Main Belt Asteroid Sample Return Mission Using Solar Electric Propulsion
- Paper number
IAC-07-A3.5.07
- Author
Dr. Bernd Dachwald, German Aerospace Center (DLR), Germany
- Coauthor
Dr. Wolfgang Seboldt, German Aerospace Center (DLR), Germany
- Coauthor
Dr. Horst W. Loeb, University of Giessen, Germany
- Coauthor
Dr. Karl-Heinz Schartner, Giessen University, Germany
- Year
2007
- Abstract
In 1995, a European-Russian Joint Study Group (JSG) presented a study report on “Advanced Interplanetary Missions Using Nuclear Electric Propulsion” (NEP). One of the investigated reference missions was a sample return from the main belt asteroid (19) Fortuna, another one was a mission to Mercury. The envisaged nuclear power plant Topaz-25, however, could not be realized and also the worldwide developments in space reactor hardware stalled. In the meantime, the Mercury mission became an ESA cornerstone mission, BepiColombo, based, however, on solar electric propulsion (SEP). Consequently, the question arose whether SEP might also be profitable for missions into the outer regions of the solar system. To assess the prospects of SEP for this kind of missions, the German Space Agency placed a study contract to the University of Giessen, with a sub-contract to the German Aerospace Center. This paper describes the results of this study for the SEP Fortuna sample return mission and compares them to corresponding chemical and NEP results. Our results show that a main belt asteroid sample return mission is feasible with existing SEP technology. The mission duration is longer than for a NEP spacecraft, but the launch mass is significantly smaller. After having reviewed the existing EP hardware in Europe, we have decided to employ for our proposed mission the RIT-22 ion thruster, which is based on the existing flight-proven RIT-10 ion thruster and which is currently under qualification at EADS-ST and the University of Giessen. Our concept employs three RIT-22. With a power consumption of 6.2 kW, each thruster provides a thrust of 175 mN at a specific impulse of 4763 s. For the power subsystem, conventional Si HI-ETA solar cells are used. It is designed to produce at BOM (begin of mission) the power that is required by the three RIT-22 ion engines at full thrust, 18.6 kW. This yields a solar array mass of 245 kg. In our trajectory calculations, we have also considered the degradation of the solar cells and their efficiency-dependence on temperature. Having arrived at Fortuna, the spacecraft drops during its stay a small autonomous surface package to sample the asteroid. The collected samples are then returned to Earth, where the spacecraft releases its 21-kg re-entry capsule to enter the atmosphere with a velocity of 12.35 km/s, less than NASA’s Stardust capsule. In total, our SEP spacecraft has a mass of 1665 kg, which has to be injected into an interplanetary transfer trajectory with zero hyperbolic excess velocity.
- Abstract document
- Manuscript document
IAC-07-A3.5.07.pdf (🔒 authorized access only).
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