Alex L. Hall Thruster S.I.N.-March 2009

This post builds on the post “The Ion Thruster”; it adds the Hall Thruster to the discussion.  The same source, the article called New Dawn for Electric Rockets by Edgar Y. Choueiri, published on the 58th page of the February 2009 issue of Scientific American, was used.  Simply put, the technology under discussion, rockets designed with electric plasma engines (EPE’s), is a relatively new technology that uses electricity to accelerate particles, thus providing acceleration in the opposite direction to the rocket in question.  EPE’s generate a much lower magnitude of thrust then a conventional chemical rocket; however, this force of acceleration can be applied for much longer, yielding a higher final velocity.  Because this magnitude is lower, this technology can only be applied outside of the atmosphere.

The most recent thruster to become a viable option for use and travel is the Hall Thruster.  Named after Edwin H. Hall, who discovered the underlying effect in 1879.  This thruster has higher thrust, but is less efficient (only 45% to 60% vs. 60% to 80%) and requires more power.  Because of the method of propulsion, this thruster attains higher exhaust velocity.  It achieves this by using what is termed the Hall current (the principle behind this current is that when two magnetic fields are placed perpendicular in a conductor the electric current will flow perpendicular to the two fields.)  The radial magnetic field causes the electrons from the Hall current to circle and accelerate about the central anode.  An external cathode provides negatively charged electrons, while Xenon atoms are injected.  The interactions between the Xenon atoms, the electrons, the Hall current, and the radial magnetic field causes the Xenon atoms to collide with the whirling electrons; which then cause the Xenon atoms to devolve into ions, forming plasma.  The plasma is then accelerated by the electro-magnetic field generated by the Hall current’s interaction with the radial magnetic field.  This technology has higher power density because it avoids the issue of the electron build up from the Ion Thruster. 

The technology in the Hall Thruster allows us to travel further then would the Ion Thruster, allowing us to explore and thrive in a way previously unachievable.