Hall effect thruster

A Hall Drive or Hall effect drive (English Hall Effect Thruster, Hall Thruster ) is a drive for spacecraft, in which positive ions are accelerated by an electric field to velocities between 10 and 80 km / s. The resulting pulse can be used by recoil principle to accelerate the spacecraft. As typical support mass xenon is used, but other rare gases such as krypton or argon are also suitable, as well as metals such as bismuth, magnesium, or zinc, or also iodine. The typical power requirement is a few 100 to 1000 W, but there have also been engines with up to 100 kW successfully tested on the ground.

Because of their similarity with ion drives, they are also often referred to as Hall ion thrusters, however, there are two engine types have different physical processes underlying that require more and more a demarcation.

History

Research and development of Hall drives date back to the 1960s, especially in the United States and the former Soviet Union. In particular, there was the Hall driving the Kaliningrad company FAKEL brought to flight maturity and are used successfully for the first time in 1971 on the satellite METEOR. Since then, more than 50 satellites were equipped with drives the company FAKEL. Developments in the USA, however, ran to the related grid ion thrusters.

Even during the Cold War, and especially after the fall of the Iron Curtain, the technology of Hall Drive in the western world was exported, and developments in France ( SNECMA ) and Italy ( Alta Space) and the USA ( Busek, Aerojet, JPL, NASA and the U.S. Air Force research Laboratories) made ​​it partly to flight application and commercialization. SMART -1 is the first European Hall Drive ( Snecma ) has been used successfully for a flight mission in 2003. The first test flight of an American Hall Drive ( Busek ) was held in 2006, the first American aircraft use, with such a drive ( Aerojet ) in 2010. In German-speaking countries is not yet researched or developed at Hall drives.

Although research is being conducted in East Asia, particularly in Japan, since the 1980s at Hall drives, yet no drive has found application in space. A South Korean drive from Satrec scheduled to fly on the satellite DubaiSat 2, 2013.

Structure and Classification

In the early days of the development of Hall drives in the Soviet Union, two different subtypes formed, which were investigated and further developed by various research groups. These differ mainly in geometry and materials used, but based around the same principle of action. Throughout history, both types were given different names, so that even today different names refer to the same type.

This Hall drives can be in the following sub- types continue to classify:

• Drive with large acceleration channel: engl. Stationary Plasma Thruster ( SPT), Russ стационарный плазменный двигатель ( СПД ). Alternative names are engl. Propulsion Plasmique Stationaire ( PPS) or Magnetic layerType (Eng. magnetic layer drive)
• Drive with a narrow acceleration channel: engl. Thruster with Anode Layer ( TAL), Russ двигатель с анодным слоем ( ДАС )

Both types have in common that they consist of an annular accelerating channel having at one end a hollow anode is mounted (SPT), or is formed by a hollow anode (TAL). SPT in the channel by means of a ceramic is formed (e.g., boron nitride), and the choice of material is essential for the life of the engine. The accelerating voltage on the anode potential is applied. The duct is concentrically surrounded by a magnet system, which is often formed by the coil, but the permanent magnets are also occasionally used. The resulting magnetic field passes through the duct, and the shape of the magnetic field lines and is critical to the performance characteristic of the engine. From an attached outside the annular drive cathode, electrons are emitted that are "trapped" in the magnetic field inside the anode, since they can no longer move out of the field. The combination of magnetic field and the prevailing between anode and cathode electric field occurs due to the Hall effect to a drift motion in the azimuthal direction, which was eponymous for these engines.

If now through the anode, the support material, usually xenon supplied, so the atoms collide with the trapped electrons and it comes to impact ionization. The ions formed are detected immediately by the electric field, accelerated and ejected from the channel of the drive, so that the thrust of the engine is achieved. Since the mass of the ions is much greater than that of the electrons, the magnetic field has less influence, so that the ions can freely pass through the channel.

The shear achieved is in the order of 10 to 100 mN, that is comparatively great for an electric engine. Through years of optimization model aircraft have been achieved with thrust efficiencies above 50 %, so an application of these engines is so attractive. In experimental models have efficiencies have been realized up to 75 %.