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

Chapter 3.0 Vehicle Design
3.3 Wing Aerodynamics
based model was created, which though approximate, can predict the actual performance of the
Entomopter over a reasonable range. These results will ultimately be validated by experimental
work.
3.3.3.2 Different Approaches
Various approaches were considered which could help formulate an aerodynamic model for
analysis and design of Entomopter. The following summarize a number of these.
3.3.3.2.1 Historical Database
The simplest approach was to take the past results presented by different researchers and transform
those results to create an empirical model by linear regression of statistical data. Most of
the research on the kinetics of birds has been performed by biologists. The research performed
by C.P. Ellington [77] reveals that a Hawk Moth wing (similar planform used by the Entomopter)
produces the following values for coefficients of lift and drag for different the angles of
attack as shown in Figure 3-108.
Figure 3-108: Hawk Moth Lift and Drag vs. Angle of Attack
Since kinematically correct flapping mimicking
that of the Hawk Moth is not practical in a manufacturable
vehicle, the flapping mode needs to be
augmented with some other technology in order
to extract the same amount of lift and thrust. Furthermore,
these values of lift coefficient meet the
requirement for flight on Earth, but are not sufficient
for flight on Mars. Hence, one is faced with
a challenge to find another contributor to lift
Figure 3-109: Typical Low Reynolds
Number Airfoil
along with flapping. One way to achieve the required values of lift is optimization of aerodynamic
parameters. As per [149], the airfoil shape can be optimized for low Reynolds number
flight. This can be as effective as increasing the lift coefficient by 50% in the case of conven-
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