A Novel Concept for Stratospheric Communications ... - Team-Logic

does not utilize a ballonet. The larger the airship platform, the more expensive it is to build, operate, and maintain.Larger airships are also more vulnerable to attack, weather and structural failure. One other key aspect of the upperstage is that it is a disposable, low cost envelope.Our research drove us to an ellipsoidal design due to the shape’s low drag characteristics and positive lift-to-dragratio throughout the range of anticipated pitch changes. The ellipsoidal shape minimizes frontal cross-sectional area(Figure 3) and rear wake size, while maximizing maneuverability against changing winds. The ellipsoidal shape ofthe upper stage is maintained at altitude by super-pressure of the helium gas and use of mass efficient internal shapecontrol spars/catenaries 2-6 . Extensive CFD analysis of the StarLight aerodynamics has been conducted, greatlyincreasing confidence in the superiority of the StarLight design.Frontal Cross-SectionalArea, m 220001800160014001200100080060040020000 20000 40000 60000 80000 100000SaucerBlimpSphereVolume, m 3Figure 3. Comparative Cross-Sectional Areas of Various Airship ShapesThe StarLight’s positive lift to drag ratio with positive pitch enables platform climbs above neutral buoyancyduring high wind surges. The altitude gained in the climb is used to accelerate the StarLight in a dive to recoverthe distance lost during the wind surge. The illustration in Figure 4 illustrates StarLight’s unique climb and divemaneuver that allows it to station keep when winds exceed thrust capability.5American Institute of Aeronautics and Astronautics