M, Faraji F, Knoll Aet al., 2022, Performance enhancement of Hall Effect Thrusters using radiofrequency excitation, Acta Astronautica, Vol: 194, ISSN: 0094-5765

Radiofrequency excitation in single-stage Hall Effect Thrusters is proposed as a method to increase the performance of these devices. The topology of the magnetic and electric field within Hall Effect Thrusters makes it possible to excite quasistatic waves which travel longitudinally through the channel across a magnetostatic field, whose resonances are found at the electron cyclotron gyrofrequency and its upper harmonics. An in-house pseudo 2-dimensional axial–radial Particle-In-Cell software developed at the Imperial Plasma Propulsion Laboratory called PlasmaSim is verified and validated against the Russian thruster SPT-100 and adapted to be used as a computational tool to analyze plasma-wave interactions. A benchmark case study for 2-dimensional axial–radial plasma simulation codes is proposed, and PlasmaSim plasma in-channel properties are evaluated in this analysis. In terms of performance, comparison between simulated and experimental measurements shows average values in agreement with thrust, specific impulse and anode efficiency, over the full range of discharge power conditions of the SPT-100. The proposed method of radiofrequency excitation is to vary the ground reference potential of the neutralizing hollow cathode at high frequency. A range of potential excitation frequencies is established on the basis of hot plasmas’ theory, with candidate frequencies varying between 0.1 GHz to 2 GHz for the plasma conditions within a SPT-100 device. Simulation’s results give a deeper insight into the nature of these waves and their propagation in the plasma. Quantitative analyses as a function of power and excitation frequency are reported, showing the impact on thruster performance and in-channel plasma properties. The thruster’s total power is taken as the sum of the DC discharge power and AC radiofrequency power, which is calculated numerically from the simulation results based on the time varying discharge current and voltage. Taking

Journal article

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