University of ColoradoDepartment of Aerospace Engineering Sciences

ASEN 4018

Project Definition Document (PDD)CU Boulder Engineers Creating Universal Boom Extensions for CubeSats (CUBE3)

Monday 16th September, 2019

ApprovalsRole Name Affiliation Approved Date

Customer Robert Marshall CU Boulder

CourseCoordinator Jelliffe Jackson CU/AES

Project CustomersName: Professor Robert MarshallEmail: Robert.Marshall@Colorado.eduPhone: 303-492-4075

Team MembersName: Bensley PearsonEmail: Bensley.Pearson@Colorado.eduPhone: 303-596-8364

Name: Rowan GonderEmail: Rowan.Gonder@Colorado.eduPhone: 303-522-0508

Name: Michael BurkeEmail: Michael.Burkeiii@Colorado.eduPhone: 720-388-0641

Name: Venus GonderEmail: Venus.Gonder@Colorado.eduPhone: 303-995-4919

Name: Collin DosterEmail: Collin.Doster@Colorado.eduPhone: 360-999-8032

Name: Roger HellerEmail: Roger.Heller@Colorado.eduPhone: 719-505-2687

Name: Travis PeccoriniEmail: Travis.Peccorini@Colorado.eduPhone: 707-322-6673

Name: Adam HuEmail: Adam.Hu@Colorado.eduPhone: 970-691-6718

Name: Michael StrongEmail: Michael.Strong@Colorado.eduPhone: 720-771-4159

Name: Britnee StaheliEmail: Britnee.Staheli@Colorado.eduPhone: 719-301-8127

Name: Evan JohnsonEmail: Evan.T.Johnson@Colorado.eduPhone: 626-353-5604

Robert A. Marshall (Sep 15, 2019)Robert A. Marshall 09/15/19

1. Problem or NeedTo date, over 1000 CubeSats have been launched into Earth orbit [1], and over 3000 more forecast to be launchedwithin the next six years. With this explosive growth in the market, interest is certain to grow in the field of deployablestructures for a variety of applications. For example, the CANVAS mission proposes deploying a magnetic fieldsensor on a carbon fiber ribbon that curls into a tubular boom in order to distance the sensitive instrument from theelectromagnetic interference (EMI) of the spacecraft electronics and power distribution subsystems. With a littleimagination, one can easily envision other applications: cameras separated by greater distance to take advantage ofparallax in measuring distance to other orbital objects, a charged particle detector set at a distance from the shadow ofthe bus, or a communications antenna able to take advantage of wavelengths not available in the constrained physicaldimensions of a standard CubeSat configuration. However, any technical solution to this particular challenge also facesthe constraints imposed by the CubeSat architecture and operating environment, specifically in the areas of physicaldimensions, mass budget, vibration response, attitude control, and survival in the space environment.

With this in mind, this project proposes to develop a novel deployable structure for use on CubeSats and capableof accommodating a notional scientific instrument. Specifically, this system will be able to deploy on command fromeither ground support equipment (GSE) or the spacecraft flight computer (FC). The structure will place a notionalinstrument payload with a mass of 500 g and physical dimensions delimited by an 8x8x8 cm cube at a distance no lessthan 60 cm from the spacecraft structure, measured from the point of closest approach between the instrument and thespacecraft. In addition, the structure will provide routing for electrical power and signal cabling to the instrument fromthe spacecraft bus. Because the attitude determination and control subsystem (ADCS) operates at 5.0 Hz, it cannotcontrol resonant modes slower than 2.5 Hz. Therefore, the structure shall have a first resonant mode greater than orequal to 2.5 Hz in addition to the ability to survive a simulated space launch vibration profile while in the stowedconfiguration. While stowed, the deployable structure with the instrument attached will occupy a space no larger than1.5 Ua. Finally, the system will provide positive confirmation via telemetry reported via the FC when deployment iscomplete.

As noted previously, solutions to this particular challenge do exist on the market. However, this project aims tooffer attractive alternatives in three key areas. The first being that the resonant frequency will be higher than that ofexisting solutions. Secondly, rather than providing for cable routing after the fact, this project will incorporate bothpower and signal wiring into the design. Finally, the cost of this project is predicted to be much lower than othersolutions on the market and potentially applicable to a wider range of mission applications.

2. Previous Work2.1. Previous Structural Designs

Due to sizing constraints of available launching platforms, deployable space structures are a necessity for furtheringthe ability to conduct studies in space. The current purposes of these structures range from communication purposesto scientific instruments and even into propulsion methods in solar sails [6]. These have all been large scale endeavors,however with the increase of CubeSat launches predicted to occur in the next 6 years, a need has arisen to scale thesedeployable structures to fit within the sizing constrains of a CubeSat. As previously mentioned, there are a number ofother solutions on the market. These vary widely in both specific application and design. Deployable CubeSat boomsgenerally fall under one of the following categories: storable extendable members (STM), telescoping masts, trussbooms, and inflatable booms.

Figure 1: STEM BoomFigure 2: TRAC Boom

STM style booms work in a method similar to that of an extendable tape measure. When retracted, the boommaterial is rolled flat around a type of cylinder. Upon deployment, the material curls into a pre-determined shape. Thisshape is typically either a cylinder, known as a storable tubular extendable member (STEM) as shown in figure 1 above,an open-ended triangle known as a triangular rollable and collapsible (TRAC) boom shown in figure 2, or a collapsible

a “U”, short for “Unit”, is a measure of CubeSat volume, where each U is a 10x10x10 cm cube.

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tube mast (CTM). This design results in an extremely compact system capable of extending a significant distance.Two commercial aerospace companies, CTD Incorporated and Roccor, currently use these designs in production. Thecompanies both use a carbon-fiber material which gives this design greater weight-savings over more conventionalsteel or aluminum based designs. However, these designs do not provide the stiffness required to support the mass ofthe magnetic field sensor. The CTD product in particular would result in a resonant frequency 1.5 Hz, well below theminimum requirement of 2.5 Hz. Furthermore, this design does not incorporate a method for cable handling. CUBE3’sdesign will allow for a minimum of twelve wires to extend from the CubeSat body to the sensor at the end of the boom.

The telescoping mast boom involves a number of nested structures that are extended by either a stored energydevice or a motor. The telescoping mast can provide a greater amount of stiffness and strength than a STEM and isfrequently used in conjunction with an internally mounted STEM as a deployment and retraction device [5].

From large spacecraft such as the ISS to smaller satellites such as the ∅rsted (the ∅rsted was still much larger thana conventional CubeSat), collapsible truss booms have been used in many applications to extend instruments awayfrom the main body of a spacecraft. To the best of this team’s knowledge, there has not been a truss boom designedthat is small and light enough for this mission’s application. Northrup Grumman’s Astromat product stows at a size ofapproximately 41” by 15” and weighs over 16kg.

Utah State University developed an inflatable boom (Aeroboom) in 2015 for use on their HAPCAD CubeSat. Thisboom was stowed in a 1U space and deployed to a length of one meter. The boom consisted of two mylar layers andone S-glass layer to provide thermal protection and rigidity. The boom inflates due to the pressure gradient betweenthe air inside the CubeSat and the vacuum of Low Earth Orbit (LEO). After deployment, a UV epoxy coating on theoutside of the boom hardened due to solar radiation. While this method meets the length and size requirements for thismission, the design has its drawbacks. Like the STEM Boom, the Aeroboom does not incorporate a method for wirehandling. Beyond that, while the Aeroboom was tested for performance at an altitude of approximately 17 miles, thissystem does not seem to have undergone the structural or vibration analysis that would be necessary for this mission.

2.2. Previous Vibration Analysis of CubeSat Boom

Due to the relatively small nature of CubeSats, the dynamics of the system can be drastically altered by the deploymentof a boom structure that can be up to three times the length of the original satellite. In order to account for this change,the dynamics of the boom must be characterized in order to ensure an adequate Attitude Dynamics and ControlSystem (ADCS) is used. A typical method used to characterize the resonant modes of a CubeSat boom structure isexperimentally using a gravity off loading system [4].

One such method is to use a Marionette paradigm in which the boom is suspended to alleviate damping and friction.It is imperative to ensure the suspension system does not drastically alter the dynamics of the system. In order to verifythis, a finite element model of the boom and suspension system can be developed and used to characterize the dynamicsof the entire boom and suspension system. This is then used to ensure the resonant modes of the suspension system arefar enough away from the resonant modes of the boom to ensure valid experimental results. The experimental setupcan then be used to characterize the eigen-frequencies, modal shapes, and damping of the deployed boom in order toexamine its effects on the dynamics of a CubeSat.

3. Specific ObjectivesTable 1 defines the levels of success for each Critical Project Element (CPE) for the CUBE3 project. Level 1 describesthe minimum criteria for meeting project requirements. Level 2 is a slight step up and describes an easily attainablegoal above the minimum standard. Levels 3 and 4 describe levels of success that are difficult to complete but aredoable within the time and budgetary limits of the project. Not all CPEs have all four levels as they were not definedby the customer or the team.

The end deliverables for this project will be a deployable boom structure housed in an accurate representation of a3U CubeSat. This physical structure will be commanded by an external Command and Control (C2) computer, used tomimic an on-board flight computer. In addition to the physical deliverables, a detailed report outlining the deployableboom structures capabilities and final test results will also be delivered.

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Table 1: Specific Objectives

Project Element Level 1 Level 2 Level 3Deployable Boom Structure (DBS):Deployment LengthValidation Method: System test

The boom can beextended to 60 cmpast the exit of thespacecraft body.

The boom can beextended to 1.0 mpast the exit of thespacecraft body.

Deployable Boom Structure (DBS):Resonant FrequencyValidation Method: System test

The boom has aresonant frequencygreater than or equalto 2.5 Hz.

Deployable Boom Structure (DBS):Total Mass and SizeValidation Method: System test

The deployableboom system and the1.5 U containmentstructure have a massof less than 1.5 kg.

The deployableboom system and the1.5 U containmentstructure have a massof less than (TBD)kg.

The deployableboom system and the1.5 U containmentstructure have a massof less than 0.9 kg.

Deployable Boom Structure (DBS):Deployment TimeValidation Method: System test

The boom fullydeploys in less than2 minutes.

The boom fullydeploys in less than(TBD) minutes.

Deployable Boom Structure (DBS):Damping TimeValidation Method: System test

The boom stops anysignificantoscillation in lessthan 2 min afterdeployment.

The boom stopsoscillation in lessthan (TBD) minutesafter deployment.

Environmental Resilience (ER)Validation Method:Thermal-Vacuum Tests

Analysis indicatesprobable 1 yearlifespan on orbit.

Vacuum testingindicates probable 1year lifespan onorbit.

TVac testingindicates probable 1year lifespan.

Software Interface (SI)Validation Method: System test

The deployableboom structure canbe commanded froman external C2computer.

Payload Connectivity (PC)Validation Method: Inspection

The system is able todeploy power anddata cables to thesensor payload at theend of the boom.

4. Functional Requirements4.1. Requirements

1. The boom shall be capable of deploying an instrument of up to 500 g with the dimensions 8x8x8 cm.

2. The deployable boom shall provide routing for power and signal cabling up to a total of 12 wires at a minimumsize of 30 AWG (3 separate differential signals and a 3-wire power setup)

3. The boom assembly in the undeployed state with the instrument attached shall have stowed dimensions within1.5 U.

4. The boom system shall be capable of receiving commands from and sending telemetry to the CubeSat flightcomputer.

5. The boom shall be capable of re-stowing into an undeployed state.

6. When fully deployed the first resonant frequency of the boom shall be greater than or equal to 2.5 Hz.

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7. The deployable boom shall survive up to 10 G vibration in the stowed configuration

8. The deployable boom shall survive the space environment in both the stowed and deployed configurations foran operational lifespan of 1 year.

9. When fully assembled, with the 500 g instrument attached, the whole boom system shall have a mass less thanor equal to 2.0 kg.

10. The boom shall extend a minimum distance of 60 cm from the attachment point of the instrument to the outeredge of the CubeSat.

4.2. Functional Block Diagram

Figure 3: Functional Block Diagram

4.3. Concept of Operations

Figure 4: Concept of Operations

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5. Critical Project ElementsCPE-1: Deployable Boom Structure

This mission centers on the deployment of a boom with suitable rigidity and length from the confines of a 1.5 UCubeSat volume. The boom must be capable of maintaining its structure with a 500 g, 8x8x8 cm instrument on itsend when fully deployed, and must itself add less than or equal 1.5 kg of mass to the greater CubeSat. Aspirationalstructural improvements to the current solution (a carbon fiber roller) include greater stiffness, higher first moderesonant frequency, and a lower price-tag [3]. Crucial to mission success is the ability of this structure to survive theenterprise of reaching space intact while fully collapsed, and testing procedures are expected to mandate that thestructure can be returned to this collapsed state post-deployment.

CPE-2: Deployment System

As the final boom design must travel collapsed and operate extended, a mechanism will need to be in place to assistthe transition. This process will likely include both mechanical and electrical elements, and will be constrained by thesame space requirements as the structure itself. It is additionally feasible that components of the deployment systemwill contribute to the structural integrity of the boom, so care will have to be taken in ensuring their durability andlongevity. The system will need to extend the boom to a locked position within two minutes and sense when the fulldeployment is complete, but must not subject the payload to more than 10g acceleration when activated or draw morethan 30W of power.

CPE-3: Environmental Resilience

This mission is to be designed for survivability in a Low Earth Orbit (LEO) environment for the duration of at leastone year, and must be capable of withstanding the accompanying vacuum, solar radiation, and thermal extremes.Each of these factors is likely to demand a degree of electrical shielding and a system-wide space readiness ratingto accomplish. Additionally, the boom must be capable of surviving the vibrational modes inflicted upon it duringnormal spacecraft operation (up to 2.5 Hz) and will require damping capabilities. Again, the expectation is that someof these features will compound the broader structural integrity of the deployed boom.

CPE-4: Software Interfacing

Operational actions such as deployment initiation and extension sensing will require software interfacing with thecomponents of the CubeSat itself. Testing will be accomplished with an external microcontroller, but the end goal willbe full integration with the electronics of the Customer’s satellite. The Customer has indicated that present softwareutilizes COSMOS interfacing, so it would be logical to follow suit where feasible.

CPE-5: Payload Connectivity

The driving force behind this mission is a desired ability to place a sensitive instrument a certain distance away fromthe main satellite bus. In order to do so, it is important to design a suitable wiring system to facilitate data and powertransmission, so the requisite wires will stretch the distance of the boom to create the electrical link between thetwo sub-systems. This appropriate wiring bundle is presently absent from the aforementioned alternative. Payloadconnection will not require software interfacing by the team, but the connective terminals will require appropriateenvironmental protections.

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6. Team Skills and Interests

Team Member Associated Skills/Interests Critical Project ElementsBurke, Michael Systems Engineering, CAD, Test,

CDR and PDR experience,Requirements Management, MATLAB

CPE-1, CPE-2, CPE-3,CPE-4, CPE-5

Doster, Collin Systems Engineering, ProjectManagement, Solidworks, AutoDeskInventor, MATLAB and SimulinkSystem Modeling and Analysis,Robotic System Design, RapidPrototyping, 3D Printing, LaserCutting, Manual and AutomaticMilling and Lathe Work, Test Designand Integration

CPE-1, CPE-2, CPE-3,CPE-4, CPE-5

Gonder, Rowan Systems Engineering, Manufacturing,CAD, Test Engineering, RequirementsManagement, CDR Experience

CPE-1, CPE-2, CPE-3

Gonder, Venus MATLAB, Rapid Prototyping, CAD,Labview, Manufacturing

CPE-1, CPE-2, CPE-3

Heller, Roger Systems Engineering,MATLAB/Simulink, SoftwareEngineering, OASIS CC/COSMOS,Microelectronics

CPE-4, CPE-5

Hu, Adam MATLAB, Testing, Prototyping,Safety

CPE-1, CPE-2, CPE-3

Johnson, Evan Electrical Engineering, QualityAssurance Engineering, MATLAB

CPE-2, CPE-4, CPE-5

Pearson, Bensley MATLAB, Prototyping, SolidWorks,Project Management, Product DesignProcess, 3D Printing, Microavionics,Systems Engineering

CPE-1, CPE-2, CPE-5

Peccorini, Travis Probability/Statistics and Analytics,MATLAB, Systems Engineering

CPE-1, CPE-2, CPE-3

Stahelli, Britnee MATLAB, Market Research, SystemsEngineering, CAD, Structural,Vibration, Material, and ThermalAnalysis, Manufacturing

CPE-1, CPE-2, CPE-3,CPE-5

Strong, Michael MATLAB, Safety, AGI STK, Testing,Software Engineering, MechanicalEngineering

CPE-1, CPE-2, CPE-4,CPE-5

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7. Resources

Need Resource SourceFabrication Bobby Hodgkinson (Manufactur-

ing), Adrian Stang (Structures), MattRhodes (Fabrication), Machine Shop(CNC Mills, Lathes, Mills, Saws/-Drills), Trudy Schwartz (Electronics),Electronics Shop (Soldering, wiring)

AERO Building

Testing (Vibrational) KatieRae Williamson (Test Coordina-tor), Unholtz-Dickie S202 VibrationShaker

AERO Building

Testing (Thermal) KatieRae Williamson (Test Coordina-tor), Thermal test chamber

LASP, Space Grant

Testing (Vacuum) KatieRae Williamson (Test Coordina-tor), Vacuum test chamber

Bioastro Lab, Escape Dy-namics test chamber, LASP

Modeling (CubeSat Atittude) ADCS (Blue Canyon Technologies) Dr. Marshall (Client), RyanStewart

Communications COSMOS software Open SourcedAdditional Funding EEF (Engineering Excellence Fund),

Outside SponsorsCU/Open Sourced

References[1] Kulu, Eric. “Nanosats Database”, Retrieved September 6, 2019, from https://www.nanosats.eu/

[2] Jackson, Jelliffe. “Project Definition Document (PDD)”, University of Colorado–Boulder, Retrieved August 29,2019, from https://canvas.colorado.edu/

[3] ”CSB-1 CubeSat Boom & Deployer”, Composite Technology Development Inc., Retrieved September 6,2019, from https://www.ctd-materials.com/wordpress/wp-content/uploads/2017/07/CSB-1-Product-Sheet.pdf

[4] ”Vibration Modal Analysis of a Deployable Boom Integrated to a CubeSat” Shepenkov, V., 2013. Re-trieved September 8, 2019, from https://www.diva-portal.org/smash/get/diva2:620604/FULLTEXT01.pdf

[5] Belvin, W.K., Straubel, M., Wilkie, W.K., Zander, M.E., Fernandez, J.M., and Hillebrandt, M.F., ”Advanced De-ployable Structural Systems for Small Satellites”, Retrieved September 8, 2019, from https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20170003919.pdf

[6] Deployables Northrop Grumman, Retrieved September 8,2019, from https://www.northropgrumman.com/Capabilities/Deployables/Pages/default.aspx

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ASEN_4018__PDD_Draft (1)Final Audit Report 2019-09-16

Created: 2019-09-15

By: Rowan Gonder (gonder.rowan15@gmail.com)

Status: Signed

Transaction ID: CBJCHBCAABAArG_MzIq7hUJMZkhjj6pl4n1GEp0A9KE8

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