Space Weather Influence on Relative Motion Control using the Touchless Electrostatic Tractor
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Space Weather Influence on Relative Motion Control using the Touchless Electrostatic Tractor Erik A. Hogan1 · Hanspeter Schaub1
Published online: 6 July 2016 © American Astronautical Society 2016
Abstract With recent interest in the use of electrostatic forces for contactless tugging and attitude control of noncooperative objects for orbital servicing and active debris mitigation, the need for a method of remote charge control arises. In this paper, the use of a directed electron beam for remote charge control is considered in conjunction with the relative motion control. A tug vehicle emits an electron beam onto a deputy object, charging it negatively. At the same time, the tug is charged positively due to beam emission, resulting in an attractive electrostatic force. The relative position feedback control between the tug and the passive debris object is studied subject to the charging being created through an electron beam. Employing the nominal variations of the GEO space weather conditions across longitude slots, two electrostatic tugging strategies are considered. First, the electron beam current is adjusted throughout the orbit in order to maximize this resulting electrostatic force. This openloop control strategy compensates for changes in the nominally expected local space weather environment in the GEO region to adjust for fluctuations in the local plasma return currents. Second, the performance impact of using a fixed electron beam current on the electrostatic tractor is studied if the same natural space weather variations are assumed. The fixed electron beam current shows a minor performance penalty (< 5 %) while providing a much simpler implementation that does not require any knowledge of local space weather conditions. Keywords Electrostatic tractor · Spacecraft charging · Space debris mitigation
Erik A. Hogan
[email protected] 1
University of Colorado at Boulder, Boulder, CO 80309, USA
238
J of Astronaut Sci (2016) 63:237–262
Introduction Recently, interest in the use of electrostatic forces for contactless tugging and remote attitude control of noncooperative objects has grown [15, 28, 30, 34]. Originally proposed for space debris mitigation at geosynchronous (GEO) altitudes, the electrostatic tugging concept relies on a combination of an attractive electrostatic force between two craft and low thrusting capability on one of the craft [28]. The attractive force acts as a virtual tether between the two objects, and a low thrust maneuver is used to tow the noncooperative object into a new orbit [15]. Considering nonsymmetrical spacecraft geometries, the charging also gives rise to torques on the craft [19, 33]. Through careful manipulation of the charging histories, these torques can be applied in a manner sufficient to despin a noncooperative object remotely [30]. This latter ability greatly simplifies any orbital servicing mission where great efforts are required to first despin objects spinning at 1 degree per second or greater [8, 9]. Generally, a noncooperative object such as space
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