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IAPS

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Date: 1974-1983. Specific impulse: 2,500 s.

The Ion Auxiliary Propulsion System project and other preflight technology work took place in the 1974 to 1983 timeframe. Flight test objectives were to verify in space the thrust duration, cycling, and dual thruster operations required for station-keeping, drag makeup, station change, and attitude control. This implied demonstration of overall thrusting times of 7,000 hours and 2500 on/off cycles.

The 8 cm diameter, mercury ion engine input power was 0.13 kW, and the thrust was 5.1 mN at a specific impulse of 2500 s. The masses of the flight thruster-gimbal beam shield unit, the PPU, and the digital controller were 3.77 kg, 6.85 kg, and 4.31 kg, respectively. The system stored 8.63 kg of mercury, and the propellant storage system weighed 1.56 kg. The IAPS successfully completed all flight qualification tests and was installed on an Air Force technology satellite. The flight of the Teal Ruby spacecraft was canceled by the Air Force due to lack of funding.

During the course of the technology and preflight programs there were a number of endurance test performed. A laboratory-type 8 cm engine was tested for 15,040 hours and 460 cycles at the 0.14kW level. An engineering model IAPS engine and PPU were successfully tested for 9,489 hours and 652cycles. The thruster and PPU were located in the same vacuum chamber during this test. In another test, an engineering model thruster was operated at full-thrust for 7112 hours and had 2571 restarts. There were no major changes in thruster performance, and no life-limiting degradation effects were observed. A single PPU was used to run two tests and had operated for 14,000 hours without malfunction.

Electrical Input Power: 0.13 kW.