Results of an on-going long duration ground test of the DS1 flight spare ion engine

TLDR

The DS1 night spare thruster (FT2) is undergoing ground testing. FT2 has operated over 4500 hours, showing a ~3000‑hour transient with reduced efficiency and 2 % lower flow rates compared to EMT2, but after the transient its performance matches EMT2 except for a 6‑V lower electron backstreaming margin.

Abstract

Ground testing of the DS1 night spare thruster (FT2) is presently being conducted. To date, the thruster has accumulated over 4500 hours of operation. Comparison of FT2 with the performance of the engineering model thruster 2 (EMT2) during the 8.2 khr test shows a transient, lasting for about 3000 hours, during which the discharge chamber efficiency decreases for both thrusters. The flow rates are 2% lower for FT2 than for EMT2 and the discharge chamber performance is 4.5% lower for FT2 during the transient. Sensitivity data obtained during the test show that the lower flow rate accounts for about half of the observed difference. After the initial transients decay, the performance of both thrusters is comparable with the exception of the electron backstreaming margin--which is 6 V lower for FT2.