Project: JB3-CBS1

Mechanical, Power, and Propulsion Subsystem Design for a CubeSat

A Major Qualifying Project Submitted to the Faculty

of WORCESTER POLYTECHNIC INSTITUTE

in partial fulfillment of the requirements for the Degree of Bachelor of Science

in Aerospace Engineering

by

Keith Cote

Jason Gabriel

Brijen Patel

Nicholas Ridley

Zachary Taillefer

Stephen Tetreault

7 March 2011

Prof. John Blandino, Project Advisor

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Abstract This project explores Worcester Polytechnic Institutes (WPI) initial venture in

experimenting with a type of picosatellite called a CubeSat. Three Major Qualifying Projects

(MQP) representing seven subsystems collaborated on the construction of a ground-based

CubeSat to test current technologies and investigate the feasibility of future CubeSat

projects at WPI. Of the seven CubeSat subsystems, this report outlines efforts of the power,

propulsion, and structure subsystems. Research on previous and current CubeSat projects

provided baseline information, giving teams the ability to select components for a Lab

Option as well as Flight Option CubeSat.

Although construction and testing of a full Lab Option CubeSat was beyond the

scope of this project, each of the three subsystems teams were able to design and/or

construct a baseline set of components for their subsystem and perform rudimentary

testing. The extensive research and recommendations detailed herein will be used by

future groups to prepare a space-ready satellite. In addition, this project (in conjunction

with two other CubeSat design teams) resulted in a fully defined Flight Option CubeSat,

including component selection and mission planning, for a 3U CubeSat carrying an Infrared

Spectrometer.

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Acknowledgements This project would not have been possible without the assistance of our advisor:

Professor John J. Blandino, Ph.D.

Associate Professor, Aerospace Engineering Program

Department of Mechanical Engineering, Worcester Polytechnic Institute

Special thanks as well to the advisors for the other CubeSat design teams:

Professor Michael Demetriou, Ph.D.

Professor, Aerospace Engineering Program

Department of Mechanical Engineering, Worcester Polytechnic Institute

Professor Nikolaos Gatsonis, Ph.D.

Director, Aerospace Engineering Program

Department of Mechanical Engineering, Worcester Polytechnic Institute

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Authorship Nicholas Ridley and Jason Gabriel wrote the Abstract, Lists, Executive Summary,

Introduction, Mission and Payload Literature Review, Goals, Methodology chapters, and the

Power Literature Review. Keith Cote and Brijen Patel wrote the Mechanical Structures

Literature Review. Stephen Tetreault and Zachary Taillefer wrote the Propulsion Literature

Review. All group members edited and revised various sections. In its final form, this report

contains equal contributions from all group members, and each section represents the

collaborative effort of multiple authors.

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Table of Contents 1 Introduction ............................................................................................................................ 11

1.1 Project Goals and Objectives ................................................................................................ 12 1.2 Power Subsystem Objectives ............................................................................................... 13 1.3 Propulsion Subsystem Objectives...................................................................................... 13 1.4 Mechanical Structure Subsystem Objectives ................................................................ 14

2 Background ............................................................................................................................. 16 2.1 General CubeSat Specifications ........................................................................................... 17

2.1.1 Power Subsystem Specifications ................................................................................ 17 2.1.2 Propulsion Subsystem Specifications ....................................................................... 17 2.1.3 Mechanical and Structural Subsystem Specifications ...................................... 18

2.2 Power Subsystem ...................................................................................................................... 21 2.2.1 Solar Cells ............................................................................................................................... 21 2.2.2 Batteries.................................................................................................................................. 22 2.2.3 Power Management and Distribution System (PMAD) ................................... 23 2.2.4 Sample CubeSat Power Systems ................................................................................. 24

2.3 Propulsion Subsystem ............................................................................................................. 26 2.3.1 Pulsed Plasma Thrusters (PPT) .................................................................................. 26 2.3.2 Vacuum Arc Thrusters (VAT) ....................................................................................... 28 2.3.3 Resistojets .............................................................................................................................. 29 2.3.4 Liquefied Gas Thrusters .................................................................................................. 30 2.3.5 Cold Gas Thrusters ............................................................................................................ 31

2.4 Mechanical and Structural Subsystem ............................................................................ 33 2.4.1 Mass Produced CubeSat Structures ........................................................................... 34 2.4.2 Custom-Designed CubeSat Structures ..................................................................... 36 2.4.3 Summary of Structural Design Approaches .......................................................... 38

3 Methodology ........................................................................................................................... 40 3.1 Research ......................................................................................................................................... 40 3.2 System Engineering Group (SEG) ...................................................................................... 40 3.3 Construction ................................................................................................................................. 41 3.4 Lab Option vs. Flight Option ................................................................................................. 49

4 Lab Option Component Selection and Analysis ............................................................. 51 4.1 Spacecraft and Payload Requirements ............................................................................ 51

4.1.1 Orbit Specifications ........................................................................................................... 51 4.1.2 Scientific Payload ............................................................................................................... 52

4.2 Power Component Selection and Analysis .................................................................... 52 4.2.1 Solar Cells ............................................................................................................................... 53 4.2.2 Batteries.................................................................................................................................. 54 4.2.3 Power Management and Distribution (PMAD) .................................................... 55

4.3 Propulsion System Selection & Analysis ........................................................................ 57 4.3.1 Propulsion Analysis........................................................................................................... 61 4.3.2 Orbital Maneuvers ............................................................................................................. 61

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4.3.3 Propellant Volume ............................................................................................................. 63 4.3.4 Atmospheric Drag .............................................................................................................. 65

4.4 Mechanical Structures Design Selection & Analysis ................................................. 66

5 Flight Option Component Selection and Analysis ......................................................... 72 5.1 Power Subsystem ...................................................................................................................... 72

5.1.1 Flight Option Solar Cells .................................................................................................. 73 5.1.2 Flight Option Battery ........................................................................................................ 73 5.1.3 Flight Option PMAD .......................................................................................................... 73

5.2 Propulsion Subsystem ............................................................................................................. 74 5.2.1 Flight Option ..................