Phase II Final Report - NASA's Institute for Advanced Concepts

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Planetary Exploration Using Biomimetics An Entomopter for Flight on Mars effects of blowing as demonstrated in the wind tunnel has yet to be achieved through the study team’s CFD efforts, though this too is an area slated for follow-on work. Consider a baseline conventional fixed wing vehicle (one wing set) with a one meter wing span and having aspect ratio of 5.874 (similar to that of the Hawk Moth-based Entomopter wing) flying near the surface at a speed of 100 meters per second. Its wing area is 0.142m 2 (1.532ft 2 ). Reference atmospheric conditions on the Mars surface are: density = 0.0000279 slugs/ft 3 , atmospheric pressure = 0.11475psia, and temperature = -20.4F. At a typical fixed wing lift coefficient of 1.0, that vehicle can carry 1.04kg (2.3lbs.) gross weight (approximately 2.8 Earth kg (6.2lbs.)) if Mars gravity is taken as 37% that of Earth’s). That represents a wing loading of only 7.3kg/m 2 (1.5lb/ft 2 ) due to the low density and pressure compared to aircraft flying on Earth at perhaps 342kg/m 2 (70lb/ ft 2 ) to more than 488kg/m 2 (100lb/ft 2 ). Based on the same pneumatic aerodynamic data used for the terrestrial pneumatic Entomopter (previous wind tunnel data for a GTRI circulation controlled wing model with the same aspect ratio), a C L of 5.3 is attainable (this is steady-state data, not flapping, which will be larger, as discussed below). Assuming that the two-winged Entomopter has the same total wing area and aspect ratio as the one meter conventional wing, giving it a reduced wing span of only 0.646m (2.12ft) per wing. At the same high flight speed (100m/s), this blown Entomopter can lift 5.53kg (12.2lbs.) on Mars (15 Earth kg (33lbs.)). Or, if one assumes the two aircraft have the same wing area and a gross weight of 1.04kg (2.3lbs.) from above, the blown Entomopter can reduce the required flight speed from 100m/s to 43.4m/s, i.e. the dynamic pressure is reduced from 7.3kg/ m 2 (1.5 lb/ft 2 ) to 1.387kg/m 2 (0.284lb/ft 2 ). Lastly, if we assume that both aircraft (aspect ratio = 5.874) fly the same flight speed (perhaps a lower value of 50m/s speed) with 1.04kg (2.3lbs.) gross weight, the blown Entomopter can do it with a total wing area of only 0.107m 2 (1.156ft 2 ) or a wing span of 0.56m (1.84ft) per wing set, compared to the span of 1.83m (6.0ft) and area of 0.569m 2 (6.126ft 2 ) for the conventional wing. The size reduction possibility is clear, however this also has implications in that were the wing to remain the same length, it could be flapped at a slower speed, thereby accommodating the effects of inertia and strength of materials. Finally, using a slot height geometry of such a size as to obtain the blown C L = 5.3 requires a C L = 0.40. At the flight speed of 100m/s, q = 7.333kg/m 2 (1.502lb/ft 2 ), and the required total slot blowing weight flow = 0.0076kg/s (0.0168lb/s), jet velocity = 538m/s (1765ft/s) and blowing pressure is 0.18kg/cm 2 g (2.5 psig), mainly due to the very low external atmospheric pressure and temperature on Mars. An additional valuable comparison can be made if appropriate wing loadings are considered along with the required flight speeds. The terrestrial pneumatically-blown Entomopter design with two wing sets (i.e., 4 wing panels: 2 front, 2 aft) has a wing loading of 3.554kg/m 2 (0.728lb/ft 2 ). For a 1m span Mars Entomopter with 2 wing sets scaled to that wing loading and an aspect ratio of 5.874, a flight weight of 1.01kg (2.24lb) can be achieved. The conventional aircraft with the same weight and aspect ratio and one wing set has a wing loading of twice that, or 7.13kg/m 2 (1.46lb/ft 2 ). Figure 3-134 shows the flight speeds required for each aircraft at those wing loadings, as well as double the wing loading for each vehicle. The conventional aircraft with C L =1.0 requires a speed of 98.4m/s to support that weight in level flight, while the same weight pneumatically blown Entomopter with attainable C L = 5.3 can fly at 30.2m/s. C.P. 152 Phase II Final Report
Chapter 3.0 Vehicle Design 3.3 Wing Aerodynamics Ellington of the University of Cambridge in his paper entitled, “The Aerodynamics of Insect- Based Flying Machines” [75] states that flapping-wing unsteady aerodynamics of insects can increase the attainable lift by a factor of 2 to 3 times the steady-state value. Unsteady data for leading-edge shed vortices of pitching helicopter rotor blades show similar trends but somewhat smaller values. So, assuming a more conservative factor of 1.5 to 2, then the pneumatically blown Entomopter can yield a C L of 7.95 to 10.6 and the resulting reduced flight speeds are 24.7 and 21.4m/s respectively. Note that since the curves are power functions of C L , doubling a large C L has lesser effect on the required speed than doubling a smaller value; in this case, doubling the Entomopter higher lift coefficient for unsteady effects reduces speed by only 9m/s. Thus the exact lift value achieved by the flapping Entomopter with its unsteady aerodynamics has a relatively lesser effect compared to the base steady value, but does serve to produce a favorable effect. However, going from the fixed wing aircraft’s lift coefficient of 1.0 to even the steadystate pneumatic value of 5.3 reduces the required speed by 68.2m/s or more than 2/3. Figure 3- 134 also shows the effect on required speed for either aircraft by doubling the weight or the wing loading, and once again, the high lift attainable by the pneumatic configuration produces a significant effect. 153
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Planetary Exploration Using Biomime
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Table of Contents Table of Contents
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List of Tables List of Tables Table
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List of Figures List of Figures Fig
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List of Figures Figure 3-54: Pressu
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List of Figures Figure 3-138: Stere
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List of Figures Figure 4-24: Averag
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List of Contributors List of Contri
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Executive Summary Executive Summary
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Chapter 1.0 Introduction Chapter 1.
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Chapter 1.0 Introduction Figure 1-2
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Chapter 1.0 Introduction 1.1 Histor
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Chapter 1.0 Introduction 1.2 Origin
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Chapter 1.0 Introduction 1.3 Missio
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1.3.3.1 Surface Imaging The Entomop
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Chapter 2.0 Entomopter Configuratio
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Chapter 3.0 Vehicle Design 3.1 Wing
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3. Density: 1.40E-2 kg/m 3 4. Press
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Chapter 3.0 Vehicle Design 3.5 Fuel
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Chapter 3.0 Vehicle Design 3.5 Fuel
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Chapter 3.0 Vehicle Design 3.6 Powe
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Chapter 4.0 Entomopter Flight Opera
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Chapter 5.0 Potential Payload Funct
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Chapter 6.0 Media Exposure 6.1 Intr
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Chapter 6.0 Media Exposure 6.3 Onli
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Chapter 6.0 Media Exposure 6.6 Spec
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Chapter 7.0 Conclusion Chapter 7.0
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Appendix A: Mars Atmosphere Data JP
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Appendix A: Mars Atmosphere Data Ge
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Appendix A: Mars Atmosphere Data Ge
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Appendix A: Mars Atmosphere Data Ma
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Appendix B: Sizing Results Appendix
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Appendix B: Sizing Results 30 Wing
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Appendix B: Sizing Results 16 Wing
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Appendix B: Sizing Results Length 0
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Appendix B: Sizing Results Lenght 0
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Appendix C: List of References Appe
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Appendix C: List of References 41.
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Phase II Final Report - NASA's Institute for Advanced Concepts

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