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

Planetary Exploration Using Biomimetics
An Entomopter for Flight on Mars
tional fixed wing flight. Similar advantage can be extracted in the case of flapping wing flight.
The optimum airfoil suggested for low Reynolds number flight should have maximum camber
and minimum thickness. Some of the suggested airfoils are shown in Figure 3-109. The pressure
distribution on an optimized airfoil as compared to a conventional airfoil is shown in Figure 3-
110.
Conventional
Optimum
Figure 3-110: Pressure Distribution for an Optimized Airfoil vs. That of a Conventional
Airfoil
However, with regard to the requirements of the Mars environment, this optimal airfoil shape in
a flapping mode would still not be able to sustain steady flight as the lift coefficient values
required for Mars are much higher than those in the Earth's atmosphere. To achieve efficient and
controllable Mars flight at slow speeds, it was decided that active flow control of the airfoils
would be used along with flapping to increase the lift values. This will be discussed in more
detail below.
After taking into consideration the lift requirement, another important aspect is the minimum
value of thrust required for forward flight. In fact, in flapping motion, the resultant force produced
has two components: lift and thrust, which should as a minimum, equal the weight and
drag respectively for a steady flight. Unlike the conventional fixed wing airplane, where thrust is
provided by engines, the sole contributor of thrust is the flapping motion. Many researchers in
the past have addressed the thrust produced as a result of flapping. Kevin D. Jones has provided
some experimental data for thrust produced by flapping motion of a 15 cm micro air vehicle in
Earth's atmosphere [133]. His experimental model used is shown below as Figure 3-111. The
experimental results are not generic and are only true for the current point solution problem, but
can be extrapolated in the close vicinity of design points for thrust predictions. The model is
fully capable of generating sufficient thrust to overcome drag values and produce forward flight
for flapping frequencies of more than 25 Hz. Although the experimental data is only available
for lower flapping frequencies (less than 12 Hz), values predicted by panel methods and CFD
analysis can be taken for the purpose of estimation.
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Phase II Final Report