nro8_200211

nro8_200211 - Electromagnetic Formation Flight Progress...

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Electromagnetic Formation Flight Progress Report: November 2002 Submitted to: Lt. Col. John Comtois Technical Scientific Officer National Reconnaissance Office Contract Number: NRO-000-02-C0387-CLIN0001 MIT WBS Element: 6893087 Submitted by: Prof. David W. Miller Space Systems Laboratory Massachusetts Institute of Technology
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I NTRODUCTION Description of the Effort The Massachusetts Institute of Technology Space Systems Lab (MIT SSL) and the Lockheed Martin Advanced Technology Center (ATC) are collaborating to explore the potential for an Electro-Magnetic Formation Flight (EMFF) system applicable to Earth-orbiting satellites flying in close formation. Progress Overview At MIT, work on EMFF has been pursued on two fronts: the MIT conceive, design, implement and operate (CDIO) class, and the MIT SSL research group. Recent work in the MIT CDIO class includes the finalizing of the design for a planar EMFF test bed. The class will be holding its Critical Design Review (CDR) on December 5, 2002, and the final hardware design presented in their CDR will be described in the December progress report. Recent work in the MIT SSL has focused on investigating specific applications of the EMFF in Low Earth Orbit (LEO), particularly with regards to managing angular momentum accumulation in LEO due to periodic disturbances. The following report discusses in detail the use of EMFF to manage angular momentum buildup, specifically due to the Earth’s magnetic field and due to its oblateness about the equator, also known as the J 2 perturbation. Results of these analyses indicate that EMFF could serve well in this application, replacing the use of thrusters to correct for J 2 accelerations, and thus removing an array’s dependence on non- renewable fuel supplies. These results are promising, as they suggest yet another application in which EMFF may be quite useful.
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A NGULAR M OMENTUM M ANAGEMENT 1. Overview EMFF has the property that all the forces generated by the electromagnets are internal to the system. Excluding any disturbance interactions with the Earth's magnetic field, EMFF cannot apply any external forces to the formation. This prevents EMFF from having the ability to change the inertial position of a formation. It also prevents changes in the total system angular momentum. While reaction wheels are used to temporarily store angular momentum changes in a formation, they are not able to change the total system angular momentum. In an ideal situation, this would not be an issue, since the angular momentum of the system would remain constant. However, disturbance forces cause unwanted torques on a satellite formation and cause a net gain in its system angular momentum. If left unchecked, the reaction wheels will eventually saturate and become useless. These disturbance torques must be accounted for, and methods for removing this unwanted angular momentum are suggested in this report.
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nro8_200211 - Electromagnetic Formation Flight Progress...

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