To realize the substantial performance benefits offered by low power arcjets in geosynchronous stationkeeping applications, lifetimes on the order of hundreds of hours are required. The principal life determining factor for an arcjet is the rate at which the electrodes erode during long periods of operation with many restarts. There are two potential erosion phenomena of primary importance. Startup erosion, in the form of spalling from thermal shock or localized melting of electrode materials, results when overly high current densities are allowed to occur. Steady-state erosion, during long duration exposure to the arc plasma, may result from chemical incompatibilities, or as in the case of the cathode tip, from sheath phenomena at arc attachment points. Startup and steady-state erosion are not entirely separable. Startup characteristics depend strongly on the relative electrode geometry, and, if these relations are altered during steady-state operation, the startup transients will change. The arcjet power supply and the gas dynamic flow field also help determine erosion rates. Extending arcjet lifetime involves resolving a complex and highly interactive set of factors. This paper summarizes the results of arcjet lifetime testing aimed at understanding and minimizing electrode erosion. Materials compatibility with N2H4, the dependence of electrode erosion on the geometry and flow field, and erosion effects associated with the arcjet power supply are the three key areas of investigation. The results reported are for thrusters using either decomposed N2H4 or cold mixed gases over a range of power from 900 W to 2000 W.
Low power arcjet life issues
Betrachtungen zur Lebensdauer von elektrothermischen Systemen niedriger Energie
AIAA-Papers ; May ; 1-11
1987
1 Seite, 19 Bilder, 1 Tabelle, 9 Quellen
Conference paper
English
AIAA | 1987
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