NH11A-1900
Mission Designs for Demonstrating Gravity Tractor Asteroid Deflection

Monday, 14 December 2015
Poster Hall (Moscone South)
Michael Busch1, Nicolas Faber2, Seigfried Eggl3, David Morrison1,2, Ashley Clark4, Chad Frost2, Belgacem A Jaroux2 and Vatsala Khetawat2, (1)SETI Institute, Mountain View, CA, United States, (2)NASA Ames Research Center, Moffett Field, CA, United States, (3)Observatoire de Paris, Paris, France, (4)Stanford University, Stanford, CA, United States
Abstract:
Gravity tractor asteroid deflection relies on the gravitational attraction between the target and a nearby spacecraft; using low-thrust propulsion to change the target’s trajectory slowly but continuously. Our team, based at the NASA Ames Mission Design Center, prepared designs for a Gravity Tractor Demonstration Mission (GTDM) for the European Commission’s NEOShield initiative. We found five asteroids with well-known orbits and opportunities for efficient stand-alone demonstrations in the 2020s. We selected one object, 2000 FJ10, for a detailed design analysis.

Our GTDM design has a 4 kW solar-electric propulsion system and launch mass of ~1150 kg. For a nominal asteroid mass of ~3 x 109 kg and diameter ~150 m, and a hovering altitude ~125 m above the asteroid’s surface, GTDM would change FJ10’s semi-major axis by ~10 km over 2 years. To measure the deflection clearly and to permit safe hovering by the spacecraft, several months of survey and characterization are required prior to the active tractoring phase of the mission. Accurate tracking is also required after the tractoring phase, to ensure that the asteroid has indeed been deflected as intended. The GTDM design includes both spacecraft and Earth-based observations of FJ10 to verify the deflection. The estimated cost of GTDM is $280 million.

Trajectory analysis for GTDM confirmed that the outcome of a deflection of any asteroid depends on when that deflection is performed. Compared to kinetic impactor deflection, the gradual deflection from a gravity tractor produces comparable results for a given total momentum transfer. However, a gravity tractor can have greater flexibility in the direction in which the target asteroid can be deflected. Asteroid deflection scenarios must be modeled carefully on a case-to-case basis.

We will review implications of the results of the GTDM study to other proposed gravity tractor demonstrations, such as that included in NASA’s Asteroid Redirect Mission.

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