Solar Sail Project AEM 4332W – Spacecraft Design Preliminary Design Review March 27, 2007 Eric Blake Jon Braam Raymond Haremza Michael Hiti Kory Jenkins Daniel Kaseforth Brian Miller Alex Ordway Casey Shockman Lucas Veverka Megan Williams (Team Lead)

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 Sail

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

Project Overview Orbit Non-Keplarian orbit Structure 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: 13.92 kg AEM 4332W - Solar Sail

Design Strategy AEM 4332W - Solar Sail

Design Strategy Orbit Trade Studies Structure 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 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 Sail

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

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

Orbit Control Problem Assumptions 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 Sail

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

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

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

Orbit Control Orbital elements AEM 4332W - Solar Sail

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

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 Sail

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

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 Sail

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

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

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

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 Sail

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 Sail

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 Sail

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 Sail

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 Sail

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

Future Work and FDR Deliverables 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 Sail

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

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 10 kg AEM 4332W - Solar Sail

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 Sail

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 Sail

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 Sail

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 Sail

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 AEM 4332W - Solar Sail

Communications Casey Shockman

Frequency X-Band: 8.4 GHz Ka-Band: 32 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 Sail

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 Sail

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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 Sail

Thermal Analysis Raymond Haremza AEM 4332W - Solar Sail

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 Sail

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 Sail

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 Sail

Carbon Fiber vs. Traditional Material Aluminum Coated Mylar 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 Force at 0.48AU = 0.348N AEM 4332W - Solar Sail

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 Sail

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

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

Thermal Control Configuration Options For MFS Integration Incorporate Thermal Doubler Hi-K Corefill Kx, Ky > 150-1500 W/mK; Kz> 40-700 W/mK High Conductivity Composite Facesheet With Kx,Ky> 150 W/mK Incorporate Heat Pipes Incorporate Deployable Radiator Where, AEM 4332W - Solar Sail Source: Thermal Management For Multifunctional Structures

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 Sail

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 Sail

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

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 =282K

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 and Carbon Fiber solar sail and find best material for our mission. AEM 4332W - Solar Sail

Power Michael Hiti

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 Sail

Power Requirements BOL Power Requirement : ~878W   Power (W) Remote Sensing Instruments Coronagraph 4 All Sky Camera 5 EUV Imager 6 Magnetograph-Helioseismograph IN-SITU Instruments Magnetometer 2 Solar Wind Ion Composition and Electron Spectrometer 3.5 Energetic Particle 3 Communications Satellite/Data Transmission 50 Attitude Control 125 Structure Heat Curing Booms 675 Misc Sliding Mass, Adjusting Array/Satellite/Antenna TOTAL 877.5 BOL Power Requirement : ~878W EOL Power Requirement: ~ 203W AEM 4332W - Solar Sail

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 Sail

Solar Array Sizing General Formulas: Pchg = Vchg* Ichg = (Vchg* Cchg)/15h PEOL = PL + Pchg PEOL = ηrad* ηangle* ηtemp* PBOL Aarray = PBOL / (ηGaAs* IS * ηpack) AEM 4332W - Solar Sail

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 Sail

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 Sail

Cchg = (PL* td ) / (Vavg * DOD) Battery Sizing General Equations: Cchg = (PL* td ) / (Vavg * DOD) Ebat = Cchg * Vavg mbat = Ebat / ebat AEM 4332W - Solar Sail

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 = 13.92 kg AEM 4332W - Solar Sail

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

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

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

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 AEM 4332W - Solar Sail