Eric Blake Jon Braam Raymond Haremza Michael Hiti Kory Jenkins Daniel Kaseforth Brian Miller Alex Ordway Casey Shockman Lucas Veverka Megan Williams (Team Lead) Solar Sail Project AEM 4332W – Spacecraft Design Preliminary Design Review March 28, 2007

AEM 4332W - Solar Sail2 Team Organization Systems Integration & Management: Megan Williams Orbit Control: Eric Blake, Daniel Kaseforth, Lucas Veverka Structures: Jon Braam, Kory Jenkins Attitude Control: Brian Miller, Alex Ordway Communications: Casey Shockman Thermal: Raymond Haremza Power: Michael Hiti

AEM 4332W - Solar Sail3 Presentation Outline Project Overview Design Strategy Subgroup work –Orbit –Structure –Attitude and Control –Communication –Thermal Analysis –Power Demonstration Acknowledgements

AEM 4332W - Solar Sail4 Project Overview Top Level Requirements The payload mass is 34 kg The payload average power draw is 24.5 Watts The final orbit should have a semi-major axis of 0.48 AU and an inclination of 60 deg The launch vehicle will provide a hyperbolic escape velocity of 0.5 km/s. A Delta II 7425 will be used for launch. The structure will fit inside the selected launch vehicle.

AEM 4332W - Solar Sail5 Project Overview MAJOR TASKS 1) Develop control law for semi-major axis change and inclination change to determine solar sail orientation. 2) Analyze transfer time for different sail sizes to determined optimum sail size. 3) Conduct a trade study between sliding mass and tip thruster attitude control systems. 4) Determine the data transfer rate and power requirements for data downlinks to Earth. Assume 2 downlinks per week to the DSN. 5) Conduct a trade study between conformal solar array and normal- pointing solar array. 6) Size the solar array to meet total power requirements. 7) Analyze the thermal properties of the solar sail spacecraft. 8) Choose a configuration and compute the total mass and moment of inertia. 9) Design a payload module. 10) Design for the satellite actuation. 11) Calculation and testing of attitude control law.

AEM 4332W - Solar Sail6 Project Overview Orbit Non-Keplarian orbit –Inclination 60° –Semi-major axis 0.48AU Structure Target mass: 500 kg Sail size: 100m x 100m Inflatable boom structure, heated curing Attitude Control Sliding mass configuration with secondary tip thruster control Interstellar compass – primary ADS Communications Ka-Band (32 GHz) Horn antennae Thermal Carbon mesh sail material Multifunctional Structure (MFS) configuration Power Power Requirements approximately 878 W Normal Pointing Solar Array area: 2.39 meters Silver-Cadmium (Ad-Cd) battery mass: kg

AEM 4332W - Solar Sail7 Design Strategy Orbit Trade Studies –Sail area versus transfer time Varied sail size and ran simulation Larger sail results in a faster transfer –Transfer maneuver variations Comparison between “hot”, “cold” and simultaneous transfer trajectories “Hot” transfer is quickest but may not be feasible due to thermal restrictions Structure Zero level sizing based on existing designs Trade Studies –Deployable space structure types –Method of rigidizing inflatable structure Stress analysis Determine power/time for boom deployment –Coordinate with Attitude Control and Power subgroups Solid Modeling

AEM 4332W - Solar Sail8 Design Strategy Attitude Control Trade Study –Sliding mass vs Tip thruster ACS Simulink modeling Communication Researched communication devices Thermal Trade Study –Solar Sail material: Mylar vs Carbon fiber mesh Research into thermal management of spacecraft Power Zero level sizing for power requirements Trade Study –Normal vs. Conformal Solar Array Solar Array sizing Battery sizing

AEM 4332W - Solar Sail9 Orbit Control Eric Blake (Simulation) Daniel Kaseforth (Control Law –Simulation ) Lucas Veverka (Control Law – Orbits)

AEM 4332W - Solar Sail10 Orbit Control Problem –How to get from Earth’s orbit to an orbit about the sun with inclination of 60° and semi-major axis of 0.48 AU using solar pressure? Assumptions –Gravity and solar pressure are only forces –Sail is rigid flat plate and does not degrade –Sail material is perfectly reflecting –Instantaneous change in sail orientation

AEM 4332W - Solar Sail11 Orbit Control Technical flow of work –Simulation Two-body force interaction (Sun, spacecraft) –Force of gravity –Force of Solar pressure

AEM 4332W - Solar Sail12 Orbit Control –Control Law Cone and clock angle equations

AEM 4332W - Solar Sail13 Orbit Control “Cold” orbit transfer

AEM 4332W - Solar Sail14 Orbit Control Orbital elements

AEM 4332W - Solar Sail15 Orbit Control Conclusions –Simulation works –Control law functions as desired Recommendations for further work –Sail shape analysis –Optimize transfer trajectory –Simulate sail degradation effects

AEM 4332W - Solar Sail16 Orbit Control FDR Presentation –Discuss control law and simulation assumptions. –Discuss possible transfer orbits. –Show simulation results. –Justify selected transfer orbit. –Discuss further work.

AEM 4332W - Solar Sail17 Structural Design Jon Braam Kory Jenkins

AEM 4332W - Solar Sail18 Solar Sail Structure and Deployment Challenge: Design a deployable structure to support the sail and deliver a scientific payload. Solution: The sail support structure consists of four inflatable, rigidizable booms attached to a payload module. Based on L’Garde solar sail demonstrator design.

AEM 4332W - Solar Sail19 Aluminum Module Aluminum Unistrut –Ti Weld Unistrut Washer Titanium Hardware Rubber Washer –Vibration Damping

AEM 4332W - Solar Sail20 Hexagonal Shape Maximize area inside capsule Maximize packing area inside module Allowable surface area for features –Antenna –Camera –Solar Panel Attachment

AEM 4332W - Solar Sail21 Sail Mount Hexagonal Shape –Mounting –Strength FEA –Add Gussets –Starburst Mount »Add connections Center Hole –Routing Wiring Propellant

AEM 4332W - Solar Sail22 Boom Geometry Packing constraints require tapered geometry. Laminate thickness t = 0.25 mm. r = 10 cm. R = 16 cm. l = 30 cm. n = number of folds. L = 72 m. Mass ≈ 20 Kg/boom R = r + t ( l/L)

AEM 4332W - Solar Sail23 Estimate Worst Case Loading Assumptions: Solar Pressure at 0.48 AU = 19.8 µN/m^2. Tip thruster forces of 150 µN. Worst case force = 0.05 N. Deployment load of 20 N in compression. Thin wall tubes. Sail quadrant loading is evenly distributed between 3 attachment points. Quadrant area 2500 m^2. Homogeneous material properties. Safety factor of 3.

AEM 4332W - Solar Sail24 Boom Material [0/90] carbon fiber laminate. Polymer film inflation gas barrier. IM7 carbon fiber, E = 276 GPa. –Low CTE. TP407 polyurethane matrix, E = 1.3 GPa. –Tg = 55 degrees C.

AEM 4332W - Solar Sail25 Expected deployment loads of 20 N in compression dictate boom sizing. Conclusion: Booms sized to meet this requirement easily meet other criteria.

AEM 4332W - Solar Sail26 Deployment Booms heated to 75 degrees C. Inflation gas pressurizes booms for deployment. Booms rigidize as they cool to Sub- Tg (glass transition) temperatures. Deployment speed is controlled by a single motor which pays out the tensioning cables at 1 cm/sec. Motor retracts tension cables after booms are rigidized to pull out the sail.

AEM 4332W - Solar Sail27 Deployed Boom with Micro PPT Tip Thrusters

AEM 4332W - Solar Sail28 Future Work and FDR Deliverables Future Work: –Sliding mass Size Placement –Effects of structural deformation on attitude control. –Investigate low frequency vibration modes. –Volume of inflation gas needed. –Proper laminate analysis. FDR Deliverables: Configuration: Solid Model stowed and deployed Total Mass/Moment of inertia Deployment Methodology Structural Analysis

AEM 4332W - Solar Sail29 Attitude Control Alex Ordway Brian Miller

AEM 4332W - Solar Sail30 Attitude Control Detailed description of trade study –Sliding Mass characteristics Power consumption –10 W Approximate control torques –Being calculated; will be sufficient Mass required –10 kg, open for refinement –Tip thruster characteristics Power Consumption –100 W Mass required –10 kg

AEM 4332W - Solar Sail31 Attitude Control Detailed description of ACS Primary use of sliding mass Tip thrusters utilized as secondary ACS Configuration chosen for a number of reasons –Thrusters require more power to operate (~1kw) –Ion ejection from ions could interfere with solar arrays –Operational life of thrusters limited to 3000 hours Sliding mass offers comparable transfer times without aforementioned drawbacks Tip thrusters chosen offer smaller force at lower power usage, no significant life restrictions, lower probability of system interference

AEM 4332W - Solar Sail32 Attitude Control Detailed description ACS cont… –Tip Thruster Selection Micro Plasma Pulsed Thruster (Micro PPT) –Solid polymer fuel bar »Eliminates need for auxiliary fuel transport infrastructure –Can be utilized in off-nominal attitude situations in addition to being an available ACS when the solar sail is not deployed

AEM 4332W - Solar Sail33 Attitude Control ADS Primary –Interstellar Compass (ISC) Low power –3.5 W Exceptional Accuracy –0.1 deg (1σ) Low mass –2.5 kg –Technology has not flown Developed by Draper Laboratory

AEM 4332W - Solar Sail34 Attitude Control ADS Secondary –Sun Sensors Located on all solar oriented exterior planes Reorient space craft in off-nominal attitude situations Provide data to orient solar arrays for optimal solar collection

AEM 4332W - Solar Sail35 Future Work Finish attitude control simulation Calculate final required mass for ACS Refine simulation using information from structures group Consider sail ejection once orbit is achieved –Independent module ACS »Reaction wheels most likely candidate

Communications Casey Shockman

AEM 4332W - Solar Sail37 Frequency X-Band: 8.4 GHz –This is the typical frequency used, so DSN is becoming overloaded at this frequency. Ka-Band: 32 GHz –Due to overloaded X-Band frequency, the DSN is migrating to Ka-Band frequency. –Can transfer data much more quickly than X- Band.

AEM 4332W - Solar Sail38 Antenna Horn –High data transfer rate with low power required. –Works directly with recently developed Small Deep Space Transponder. –New design works with X-Band and Ka-Band transmit as well as X-Band receive. –Lighter and smaller than parabolic reflector or array. –High gain.

AEM 4332W - Solar Sail39

AEM 4332W - Solar Sail40

AEM 4332W - Solar Sail41 Current/Future Work Currently, I am working on a design space to optimize values for power required, antenna sizing, pointing accuracy, and signal to noise ratio. Problems include finding accurate equations for horn antenna systems.

AEM 4332W - Solar Sail42 Thermal Analysis Raymond Haremza

AEM 4332W - Solar Sail43 Carbon Fiber Mesh Carbon Fiber Mesh developed by ESLI Mesh is composed of a network of carbon fibers crisscross linked into a matrix that is mostly empty space. 200 times thicker than the thinnest solar sail material, but so porous that it weighs the same

AEM 4332W - Solar Sail44 Common Problems Traditional materials –tear easily –require heavy support structure to maintain tension –can build up static electricity –UV degrades and melt at high temperatures

AEM 4332W - Solar Sail45 Carbon Fiber Mesh Can tolerate temps as high as 4,500 deg F Small areal mass density: 30μm thickness compared to 2μm with same area density (~5g/m^2) Immune to UV degradation Ability to self-deploy, the carbon scrub-pad material could be packed so it pops out flat once released. This can eliminate the need for any complicated mechanical deployment mechanism, which decrease mass of the craft. Easier to deploy because it doesn’t cling or wrinkle Higher Melting Point

AEM 4332W - Solar Sail46 Carbon Fiber vs. Traditional Material Using sample microtruss which is formed from perfectly electrical conducting (PEC) wires. The time-average force on the sail can be found using physical optics assuming microtruss is illuminated by a uniform plane wave (UPW) and Carbon FiberAluminum Coated Mylar Force at 0.48AU = 0.348N

AEM 4332W - Solar Sail47 CP1 Solar Sail Material Developed by SRS Technologies created a 5 micro meter thick film constructed of CP1 with an aluminized front surface and a black emissive black surface. CP1 is a unique polymer which has favorable structural characteristics. Source: Scalable Solar Sail Subsystem Design Considerations

AEM 4332W - Solar Sail48 Thermal Analysis of Payload Module Found an innovative way to configure spacecraft parts which eliminate chassis, cables and connectors. MFS (Multifunctional Structures) achieves this by using MCM (multichip modules) and dissipating its heat through a thermal core fill, and utilizing aluminum honeycomb sandwiched between 2 fiber reinforced cyanate ester composite faceplates. This high density configuration increases payload-mass fraction and provides major weight volume and cost savings.

AEM 4332W - Solar Sail49 MFS Configuration Thermal copper strap used to transfer heat to radiator surface. Multichip Module - Specialized electronic package where multiple integrated circuits are packaged to do many jobs with one module. Hi-K facesheets (K13C2U) Aluminum Honeycomb Edge corefill High Conductivity Filler Kz = 700 W/mK High K Isotropic Carbon- Carbon Doubler Kz

AEM 4332W - Solar Sail50 Thermal Control of MFS In order to dissipate waste heat from the MCM along with solar energy loads on the outer skin. Radiation Equation Lateral Conductance Setting equal and solving for temp of baseplate yields Rate of heat flow Effective rad environment Emissivity of radiator Temp of base plate Heat flow path length Average radiator temp Cross sectional area Material thermal conductivity

AEM 4332W - Solar Sail51 Thermal Control Configuration Options For MFS Integration High Conductivity Composite Facesheet With Kx,Ky> 150 W/mK Incorporate Thermal Doubler Hi-K Corefill Kx, Ky > W/mK; Kz> W/mK Incorporate Heat Pipes Incorporate Deployable Radiator Where, Source: Thermal Management For Multifunctional Structures

AEM 4332W - Solar Sail52 Confirmation of MFS The Multifunctional Structure was successful based on the data returned from the Deep Space 1 mission. This mission the MFS was tested by powering it up once every two weeks which provided a data set containing health and status information, electrical- conductivity test data, and thermal-gradient measurements. The thermal-gradient data proved to stay within operating conditions.

AEM 4332W - Solar Sail53 Thermal Analysis of Boom Supports Carbon fiber booms need to maintain temperatures below 40 deg C. To achieve this a coating will be applied to the outside of the carbon fiber. By using the radiation equation and basic thermodynamics the required coefficient of absorbtivity, emmisivity can be found that satisfy these constraints. From these coefficients a coating can be chosen.

AEM 4332W - Solar Sail54 Thermal Properties of Carbon Fiber Boom Carbon fiber properties: R=13 cm Thickness =.25mm Length = 72 m K = 400 W/m Density = 1490 kg/m^3 Setting equal to each other and solving for temperature of the surface of the boom yields: R

Material Selection for Boom By graphing different values of absortivity and emmisivity the proper Coating can be found that will keep the boom under 313K. White Paint S13G-LO with, gives T =252K

AEM 4332W - Solar Sail56 Material Selection for Boom By graphing different values of absortivity and emmisivity the proper coating can be found that will keep the boom under 313K. White Paint (S13G-LO) with, gives T =252K

AEM 4332W - Solar Sail57 Future Work I plan on further investigating and analyzing the spacecraft components such as the fuel tank, additional thermal control methods, and complete analysis of MFS integration into the spacecraft configuration. Also working together with orbit group to run simulations with Aluminized Mylar, Kapton Carbon Fiber, and CP1 solar sails and find best material for our mission.

Power Michael Hiti

AEM 4332W - Solar Sail59 Objectives Determine the amount of power required to support the payload, and all other components of the spacecraft. Perform a trade study to determine whether to use a normal- pointing solar array or a fixed solar array. Determine the size and type of the solar array Determine the size and type of the batteries that will be used

AEM 4332W - Solar Sail60 Power Requirements BOL Power Requirement : ~878W EOL Power Requirement: ~ 203W Power (W) Remote Sensing Instruments Coronagraph4 All Sky Camera5 EUV Imager6 Magnetograph- Helioseismograph4 IN-SITU Instruments Magnetometer2 Solar Wind Ion Composition and Electron Spectrometer3.5 Energetic Particle3 Communications Satellite/Data Transmission50 Attitude Control 125 StructureHeat Curing Booms675 Misc Sliding Mass, Adjusting Array/Satellite/Antenna50 TOTAL877.5

AEM 4332W - Solar Sail61 Normal Pointing Solar Array Benefits: –A fold out array can be used to utilize its reflectance and thermal characteristics for thermal management –A sun tracker will already be being used –Able to collect maximum possible solar energy –Panels could be positioned to minimize thermal and radiation damage

AEM 4332W - Solar Sail62 Solar Array Sizing General Formulas: P chg = V chg * I chg = (V chg * C chg )/15h P EOL = P L + P chg P EOL = η rad * η angle * η temp * P BOL A array = P BOL / (η GaAs * I S * η pack )

AEM 4332W - Solar Sail63 Solar Array Sizing Normal Pointing Array Assuming: –a temperature efficiency reduction of ~40% –a radiation degradation of ~50% –a packing efficiency of ~90% –Gallium Arsenide cells Approximate Solar Array Area: 2.39m^2

AEM 4332W - Solar Sail64 Solar Array Sizing Conformal Solar Array Assuming: –a temperature efficiency reduction of ~55% –a radiation degradation of ~55% –cosine loss of ~81% –a packing efficiency of ~90% –Gallium Arsenide cells Approximate Solar Array Area: 4.37m^2

AEM 4332W - Solar Sail65 Battery Sizing General Equations: C chg = (P L * t d ) / (V avg * DOD) E bat = C chg * V avg m bat = E bat / e bat

AEM 4332W - Solar Sail66 Battery Sizing Ag-Cd batteries will be used for their reasonable energy density and cycle life Assuming: –a bus voltage of 28V – a DOD of ~25% –a maximum load duration of 2.0h Battery Mass = kg

AEM 4332W - Solar Sail67 Components Spectrolab Cells and Panels –28.3% efficiency –84 mg/cm^2 (cells) –2.06 kg/m^2 (panel)

AEM 4332W - Solar Sail68 Components Moog Solar Array Drives –Two-axis solar array drive –Power = 4W per axis –Mass = 4.2 kg

AEM 4332W - Solar Sail69 Future Work Refining sizing of battery and solar panel with more specific power requirements

AEM 4332W - Solar Sail70 Demonstration For FDR, we plan to have a demonstrated orbit which includes pointing requirements and attitude control.

AEM 4332W - Solar Sail71 Acknowledgements Stephanie Thomas, Princeton Satellite Systems Professor Joseph Mueller, University of Minnesota Professor Jeff Hammer, University of Minnesota Dr. William Garrard, University of Minnesota Kit Ruzicka, University of Minnesota