ESA develops power system for ion propulsion engines

I did some research about alternative ways to power ion propulsion engines upon my return from the NASA JPL, after witnessing the rocket engine's new design and tests.

I was intrigued by a neat design for power management for ion propulsion engines funded by the Spanish Ministry of Science. The design was proposed for BepiColombo, a European Space Agency (ESA) mission in cooperation with Japan to explore Mercury, the closest planet to our Sun, in 2017.

The main power source being considered will be a 14kW (Gallium Arsenide triple junction cells) solar array. The power from the solar panels will be conditioned by the power conditioning and distribution unit (PCDU) to create the main 100V regulated bus that will power the ion propulsion engine. When solar panels are used to supply power to an electric propulsion system it is then known as solar electric propulsion (SEP).

A sequential switching shunt maximum power regulator (S3MPR) was proposed. This design will consist of two independent regulators, the first to control the maximum power point 1 (MPP1) bus (solar array [SA] power) and the second to control the electronic propulsion (EP) bus output voltage. It is noted that the most widely used regulator for fast control of the solar array power is the sequential switching shunt regulator (S3R).

For the control of the output electric propulsion voltage the Weinberg Boost Regulator was chosen due to its typical use as a high power boost architecture. The switching shunt regulator controls the solar array to operate at its MPP bus voltage (Vmpp) at all times with a voltage reference derived from a MPP detector.

The SA control functions like a standard regulated bus S3R, with the exception that the fixed reference voltage is replaced by the variable MPP detector reference voltage. The MPP bus voltage is stepped up by a set of Weinberg Boost Regulators, operating in parallel, to generate the 100V EP regulated bus needed for the engine (Figure 1).

Figure 1: A block diagram of the power conditioning and distributed unit proposed in "Power System for Electrical Propulsion in Space Applications" (Reference 1).

This design is one architectural solution to drive an ion propulsion engine. An ideal solution would be to drive the engine directly from the solar panels in the future. Does anyone know of any ideas to help implement that goal?

- Steve Taranovich

Reference

Power System for Electrical Propulsion in Space Applications, E. Maset, E. Sanchis-Kilders, A. Ferreres, J.B. Ejea, V. Esteve, J. Jordan, A. Garrigos, J.M. Blanes, A.H. Weinberg, LEII / University of Valencia, University Miguel-Hernandez, Weinberg Electronic Innovations Ltd.