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DS1 Flight Spare Ion Thruster Keeps on Ticking

At the end of August the ongoing life test of the Deep Space 1 Flight Spare Ion thruster passed a major milestone by processing 200 kg of xenon propellant. This remarkable achievement is a tribute to everyone at NASA's Glenn Research Center, Boeing, and JPL who participated in the development of the thruster, and to the team at JPL, now being led by Anita Sengupta, who have executed this enormously difficult test.

A throughput of 200 kg per thruster, in addition to being a nice round number, is required for the ion propulsion system on the Dawn spacecraft to be single fault tolerant throughout the mission. Many other potential near-term SEP missions will also benefit from the higher throughput that this test (and supporting analyses) enable.

The thruster continues to operate well after 24,700 hours. It is fairly clear now that the first failure mode for the thruster operating at full power is electron backstreaming that results from erosion of the holes in the outer grid of the ion accelerator system. We expect to reach this point in November, after which the thruster will no longer function at full power, but will still be fully functional at the low-power end of the throttle range. Many missions, including Dawn, require extended operation at the low power end of the throttle range during the later stages of the mission.