Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Wall-less Hall thruster may power future deep space missions

28.10.2015

French scientists have experimentally optimized the operation of the first wall-less Hall thruster prototype, a novel electric rocket engine design suitable for long-duration, deep space missions

Hall thrusters are advanced electric rocket engines primarily used for station-keeping and attitude control of geosynchronous communication satellites and space probes. Recently, the launch of two satellites based on an all-electric bus has marked the debut of a new era - one in which Hall thrusters could be used not just to adjust orbits, but to power the voyage as well. Consuming 100 million times less propellant or fuels than conventional chemical rockets, a Hall thruster is an attractive candidate for exploring Mars, asteroids and the edge of the solar system. By saving fuel the thruster could leave room for spacecraft and send a large amount of cargo in support of space missions. However, the current lifespan of Hall thrusters, which is around 10,000 operation hours, is too short for most space explorations, which require at least 50,000 operation hours.


PPS-FLEX firing in wall-less mode in the PIVOINE-2g vacuum chamber.

Credit: CNRS/LAPLACE and CNRS/ICARE

To prolong the lifespan of Hall thrusters, a team of researchers from the French National Center for Scientific Research have experimentally optimized the operation of a novel, wall-less thruster prototype developed a year ago by the same team. The preliminary performance results were satisfactory, the team said, and pave the way toward developing a high-efficiency wall-less Hall thruster suitable for long-duration, deep space missions. The researchers present their work in a paper published this week in the journal Applied Physics Letters, from AIP Publishing.

Hall thrusters are electric rocket engines using a super high speed (on the order of 45,000 mph) stream of plasma to push spacecraft forward. Their operating principle relies on the creation of a low-pressure quasi-neutral plasma discharge in a crossed magnetic and electric field configuration. The propellant gas, typically xenon, is ionized by electrons trapped in the magnetic field.

In the conventional Hall thruster configuration, the magnetized discharge is confined to an annular dielectric cavity with the anode at one end, where the gas is injected, and an external cathode injecting electrons. Ionization of the propellant gas occurs inside the cavity, with ions accelerated by the electric field that stretches from the interior to the exterior of the cavity.

"The major drawback of Hall thrusters is that the discharge channel wall materials largely determine the discharge properties, and consequently, the performance level and the operational time," said Julien Vaudolon, the primary researcher in the Electric Propulsion team led by Professor Stéphane Mazouffre in the ICARE-CNRS Laboratory, France.

Vaudolon explained that the wall materials play a role in the plasma properties mainly through secondary electron emission, a phenomenon where high-energy ions hit the channel wall surface and induce the emission of secondary electrons. Additionally, the erosion of the discharge cavity walls due to bombardment of high-energy ions shortens the thruster's lifetime.

"Thus, an effective approach to avoid the interaction between the plasma and the discharge channel wall is to move the ionization and acceleration regions outside the cavity, which is an unconventional design named a Wall-Less Hall Thruster," Vaudolon said.

Last year, the team developed a small-scale, wall-less thruster prototype based on a classical Hall thruster. At first the researchers simply moved the anode to the channel exhaust plane. However, this first wall-less thruster turned out to be a low-performance device, as the magnetic field lines are perpendicular to the thruster axis, which cross the anode placed at the channel exhaust plane.

"Magnetic fields are used to trap hot electrons injected from the external cathode and prevent them from reaching the anode," Vaudolon said. "Basically an electron travels along the magnetic field line. If the magnetic field lines cross the anode, a large portion of hot electrons will be collected at the anode and won't take part in the ionization of the xenon atoms, resulting in high discharge current, low ionization degree, and consequently, low performance level."

To optimize the wall-less prototype and make the magnetic lines avoid the anode surface, the team rotated the magnetic barrier by 90 degrees, so that it injected the magnetic field lines parallel with the axial direction. The anode was still placed at the channel exhaust plane, but its shape is curved to avoid any interaction with the magnetic field lines.

Based on the PPS-Flex, a 1.5 kilowatts class thruster designed by the GREM3 Team at LAPLACE Laboratory, France and capable of modifying the magnetic field topology over a broad range of configurations, the team has validated their optimization strategies by modifying several parts and parameters of the thruster. The measurement of some operation parameters such as the thrust level, anode efficiency and far-field ion properties displayed a satisfactory performance level. However, Vaudolon said, some further optimization is still needed for the thruster's efficient operation at high power.

"The wall-less thruster allows scientists to observe regions of the plasma previously hidden behind the channel walls. Now the plasma region can be observed and diagnosed using probes and/or laser diagnostic tools," Vaudolon said. He also pointed out that the access to key regions of the plasma facilitates a thorough investigation of plasma instability and small-scale turbulence for a better understanding of the discharge physics and anomalous electron transport.

"Despite decades of research, the physics of Hall thrusters is still far from being understood, and the device characterization methods still rely on trials and testing, leading to expensive efforts," Vaudolon said. "The major difficulty in developing predictive simulations lies in modeling the interaction between plasma and wall. The wall-less design would be an effective solution, potentially making future predictive simulations feasible and reliable."

After the lessons learned from the testing of the PPS-Flex version, the team's next step is to design a dedicated wall-less Hall thruster and fully exploit the possibilities offered by a wall-less architecture.

###

The article "Optimization of a wall-less Hall thruster," is authored by Julien Vaudolon, Stéphane Mazouffre, Carole Hénaux, Dominique Harribey and Alberto Rossi. It will be published in the journal Applied Physics Letters on October 27, 2015 (DOI: 10.1063/1.4932196). After that date, it can be accessed at: http://scitation.aip.org/content/aip/journal/apl/107/17/10.1063/1.4932196

The authors of this study are affiliated with the French National Center for Scientific Research, ICARE Laboratory and LAPLACE Laboratory.

ABOUT THE JOURNAL

Applied Physics Letters features concise, rapid reports on significant new findings in applied physics. The journal covers new experimental and theoretical research on applications of physics phenomena related to all branches of science, engineering, and modern technology. See: http://apl.aip.org

Media Contact

Jason Socrates Bardi
jbardi@aip.org
240-535-4954

 @jasonbardi

http://www.aip.org 

Jason Socrates Bardi | EurekAlert!

More articles from Physics and Astronomy:

nachricht Computer model predicts how fracturing metallic glass releases energy at the atomic level
20.07.2018 | American Institute of Physics

nachricht What happens when we heat the atomic lattice of a magnet all of a sudden?
18.07.2018 | Forschungsverbund Berlin

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Future electronic components to be printed like newspapers

A new manufacturing technique uses a process similar to newspaper printing to form smoother and more flexible metals for making ultrafast electronic devices.

The low-cost process, developed by Purdue University researchers, combines tools already used in industry for manufacturing metals on a large scale, but uses...

Im Focus: First evidence on the source of extragalactic particles

For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.

To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...

Im Focus: Magnetic vortices: Two independent magnetic skyrmion phases discovered in a single material

For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.

Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...

Im Focus: Breaking the bond: To take part or not?

Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.

A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...

Im Focus: New 2D Spectroscopy Methods

Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.

"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Leading experts in Diabetes, Metabolism and Biomedical Engineering discuss Precision Medicine

13.07.2018 | Event News

Conference on Laser Polishing – LaP: Fine Tuning for Surfaces

12.07.2018 | Event News

11th European Wood-based Panel Symposium 2018: Meeting point for the wood-based materials industry

03.07.2018 | Event News

 
Latest News

A smart safe rechargeable zinc ion battery based on sol-gel transition electrolytes

20.07.2018 | Power and Electrical Engineering

Reversing cause and effect is no trouble for quantum computers

20.07.2018 | Information Technology

Princeton-UPenn research team finds physics treasure hidden in a wallpaper pattern

20.07.2018 | Materials Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>