Mission Design for a SEP Mission to Saturn

Paper number

IAC-09.C4.8.7

Author

Prof. Bernd Dachwald, University of Applied Sciences Aachen / FH Aachen, Germany

Coauthor

Mr. Andreas Ohndorf, DLR GSOC, Germany

Coauthor

Mr. Jörn Spurmann, DLR GSOC, Germany

Coauthor

Dr. Horst W. Loeb, University of Giessen, Germany

Coauthor

Dr. Karl-Heinz Schartner, Giessen University, Germany

Coauthor

Dr. Wolfgang Seboldt, German Aerospace Center (DLR), Germany

Year

2009

Abstract

The massive interest in outer solar system exploration was recently confirmed by the proposed NASA and ESA flagship missions to Jupiter and Saturn. Within Europe, the Titan AND Enceladus Mission (TANDEM), a mission to explore the Saturnian System with special emphasis on the two moons Titan and Enceladus, was selected for study within ESA's Cosmic Vision 2015-2025 plan. TANDEM was later incorporated into a joint NASA/ESA Titan Saturn System Mission (TSSM) proposal. Very recently, however, it was given second priority w.r.t.\ the joint NASA/ESA Europa Jupiter System Mission (EJSM) proposal.

In this paper, an optimized mission design for a TANDEM-based solar electric propulsion (SEP) mission is described, a mission design that proves the capability of SEP even for missions into the outer solar system. Albeit the very recent programmatic developments, the proposed mission design remains valid and TSSM might be resumed in the future. As a suitable gravity assist sequence for a chemical transfer to Saturn is not available between 2015-2025, we investigate a SEP mission scenario for the interplanetary transfer, the propulsion system being based on the German RIT ion engine. As compared to previous Titan explorer studies that use SEP, an extended exploration of the spacecraft parameter space is performed within this paper and the optimal interplanetary trajectory is calculated for each setting. The design parameters are the number of engines (maximum thrust level), the specific impulse (beam voltage) of the engines, and the size (power level) of the solar power generator. Additionally, an optimization of the launcher-provided hyperbolic excess energy is carried out. As a new approach to outer solar system mission optimization, a thruster with variable specific impulse in combination with a realistic solar power generator degradation model is implemented.

The presented SEP mission design yields -- without gravity assist -- a faster transfer and an increased payload fraction as compared to the Cassini/Huygens mission. Additionally, in contrast to the original TANDEM mission concept, which intends to use two launch vehicles, the presented SEP mission design requires only a single Ariane 5 ECA launch. Because no gravity assist maneuvers are employed, the presented trajectory design yields also a higher mission flexibility.

Abstract document

IAC-09.C4.8.7.pdf

Manuscript document

IAC-09.C4.8.7.pdf (🔒 authorized access only).

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