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

Chapter 7.0 Conclusion
Chapter 7.0 Conclusion
The Entomopter was originally conceived as a terrestrial vehicle for operation inside buildings.
Unique features such as an anaerobic propulsion system and biologically-inspired wings capable
of generating abnormally high coefficients of lift were recognized as having application to slow
flight in the lower Mars atmosphere. The Entomopter does not rely on a purely biomimetic paradigm
for flight, but goes beyond biomimetics by using a resonantly-tuned circulation-controlled
pair of autonomically-beating wings that enable slow flight and landing as well as higher
maneuverability than can be achieved with a fixed wing vehicle.
A series of Mars flight scenarios were defined that could take advantage of the unique performance
envelope offered by a Mars Entomopter. In particular the ability to launch from a moving
rover, conduct nearby aerial surveys, and return for refueling offered, for the first time, the hope
that flight missions could be conducted repetitively over extended periods. Various fuels were
investigated for use with the Entomopter’s Reciprocating Chemical Muscle. These fuels were
analyzed for their compatibility with space flight and operation in the Mars environment. An
analysis was also performed to determine the trade off between bringing fuel from Earth to
Mars, as opposed to the creation of fuel in situ from components found in the Mars Environment.
Because most fuels of interest require hydrogen as a constituent, an analysis was conducted
to determine the break point beyond which it was more cost-effective to manufacture fuel
on Mars rather than supporting the infrastructure for its transport from Earth. This break point
was found to be on the order of 300 days. However with the recent discovery of water in the surface
layers of Mars, the ability to scavenge a ready source of naturally-occurring hydrogen may
make in situ fuel production more attractive.
The most important considerations for Entomopter flight on Mars are weight reduction and wing
aerodynamics. Analyses of wing size, wing material, angles of attack, and wing beat frequencies
were conducted as an aid in bounding the design space for the sizing of the Mars Entomopter. A
design point was chosen as the local optimum based predominantly on power and strength of
materials criteria, and although this was used as a basis for other calculations, it does not represent
the optimum design point, for all missions or operational conditions.
The leading edge vortex has been shown to be the primary cause of enhanced lift during the
wing flap. The LEV is dynamic, changing in diameter and speed as the wing flaps. It rolls along
the surface of the wing at an angle (about 45°) and eventually detaches as a shed vortex. The
direction of the vortex rotation tends to drive forward velocity air up and over the vortex so that
it can reattach to the wing. This is effectively increasing the camber of the wing without inducing
the drag that would otherwise be associated with a physical camber of the same size. Blowing
of the flapping wing should not only keep this leading edge vortex attached longer, but also
enhance the air moving over the vortex. The benefits of this blowing mechanism are essential for
Entomopter flight on Mars.
The CFD efforts performed during this NIAC study have attempted to validate the efficacy of
blown wing operation under the conditions encountered in the lower Mars atmosphere. Because
the notion of blown wing aerodynamics in the unsteady aerodynamic context of the flapping
wing is an absolutely new area for research, new codes and techniques have had to be developed
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