2006 Ohio Student Research Forum

Abstract

Performance Optimization of the High Altitude Morphing Aircraft (HAMAC)
Melody Mayle
Ohio State University
Department of Aerospace Engineering
Mentor: Dr. Gerald Gregorek

The High Altitude Morphing Aircraft (HAMAC) is intended for observation and communication purposes. It is designed to fly between 70,000 and 100,000 feet above sea level and carry a payload of twenty-five pounds. It will be solar-powered during the day and will rely on fuel cells and/or batteries at night. The air in which a near-space platform such as HAMAC is designed to fly has such a low density that it is especially important to construct an aerial vehicle with a low wing loading—this means building a wing area great in size, which also allows more solar cells, but using materials light in weight. This leaves no room for control surfaces such as rudders, ailerons, and elevators. HAMAC will have a gimbal propeller not only for propulsion, but also for additional stability and control. Finally, HAMAC will have morphing wings that will change in shape and area to acquire optimal flight at the different altitudes.

The most efficient method of testing the wing configurations for their stability is constructing the numerous wing possibilities then flying them in the wind tunnel. Initially, the wings were going to change shape by rotating about a pin in the fuselage, but half way through the research project, a team member working on the morphing wing aspect introduced a wing that folds up similar to an accordion. With this new configuration, the need for flexing solar cells can be eliminated.

Before the change in wing configurations, a few models were constructed out of balsa wood and garbage bags then flown in the wind tunnel. Two geometries were tested—wings shaped like a sector of a circle and those shaped like a triangle—with varying sweep angles. Though the sector wings flew better in the tunnel, it would have been more practical to construct triangular wings. With a rounded trailing edge as with the sector geometry, there may be extra “flutter” in the downwash and there would be more difficulty in constructing rear support. But the new wing design has the geometry of a sector, but all the folds are what make building the model most complicated. At this point, it is necessary to duplicate this new model and fly it in the wind tunnel in order to test its stability.

Plots in Excel have also been created to predict flight performance using graphical data and a lift to drag ratio of 4.5 taken from former wind tunnel tests. These graphs relate the lift coefficient with velocity and wing loading and relate lift, drag, and horsepower with angle of attack and velocity. Together, these determine the power required in order to fly a plane a particular size and speed. The next step is to use these performance predictions and the wing configuration proven to fly most stable by the wind tunnel tests to design a radio control model of HAMAC to be flow at sea level. This will prove that it is possible to fly an aircraft with no control surfaces.