Advanced Electric Propulsion Research Articles

Characterization method of conductive film state of micro-cathode arc thrusters

Micro-Cathode Arc Thruster (μCAT) is an advanced electric propulsion system developed in the past decades to meet the maneuvering requirements of space microsatellites. However, the constraint on the its application is the short lifespan of the thruster. This is attributed to the conductive film, a key component of thruster discharge. In this study, we propose a measurement method for μCAT conductive film, and enables the evaluation of the evolution process of film thickness. The method is based on the four-probe resistivity testing theory and size effect fitting model, and establishes a method for characterizing the thickness and resistivity of μCAT conductive films. A comparison was made between the corrected resistivity test results of 1, 2, 5, and 10 μm film and the fitting results of the titanium film, revealing an error ofapproximately 10%. Additionally, a total of 2500 ignition experiments were conducted to verify the film thickness and resistance measurement of this method. This research serves as a valuable basis for the lifetime investigation of μCAT. Consequently, the thickness of the film progressively decreases with each discharge cycle, and the resistivity exhibits a corresponding increase due to the size effect. This method could be used as an effective method for exploring the μCAT lifespan and performance.

Advanced Electric Propulsion Concepts for Fast Missions to the Outer Solar System and Beyond

Electric Propulsion (EP) comprises all types of space propulsion in which a certain amount of propellant is ionized and then accelerated by electric or magnetic fields, or both. This propulsion technology allows for much higher specific impulses (Isp > 2,000 s) than conventional chemical propulsion (Isp < 500 s), resulting in a major reduction of the propellant mass or a considerably higher final speed for a certain space mission. Hence, EP can enable very challenging space missions as DAWN has clearly shown. Furthermore, an EP system coupled with an advanced nuclear reactor could enable fast manned missions to Mars (one-way travel times less than 4 months). This propulsion technology can be scaled up to even higher specific impulses (Isp > 5,000s). However, the power needed for the same thrust is also increasing. An Oberth maneuver performed very close to the Sun could provide the additional power to a high-Isp Solar Electric Propulsion (SEP) system in order to reach the needed delta-v for challenging interstellar precursor missions. A breakthrough in power source specific mass is needed in order to enable missions with ultra-high specific impulses (> 10,000 s); this breakthrough could be realized having the power source not on board, as with Laser-powered Electric Propulsion (LEP), where the needed power is beamed to the spacecraft from an external laser source. In this case the on-board power source is limited to a light-weight photovoltaic receiver/converter. The development of ultra-high Isp ion thrusters powered by an external laser source could enable the most challenging interstellar precursor missions up to the Oort Cloud and beyond. This paper gives an update on the status of these advanced propulsion concepts, and provides some examples of interstellar precursor missions enabled by advanced EP systems which could be launched before 2040. Keywords: Interstellar, Electric Propulsion, Oberth, Laser

An Optimized Electric Propulsion System for Hyperloop Applications

In this paper, an advanced electric propulsion system (EPS) is designed for an ultra-fast electric train. The proposed system consists of a slotless dual-sided linear synchronous motor (DSLSM) and a three-step track powering topology. A multi-objective optimization workflow based on a reduced-order model of DSLSM is used to optimize the permanent magnets (PMs) and the winding dimensions to maximize the thrust force density and efficiency. The optimized model is validated using the finite element analysis (FEA). Then, a new fault-tolerant control algorithm is proposed for the optimized DSLSM fixing the mover in the center of the DSLSM under any airgap disturbance. Finally, a high-fidelity switching model of the complete EPS is developed. The performance of the proposed EPS is verified using a real-time hardware-in-the-loop (HIL) simulator under normal and faulty conditions.

Energy Flow and Electric Drive Mode Efficiency Evaluation of Different Generations of Hybrid Vehicles under Diversified Urban Traffic Conditions

Hybrid propulsion dedicated to light duty vehicles is seen as an evolutionary change from internal combustion engine (ICE) to electric propulsion. Widespread direct replacement of convection ICEs in the current energy system is impossible because ICEs are vehicles’ main source of mechanical energy. The hybrid powertrain uses the advantages of electric propulsion with the ability to charge the traction battery or have the internal combustion engine assist the system. The article compares different types of hybrid drives (with a small share of plug-in hybrid propulsion) under typical urban driving conditions. Nine vehicles were tested, and the tests were conducted over several months in various cities in Poland. The terms of the research conducted were not under the requirements of the driving test. However, they are authoritative when using the vehicle in real traffic conditions. Such conditions take into account many aspects that are relevant to a road test. It was found that urban conditions are a very suitable environment for hybrid propulsion systems, as they cover more than 50% of the distance in electric mode, regardless of the initial battery charge, in most cases.

Single- and two-photon absorption laser-induced fluorescence spectroscopy in rare gases for gridded ion thruster diagnostics

Methods based on laser-induced fluorescence spectroscopy are widely used for spatially resolved non-intrusive diagnostics of atomic or molecular densities and velocity distributions in plasma applications. With regard to electric space propulsion, one focus is on the investigation of rare gases such as xenon or krypton, which are currently the favored propellants in gridded ion- and Hall-effect thrusters. For gridded ion engines, diagnostics of neutral atoms is of interest since charge-exchange processes between neutrals and ions are the main driver of accelerator grid erosion, which limits the lifetime of a gridded ion thruster. Extending the capabilities of the advanced electric propulsion diagnostics platform which has been developed by the IOM and partners, single- and two-photon absorption laser-induced fluorescence diagnostics have been set-up recently at our institute. Both experimental set-ups, and as a series of first applications, measurements of krypton neutrals in the plume of the radiofrequency ion thruster RIT-10 (ArianeGroup GmbH), and xenon neutrals within the discharge chamber of a gridded radiofrequency ion source developed at IOM, are presented.

Orbital Maneuvers of Earth Observing Satellites Using Electric Propulsion Systems

The paper gives examples of orbital maneuver execution of spacecraft (SC) using orbit correction propulsion system (OCPS) based on electric propulsion (EP). The high velocity of the propellant flow achieved in EP allows for orbital maneuvers with significantly lower propellant flow rate than in conventional propulsion systems. The time required to perform the orbital maneuvers using EP is connected with the available on-board power. It is typically much greater than such time needed for conventional jet propulsions. The advantages of EP are realized if mission allows a long-time operation of the propulsion system. Since the early 1970s stationary plasma thrusters (SPTs) developed on the base on the concept proposed by A.I. Morozov are used on the SC Meteor. With the help of OCPS based on SPT EOL-1, SC Meteor was installed on the conventionally synchronous orbit, which provides a fixed grid of tracks with a period of T = 102.31 min. In this case, a complete overview of all daily Earth’s surface with the bandwidth of 2900 km is obtained. In recent decades, there has been a steady trend toward miniaturization of space equipment, which requires the development of acceptable thrusters to meet new requirements. Typical total impulses of thrust required for OCPS are reduced several times. At present, a number of space constellations are being developed in Russia based on small SC with a mass from 60 to 500 kg. VNIIEM Corporation creates a space constellation IONOZOND, designed to monitor the geophysical conditions. The description of the IONOZOND constellation is given and the options for using of various OCPS, in particular, based on SPT, ion and pulsed plasma thrusters are considered. It is shown that their use in small SC can significantly increase the economic efficiency of remote sensing orbital constellations.

Integrated Power System Health Assessment of Large-Scale Unmanned Surface Ships Based on Convolutional Neural Network Algorithm

These paper studies the large unmanned ship of the most advanced electric propulsion method. Its integrated power system is complex in structure with many equipment and often performs long-range operations. The key factor of the large unmanned ship is the integrated power system of healthy operation. This paper analyzes the parameters affecting the health of the system from three aspects: the system parameters, the unmanned ship’s navigation state parameters, and the environmental parameters and designs a kind of unmanned ship integrated power system health based on Evaluation algorithm of convolutional neural network with high accuracy. In this paper, the feasibility and superiority of convolution neural network algorithm are verified through the comparative simulation analysis of BP neural network and deep belief network.

Transport Coefficients of Two-temperature Lithium Plasma for Space Propulsion Applications

Lithium has been proposed as an attractive metal propellant for advanced electric propulsion. In our current work, transport coefficients including the viscosity, thermal conductivity, and electrical conductivity of lithium plasma under both the equilibrium and non-equilibrium conditions are calculated based on a two-temperature model. The collision integrals used in calculating the transport coefficients are significantly more accurate than values used in previous theoretical studies, resulting in more reliable values of the transport coefficients. Results are computed for different degrees of thermal non-equilibrium, i.e. the ratio of electron to heavy particle temperatures, from 1 to 15, with the electron temperature ranging from 300 to 60,000 K in a wide pressure range from 0.0001 to 100 atm. We compare our calculated results with existing published results and discrepancies are found and explained.

Advanced Electric Propulsion Diagnostic Tools at IOM

Recently, we have set up an Advanced Electric Propulsion Diagnostic (AEPD) platform [1], which allows for the in-situ measurement of a comprehensive set of thruster performance parameters. The platform utilizes a five-axis-movement system for precise positioning of the thruster with respect to the diagnostic heads. In the first setup (AEPD1) an energy-selective mass spectrometer (ESMS) and a miniaturized Faraday probe for ion beam characterization, a telemicroscope and a triangular laser head for measuring the erosion of mechanical parts, and a pyrometer for surface temperature measurements were integrated. The capabilities of the AEPD1 platform were demonstrated with two electric propulsion thrusters, a gridded ion thruster RIT 22 (Airbus Defence & Space, Germany, [13]) and a Hall effect thruster SPT 100D EM1 (EDB Fakel, Russia, [1,4]), in two different vacuum facilities.

An advanced electric propulsion diagnostic (AEPD) platform for in-situ characterization of electric propulsion thrusters and ion beam sources

Experimental characterization is an essential task in development, qualification and optimization process of electric propulsion thrusters or ion beam sources for material processing, because it can verify that the thruster or ion beam source fulfills the requested mission or application requirements, and it can provide parameters for thruster and plasma modeling. Moreover, there is a need for standardizing electric propulsion thruster diagnostics in order to make characterization results of different thrusters and also from measurements performed in different vacuum facilities reliable and comparable. Therefore, we have developed an advanced electric propulsion diagnostic (AEPD) platform, which allows a comprehensive in-situ characterization of electric propulsion thrusters (or ion beam sources) and could serve as a standard on-ground tool in the future. The AEPD platform uses a five-axis positioning system and provides the option to use diagnostic tools for beam characterization (Faraday probe, retarding potential analyzer, ExB probe, active thermal probe), for optical inspection (telemicroscope, triangular laser head), and for thermal characterization (pyrometer, thermocamera). Here we describe the capabilities of the diagnostic platform and provide first experimental results of the characterization of a gridded ion thruster RIT-μX.

(Invited) High Power SiC Power Processing Unit Development

The NASA space flight program can be divided into manned and unmanned programs with each contributing and ultimately setting the stage for advanced space transportation systems, future space habitats, and spacecraft that can send humans deep into the solar system. Most spacecraft use solar arrays for the main source of power except for those that had relatively short flight duration, or for deep space probes that were designed for very long flight duration. As the vision for space exploration evolves; spacecraft, space stations, and space habitats power needs increase exponentially thus creating the need for more efficient and revolutionary power technologies. NASA is investing in the most cutting-edge power technologies to enable the human space exploration beyond the earth vicinity. The NASA Human Exploration Framework Team (HEFT) recommended demonstrating Spacecraft buses with increasing power & decreasing specific mass to enable advanced electric and plasma propulsion spacecraft that will decrease trip times to Mars and beyond. Primary or auxiliary electric propulsion systems provide many potential benefits to the spacecraft developer when compared to chemical propulsion systems. The high specific impulse provided by electric thrusters substantially reduces the amount of propellant required to achieve a given mission. This mass savings can be leveraged in many ways including reduction of spacecraft mass, reduced launch vehicle requirements, increased on-orbit lifetime, or increased payload. Recent advances in solar array technology that produce more efficient and lighter solar arrays have enabled the notion of high power spacecraft as large as 300kW to MW class. These high power systems will require high power, higher voltage distribution and power converters all requiring high voltage parts. In response to these technology needs, NASA GRC has been developing a solar electric power processing unit that would operate from a nominal 300VDC spacecraft bus. The unit utilizes 1200V commercial silicon carbide power MOSFETs and high voltage SiC schottky diodes. This developments main objective is to demonstrate the capability of high power, high voltage, and power processing for a 2000-second specific impulse Hall Effect Thruster. To date this development has demonstrated the mass and efficiency gains which using silicon carbide at high voltage provides illustrating the need for radiation hardened space rated components.

Electric Propulsion Applied for Research Vessel

In the present work a research boat or specifically for geography was developed where the electric propulsion was chosen, for the reason that advantages of electric propulsion in this type of vessel. The dimension the power necessary to propulsion the ship is necessary to account the wholly weight of the ship and her navigation velocity. In this work the weight of the every part of the ship were considerate, as: electric equipment, mechanic equipment, hull structure, and crane, etc. Then the preliminary design of the hydrographic boat was developed where a group of the three engineers was constituted for realize this work.

Concepts for a low-cost Mars micro mission

This paper summarises three novel micro-mission concepts for the low-cost exploration of the Martian system. These concepts have been studied under national funding with the aim of defining highly cost-effective options for the delivery of on-board instrumentation into Mars orbit for remote sensing or deployment of lander packages for surface exploration of the Martian system. All three missions use advanced electric propulsion to improve payload mass performance and miniaturised avionics either in the spacecraft bus or payload. Broadly, the three concepts are categorised according to mass: a constellation of micro-satellites (120 kg) in low Mars polar orbit for global atmospheric circulation/climate monitoring using radio occultation techniques; a single mini-satellite (310 kg) for studying composition and origins of Mars’ moons Deimos and Phobos; and a single larger spacecraft (800 kg) based on a standard launcher adapter cone and carrying multiple micro-penetrators for measuring sub-surface water ice composition at pre-determined locations on the surface of Mars.

POWOW: power without wires: a SEP concept for space exploration

Electric propulsion has emerged as a cost-effective solution to a wide range of satellite applications. Deep Space 1 successfully demonstrated electric propulsion as the primary propulsion source for a satellite. The POWOW concept is a solar-electric propelled spacecraft capable of significant cargo and short trip times for traveling to Mars. It would enter aerosynchronous orbit and from there, beam power to surface installations via lasers. The concept has been developed with industrial partner expertise in high efficiency solar cells, advanced concentrator modules, innovative arrays, and high power electric propulsion systems. The latest version of the spacecraft, the technologies used, and trip times to Mars are presented. The POWOW spacecraft is a general purpose solar electric propulsion system that uses new technologies that are directly applicable to commercial and government spacecraft with power levels ranging from a LEO power level of 4 kW up to GEO spacecraft about 1 MW. The system is modular, expandable, and amenable to learning curve cost projection methods.

Reexamination of Superconductive Homopolar Motors for Propusion

ABSTRACT Superconducting homopolar motor concepts with accompanying auxiliary systems have been examined in a quick‐look assessment for their impact on ship designs utilizing the Navy's Advanced Surface Ship Evaluation Tool (ASSET) developed by the Naval Surface Warfare Center Carderock Division. An existing ASSET DDG51‐FLT2A “like” ship model was used as a convenient means of evaluating the ship impact of the superconducting homopolar, and other advanced electric propulsion systems. For simplicity, all ship impact benefits due to increased power density and efficiency are taken in increased fuel capacity and thus, increased ship operating range. Previous studies have shown that superconducting homopolar motors are well suited to Navy propulsion systems due to their inherent low noise generation, high power density, and efficiency. Homopolar motors are the only true direct current electrical motors and produce very smooth torque because they have no magnetic field pulsations or alternating currents. The Annapolis Laboratory of the Naval Surface Warfare Center is reexamining superconducting homopolar motor technology in light of the resurgent interest in a more electric Navy and because of significant advancements in two key homopolar component technologies. Extensive development of mechanical cryogenic refrigerators has resulted in liquid cryogen‐free superconducting magnets. Magnet systems utilizing cryogen‐free technology have been kept at superconducting temperatures for over two years (18,000 hrs.) with no maintenance. Development of dry copper‐fiber and multiple‐foil copper brushes has eliminated the need for liquid metal current collectors used in early homopolar motors. Basic wear measurements imply replacement times of tens of thousands of full‐power motor hours. Superconductive homopolar motor designs utilizing the new solid collectors are comparable in size to those for previous designs, and show only small increases in machine size as voltage increases from 200V to 2,000V As a result, the operating voltage of a homo‐polar machine can now be selected on an overall system basis in the same way as conventional alternating current systems. Advances in these key technologies and the promising results of the ship impact assessments indicate that a closer examination of superconducting homopolar motors for propulsion is warranted.

Closed Cycle Gas Turbine Nuclear Power Plant for Submarine Propulsion

ABSTRACT The pressurized light water reactor (PWR) propulsion plant and related machinery occupy about 50% of the interior usable volume of present nuclear attack submarines. If a smaller general purpose attack submarine with significant warfare capability is desired, then substantial reductions in size will require new, innovative technology for the propulsion plant. One such technology with promise for a revolutionary improvement in nuclear propulsion system performance in a reduced physical envelope is a high temperature gas‐cooled reactor (HTGR) as the heat source in a closed gas turbine (Brayton) cycle driving an advanced electric propulsion plant. Direct and indirect closed Brayton cycle gas turbine propulsion plant parameters are developed for a reference attack submarine.

Two-dimensional magnetic field evolution measurements and plasma flow speed estimates from the coaxial thruster experiment

Local, time-dependent magnetic field measurements have been made in the Los Alamos coaxial thruster experiment (CTX) [C. W. Barnes et al., Phys. Fluids B 2, 1871 (1990); J. C. Fernández et al., Nucl. Fusion 28, 1555 (1988)] using a 24 coil magnetic probe array (eight spatial positions, three axis probes). The CTX is a magnetized, coaxial plasma gun presently being used to investigate the viability of high pulsed power plasma thrusters for advanced electric propulsion. Previous efforts on this device have indicated that high pulsed power plasma guns are attractive candidates for advanced propulsion that employ ideal magnetohydrodynamic (MHD) plasma stream flow through self-formed magnetic nozzles. Indirect evidence of magnetic nozzle formation was obtained from plasma gun performance and measurements of directed axial velocities up to vz∼107 cm/s. The purpose of this work is to make direct measurement of the time evolving magnetic field topology. The intent is to both identify that applied magnetic field distortion by the highly conductive plasma is occurring, and to provide insight into the details of discharge evolution. Data from a magnetic fluctuation probe array have been used to investigate the details of applied magnetic field deformation through the reconstruction of time-dependent flux profiles. Experimentally observed magnetic field line distortion has been compared to that predicted by a simple one-dimensional (1-D) model of the discharge channel. Such a comparison is utilized to estimate the axial plasma velocity in the thruster. Velocities determined in this manner are in approximate agreement with the predicted self-field magnetosonic speed and those measured by a time-of-flight spectrometer.

Advanced Electric Propulsion, Power Generation, and Power Distribution

ABSTRACTInvestigations into the development of electric drive systems for both submarines and surface ships have been ongoing for several years. These studies led us to the conclusion that accepted contemporary concepts did not offer the full potential envisioned for electric drive. These concepts did not fully consider non‐developmental (existing) technology, and the evolutionary approach to system development did not adequately address ship system interface, cost and other shipbuilder concerns.A “clean sheet” approach was taken to designing advanced electric propulsion, generation and power distribution systems and equipment. Primary objectives were reduced cost, weight, and volume with improved arrangement flexibility, operation, power allocation, growth potential, reliability, maintainability, survivability and efficiency.This paper focuses on the technologies involved with component development, the installation of the system on a typical submarine, and the resulting benefits.

Electric propulsion: An evolutionary technology

The NASA Lewis Research Center (LeRC) conducts and directs an electric propulsion research and technology program aimed at providing high-performance electric propulsion system options for a broad range of near and far-term missions. This evolutionary program emphasizes the development of propulsion systems for three classes of missions: (1) near term auxiliary propulsion applications such as North-South Stationkeeping for next generation communications satellites and orbit maintainence for orbiting platforms such as Space Station Freedom; (2) advanced solar electric propulsion and SP-100-class nuclear electric propulsion for Earth-space orbit transfer and robotic planetary missions; and (3) very high power systems to support major space missions including the Space Exploration Initiative. To cover widely disparate mission requirements, the LeRC program includes research on electrothermal, electrostatic, and electromagnetic systems. This paper provides an overview of the LeRC program with a focus on recent progress.

Characterization of advanced electric propulsion systems

Covers advancements in spacecraft and tactical and strategic missile systems, including subsystem design and application, mission design and analysis, materials and structures, developments in space sciences, space processing and manufacturing, space operations, and applications of space technologies to other fields.