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After successfully completing the Deep Space 1 mission, work
started toward the development of a higher power, high performance ion
propulsion system. A development program was needed to develop a new ion PPU to
provide much higher voltages required for high specific impulse and to overcome
some of the difficulties encountered with the NSTAR PPU design.
In 2000, Boeing Electron Dynamic Devices was competitively selected to
develop a new beam supply for this PPU. This effort resulted in a beam power
module, shown in Figure 1, that used a dual-mode (phase-shift and pulse-width
modulation) full-bridge converter and a higher switching frequency to process up
to 1 kW of power at efficiencies in excess of 96%. Multiple modules can be
paralleled to scale the design to high power. In 2002, this effort was
rolled-over to the NEXT program to complete the development of a full 7.0 kW
breadboard PPU, shown in Figure 2. The rest of the power supplies for the PPU
were based on the NSTAR design but operating at higher frequency to reduce PPU
mass.
In August 2003 at the end of Phase 1, this breadboard PPU was successfully
integrated with a 40-cm NEXT engineering model thruster and a propellant
management system (PMS) in VF-5. An engineering model PPU will be developed in
Phase 2.
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