SERT II
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The SERT II development program which started in 1966 included thruster ground tests of 6742 hours and 5169 hours duration. A prototype version of the SERT II spacecraft was ground-tested for a period of 2400 hours with an operating ion engine. The spacecraft was launched into a 1000-km-high polar orbit on February 3, 1970. In addition to diagnostic equipment and related IPS hardware, the spacecraft had two identical 15 cm diameter, mercury ion engines and two PPUs. Flight objectives included in-space operation for a period of 6 months, measurement of thrust, and demonstration of electromagnetic compatibility. The thruster maximum power level was 0.85 kW, and this provided operation at a 28-mN thrust level at 4200 s specific impulse. Flight data were obtained from 1970 to 1981 with an ion engine operating intermittently in one of three different modes, namely, HV ion extraction, discharge chamber operation only, or just neutralizer operation.
Major results were that two mercury engines thrusted for periods of 3781 hours and 2011 hours. Test duration was limited due to shorts in the ion optical system. Thrust measured in space and on the ground agreed within the measurement uncertainties. Up to 300 thruster restarts were demonstrated. A PPU accumulated nearly 17,900 hours during the course of the mission. Additionally, the IPS was electromagnetically compatible with all other spacecraft systems.
Major results included, two mercury thrusters operated for 2011 hrs and 3781 hrs. Test duration was limited due to shorts in the ion optical system. Thrust measured in space and on the ground agreed within measurement uncertainties. Up to 300 thruster restarts were demonstrated. A PPU accumulated nearly 17,900 hrs during the mission. The IPS showed that it was EM compatible with all other spacecraft systems.
The preceding was an excerpt from:
Sovey, J. S., Rawlin, V. K., and Patterson, M. J.: "Ion Propulsion
Development Projects in U. S.: Space Electric Rocket Test 1 to Deep Space
1." Journal of Propulsion and Power, Vol. 17, No. 3, May-June 2001, pp.
517-526.