Magnetic field oscillating amplified thruster

The Magnetfeldoszillationsantrieb (English magnetic field oscillating amplified thruster, MOA), often referred to in the press as a plasma thruster, is a versatile electro- thermo- dynamic system that is able to accelerate nearly every medium to high outflow velocities and thus expel a plasma jet.

To accomplish this, the system uses so-called Alfvén waves back, a physical principle of magnetohydrodynamics, which was first predicted by the later Nobel laureate Hannes Alfvén in 1942 and stating that varying magnetic fields in electrically conductive media (eg plasma, saline water, etc.) density waves cause. These waves are able to entrain particles in the medium with and to accelerate them to very high velocities (or high-energy).

Areas of application

Because of the high attainable exhaust velocity and high specific impulse associated or high particle there are two main application areas: space and the surface treatment of certain materials ( coating). In the first case, the high exhaust velocity due to the high energy means a much smaller mass support requirement compared to conventional ion thrusters, in the second case a large penetration depth into the material to be treated. Thus, for example, steel, aluminum, glass and plastics, but also can be cured as desired and adapted to the required properties.

Apart from the high particle energies and outflow velocities, the MOA concept also has the advantage that it is largely free of corrosion. The magnetic fields, which come to generate the Alfvén waves are used, prevent the high-energy particles come with the wall or other structure component into contact and thereby cause damage.

Structure of the MOA system

Substantially all of the MOA system consists of five sub-elements:

• Plasma source,
• A central tube,
• Primary coil,
• Secondary coil,
• Supply and control unit.

The plasma generator produces a continuous stream of ionized particles which drift towards the outlet nozzle in the central tube. These particles may be, for example nitrogen or hydrogen molecules, as well as atoms of the noble gases argon or xenon. Since they are ionized, they react to the two magnetic fields, which are defined by the primary and the secondary coil. The primary coil is permanently in operation and forms the magnetic nozzle while the secondary coil is cyclically turned on and off so as to deform the field lines in the overall system. This deformation creates the Alfvén waves which are used to transport and the compression of the drive medium in the next step. The entire system is controlled by the supply and control unit.

Since the MOA approach requires a plasma source to generate the ionized particles, it is in principle an electric drive system, like other ion propulsion too. By the interaction of the magnetic fields which bunches are also compressed and heated, thus forming an electrostatic thermodynamic system is obtained from the overall system. This combination of electric and thermodynamic system combines the advantages of both areas, as it has on the one hand the high efficiency of electric drive systems, but can also accelerate a variety of particles - such as a thermal system - and thus produce a relatively high boost. The combination of high particle energy and outflow velocity and relatively high thrust is exceptional in this form. The high flexibility by changing the mass flow or of the electrical power is unique at this time.

State of development

Once a drive has been proposed on the basis of Alfvén waves mid -1980s, the MOA concept was first implemented at the Technical University Graz. At the Institute of Communication Networks and Satellite Communications also the prototype of the engine has been tested in a vacuum chamber and the measurement results confirmed the feasibility of the project. The data were presented at the International Astronautical Congress in Fukuoka, Japan, on 21 October 2005. The company Qasar Technologies GmbH newly established to implement the technology will continue to develop and test potential terrestrial applications, both with respect to a possible application in aerospace, as well as for the surface treatment. In the summer of 2005, the MOA prototype has the TRL 5 (Technology Readiness Level ) achieved, and thus demonstrated its function in a relevant environmental conditions (vacuum chamber ).

Possible prospects for the technology, scientists can see the air and space company EADS, aircraft manufacturers such as Boeing, Hughes Network Systems and Alcatel Alenia Space and materials specialists and the automotive industry.