Aircraft Energy Gain From an Atmosphere in Motion

J. Philip Barnes www.HowFliesTheAlbatross.com
Aircraft Energy Gain From an Atmosphere in Motion 15 June 2015 update J. Philip Barnes This morning’s presentation continues the theme “Aircraft Energy Gain From an Atmosphere in Motion.” Yesterday we showed how the wandering albatross uses its dynamic soaring technique to extract energy from the vertical profile of horizontal wind. Today’s presentation will suggest an architecture for efficient electric flight in still air. We will then discover that such architecture provides regeneration essentially for free. So, we’ll capitalize on that and characterize the energy gained by a regen electric aircraft in horizontal and/or vertical wind. Part 2 of 2 J. Philip Barnes

Efficient Electric Flight
Part 2 of 2: Efficient Electric Flight - The Regeneration Factor 28 June 2015 J. Philip Barnes This graphic represents a regen electric aircraft, storing electrical energy in ridge lift where the updraft matches the sink rate of the aircraft including the effect of regeneration. The propellers are operating as turbines driving motor-generators recharging the battery. The regen does this by taking airborne the "regenerative braking" technology pioneered by the Toyota Prius.

Presentation Contents
The visionaries Windprop Updrafts Regenosoar Brushless MG The presentation will first introduce two visionaries of regenerative electric flight. We will then review and renew the basic principles of dual-role machines represented by the propeller-turbine and brushless motor-generator. We’ll then compare the usual “chopping” speed control with the more-efficient “boost” architecture employed by today’s ground electric vehicles. Next, we’ll introduce a conceptual regen. We will then finish up with some computed or measured information on updrafts. M-G iGBT VM Power Electronics Regenerative Electric-powered Flight J. Philip Barnes

Regenerative Electric-powered Flight J. Philip Barnes

Hermann Glauert “Consider the case of a windmill on an aeroplane”
The historical basis for our present study of regenerative electric flight includes the work of several great theorists and experimenters. To mention just two, we begin with the great British aerodynamicist Hermann Glauert. Author of a classic 1926 text on aerodynamics, Glauert suggested that we "consider the case of a windmill on an aeroplane." He offered no specific application at the time, but he knew the airborne wind turbine would one day find use and he applied his considerable skills toward its analysis. Regenerative Electric-powered Flight J. Philip Barnes

Paul MacCready Regenerative electric flight
concept “with caution,” ‘99 The visionary American engineer Paul MacCready brought us the first human-powered flight. He was also pioneer in the technology of ground electric vehicles, solar-powered flight, and paleo-aero engineering. In his seminal paper of 1999, MacCready introduced "with caution" the concept of regenerative electric flight. Although in his paper he did not offer a specific configuration, MacCready imagined and described a complete “regen” flight. Regenerative Electric-powered Flight J. Philip Barnes

Rotor velocity diagram - "Pinwheeling" & “Betz” conditions
Vo W2 Helical wake w r Blade section Looking outboard, Blade at 3 o’clock Chord line b Angle of attack = 0, hub-to-tip wr tanb = Vo Therefore: r tanb = Vo /w = R tan btip Approaches "Betz Condition“ Axial wind Vo Rotational wind, w r Relative wind W1 b Here we show a simplified velocity diagram for any section of a propeller or turbine blade, looking outboard with the blade at 3-o’clock and with the rotation vector pointed forward. For the purposes of this diagram, the rotor is unloaded with uniformly zero angle of attack from hub to tip. From the geometry of the velocity diagram we see that this "pinwheeling" condition is characterized by holding constant from hub to tip the group (r tanb). This twist distribution closely approaches the “Betz Condition” representing the most efficient propeller or turbine operation. Regenerative Electric-powered Flight J. Philip Barnes

Windprop Blade Angle and Operational Mode
V w r L b W Propeller V w r b W Pinwheel V w r -L b W Turbine For pinwheeling, the blade section with uniform pitch has zero angle of attack from hub to tip. If we now increase the rotational speed while holding constant airspeed, the blade will develop lift, thrust, and torque as a propeller. Conversely, reducing rotational speed, the blade will develop negative values thereof, thus acting as a turbine. We are thus led to define a new term, the “speed ratio” (s), which applies to both propeller and turbine operation, and which also highlights the pinwheeling regime where the speed ratio is unity. Although the speed ratio (s) enjoys some similarity to the familiar “advance ratio” (J), only (s) describes at once whether we have propeller, pinwheel, or turbine operation. Define: “Speed ratio,” s  v / vpinwheel = v / [ wR tanbtip ] Similar to advance ratio (J) but meaningful for 3 modes Regenerative Electric-powered Flight J. Philip Barnes

Windprop Efficiency and Thrust
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 0.0 0.2 0.4 h Speed Ratio, s ≡ v / (w R tan bt) Efficiency 2 8 Low-RPM Blades bt = 30o Propeller f v / (t w) Turbine t w / (f v) Speed Ratio, s ≡ v / (w R tan bt) 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 -0.4 -0.3 -0.2 -0.1 0.0 0.1 0.2 0.3 0.4 B=2 2 B=8 8 Force Coef., F ≡ f/(qpR2) Propeller ~ climb Comparable efficiency by mode Eight blades spin slow & quiet Climb power ~ 7x cruise power Two windprops, same thrust and diameter Propeller ~ cruise Given symmetrical sections and the hub-to-tip uniformity of the pinwheeling condition, it should be no surprise to learn that increasing or decreasing rotational speed on either side of pinwheeling yields similar peak efficiencies for propeller and turbine operation. The calculated efficiencies shown above are based on the author’s method (SAE ) which has been validated with test data, and which numerically integrates wake-induced velocities and solves a system of linear equations for blade loading. Let’s now compare the characteristics of two windprops of the same thrust and diameter, one spinning slowly with eight high-pitch blades, the other spinning fast with two low-pitch blades. In each case we will use the previously-described symmetrical sections and twist. Versus speed ratio, we find that both windprops exhibit peak efficiencies around 84% for both propeller and turbine operating regimes. The 8-blade, high-pitch rotor will of course be much quieter than its 2-blade counterpart. Also, a multi-blade, high-pitch rotor enables higher airspeed with its reduced tip Mach number. A companion plot shows the force coefficient (F) versus speed ratio (s). As expected, the force is positive for propeller operation and negative for turbine operation. Since RPM is dramatically reduced for regeneration, the corresponding force and power are much lower than those for climb. High-RPM Blades bt = 14o Regeneration Max efficiency Regen capacity Pinwheel Regenerative Electric-powered Flight J. Philip Barnes

BLDC M-G & inverter-rectifier: System efficiency
“Equivalent brushed” machine kw Inverter- Rectifier w i t tw = em i em= k w t = k i M-G eb We are indebted to the brushed machine for a good understanding of motor-generator operating principles. However, a brushed machine suffers various limitations, not the least of which is voltage. A brushless machine can operate at 1000V or higher, but the machine now has a three-wire interface and it must be electronically commutated. The so-called “brushless DC” machine shown here operates in effect as an AC machine. Depending on rotor position, the two phases most closely aligned with the magnet are energized. But the brushless motor-generator as a system with its inverter-rectifier has the same two-wire interface with the battery and follows the same principles as a DC brushed machine, in that the generated EMF is proportional by the “EMF constant” (k) to rotational speed, and the torque is proportional by that same constant to current.* Whether the electrical machine is brushed or brushless, the system motoring theoretical efficiency is given by the ratio of motor-output shaft power (product of torque and rotational speed) to battery “electromotive” power (product of battery EMF and current). Here, we note that battery terminal voltage will be less than battery EMF due to internal battery resistance, and that battery internal power loss is a key constituent of system efficiency). Taking this a step further with the same basic principles, the system motoring theoretical efficiency is found to be proportional to rotational speed. The inverse ratio represents system regenerating theoretical efficiency. Let’s next take a look at test data which validates our first-principle model of system theoretical efficiency. * The EMF constant, having units of Volts per radian/sec, is inversely proportional to the modeler’s electric-flight motor parameter “Kv” having units of Volts/RPM. Motoring efficiency = tw / (eb i) = em i / (eb i) = k w / eb Regen. efficiency = eb i /(tw) = eb i / (em i) = eb /(k w) Regenerative Electric-powered Flight J. Philip Barnes

Motor-generator & Battery ~ Performance Envelope and Data
100% Duty Cycle eb /(kw) CURRENT GROUP, i Rt / eb THEO. EFFICIENCY, kw/eb TORQUE GROUP, t Rt / (k eb) MOTORING EEMCO 427D100 24V / 15,000 RPM k = N-m/A Rt = Ohm REGENERATION LMC "generator curve" 48V / 3,600 RPM k = 0.16 N-m/A Rt = Ohm LMCLTD.net Windprop synergy i The chart above shows, versus a non-dimensional rotational speed, both theoretical (dashed blue curves) and measured (solid red curves) system efficiencies for a motor-generator and battery. Note that the theoretical ideal motoring efficiency instantly falls to zero at the “base speed,” analogous to windprop pinwheeling, where battery and machine EMFs are balanced such that no work occurs. Together with the component efficiency test data, we characterize and non-dimensionalize the torque and current, including the effect of system total electrical resistance. Two DC machines, with some similarities but also with many differences, were used for the above plot (data for a given machine, both motoring and generating, is scarce). However, a wide range of DC machines (with permanent magnets or otherwise fixed magnetic field strength) will exhibit similar trends. At a “speed ratio” below unity, we have motoring operation. Above unity speed ratio we have regeneration. Near unity speed ratio, the first-principle model fails because there, for a real machine, the torque loss remains as motoring torque or generated current vanish. Thus for a real machine, the efficiency follows the trends of the test data shown. For the most efficient machines, efficiency peaks will push (red arrows) more deeply into the "corners" of the theoretical limits. For both motoring and regeneration at full power (no chopping), the test data approaches asymptotically the trends predicted by our first-principle model of theoretical efficiency. Notice the extraordinary synergy of the motor-generator efficiencies shown above, when compared to the windprop efficiencies shown earlier herein. Both machines (motor-gen and windprop) have a "neutral point" (at unity speed ratio) and both exhibit optimal efficiencies (around 80%) at rotational speeds 10-15% above or below the "neutral, base, or pinwheeling" rotational speed. t Phil Barnes Apr Regenerative Electric-powered Flight J. Philip Barnes

“Six-pack” inverter-rectifier ("inverting" for motoring)
VB 1 2 3 -7V 15V S N This is a “six-pack” inverter which, as we shall show, also serves as a rectifier. This ingenious device, which as been around for several decades, in effect converts two-wire DC to 3-wire AC. Upper-lower diagonal pairs of transistors are alternately operated as switches to connect one phase to battery voltage and the other phase to ground. The remaining phase floats until it is immediately put to use in the subsequent 60-deg-segment commutation. Thus, the magnetic field and rotor together spin around with the electronic commutation. Also, we see that the inverter doesn’t really “invert” the voltage. Instead, it toggles the three M-G terminal voltages between zero and battery voltage. Nevertheless, the resulting waveforms at each terminal in effect deliver AC power to the so-called “brushless-DC“ machine. Inverter converts 2-wire DC to 3-wire "AC“ Alternating transistor “diagonal pairs” Commutation toggles each phase 0-to-VB Relatively low frequency at full power Regenerative Electric-powered Flight J. Philip Barnes

Six-pack inverter-rectifier (rectification for regeneration)
Snapshot e1 - e3 > eB 1 1 2 2 eB Diodes provide "free" regen! 3 3 If the motor-generator EMF were somehow greater than battery voltage (we will soon discuss how) the inverter will serve as a rectifier and, together with the motor-gen, deliver largely DC current with minor ripple to the battery. Such regeneration occurs via the flyback diodes which impose a small loss of about 0.7V. With iGBTs, rectification ignores the ongoing commutation since the iGBTs conduct only in the motoring direction. Current to battery! M-G max delta EMF exceeds battery EMF Six-pack rectifies 3-wire AC into 2-wire DC Battery recharged through flyback diodes IGBTs unidirectional: commutation ignored Regenerative Electric-powered Flight J. Philip Barnes

Cruise efficiency penalty when “chopping” the main current
BLDC commutation voltage waveform (full power) has “relatively-low” frequency ion iav | | dt | t | Commutation with chopping PWM superimposed (cruise) has “very-high” frequency Typical PWM switching freq. f ≈ 20 kHz (inaudible) Per-iGBT switching energy loss S ≈ 20 mJ per cycle Chopping loss = f S = 0.4 kW ≈ 10% in loitering flight At full power, commutation is a relatively low-frequency switching which matches phase operation to rotor position. To reduce power for cruise, pulse-width modulation (PWM) is often employed to implement high-frequency "chopping" which is superimposed on the commutation square wave. The switching power loss is given by the product of switch energy loss and switch frequency. Assuming 20 mJ switch-cycle loss and 20kHz frequency, the switching power loss is 0.4 kW. With a system operating near 4 kW in loiter (max L/D, steady-level flight), this switching loss amounts to about 10%. DC boost converter eliminates part-power chopping loss Regenerative Electric-powered Flight J. Philip Barnes

DC boost converter - efficiency and regen application
"Evaluation of 2004 Toyota Prius," Oakridge National Lab, U.S. Dept. of Energy 233 Vdc in kW 97% power-conditioning efficiency for any mode Regen M-G Motor PWM iGBT C L VB Cruise Climb Regen As an alternative to chopping at part power, we can implement a DC boost converter (DCBC), a key component used by the Toyota Prius. Roughly speaking, this component doubles or triples the voltage of either the battery or the motor-generator, depending on mode. The actual voltage boost is adjusted by the duty cycle of pulse-width modulation applied to the gate of the single transistor within the DC boost converter. The main current is largely constant, regardless of mode. Most importantly, the efficiency is about 97% throughout the operating range including climb, cruise, and regeneration. An added advantage of the DCBC is a substantial reduction in the required battery “totem pole” voltage. DC boost converter efficiently integrates windprop & motor-gen IGBT gate PWM duty cycle adjusts battery or M-G voltage boost Efficient bi-directional power over the full operating range Regenerative Electric-powered Flight J. Philip Barnes

“Chop” Vs. “boost” architectures compared
PWM superimposed on commutation i Inverter- Rectifier w "Chopper" architecture PWM main current chop 540V battery 10% loss at loiter Regen: none or inefficient 540V batt. M-G t Commutation i DC Boost Converter 2-way boost Inverter- Rectifier w "Boost" architecture PWM sets DCBC boost 200V battery 03% loss at loiter Regen capable & efficient Here we compare the “chop” and “boost” electrical power architectures. With chopping, the battery voltage is sized to overcome the generator EMF at high cruising speed. For the Toyota Prius, such actually approaches 600V. Thus the inverter-rectifier transistors in effect cyclically connect and disconnect the M-G phases from relatively high voltage battery. Regeneration with this architecture will be either unavailable or inefficient with transient characteristics likely used to generate voltage spikes exceeding battery voltage. With the “boost” architecture, the PWM applies relatively low-voltage to the gate of the DCBC IGBT, with main current largely constant. This architecture remains near 97% efficiency for all operating modes, including regeneration. However, the weight and volume of the DCBC for contemporary EVs are approximately those of a briefcase stuffed with books. 200V batt. M-G t PWM Regenerative Electric-powered Flight J. Philip Barnes

Regenosoar 8-blade rotors Counter rotors Low RPM, quiet,
Low tip Mach Counter rotors Symmetric flow Zero net torque Ground handling No assistance req'd Winglet tip wheels Pusher Config., laminar flow, no helix upset Pod-air-cooled MG & PE The graphics above, and those to follow, introduce Regenosoar, fully math-modeled with parametric equations and rendered with Blender 3D open-source software including its integrated Python programming platform. Here we show orthographic and other views, together with various features, representing our concept for a regenerative-electric aircraft. Taking airborne the regenerative-braking electrical power architecture of contemporary ground electric vehicles, the regen uses its windprops as propellers for takeoff and climb, then as airborne wind turbines to regenerate stored energy in ridge lift, thermals, final descent, landing roll, and parked in the wind on the field. The fixed-geometry windprops employ symmetric sections of uniform pitch (r tanb = R tanbtip) and rotate at relatively high RPM for takeoff and relatively low RPM for regeneration. As shown in our earlier studies, the windprops have similar peak efficiencies (Glauert’s definitions thereof) near 83% for motoring and regeneration. The wing of Regenosoar has 16-m span and an aspect ratio of 16. The windprop diameter is 1.08-m (the author’s original manuscript mistakenly quoted this dimension as the radius). Herein, we study optimal operation of Regenosoar in various operating modes. In the case of regeneration, such includes the sink-rate increment of the installed and operating windprops. Regen parked in the wind with safety perimeter Regenerative Electric-powered Flight J. Philip Barnes

Regenerative Electric-powered Flight J. Philip Barnes

J. Philip Barnes www.HowFliesTheAlbatross.com June 2015
Test data – Wind statistics (terrestrial) r ≈ (2.735 / Wmax ) [ sin { p (1 - W/Wmax) 2.5 } ] 1.6 J. Philip Barnes April AGARD AG-243 Wind Energy, p. 2-14 ASME J. Solar Energy, V. 128, p. 533 Here we show horizontal wind speed probability distributions at two terrestrial wind-turbine sites. The area under any such curve is unity and dimensionless, so the units of probability density are the inverse of those for wind speed. We have also introduced a suggested curve fit which applies to any site, whereby an increase in maximum wind speed corresponds to a reduction of peak probability density. The particular curve fit offered does not extend to infinity, instead showing zero probability density at maximum wind speed. Area = 1.0 for any Wmax J. Philip Barnes June 2015

Ridge lift analysis ~ Courtesy of Hermann Glauert
U = 0.3 Wo Wo U = 0.5 Wo Stream function study Courtesy of Hermann Glauert’s application of the stream function in his classic 1926 text, the above graphic superimposes a uniform stream with a point source to calculate the paths and velocities of streamlines representing the interaction of uniform horizontal wind with a rounded cliff. If the regen flies anywhere within the larger circle, the local updraft (U) will be at least 30% of the undisturbed wind speed (Wo). Flying anywhere within the smaller circle has an updraft at least 50% of the wind, whereby a regen aircraft with a regenerating sink rate of 2.5-m/s in still air remains aloft in ridge lift which originates from a 5 m/s wind. We next answer the questions “how does the regen still-air sink rate vary with airspeed?” and “how much power is regenerated?” Regenerative Electric-powered Flight J. Philip Barnes

Clean Max efficiency regen Max capacity regen The still-air “clean” sink rate (windprops, booms, and pods removed) of the regen is given by the “aero term” nn(D/L)V, where (nn ≡ L/W) is the normal load factor, (D/L) the lift-drag ratio, and (V) the airspeed. Our thrust-drag accounting specifies a drag “polar” for the clean configuration, and assigns windprop operation and installation effects, including interference and trim, to “propulsion.” The still-air installed climb rate with propeller operation (or still-air installed sink with regeneration) is obtained from the product of the “aero term” and the “propulsion term” (T/D–1), where (T/D) is the thrust/drag ratio and where thrust is negative with regeneration. For either operating mode, (T/D) depends on system efficiency including windprop and motor-gen losses, battery resistance, cable loss, and power-conditioning. Assuming from the previous two slides 5-m/s wind and near-optimal ridge lift, our regen flies at km/hr with an installed still-air sink rate of 2.5-m/s, as seen in the graphic above, and with 3-kW regenerated, as seen in the next chart. Regenerative Electric-powered Flight J. Philip Barnes

Windprop speed ratio 1.45 1.15 1.75 Max capacity regen Max efficiency regen Regenerative Electric-powered Flight J. Philip Barnes

Conditions for total energy gain with regeneration
“Physics” require: Updraft (or descent) High L/D, low sink High system efficiency Trade 2% prop. efficiency benefit of symmetric blades for +TBD% range via regen Since it is quite possible to lose total energy while storing internal energy, we seek the combination of conditions that will increase total energy. The formula above relates the total climb rate to the total sink rate. The total climb rate is the rate of change, per unit weight, of kinetic, potential, and stored energy. To gain total energy, the physics require a threshold updraft, high L/D, low wing loading, and high efficiencies. The “exchange-ratio” parameter (e) represents turbine system efficiency or the inverse of propeller system efficiency, as applicable, in either case including the battery & cable resistance, power control, motor-gen, and windprop. Although we could camber the propeller blades in an attempt to gain 2% more range, we would lose the opportunity for potentially much greater increase in range afforded by regeneration, which depends on efficient turbine operation. Thus we postulate that symmetric blades yield the best configuration overall, unless the sortie is to be flown in still air. “Clean” sink rate Windprop Effect Updraft Regen benefits include: Steep final descent Landing thrust reversal Ground wind recharge “Total Sink” “Total Climb”

Thermal Updraft Contours
1oC warmer-air column 20-minute lifetime ~ solar power x 10 Elevation, zo ~ m U ~ m/s 1 2 3 4 Total Energy = Kinetic + Potential Total Energy = Kinetic + Potential + Stored We now study both ground-observed climb and total climb for a regen in a thermal. In the graphic above, we show a representative thermal, including contours of local updraft velocity (u,m/s), with a diameter of 200-m at its base and 1-km diameter at its top where the elevation is perhaps 4-km. A thermal is aptly named, since its air temperature is typically 1oC higher than that of the surrounding air. In this example, the peak-updraft core of 5-m/s resides at an elevation of 1000-m. At the top of the thermal, updraft falls to zero. Thermalling close to the core yields a relatively strong updraft, but also a relatively-high normal load factor and still-air sink rate. Thus, we are interested in the optimum turn radius, or its companion normal load factor, at each elevation. 5 Regenerative Electric-powered Flight J. Philip Barnes

Climb rate Equilibrium Regeneration Optimum Climb rate, m/s
The contour plots above represent ground-observed climb rate, versus load factor and elevation, for the regen in the thermal operating with max-efficiency regeneration. The aircraft can thermal over a wide range of normal load factors, with associated bank angles and turn radii (as described in our SAE paper “Flight Without Fuel”), but a specific "load-factor-altitude trajectory" yields the fastest climb, should rapid climb with regeneration be of interest. The white contour represents equilibrium regeneration, whereby the regen falls through the air at the same rate as the air rises. Such equilibrium can be sustained either "very low" or "very high" in the thermal. In the region between the upper and lower limits of equilibrium regeneration, the aircraft climbs in the thermal, even with max regeneration. One scenario for rapid-regen climb might be to make the most of a thermal which will soon vanish. Regenerative Electric-powered Flight J. Philip Barnes

Energy rate Sinking and Regenerating Climbing and Regenerating Optimum
Energy rate, m/s Perhaps a more likely objective would be maximum total climb in the thermal. This is shown in the contour plots above, again for max-efficiency regen. The optimum energy trajectory is indicated by the dashed curve, with tight turns (~ 1.45-g) near the base of the thermal and wide turns (~ 1.15-g) near the top. It is interesting to note that along the “zero contour,” the regen loses potential energy at the same rate as it gains stored energy. But generally inside this contour, the regen gains both potential and stored energy as it climbs and regenerates in the thermal. Regenerative Electric-powered Flight J. Philip Barnes

Conclusions – Regenerative Electric Flight
The visionaries Windprop Updrafts A regen is coming soon to an airport near you! Regenosoar Brushless MG We have followed Hermann Glauert’s advice to “consider the case of a windmill on an aeroplane.” We also studied in depth implementation of Paul MacCready’s concept for regenerative electric flight. We learned of the extraordinary synergy of the windprop and motor-generator, both having a “neutral point” and similar dual-role peak efficiencies on either side of the neutral-point rotational speed. We found that a many-bladed, high-pitch, low-RPM windprop has similar efficiency as a high-speed, two-blade rotor of the same diameter and thrust, but that the many-blade option is much quieter, and potentially faster, in having a much lower tip Mach number. We found that the best architecture for electric flight in still air is one which provides for regeneration in moving air, whether or not we are interested in regeneration. This is because the popular method of “chopping” to throttle down for cruise is much less efficient than the “DC-boost” architecture pioneered by the Toyota Prius to enable much-reduced battery voltage as well as to enable efficient regeneration. We learned that the benefits of incorporating regeneration include greater range and endurance, steep final descent, landing-roll reverse thrust, and recharge in the wind on the ground. Depending on wind, weather, and geography, our regen may come within reach of flight without fuel (whether it is sunny or cloudy). For the coming era of green electric flight, we predict that “a regen is coming soon to an airport near you.” M-G iGBT VM Power Electronics Regenerative Electric-powered Flight J. Philip Barnes

J. Philip Barnes www.HowFliesTheAlbatross.com
About the Author Phil Barnes has a Master’s Degree in Aerospace Engineering from Cal Poly Pomona. He is a Principal Engineer and 34-year veteran of air vehicle and subsystems performance analysis at Northrop Grumman, where he presently supports both mature and advanced tactical aircraft programs. Author of several SAE and AIAA technical papers, and often invited to lecture at various universities, Phil is presently leading several Northrop Grumman-sponsored university research projects including an autonomous thermal soaring demonstration, passive bleed-and-blow airfoil wind-tunnel test, and application of Blender 3D and Python for parameterization and visualization of aircraft geometry and flight simulation. Outside of work, Phil is a leading expert on dynamic soaring of the wandering albatross, and he is pioneering the science of regenerative-electric flight. J. Philip Barnes

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