LionSat, Team 4
Proposal for Magnetic Torquer Project
Team Members: Rick Krauland
Adam Salerno
Matt Sams
Asa Wagner
EE 403W
Section 1
Oct. 2, 2003
Table of Contents
Abstract ………………………………………………………... 1
Introduction …………………………………………………… 2
Project Theory ………………………………………………… 3
Project Implementation ………………………………………. 5
Conclusion …………………………………………………….. 7
Appendix A: Financial Summary ……………………………. 8
Appendix B: Gantt Chart …………………………………….. 9
Appendix C: Statement of Work …………………………….. 10
References ..……………………………………………………. 11
Abstract
The objective of our project is to design, implement, and test the attitude control system of the Pennsylvania State University Local Ionosphere Satellite (LionSat). The control device for this particular nanosatellite is known as a magnetic torque rod, or torquer. A torquer is an electromagnet consisting of an insulated, current-carrying wire wound about a magnetic core rod and enclosed in a protective, non-magnetic housing.
Our specific goal is to design and implement the optimal torque rod capable of producing 10 Am2. To this end, we will be constructing and testing torquers made using different core materials. We will then contrast the output magnetic moments in an attempt to identify the most functional and dimensionally efficient core material.
There are three specific processes involved in this project:
This proposal includes a description of the theory behind the torquer design and testing, as well as an overview of the implementation processes required to carry out the physical construction and testing. Ancillary information includes an organizational Gantt chart, a statement of work, and a financial summary of the project.
Introduction
The objective of our project is to design, implement, and test one subsystem of the Pennsylvania State University Local Ionosphere Satellite (LionSat). The LionSat program encompasses five main goals as follows:
Our team will focus on the attitude control subsystem. This subsystem requires the use of a magnetic torquer to correct for small attitude changes of the satellite while in orbit. If the attitude changes are left uncorrected, the satellite's orientation would make it unusable for the intended scientific measurements. The magnetic torquer consists of a cylindrical metallic core wrapped with wire. This solenoid is, in effect, an electromagnet that can be controlled by the varying of current through the surrounding wire. The purpose of the solenoid is to create a magnetic field that can correct for the subtle effects of the earth's magnetic field. Our finalized design for the magnetic torquer will eventually be linked to a control system that will regulate the current flow scheme of the wire.
Our design must take into account several factors:
We plan to construct several prototypes consisting of different core materials. Each prototype will be tested to determine which design will most efficiently provide us with our desired magnetic moment output of 10 Am2.
Theory
Fabrication:
Fabricating a magnetic torquer involves implementing a solenoid using a metal core wrapped with wire. The performance of the solenoid will depend on a number of factors. These factors include the following:
The main concern when fabricating a solenoid, especially for comparison purposes, is to be sure the number of turns of wire (N) on each solenoid is the same. Our sponsor has provided us with a spooling device for small gauge wire, which will result in maximum efficiency and precision. The primary equations relating to solenoid construction are listed below:
#, where#is the resultant force produced by the solenoid.
T = NIAB*sin (Θ), where T is the resultant torque produced by the solenoid.
Testing:
Once the fabrication process is complete, we will compare the different torquers we made via a magnetometer. The ultimate outcome of this test will be deriving magnetic moment values (M). The magnetometer will provide a number of magnetic field strength values, depending on the voltage applied to the solenoid. Plugging the obtained values of Br into the equations listed below, we will derive the desired moment.
#
Figure 1. Definition of Variables
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Implementation
Materials:
The focus of this project will be the comparison of magnetic cores made of different materials. To this end we will have to locate and order at least two cores made from each type of material cut to the dimensions of our space constraints (40 cm long). Cores with common dimensions will ensure that our tests will indeed result in a side by side comparison of the various core materials.
Knowing the voltage and power constraints, we will have to size the wire appropriately for both the amount of current and the expected number of turns required to achieve the proper magnetic moment. Knowing that typical insulated magnet wire is acceptable, we will then have to locate and purchase the proper length and gauge of insulated wire.
We will also need to determine connection needs for the control device. Meetings with the LionSat attitude control engineer and our sponsors will help to determine what type of interface we will need to purchase.
The final material consideration will be the non-magnetic protective sealant and housing. Cost, protective functionality, and availability will be the driving factors in choosing the materials. Research indicates that fiberglass and aluminum are effective housing materials.
Cost and vendor research will be completed as the above decisions are made.
Construction:
Construction will consist of winding the specified wire about the core, insulating the winding, and enclosing the torquer in the protective housing. Our sponsors have acquired a spooling device on EBay, which we are told can be used for the winding construction. The insulative coating will be applied after the winding process is complete. The final steps will be making a robust electrical connection to the control interface and enclosing the torque rod in a sturdy housing.
Testing:
The final step in the process of core comparison is the actual testing of the different prototypes. Our sponsors have provided us with a technical paper entitled “On Determining Dipole Moments of a Magnetic Torquer Rod – Experiments and Discussions.“
This paper describes a developed process for testing and calculating torquer moment. In this specific test we will use a magnetometer placed axially at a distance twice the length of the rod to measure the magnetic flux density. The experiment will need to take place in an open field so as to avoid magnetic field interference created by nearby magnetic materials present inside any building. Using this paper we will attempt to recreate the test set up. We will have to locate a magnetometer with sensitivity to four decimal places, as well as a sufficient power source and a laptop to acquire data. The acquired magnetic flux data can be converted to magnetic moment numbers using a formula presented in the paper. Data analysis can then be conducted.
Conclusion
Our magnetic torquer prototype will be the basis for the attitude control for Penn State's LionSat project. The magnetic torquers will create a magnetic moment, which will allow the nanosatellite to be oriented with the Earth's magnetic field.
In order to successfully complete our problem statement, we will determine what core material is best suited for our application. Before we can begin building the prototypes used for testing the various core materials, we will calculate the number of wire wrappings required to create a moment of 10Am2, find suppliers capable of delivering to us the different core materials within our timeframe, and order the necessary torquer components. To determine the best material we will build several prototypes and recreate an already developed test method which can accurately measure the magnetic moment using a magnetometer.
The result of our project will be a recommendation regarding torquer materials along with detailed a testing procedure for measuring the magnetic moment. With our established bi-weekly LionSat meetings and the support of the entire LionSat team, we are confident that we can build and test a prototype magnetic torquer within our time constraints.
Appendix A
Financial Section
Labor Costs
$8,400
Fringe Costs
$1,260
Parts
Total Parts
$600
Overhead Costs
$4,104
Total Project Cost
$14,364
Appendix B
Gantt Chart
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Figure 1: Gantt Chart
Appendix C
Statement of Work
Deliverables:
Project Team Responsibilities:
References:
Lee, J., and A. Ng, 2002: “On Determining Dipole Moments of a Magnetic Torquer Rod — Experiments and Discussions“ Canadian Aeronautics and Space Journal, Vol 48, No. 1, pg. 61-67.
Halliday, D, R. Resnick, and J. Walker: “Fundamentals of Physics“ John Wiley & Sons Inc., Ney York, 1997.
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