A Graphite Orificed Hollow Cathode for an Argon Magnetoplasmadynamic Thruster

Abstract

An orificed hollow cathode with a lanthanum hexaboride insert is implemented for an argon-fed magnetoplasmadynamic thruster (MPDT) to investigate cathode life extension technology. The design of the cathode is developed and justified, and the design of an accompanying thruster for test purposes is detailed. Finite element models are built to ensure the thermal and static stability at steady-state of the operating thruster. Upon firing, it is found that the cathode ablates at a much higher rate with the lanthanum hexaboride insert than without it present. This may be due to a number of confounding factors, including water vapor retention, too-dense current densities, or mass transfer onto the insert. Further research is warranted into graphite orificed hollow cathodes, especially in regards to keeper technology, to prevent ion bombardment and improve cathode life.