Prospects of Using a Pulsed Electrostatic Tractor With Nominal Geosynchronous Conditions

Abstract

The geosynchronous (GEO) orbital regime is becoming cluttered with derelict space debris, which raises the collision risk for satellites in a very valuable orbit. Touchless reorbiting options have been proposed for moving this debris to a graveyard orbit to avoid the risk of physically docking with large, multiton defunct satellites that can be tumbling at several degrees per second. This paper investigates the electrostatic tractor (ET), which uses an electron beam mounted on a tug spacecraft to irradiate a passive debris object. The tug quickly rises to a positive steady-state voltage, and the debris quickly falls to a negative steady-state voltage to create an attractive tugging force. The tug maintains a fixed relative position during the reorbit using inertial thrusting. The Coulomb force can be used as a means of touchless actuation for geosynchronous debris reorbiting, detumbling, and formation flying. This paper investigates the prospects of using a beam with pulsed current. The off-pulsing periods can have benefits for sensing and thrusting applications, and the pulsing charging can lead to higher force levels for the same electrical power used in particular conditions. A Monte Carlo analysis is performed to study the mean electrostatic force, considering a range of beam currents, voltages, pulsing duties cycles, and vehicle sizes. Power-limited regions are identified where the pulsed tractor has a magnitude that is comparable or greater than the mean continuous beam force. This creates interesting alternate methods to implement an ET while having periodic off periods. The tractor performance is illustrated through the debris reorbiting scenario. A detailed equal power analysis determines that even duties cycles as low as 10%–20% can lead to forces comparable to the continuous beam performance, or even do better for some powers.