Design of Solar Powered Airplanes for Continuous Flight

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AAUTONOMOUSUTONOMOUS SSYSTEMSYSTEMS LLABAB

André Noth Doctoral Exam – September 30, 2008

Autonomous Systems Lab ETH Zentrum http://www.sky-sailor.ethz.ch/ Tannenstrasse 3, CLA E-mail: [email protected] 8092 Zürich, Switzerland 1/30 Outline

• Introduction • Design Methodology • Sky-Sailor Design • Sky-Sailor Prototype • Scaling • Conclusion

André Noth Phd Defense Autonomous Systems Lab ETH Zürich, 24.09.08 1/30 Motivations & Objective

• Project started with an ESA feasibility study

Introduction Mars exploration y Motivations y History of Solar Flight Satellites + extensive coverage, good resolution y State of the Art y Contributions - place of interest not freely selectable Design Methodology Gap for systems with + high-resolution imagery Sky-Sailor Design ? Sky-Sailor Prototype + extensive & selectable coverage Scaling Conclusion Rovers + excellent resolution, ground interaction - reduced range, limited by terrain

Î Study the feasibility of solar powered flight on Mars Î Develop and realize a fully functional prototype on Earth and demonstrate continuous flight

André Noth Phd Defense Autonomous Systems Lab ETH Zürich, 24.09.08 2/30 History of Solar Flight

• Started in 1974 • 90 solar powered airplanes listed from 1974 to 2008 Introduction y Motivations y History of Solar Flight Sunrise (1974) Gossamer Penguin (1980) Sunseeker (1990) Solong (2005) y State of the Art st st st 1 manned solar manned, crossed 1 continuous flight, y Contributions 1 solar powered flight powered flight the USA in 21 flight used thermals Design Methodology Sky-Sailor Design Sky-Sailor Prototype Scaling Conclusion

70’s 80’s 90’s 2000’s

Solar Riser (1979) Solar Challenger (1981) Helios (1999) Zephyr (2005) André Noth manned, battery solar manned, channel umanned, flew at umanned, flew 83h Phd Defense charged for short flights crossing > 29’000 m Autonomous Systems Lab ETH Zürich, 24.09.08 3/30 State of the art

Many solar airplanes in History Î … but no clear design methodologies explained

Introduction Î anyway useful practical papers on case studies y Motivations y History of Solar Flight [BOUCHER79, MACCREADY83, COLELLA94] y State of the Art y Contributions [ULM96,BRUSS91] Design Methodology Many design methodologies… Sky-Sailor Design Sky-Sailor Prototype Î … but rarely validated with a prototype [REHMET97, WEIDER06] Scaling Conclusion Î very often nice design methods [IRVING74, YOUNGBLOOD82, BAILEY92] but based on weak models for: • Weight prediction design method • Efficiencies

Î ends with irrealistic designs math. models [RIZZO08, ROMEO04] André Noth Phd Defense Autonomous Systems Lab ETH Zürich, 24.09.08 4/30 Contributions

• Design methodology

Introduction – Simplicity y Motivations y History of Solar Flight – Large design space y State of the Art y Contributions – Concrete and experienced based Design Methodology – Flexible and versatile Sky-Sailor Design Sky-Sailor Prototype Scaling Conclusion • Theory validation with a prototype – Achieve > 24h flight – Autonomous control

• Draw up a state of the art on solar aviation –History André Noth Phd Defense – Publications Autonomous Systems Lab ETH Zürich, 24.09.08 5/30 Design Methodology

Introduction Design Methodology y Required Energy y Solar Energy y Weight Models y Resolution

Sky-Sailor Design Sky-Sailor Prototype Scaling Conclusion

André Noth Phd Defense Autonomous Systems Lab ETH Zürich, 24.09.08 6/30 Design Methodology

Energy balance

Introduction Design Methodology y Required Energy y Solar Energy y Weight Models y Resolution

Sky-Sailor Design Sky-Sailor Prototype Scaling Conclusion Weight balance Lift L

Thrust T Drag D

Weight mg André Noth Phd Defense Autonomous Systems Lab ETH Zürich, 24.09.08 6/30 Methodology

• Sizing the airplane : hen & egg problem

Introduction Airplane Parts Design Methodology Weight balance •Solarcells y Required Energy y Solar Energy •Battery y Weight Models •Airframe y Resolution • Payload •… Aerodynamics & flight conditions? Sky-Sailor Design Sky-Sailor Prototype Î Total weight Î Level Flight Power Scaling Conclusion

Energy balance

• This loop can be solved: AAIteratively (trying existing components, refining the design) Analytically (using mathematic models of the components) André Noth BB Phd Defense Autonomous Systems Lab ÎAllows to establish some general design principles ETH Zürich, 24.09.08 7/30 Required Energy

• Equilibrium at steady level flight

ρ 2 3 L ==mg CSvL C ()2mg Introduction 2 D PDvlevel ==3/2 Design Methodology CSρ ρ 2 L y Required Energy DT== CD Sv y Solar Energy 2 y Weight Models y Resolution

Sky-Sailor Design • Power required η η η η Sky-Sailor Prototype 1 ctrl mot grb plr Scaling PPelectot= level Plevel Conclusion ηηηηctrl mot grb plr Pelectot 1 PP+ ++()PPav pld av pld becη ηbec

• Daily energy required

⎛⎞T EPT=+night André Noth elec tot elec tot⎜⎟ day Phd Defense ηηchrg dchrg Autonomous Systems Lab ⎝⎠ ETH Zürich, 24.09.08 8/30 Required Energy

Introduction Design Methodology y Required Energy y Solar Energy y Weight Models y Resolution

Sky-Sailor Design Sky-Sailor Prototype Scaling Conclusion

André Noth Phd Defense Autonomous Systems Lab ETH Zürich, 24.09.08 8/30 Solar Energy

• Daily average solar irradiance – Irradiance ~ cosine IT Introduction E = max day η Design Methodology day densityπ /2 wthr y Required Energy I T y Solar Energy – max day = f(date, location, weather) y Weight Models y Resolution Sky-Sailor Design • Daily energy obtained Sky-Sailor Prototype Scaling EEelectot= day density A scη scηη cbr mppt A Conclusion Eday density sc Eelectot

ηsccbrη ηmppt

• Daily energy required = Daily energy obtained

Î We compute Asc

André Noth Phd Defense Autonomous Systems Lab ETH Zürich, 24.09.08 9/30 Required Energy

Introduction Design Methodology y Required Energy y Solar Energy y Weight Models y Resolution

Sky-Sailor Design Sky-Sailor Prototype Scaling Conclusion

André Noth Phd Defense Autonomous Systems Lab ETH Zürich, 24.09.08 9/30 Weight Prediction Models

• Fixed Masses

• Payload mpld Introduction

Design Methodology • Avionic System (Autopilot) mav y Required Energy y Solar Energy y Weight Models • Airplane Structure y Resolution

Sky-Sailor Design – In the literature Sky-Sailor Prototype • [BRANDT95, GUGLIERI96,…] consider WkS = ⋅ Scaling af Conclusion Î valid locally • [HALL68] calculated all airframe elements separately Î complex, only valid for 1000-3000 lbs airplanes

0.311 0.778 0.467 • [STENDER69] proposed WnSARaf = 8.763 Î very widely adopted

0.656 0.651 Î adapted by [RIZZO04] to UAV WSARaf =15.19 André Noth Phd Defense Autonomous Systems Lab ETH Zürich, 24.09.08 10/30 Weight Prediction Models

• Verification of these models – Database of 415 sailplane Introduction – Structure Weight vs Area Design Methodology y Required Energy ÎModels don’t fit well y Solar Energy y Weight Models y Resolution

Sky-Sailor Design optimistic Sky-Sailor Prototype • New model proposed Scaling Conclusion – Same equation, new coef. pessimistic – Least square method fit – Data set divided in two – 5 iterations = 5 qualities – Best 5% model:

Keywords: Wing weight to area , wing area as a function 3.10− 0.25 of structural weight, great flight diagram, Tennekes, wing WbARaf =⋅0.44 mass to area, mass to surface, area to mass, surface to André Noth mass. Phd Defense Autonomous Systems Lab ETH Zürich, 24.09.08 11/30 Weight Prediction Models

Overview Biologists already studied flying in nature to extract tendencies

Introduction Design Methodology [TENNEKES92] presented the y Required Energy « Great Flight Diagram » y Solar Energy Clear cubic tendancy y Weight Models y Resolution

Sky-Sailor Design Our model is // to Tennekes curve Sky-Sailor Prototype Scaling [STENDER69,RIZZO04] seem Conclusion incoherent

Keywords: Wing weight to area , wing area as a function of structural weight, great flight diagram, Tennekes, wing mass to area, mass to surface, area to mass, surface to mass.

André Noth Phd Defense Autonomous Systems Lab ETH Zürich, 24.09.08 Required Energy

Introduction Design Methodology y Required Energy y Solar Energy y Weight Models y Resolution

Sky-Sailor Design Sky-Sailor Prototype Scaling Conclusion

André Noth Phd Defense Autonomous Systems Lab ETH Zürich, 24.09.08 12/30 Weight Prediction Models

• Solar Cells – Surface = f(cells properties, required energy) Introduction – Weight proportionnal to the surface Design Methodology y Required Energy mAkk=+( ) y Solar Energy scscscenc y Weight Models y Resolution

Sky-Sailor Design • Maximum Power Point Tracker Sky-Sailor Prototype Scaling – Study of high efficiency MPPT Conclusion Î WeightlinearwithPmax

mkPmppt= mppt sol max

= kAmpptIm axηη sc cbr η mppt sc

• Batterie – Weight proportionnal to capacity

André Noth Tnight Phd Defense mPbat= elec tot Autonomous Systems Lab ηdchrgk bat ETH Zürich, 24.09.08 13/30 Required Energy

Introduction Design Methodology y Required Energy y Solar Energy y Weight Models y Resolution

Sky-Sailor Design Sky-Sailor Prototype Scaling Conclusion

André Noth Phd Defense Autonomous Systems Lab ETH Zürich, 24.09.08 13/30 Weight Prediction Models

• Propulsion group – Existing models but none is proven on a large range Introduction – Very large databases created Design Methodology y Required Energy 2264 motors y Solar Energy y Weight Models 170 electronics controllers y Resolution Interpolated Models Sky-Sailor Design 997 gearboxes Sky-Sailor Prototype 673 propellers Scaling Conclusion

André Noth Phd Defense Autonomous Systems Lab ETH Zürich, 24.09.08 Keywords: Mass to power ratio of motors / Power to mass ratio of electrical motors, piezoelectric motors, Motor mass to power ratio / Motor power to mass ratio of electromagnetic motors, brushed and brushless motors energy density, power density, density of energy, density of power. 14/30 Summary and Resolution

Introduction Design Methodology y Required Energy y Solar Energy y Weight Models y Resolution

Sky-Sailor Design Sky-Sailor Prototype Scaling Conclusion

Mission parameters Airplane’s shape variables Others: Technological parameters

André Noth Phd Defense Î Search b and AR for which the loop has a solution Autonomous Systems Lab ETH Zürich, 24.09.08 15/30 Sky-Sailor Design

Introduction Design Methodology Sky-Sailor Design y Math. Application y Real-Time Simulation

Sky-Sailor Prototype Scaling Conclusion

André Noth Phd Defense Autonomous Systems Lab ETH Zürich, 24.09.08 16/30 Methodology application

• Mission parameters

– Solar flight possible 3 months in summer (Tday=13.2h) Introduction – 50g payload consuming 0.5W Design Methodology Sky-Sailor Design – Flight location CH, at 500m above sea level y Meth. Application y Real-Time Simulation

Sky-Sailor Prototype Scaling Conclusion

André Noth Phd Defense Autonomous Systems Lab ETH Zürich, 24.09.08 16/30 Methodology application

Introduction Design Methodology Sky-Sailor Design y Meth. Application y Real-Time Simulation

Sky-Sailor Prototype Scaling Conclusion

• Sky-Sailor Layout –3.2m wingspan –0.78m2 wing area (0.525m2 covered by cells) André Noth Phd Defense – 14.2W for level flight (electrical) Autonomous Systems Lab ETH Zürich, 24.09.08 16/30 Real-Time Simulation Objectives – Validate the design

Introduction – Analyze energy flows on the airplane each second Design Methodology – Rapidly see influence of parameters change Sky-Sailor Design y Meth. Application y Real-Time Simulation

Sky-Sailor Prototype Scaling Conclusion

André Noth Phd Defense Autonomous Systems Lab ETH Zürich, 24.09.08 17/30 Real-Time Simulation

Simulation of a 48 h flight – On the 21st of June Introduction – On the 4th of August (+1.5 month) Design Methodology Sky-Sailor Design y Meth. Application y Real-Time Simulation

Sky-Sailor Prototype Scaling Conclusion

André Noth Phd Defense Autonomous Systems Lab ETH Zürich, 24.09.08 18/30 Sky-Sailor Prototype

Introduction Design Methodology Sky-Sailor Design Sky-Sailor Prototype y Config & Structure y Aerodynamics y Solar Generator y Propulsion y Autopilot y Modeling & Control y Experiments

Scaling Conclusion

André Noth Phd Defense Autonomous Systems Lab ETH Zürich, 24.09.08 19/30 Sky-Sailor Prototype

Configuration 3 axis glider, V-tail, constant chord Adapted from « Avance » record airplane of W. Engel Introduction Naturally stable Design Methodology Structure Sky-Sailor Design Sky-Sailor Prototype Composite materials (Carbon, Aramide, Balsa) y Config & Structure Spar-Ribs construction method y Aerodynamics Wingspan 3.2 m y Solar Generator y Propulsion Surface 0.776 m2 y Autopilot y Modeling & Control Empty Weight 0.725 kg y Experiments

Scaling Conclusion

André Noth Phd Defense Autonomous Systems Lab ETH Zürich, 24.09.08 19/30 Aerodynamics

Dedicated Airfoil we3.55-9.3 Nominal flight speed 8.4 m/s Nominal flight power (2.55 kg) 9 W Introduction Design Methodology Glide ratio 23.5 Sky-Sailor Design Vertical glide speed 0.35 m/s Sky-Sailor Prototype y Config & Structure y Aerodynamics y Solar Generator y Propulsion y Autopilot y Modeling & Control y Experiments

Scaling Conclusion

André Noth Phd Defense Autonomous Systems Lab ETH Zürich, 24.09.08 20/30 Solar Generator

Introduction Design Methodology Sky-Sailor Design Sky-Sailor Prototype y Config & Structure y Aerodynamics y Solar Generator 216 RWE solar cells (17% eff, ~90 W max) y Propulsion y Autopilot – encapsulated into 3 solar panels y Modeling & Control y Experiments – non reflective encapsulation

Scaling Conclusion Maximum Power Point tracker – 97 % efficiency for 25 g and 90 W

Lithium-Ion battery – 250 Wh, 1.056 kg Î 240 Wh/kg André Noth Phd Defense – cycle efficiency 94.8 % Autonomous Systems Lab ETH Zürich, 24.09.08 21/30 Propulsion group

Introduction Design Methodology Sky-Sailor Design High efficiency Propeller from E. Schöberl Sky-Sailor Prototype – 60 cm diameter y Config & Structure –Carbon y Aerodynamics y Solar Generator – 85.6 % efficiency y Propulsion y Autopilot y Modeling & Control Î Program created to select the best motor & gearbox combination y Experiments out of 2600 motors Scaling Conclusion Gearbox – Spur gearhead, own development

Brushless Motor (LRK Strecker) – 86.8% efficiency – Excellent cooling – Low weight

André Noth Phd Defense Autonomous Systems Lab Jeti Advance 45 Opto Plus brushless controller ETH Zürich, 24.09.08 22/30 Autopilot

• Special needs (solar panels monitoring,…) • Extreme weight & power constraints Î Own Control & Navigation System Introduction Link to videos: http://www.sky-sailor.ethz.ch/videos.htm Design Methodology Sky-Sailor Design Sky-Sailor Prototype y Config & Structure y Aerodynamics y Solar Generator y Propulsion y Autopilot y Modeling & Control y Experiments

Scaling Conclusion

André Noth Phd Defense Autonomous Systems Lab ETH Zürich, 24.09.08 23/30 Modeling & Control

Goals Tune controller parameters Test Navigation algorithms Introduction Evaluate airplane capabilities Design Methodology 7 Sky-Sailor Design Sky-Sailor Prototype FFtot=+ prop∑ FF Li + di i=1 y Config & Structure 7 y Aerodynamics y Solar Generator Mtot= ∑MFrFr i+×+× Li i di i y Propulsion i=1 y Autopilot y Modeling & Control Fprop = fxU(, 1 ) y Experiments ρ F = C Sv2 Scaling li li2 i Conclusion FC= ρ Sv2 di di2 i M =⋅CSvchordρ2 imii2 i

[CCldm111 C]= fAoaU(,) i 2 [] []CCCli di mi= fAoa()fori=2,3,4 i []CC C= fAoaU(,) []ldm555 i 3 André Noth CC C= fAoaU(,) Phd Defense ldm666 i 4 Autonomous Systems Lab CCldm777 C= fAoaU(,) i 5 ETH Zürich, 24.09.08 24/30 Experiments

• Several tests with subgroups – Efficiencies increase – Weight reduction Introduction Design Methodology – Adding functionnalities Sky-Sailor Design – Safety increase Sky-Sailor Prototype y Config & Structure y Aerodynamics y Solar Generator • Flight tests with a y Propulsion y Autopilot non-solar proto y Modeling & Control y Experiments – Aerodynamics validation

Scaling – Power consumption verification Conclusion – Autopilot electronic tests – Control & Navigation tuning

• Flight tests with the Sky-Sailor – Solar charge – Long flights (>3h) André Noth Phd Defense – 24 hours flight Autonomous Systems Lab Flight videos: ETH Zürich, 24.09.08 http://www.sky-sailor.ethz.ch/videos.htm 25/30 27 hours flight, 21st of June 2008

Conditions – Excellent irradiance – Bad wind conditions Î more power needed during the day Introduction Design Methodology Sky-Sailor Design Achievements Sky-Sailor Prototype y Config & Structure – Duration: 27h05 y Aerodynamics y Solar Generator – Distance: 874 km y Propulsion y Autopilot – Av. speed: 8.4 m/s y Modeling & Control y Experiments – Mean power: 23+1.9W

Scaling –Eused:675 Wh Conclusion –Eobtained:768 Wh

Î Continuous flight proved to be feasible without André Noth Phd Defense thermic or altitude gain Autonomous Systems Lab ETH Zürich, 24.09.08 25/30 Scaling & Other considerations

Introduction Design Methodology Sky-Sailor Design Sky-Sailor Prototype Scaling y Down: MAV y Up: Manned & Hale y Epot & Thermal

Conclusion

André Noth Phd Defense Autonomous Systems Lab ETH Zürich, 24.09.08 26/30 Down Scaling Drawbacks – Efficiency of propulsion group Ô

Introduction – At low power, DC motor but no BLDC Design Methodology Sky-Sailor Design – Efficiency of aerodynamic Ô (low Re) Sky-Sailor Prototype – Servos below 5 grams Î poor quality Scaling y Down: MAV – High E batt not easily scalable y Up: Manned & Hale density y Epot & Thermal – Autopilot sensors limited (due to Conclusion weight, ex: no tiny GPS or IMU – Silicon solar cells scale in 2D (not 3D) • Not flexible for low radius • Weight percentage Ò

– MPPT efficiency Ô (Vdiode loss/VMPPT Ò)

André Noth Î No 24h solar flight at MAV size, but day flight possible Phd Defense Autonomous Systems Lab ETH Zürich, 24.09.08 26/30 Up Scaling

Drawback Introduction 3 Design Methodology – Structure weight ~ b Sky-Sailor Design – Theory said it should be ~ b2 Sky-Sailor Prototype Scaling ÎThe bigger they are, the y Down: MAV y Up: Manned & Hale lighter the construction y Epot & Thermal method has to be Conclusion ÎFragility & Risks

Î Continuous flight possible only for 1 or 2 passengers but… Î Low speed (long flights) Î No comfort possible

André Noth Phd Defense Autonomous Systems Lab ETH Zürich, 24.09.08 27/30 Potential Energy & Thermal soaring

Two possibilities to increase flight endurance are:

Introduction Design Methodology Sky-Sailor Design – Use of altitude to store energy Sky-Sailor Prototype Scaling + less battery needed y Down: MAV y Up: Manned & Hale - altitude varies Î aerodynamics not optimized for a y Epot & Thermal

Conclusion fixed density

– Thermal soaring + free climbing, save energy - require a method to detect & soar thermal

André Noth Phd Defense Autonomous Systems Lab ETH Zürich, 24.09.08 28/30 Conclusion

• Methodology developed – Simple and versatile Introduction – Valid on a large range Design Methodology – Solid weight & efficiency models Sky-Sailor Design – Allows fast feasibility studies Sky-Sailor Prototype Scaling – Allows to identify bottle necks Conclusion • Prototype built – Validation of the design – Continuous flight proven – Very good know-how acquired

André Noth Phd Defense Autonomous Systems Lab ETH Zürich, 24.09.08 29/30 Conclusion

• Scaling problems – Down: efficiencies and aerodynamics Introduction – Up: large wing structure Design Methodology Sky-Sailor Design • Outlook Sky-Sailor Prototype – Increase # parameters (efficiency = f(power)) Scaling Conclusion – Flight algorithm learning energy saving – Thermal soaring – Building: improve costs, time & robustness

André Noth Phd Defense Autonomous Systems Lab ETH Zürich, 24.09.08 29/30 Future of solar aviation

• MAV size – Needs still many improvements (eff, aerodynamics, batteries)

Introduction • At 2-10 meters Design Methodology – Forest fire monitoring Sky-Sailor Design – Pipeline surveillance Sky-Sailor Prototype –… Scaling Î In 10 years with tech. improvements (batteries, solar cell) Conclusion • HALE – Act as mobile phone antenna – Real need to stay airborne Î Will require many improvements (structure,batteries)

• Manned airplane (transportation) – High fragility, risks and long trips – Even with a 100% eff. airplane, problem is the sun! Î A better idea would be to:

ÎTransform Esolar on the ground Æ H2 ÎUse H2 in flight (fuel cell & electrical motor)

André Noth Phd Defense Autonomous Systems Lab ETH Zürich, 24.09.08 29/30 Thank you for your attention

Introduction Questions ? Design Methodology Sky-Sailor Design Sky-Sailor Prototype Scaling Conclusion

Special Thanks to: – Prof. Siegwart and the entire ASL

André Noth – Walter Engel & all the people who worked on the project Phd Defense Autonomous Systems Lab – Doctoral comity ETH Zürich, 24.09.08 29/30 Appendices

• Solar Generator • Overall – Spectrum, Albedo, Sun angle – Energy Chain

Introduction – Tday & Imax – Solar Airplane: light and slow Design Methodology – Best research cell efficiencies – Weight-Power-Autonomy Sky-Sailor Design – I-V curve – Methodology Resolution Sky-Sailor Prototype – MPPT – 30 Parameters – Integration in the wing – Weight distribution Scaling Conclusion • Energy Storage • Applications – All solutions – Potential applications – Energy density of fuel – Sky-Sailor – Lithium-Ion battery evolution – MAV • Propulsion Group – Manned – Motors – HALE – Propeller – Mars – Weight prediction models • Other • Autopilot – Using thermals – Schematic – Sun Surfer – Telemetry – Design phases – Power consumption – Airframe model – Placement – 27 hours flight – GUI (thermals) – Simulation & modeling André Noth Phd Defense Autonomous Systems Lab ETH Zürich, 24.09.08 29/30 Solar Generator

Solar Generator

André Noth Phd Defense Autonomous Systems Lab ETH Zürich, 24.09.08 Solar Energy

Solar Spectrum

Direct, diffused and reflected light

André Noth Phd Defense Angle of incidence Autonomous Systems Lab ETH Zürich, 24.09.08 variation Variation of Tday and Imax along year

André Noth Phd Defense Autonomous Systems Lab ETH Zürich, 24.09.08 Solar Cells Research

André Noth Phd Defense Autonomous Systems Lab ETH Zürich, 24.09.08 Solar Cell

André Noth Phd Defense Autonomous Systems Lab ETH Zürich, 24.09.08 MPPT

André Noth Phd Defense Autonomous Systems Lab ETH Zürich, 24.09.08 Solar cells integration Structure

André Noth Phd Defense Autonomous Systems Lab ETH Zürich, 24.09.08 Energy storage

Energy Storage

André Noth Phd Defense Autonomous Systems Lab ETH Zürich, 24.09.08 Energy storage solutions

André Noth Phd Defense Autonomous Systems Lab ETH Zürich, 24.09.08 Energy Storage

Energy density of some reactants [kWh/kg] (LHV Lower heating value)

0 10 20 30 Hydrogen 33.3

Methane 13.9

Propane 12.9

Gasoline 12.2

Diesel 11.7

Oil (Colza,…) 10.4

Ethanol 7.5

Methanol 5.6

Sugar 4.4

Best 2008 LiIon Battery 0.2

André Noth Phd Defense Autonomous Systems Lab ETH Zürich, 24.09.08 Î Important to keep in mind Availability / Efficiency of converters Lithium-Ion battery evolution

Energy density + 6.6%/year Price - 17%/year André Noth Phd Defense Autonomous Systems Lab ETH Zürich, 24.09.08 Propulsion Group

Propulsion Group

André Noth Phd Defense Autonomous Systems Lab ETH Zürich, 24.09.08 Motors

André Noth Phd Defense Autonomous Systems Lab ETH Zürich, 24.09.08 Propeller

André Noth Phd Defense Autonomous Systems Lab ETH Zürich, 24.09.08 Weight prediction models Propellers Brushless controllers

Gearboxes

André Noth Phd Defense Autonomous Systems Lab ETH Zürich, 24.09.08 Autopilot

Autopilot

André Noth Phd Defense Autonomous Systems Lab ETH Zürich, 24.09.08 Autopilot overview

André Noth Phd Defense Autonomous Systems Lab ETH Zürich, 24.09.08 Telemetry

André Noth Phd Defense Autonomous Systems Lab ETH Zürich, 24.09.08 Autopilot power consumption

André Noth Phd Defense Autonomous Systems Lab ETH Zürich, 24.09.08 Element placement in fuselage

André Noth Phd Defense Autonomous Systems Lab ETH Zürich, 24.09.08 GUI (thermals)

André Noth Phd Defense Autonomous Systems Lab ETH Zürich, 24.09.08 Modeling & Simulation

André Noth Phd Defense Autonomous Systems Lab ETH Zürich, 24.09.08 Overall

Overall

André Noth Phd Defense Autonomous Systems Lab ETH Zürich, 24.09.08 Energy chain

A succession of losses….

André Noth Phd Defense Autonomous Systems Lab Î Important to Ò efficiencies ETH Zürich, 24.09.08 Why are solar airplanes large and slow ?

1 2 L = CSvL ρ 2 CD Speed v x CL

1 2 Thrust T DCSv= D ρ 2 C x D C L Weight mg

1. Equilibrium of forces 2. Ratio between L and D is equal to CL/CD Î the same ratio occurs between thrust and weight Î independent of v, it only requires Sv2 constant

3. Power for level flight is thus Prequired = T⋅ v = (mg ⋅⋅CCDL/) v 4. A way to reduce the power is to lower the speed v 2 André Noth Î in order to keep the lift (Sv constant), S needs to be increased Phd Defense Autonomous Systems Lab ETH Zürich, 24.09.08 Î Solar airplanes generally have large wings and a low speed Weight – Power - Autonomy

André Noth Phd Defense Autonomous Systems Lab ETH Zürich, 24.09.08 Methodology Resolution

mm=+ctrl m payload + m struct + m solar ++ m batt m mppt + m prop 3 1 x maaaaaaa−+++()() m2 =++++ aaaaa()() aab1 0178956 b 27956 34 aa The equation of10 the total mass is 11 1 3 ma−=+ m2 a abx1 N10b 11 4 a13 a12 André Noth It can be shown that it has a solution if: Phd Defense Autonomous Systems Lab 2 4 ETH Zürich, 24.09.08 aa≤ 12 13 27 30 Parameters

André Noth Phd Defense Autonomous Systems Lab ETH Zürich, 24.09.08 Sky-Sailor weight distributions

André Noth Phd Defense Autonomous Systems Lab ETH Zürich, 24.09.08 Applications

Applications

André Noth Phd Defense Autonomous Systems Lab ETH Zürich, 24.09.08 Potential Applications

• high altitude communication platform • law enforcement • border surveillance • forest fire fighting • power line inspection •…

André Noth Phd Defense Autonomous Systems Lab ETH Zürich, 24.09.08 Sky-Sailor

What is the influence of battery technology on the maximal flying altitude ?

André Noth Phd Defense Autonomous Systems Lab ETH Zürich, 24.09.08 MAV

André Noth Phd Defense Autonomous Systems Lab ETH Zürich, 24.09.08 Manned

André Noth Phd Defense Autonomous Systems Lab ETH Zürich, 24.09.08 HALE Platform

Payload: 300 Kg Altitude: 21’000 m Mission time: 3 months in summer

André Noth Phd Defense Autonomous Systems Lab ETH Zürich, 24.09.08 HALE Platform

André Noth Phd Defense Autonomous Systems Lab ETH Zürich, 24.09.08 Mars design

André Noth Phd Defense Autonomous Systems Lab ETH Zürich, 24.09.08 Storing Potential Energy

André Noth Phd Defense Autonomous Systems Lab ETH Zürich, 24.09.08 Using Thermals

André Noth Phd Defense Autonomous Systems Lab ETH Zürich, 24.09.08 Link to videos: http://www.sky-sailor.ethz.ch/videos.htm Sun-Surfer

Objective: Î reduce the scale and cost Î develop low-cost solar MAVs with payload capacity of ~40 gr

Sun-Surfer I Wingspan: 0.77 meters Weight: 115 g P level flight: 1 W P solar : 3 W

Sun-Surfer II Wingspan: 0.78 meters Weight: 190 g P level flight: 2.4 W

André Noth P solar : 8 W Phd Defense Autonomous Systems Lab ETH Zürich, 24.09.08 Design Phases

André Noth Phd Defense Autonomous Systems Lab ETH Zürich, 24.09.08 Airframe model

André Noth Phd Defense Autonomous Systems Lab ETH Zürich, 24.09.08 27 hours flight

André Noth Phd Defense Autonomous Systems Lab ETH Zürich, 24.09.08