Phase II Final Report - NASA's Institute for Advanced Concepts
Phase II Final Report - NASA's Institute for Advanced Concepts
Phase II Final Report - NASA's Institute for Advanced Concepts
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Planetary Exploration Using Biomimetics<br />
An Entomopter <strong>for</strong> Flight on Mars<br />
effects of blowing as demonstrated in the wind tunnel has yet to be achieved through the study<br />
team’s CFD ef<strong>for</strong>ts, though this too is an area slated <strong>for</strong> follow-on work.<br />
Consider a baseline conventional fixed wing vehicle (one wing set) with a one meter wing span<br />
and having aspect ratio of 5.874 (similar to that of the Hawk Moth-based Entomopter wing) flying<br />
near the surface at a speed of 100 meters per second. Its wing area is 0.142m 2 (1.532ft 2 ).<br />
Reference atmospheric conditions on the Mars surface are: density = 0.0000279 slugs/ft 3 , atmospheric<br />
pressure = 0.11475psia, and temperature = -20.4F. At a typical fixed wing lift coefficient<br />
of 1.0, that vehicle can carry 1.04kg (2.3lbs.) gross weight (approximately 2.8 Earth kg (6.2lbs.))<br />
if Mars gravity is taken as 37% that of Earth’s). That represents a wing loading of only 7.3kg/m 2<br />
(1.5lb/ft 2 ) due to the low density and pressure compared to aircraft flying on Earth at perhaps<br />
342kg/m 2 (70lb/ ft 2 ) to more than 488kg/m 2 (100lb/ft 2 ).<br />
Based on the same pneumatic aerodynamic data used <strong>for</strong> the terrestrial pneumatic Entomopter<br />
(previous wind tunnel data <strong>for</strong> a GTRI circulation controlled wing model with the same aspect<br />
ratio), a C L of 5.3 is attainable (this is steady-state data, not flapping, which will be larger, as<br />
discussed below). Assuming that the two-winged Entomopter has the same total wing area and<br />
aspect ratio as the one meter conventional wing, giving it a reduced wing span of only 0.646m<br />
(2.12ft) per wing. At the same high flight speed (100m/s), this blown Entomopter can lift 5.53kg<br />
(12.2lbs.) on Mars (15 Earth kg (33lbs.)). Or, if one assumes the two aircraft have the same wing<br />
area and a gross weight of 1.04kg (2.3lbs.) from above, the blown Entomopter can reduce the<br />
required flight speed from 100m/s to 43.4m/s, i.e. the dynamic pressure is reduced from 7.3kg/<br />
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 =<br />
5.874) fly the same flight speed (perhaps a lower value of 50m/s speed) with 1.04kg (2.3lbs.)<br />
gross weight, the blown Entomopter can do it with a total wing area of only 0.107m 2 (1.156ft 2 )<br />
or a wing span of 0.56m (1.84ft) per wing set, compared to the span of 1.83m (6.0ft) and area of<br />
0.569m 2 (6.126ft 2 ) <strong>for</strong> the conventional wing. The size reduction possibility is clear, however<br />
this also has implications in that were the wing to remain the same length, it could be flapped at<br />
a slower speed, thereby accommodating the effects of inertia and strength of materials.<br />
<strong>Final</strong>ly, using a slot height geometry of such a size as to obtain the blown C L = 5.3 requires a<br />
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<br />
blowing weight flow = 0.0076kg/s (0.0168lb/s), jet velocity = 538m/s (1765ft/s) and blowing<br />
pressure is 0.18kg/cm 2 g (2.5 psig), mainly due to the very low external atmospheric pressure<br />
and temperature on Mars.<br />
An additional valuable comparison can be made if appropriate wing loadings are considered<br />
along with the required flight speeds. The terrestrial pneumatically-blown Entomopter design<br />
with two wing sets (i.e., 4 wing panels: 2 front, 2 aft) has a wing loading of 3.554kg/m 2<br />
(0.728lb/ft 2 ). For a 1m span Mars Entomopter with 2 wing sets scaled to that wing loading and<br />
an aspect ratio of 5.874, a flight weight of 1.01kg (2.24lb) can be achieved. The conventional<br />
aircraft with the same weight and aspect ratio and one wing set has a wing loading of twice that,<br />
or 7.13kg/m 2 (1.46lb/ft 2 ). Figure 3-134 shows the flight speeds required <strong>for</strong> each aircraft at<br />
those wing loadings, as well as double the wing loading <strong>for</strong> each vehicle. The conventional aircraft<br />
with C L =1.0 requires a speed of 98.4m/s to support that weight in level flight, while the<br />
same weight pneumatically blown Entomopter with attainable C L = 5.3 can fly at 30.2m/s. C.P.<br />
152<br />
<strong>Phase</strong> <strong>II</strong> <strong>Final</strong> <strong>Report</strong>