Outer planet missions with electric propulsion systems--part I.(Research Article)(Report)

1. Introduction

In October 1998, NASA launched Deep Space 1 (DS1) that was the first deep space mission having been propelled by solar electric propulsion [1, 2]. Later, Smart-1 (ESA-2003) and Hayabusa (Japan-2003) were launched. With the successful demonstration made by the Deep Space 1, many studies have been performed to show the applicability and performance of Solar Electric Propulsion (SEP) for deep space missions [3].

A Neptune Orbiter mission is examined utilizing single propulsion systems and combinations of Solar Electric Propulsion (SEP), Radioisotope Electric Propulsion (REP), and chemical systems to compare the concepts (5). Electric propulsion systems, while highly efficient, produce only a small thrust value; this is why electric propulsion is also called low thrust. As a consequence, the engine operates in long arcs of the trajectory.

[FIGURE 1 OMITTED]

Several U.S.A space missions used Radioisotope Electric Propulsion (REP) system. In particular, some of them used generator of the radioisotope thermoelectric type (Lincoln Experimental Satellite "LES" 8 and 9, Voyager 1 and 2, Galileo, Ulysses, Cassini, New Horizons). Nuclear Electric Propulsion (NEP) uses a reactor power system to provide the electricity for thrusters that ionize and accelerate propellant to produce thrust. The combination of nuclear electric power systems and electric thrusters has been studied by NASA and other agencies since the 1950s. Reactor power system design and development has received considerable attention, despite only one U.S space flight experience, the SNAP-10A (Systems Nuclear Auxiliary Power Program).

[FIGURE 2 OMITTED]

Figure 1(a) shows the availability of energy of several sources. Notice that the radio isotopic (REP) and nuclear electric propulsion (NEP) have more advantage when compared to the solar electric propulsion (SEP) for a long time trip. The variation of the solar power with the distance from the Sun is shown on Figure 1(b).

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