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Flight Without Fuel Regenerative Soaring Theory July 2008 Update

Flight Without Fuel Regenerative Soaring Theory July 2008 Update Originally Presented at ESA 2006 Western Workshop J. Philip Barnes Pelican Aero Group. Important notes to Readers: View “ point-by-point ” via Slide Show (F5) View or Print “Notes Pages” for slide text.

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Flight Without Fuel Regenerative Soaring Theory July 2008 Update

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  1. Flight Without Fuel Regenerative Soaring Theory July 2008 Update Originally Presented at ESA 2006 Western Workshop J. Philip BarnesPelican Aero Group Important notes to Readers: View “point-by-point” via Slide Show (F5) View or Print “Notes Pages” for slide text Flight Without Fuel - Regenerative Soaring www.esoaring.com J. Philip Barnes

  2. Presentation Contents • Introduction to Regenerative Soaring • Introduction to Regenerative Soaring • Modeling a Representative Thermal • Sailplane & Regen Design Comparison • Weight & Size Impacts of Adding Regen • Performance ~ New formulation, New insight • Windprop Aerodynamics & Performance • Flight in the Thermal, with & without regen • Preview ~ “solar-augmented” regen soaring • Conclusions ~ “flight without fuel” Flight Without Fuel - Regenerative Soaring www.esoaring.com J. Philip Barnes

  3. Introduction to Soaring • Soaring flight is sustained by atmospheric motion • Repeated “energy cycle” keeps the aircraft aloft • Requires high efficiency: aero, structural, & systems • Requires strategy and intelligent maneuvering • Classical: float up in a thermal ~ glide to next thermal • High-performance sailplane • Dynamic: “wind profile” ~ upwind climb / d’wind dive • Wandering albatross in 20-m boundary layer over flat sea • Regenerative: “windprop” dual-role windmill / prop • “Regen” in thermal ~ cruise / pinwheel glide to next thermal • Option:“solar-augmented” glide, in lieu of pinwheeling Flight Without Fuel - Regenerative Soaring www.esoaring.com J. Philip Barnes

  4. Regen Powertrain • Windprop • Fixed rotation direction • Sign change with mode • Thrust • Torque • Power • Current Speed Control Motor Gen Optional solar panel Optional Gearbox ESU • Energy Storage: • Battery • Ultra capacitor • Flywheel motor-generator • Self-contained takeoff • Emergency cruise/climb • “Flight without fuel” Flight Without Fuel - Regenerative Soaring www.esoaring.com J. Philip Barnes

  5. Elevation and Total Specific Energy • 3 “elevations” to analyze regenerative soaring • zo Elevation above the ground • z  Elevation relative to the “local airmass” • relative to ground-based observer for still air • relative to balloon-based observer in a thermal • zt “Total elevation” or “total specific energy” • Total system energy per unit vehicle weight • kinetic + potential + stored • Corresponding “Climb” rates (m/s) herein: • dzo/ dt  climb rate seen by ground-based observer • dz / dt  climb rate (), relative to local airmass • dzt / dt  Rate of change of total specific energy Flight Without Fuel - Regenerative Soaring www.esoaring.com J. Philip Barnes

  6. Presentation Contents • Introduction to Regenerative Soaring • Modeling a Representative Thermal • Sailplane & Regen Design Comparison • Weight & Size Impacts of Adding Regen • Vehicle Performance ~ Steady climb or sink • Windprop Aerodynamics & Performance • Flight in the Thermal, with & without regen • Preview ~ “solar-augmented” regen soaring • Conclusions ~ “flight without fuel” Flight Without Fuel - Regenerative Soaring www.esoaring.com J. Philip Barnes

  7. Characteristics of a Thermal • Rising column of air ~ 1oC warmer than ambient • 20-min lifetime; grows with square root of time • Updraft core at about 25% of thermal height • Low-level: fed from the side ~ cylindrical shape • Mid-level: fed from above & sides ~ conical shape • Approximate thermal model herein: • Hybrid of data from Scorer, Carmichael, & Allen • Thermal envelope, Radial decay, Core location • “Static & mature” ~ 4-km height, 5-m/s core • Assumed to support 16-min of thermalling Flight Without Fuel - Regenerative Soaring www.esoaring.com J. Philip Barnes

  8. Thermal Updraft Contours • 1oC warm-air column • 20-min lifetime • ~ solar power x 10 Total Energy = Kinetic + Potential + Stored Total Energy = Kinetic + Potential Flight Without Fuel - Regenerative Soaring www.esoaring.com J. Philip Barnes

  9. Presentation Contents • Introduction to Regenerative Soaring • Modeling a Representative Thermal • Sailplane & Regen Design Comparison • Weight & Size Impacts of Adding Regen • Vehicle Performance ~ Steady climb or sink • Windprop Aerodynamics & Performance • Flight in the Thermal, with & without regen • Preview ~ “solar-augmented” regen soaring • Conclusions ~ “flight without fuel” Flight Without Fuel - Regenerative Soaring www.esoaring.com J. Philip Barnes

  10. Weight & Size Impact of Adding Regeneration 265-kg Sailplane 13-m span, A=16 400-kg Regen 16-m span, A=16 Flight Without Fuel - Regenerative Soaring www.esoaring.com J. Philip Barnes

  11. Sailplane 3-View • 265 kg • 13-m • A=16 Flight Without Fuel - Regenerative Soaring www.esoaring.com J. Philip Barnes

  12. “RegenoSoar” 3-View • 400 kg • 16-m • A=16 Flight Without Fuel - Regenerative Soaring www.esoaring.com J. Philip Barnes

  13. RegenoSoar ~ In Flight Flight Without Fuel - Regenerative Soaring www.esoaring.com J. Philip Barnes

  14. Presentation Contents • Introduction to Regenerative Soaring • Modeling a Representative Thermal • Sailplane & Regen Design Comparison • Weight & Size Impacts of Adding Regen • Performance ~ new formulation, new insight • Windprop Aerodynamics & Performance • Flight in the Thermal, with & without regen • Preview ~ “solar-augmented” regen soaring • Conclusions ~ “flight without fuel” Flight Without Fuel - Regenerative Soaring www.esoaring.com J. Philip Barnes

  15. Section and Vehicle Drag Polars Min Sink here Section Windprop System Removed Max L/D here cDo Sailplane and “clean” Regen 1.50 Lift Coefficient, c or c A = 16 L l cLmax 1.25 1.00 0.75 0.50 0.25 Drag Coefficient, c or c D d 0.00 0.00 0.01 0.02 0.03 0.04 0.05 Flight Without Fuel - Regenerative Soaring www.esoaring.com J. Philip Barnes

  16. Vehicle Performance ~ New Formulation, New Insight Derive steady-climb Eqn v l= nn w t-d f g g w dz/dt = [ nn(d/l)v ] [ t/d - 1 ] Note:nn= cosg /cosf cL= nn w / (qs) • Regen t /d • climb:  6.3 • cruise: = 1.0 • solar-aug glide:  0.5 • pinwheel glide:  -0.1 • efficient regen (thermal):  -0.4 • capacity regen (descent):  -1.0 • Sailplane • t/d=0 (no thrust) • sink rate (-dz/dt) = nn(d/l)v • Sailplane and Regen • sink increases with g-load (nn) • sink increases with airspeed (v) Flight Without Fuel - Regenerative Soaring www.esoaring.com J. Philip Barnes

  17. Load Factor (nn) ~ “g-load” and Turn Radius Load Factor and Bank Angle 50 f o Bank Angle, 40 Load Factor and Turn Radius 30 400 - 1 f = g cos (cos / n ) 1.05 n 20 350 n 2 = g f r v cos /( g tan ) n 300 10 Turn Radius, m 1.1 250 Load Factor, n ~ g n 0 200 1.2 1.0 1.1 1.2 1.3 1.4 1.5 1.6 150 l= nn w v Thermalling 1.4 1.6 100 f g 50 Airspeed, v_km/h 0 0 20 40 60 80 100 120 140 w nn l / w = cosg / cosf Glide: nn 1 Turn: nn 1 / cosf Flight Without Fuel - Regenerative Soaring www.esoaring.com J. Philip Barnes

  18. Load Factor and “Clean” Sink Rate “Clean” REGEN Windprop system removed but system weight retained Sailplane 0.0 dz/dt ~m/s Sea level Max L/D 2 25 kg / m Min Sink A = 16 -0.5 1.0 -1.0 1.2 1.4 -1.5 1.6 g-Load, n n -2.0 Airspeed, v ~ km/h -2.5 50 60 70 80 90 100 110 120 130 140 150 Flight Without Fuel - Regenerative Soaring www.esoaring.com J. Philip Barnes

  19. Presentation Contents • Introduction to Regenerative Soaring • Modeling a Representative Thermal • Sailplane & Regen Design Comparison • Weight & Size Impacts of Adding Regen • Vehicle Performance ~ Steady climb or sink • Windprop Aerodynamics & Performance • Flight in the Thermal, with & without regen • Preview ~ “solar-augmented” regen soaring • Conclusions ~ “flight without fuel” Flight Without Fuel - Regenerative Soaring www.esoaring.com J. Philip Barnes

  20. Windprop Blade Angle and Operational Mode b Turbine Propeller Pinwheel L b b v v v w r -L w r w w r w w • Pinwheeling: No thrust, no torque, small drag • Efficient prop : ~115% pinwheel rotational speed • Efficient turbine: ~ 85% pinwheel rotational speed • Specify symmetrical sections & uniform pitch • Define: “Speed ratio,” S  v / vpinwheel = v / [ wr tanb ] Flight Without Fuel - Regenerative Soaring www.esoaring.com J. Philip Barnes

  21. Windprop Wake and Blade Loading Horseshoe Vortices • Pitch: • helix length per rotation • htip = 2 p R tan btip • Uniform pitch: • r tanb = R tanbtip • Blade tip angle (btip): • 14o ~ low pitch • 30o ~ high pitch • More blades at fixed thrust & diameter: • More wakes (one per blade) • Higher pitch ~ wakes farther aft / rotation • Lower rotational speed, lower tip Mach • Upshot: ~ similar efficiency, 2 to 8 blades Flight Without Fuel - Regenerative Soaring www.esoaring.com J. Philip Barnes

  22. Windprop Efficiency & Thrust o o b b = 14 = 30 Low-speed 8 Blades, tip tip 1.0 8_30 Efficiency 0.8 2_14 c c l_min l_max b Blades_ Propeller Turbine tip 0.6 o 2 _14 t w h t w ( f v ) / ( ) ( ) / ( f v ) o 8 _30 Airspeed Thrust per windprop Rotational speed Torque 0.4 Zero Thrust Zero Torque 0.2 w b R S = v / ( tan ) Speed Ratio, tip 0.0 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.0 0.9 2 p R Propeller ~ climb Force Coefficient , F = f / ( q ) 0.8 Total thrust Climb rate Number of windprops Dynamic pressure High-speed 2 Blades, B=8 0.7 B=2 0.6 0.5 0.4 g-load (drag/lift) airspeed wing area 0.3 F Propeller ~ cruise Sym. Sections 0.2 b b tan R r = tan Max efficiency tip 0.30 0.1 Blade Geometry Regeneration Max capacity 0.25 0.0 Regeneration Pinwheel 0.20 R Chord, c/ -0.1 0.15 F= -0.011 @ B=2 Thickness 2 -0.2 0.10 F= -0.008 @ B=8 8 hub -0.3 0.05 w b R S = v / ( tan ) Speed Ratio, R r / tip -0.4 0.00 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 0.00 0.25 0.50 0.75 1.00 Flight Without Fuel - Regenerative Soaring www.esoaring.com J. Philip Barnes

  23. Interim Summary ~ Windprop Aerodynamics • Comparable installed efficiencies for: • 8-blade low-speed, high-pitch, with gearbox • 2-blade high-speed, low-pitch, w/o gearbox • 8-blade windprop has the edge overall: • 25% less pinwheel drag (@ S ~ 1.0, zero torque) • 35% more max-capacity regen (@ S ~ 1.75) • Quiet operation and reduced tip Mach number • Windmilling is “power limited” vs. propeller oper. • Turbine operation decelerates captured streamtube • Increasing regen reduces rotation speed & power Flight Without Fuel - Regenerative Soaring www.esoaring.com J. Philip Barnes

  24. Presentation Contents • Introduction to Regenerative Soaring • Modeling a Representative Thermal • Sailplane & Regen Design Comparison • Weight & Size Impacts of Adding Regen • Vehicle Performance ~ Steady climb or sink • Windprop Aerodynamics & Performance • Flight in the Thermal, with & without regen • Preview ~ “solar-augmented” regen soaring • Conclusions ~ “flight without fuel” Flight Without Fuel - Regenerative Soaring www.esoaring.com J. Philip Barnes

  25. Regenerative Soaring Equation “Total Climb” Updraft “Total Sink” Rate of change of total specific energy Effect of windprop Still-air “clean” sink rate • “Exchange Ratio,” as applicable: • turbine system efficiency ~71% • 1 / propeller system efficiency • 0 for pinwheeling (no exchange) Flight Without Fuel - Regenerative Soaring www.esoaring.com J. Philip Barnes

  26. Application of the Regenerative Soaring Equation Flight Without Fuel - Regenerative Soaring www.esoaring.com J. Philip Barnes

  27. Climb in the Thermal ~ Ground-observed ~ dzo/dt 3500 Sailplane Max efficiency Regen z ~ m o dzo /dt ~ m/s 3000 0.0 0.0 0.0 0.5 0.0 2500 0.5 Slower Climb (Regenerating) 1.0 1.0 0.5 1.0 1.0 1.5 1.0 Equilibrium Regeneration (unexciting) 1.5 1.5 2000 2.0 Optimum 2.0 2.5 1500 2.6 m/s 2.2 2.5 2.0 1000 2.0 1.5 1.5 1.0 0.0 0.5 1.0 0.0 0.5 500 1.0 0 0.0 0 1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 Load Factor ~ nn Flight Without Fuel - Regenerative Soaring www.esoaring.com J. Philip Barnes

  28. “Total Climb” or Total Energy Rate ~ dzt/dt 3500 Sailplane Max efficiency Regen z ~ m o dz /dt ~ m/s 3000 t 0.0 0.0 0.5 Competitive Total energy rate 0.5 2500 1.0 1.0 1.0 1.0 1.5 1.5 Optimum 1.5 2000 2.0 2.0 Optimum 2.5 1500 2.6 2.5 m/s 2.5 2.5 1000 2.0 2.0 1.5 1.5 0.0 0.0 0.5 0.5 1.0 1.0 500 0 1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 Load Factor ~ nn Flight Without Fuel - Regenerative Soaring www.esoaring.com J. Philip Barnes

  29. Time to Climb and Energy Gain Total Specific Energy Integration Time-to-Climb Integration Total Specific Energy Gain = Area Under Curve Time = Area Under Curve 1.50 1/(dz /dt) ~ s/m o 1.25 2500-m @ 20-min 1.00 2200-m @ 16-min 0.75 2000-m 0.50 2000-m 0.25 0.00 2500-m @ 16-min 500 750 1000 1250 1500 1750 2000 2250 2500 Elevation, z ~ m o 1.50 (dz /dt) / (dz /dt) ~ dimensionless t o 1.25 1.00 0.75 0.50 0.25 0.00 500 750 1000 1250 1500 1750 2000 2250 2500 Elevation, z ~ m o Flight Without Fuel - Regenerative Soaring www.esoaring.com J. Philip Barnes

  30. Regen Feature Increases Effective L/D z ~ m o 7-km cruise Sailplane: 61-km, L/D = 30.3 2500 Regen: 49-km, L/D = 28.6 (Pinwheel glide) A 2000 From A-B: L/D = 32.8 1500 16-min:Dzt = 2000-m 1000 500 B Range, km 0 5 10 15 20 25 30 35 40 45 50 55 60 65 Sustainable Energy Cycle For Each Aircraft 3000 Sailplane: Dzo = 2000-m Regen: Dzo = 1700-m De= 300-m 0 Flight Without Fuel - Regenerative Soaring www.esoaring.com J. Philip Barnes

  31. Presentation Contents • Introduction to Regenerative Soaring • Modeling a Representative Thermal • Sailplane & Regen Design Comparison • Weight & Size Impacts of Adding Regen • Vehicle Performance ~ Steady climb or sink • Windprop Aerodynamics & Performance • Flight in the Thermal, with & without regen • Preview ~ “solar-augmented” regen soaring • Conclusions ~ “flight without fuel” Flight Without Fuel - Regenerative Soaring www.esoaring.com J. Philip Barnes

  32. Preview ~ Solar-Augmented Regenerative Soaring • Add solar panels to perhaps 75% of wing area • Solar package delivers ~150 W/m2_panel • Not intended to sustain level flight for regen herein • Thus “solar-augmented,” not “solar-powered” • Solar-augmented glide between thermals • Adds thrust (vs. small drag penalty of pinwheeling) • Operate in propeller mode at about half of level-flight thrust • Significantly enhanced effective L/D during glide • Sustainable: powered glide consumes no stored energy • Solar feature promotes “landing on a full charge” • Solar feature resolves “loss of charge” on the ground Flight Without Fuel - Regenerative Soaring www.esoaring.com J. Philip Barnes

  33. Conclusions ~ Flight Without Fuel • Windprop: comparable & good efficiency in either mode • Regen flight emulates that of a sailplane • Regen climbs in the thermal during regeneration • “Earn & spend” short cruise; pinwheel glide to next thermal • Regenerative soaring is sustainable • Stored energy is reserved for emergency cruise/climb • Regen soaring is competitive with classical soaring • Regen loses 8% range compared to sailplane, but: • Regen exhibits 8% higher effective L/D than sailplane • Additional regen-unique strategies yet to be discovered • Solar augmentation adds significant benefits • Theory says thumbs up ; Now let’s build and fly! Flight Without Fuel - Regenerative Soaring www.esoaring.com J. Philip Barnes

  34. About the Author Phil Barnes has a Master’s Degree in Aerospace Engineering from Cal Poly Pomona and a Bachelor’s Degree in Mechanical Engineering from the University of Arizona. He has 25-years of experience in the performance analysis and computer modeling of aerospace vehicles and subsystems at Northrop Grumman. Phil has authored technical papers on aerodynamics, gears, and flight mechanics. Drawing from his SAE technical paper of similar title, this presentation brings together Phil’s knowledge of aerodynamics, flight mechanics, geometry math modeling, and computer graphics with a passion for all types of soaring flight. Flight Without Fuel - Regenerative Soaring www.esoaring.com J. Philip Barnes

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