Novel Aeronautical Engineering Student Project: Developing Ultra-Light-Weight Aerial Vehicle Design and Proof of Concept

For students studying aeronautical engineering, one of the most exciting and motivating components of their curriculum is often their experience with novel aeronautical engineering student projects. In this paper, a novel inflatable structure concept is suggested for the design and manufacture of ultra-light-weight aerial vehicles, for example personal glider planes, humanpowered planes, UAVs and outer-space devices. This paper will present a brief description of the novel design summarized below, and will also present alternatives for integration into various levels of aeronautical engineering curricula. The author is keen on providing support for one or several engineering programs to incorporate the novel student project, where there is interest and support from the faculty and institution. Interested programs would have the opportunity to pioneer design and testing of the novel concept with their students. The proposed structure is fully collapsible when deflated permitting simple storage and easy transportation. Unlike previously known pressurized aeronautical structures, the concept yields flush aerodynamic surfaces similar to those obtainable by rigid structures, therefore assuring undisturbed air flow. Wings can be constructed with twist and dihedral geometry. In addition, the structure is capable of morphing during flight, permitting variation of its airfoil camber to optimized vehicle performance according to needs. The structure consists of three basic components, i.e., spar, rib and outer skin each inflated a different pressure. All components are formed from flexible thin lamina. The spars are tapered cylinders preferably reinforced with fibers. Ribs exactly reproduce wings and fuselage contour at its particular station. The outer skin rests on the rib’s perimeter. The structure exhibits very high strength-weight ratio so as to allow the design of a 15 meter wing span human-powered plane weighting about 10 kilogram. A pilot could effortlessly carry such ultra-light-weight plane over his or her shoulders while running for safe takeoff or controlled landing. Such truly unassisted and controllable human-powered flight would symbolize achieving the long sought-after dream of flying almost like birds. Overview of the Proposed Structure A novel implementation of the inflatable structure (or pressurized structure) concept to build ultra-light-weight aerial vehicles specifically designed for human-powered flight is proposed. The main objective is: (1) to dramatically reduce the total weight and cost of manufacture of such an ultra-light-weight aircraft in comparison to the use of conventional rigid structures; (2) to permit safe takeoff and landing without on-board or external power assistance or on-land personnel help; (3) to offer the possibility of gradually varying the wing geometry in-flight to optimize aerodynamic performance according to flight conditions; and (4) to simplify storage and transportation of the aircraft after deflation. P ge 22105.2 It has been widely demonstrated that inflatable aircraft are resistant to violent impact because they do not break or permanently deform. They survive accidents where rigid structure aircrafts fail to survive. Accordingly, the proposed concept could also reduce the injury risk of the pilot involved in an accident. This concept was originally presented in an abbreviated form on February 7 and April 21 2007, see reference [1]. After a concise description of previous types if inflatable structure aerial vehicles, the novel concept is presented, and two kinds of ultra-light-weight aerial vehicles are suggested. Finally, a plan to integrate the idea into aeronautical student curricula is proposed for faculty. Historical Background Records of inflatable structures date back to antiquity; a popular contemporary application is the motor vehicle tire. Other useful applications include; ramps for emergency exit from airplanes, the automotive air bag, inflatable kites for surfing, inflatable parachutes, satellite and interplanetary inflatable devices and special components for military applications. Between the years 1955 and 1962, the Goodyear Aircraft Company designed and built 12 inflatable aircraft for military rescue missions: the Inflatoplanes model GA-468 (a 40 HP singleseater) and GA-466 (a 60 HP two-seater), see references [2] and [3]. The ILC Dover Company built the Apteron, a radio-controlled inflatable flying-wing, see reference [4]. There are several examples of inflatable sports aircraft. The most simple and popular concept is the paraglider that self-inflates by ram-air pressure. Small UAV (Unmanned Aerial Vehicle) development by the ILC Dover Company and the University of Kentucky can be found in [5]. NASA has investigated several inflatable aircraft applications, see [6]. Brief information about the evolution of modern inflatable aircraft and pertinent bibliography list is found in reference [7]. The first, and perhaps only, work with inflatable human-powered aircrafts is attributed to Dan Perkins who around 1956 in Cardington, England successively built three prototypes of humanpowered aircraft with pressurized wings. Although the first three failed to fly, his fourth and last, the Reluctant Phoenix, flew for the first time in 1965 inside an airships hangar. His first aircraft weighed 28 kg., his last 17.2 kg. See pages 24-27 and pages 67 to 70 in reference [8]. No constructive details were found for the Reluctant Phoenix, though apparently the wing spar and the ribs were made from rigid material. The reader will find in reference [9] valuable historical, technical and practical information which, in spite of being dedicated to hang gliding, directly relates to the subject of this proposal. A vast amount of recent works demonstrate the high technological maturity level reached by inflatable structures, see references [10] and [11]. It is important to bear in mind that all human-powered flights thus far have taken place near the ground to benefit from the ground effect that reduces induced drag. For example, flying at altitude of 2 tenths of the wingspan, the glide ratio can be increased by 50%, meaning that the power to maintain constant speed level flight would be reduced to 66% of that required for free flight. Therefore, our ultimate objective is to achieve human-powered flight at altitudes greater than 2 wing spans. Until now human-powered flight was demonstrated at very low altitude, about one-half wing span, in almost still air. P ge 22105.3 Since Icarus and his father Daedalus of legend, human aspiration continues to strive to achieve human flight without the assistance of a catapult launcher, towed launch, cliff or down a slope launch, without ground help to stabilize the wing tip, without storage of energy, only propelled by the muscle power supplied by the pilot to a propeller to develop thrust while reaching sufficient altitude to evade favorable ground effect. A historical review of human-powered flight attempts is found in references [8] and [9]. The first officially recognized takeoff and landing by the pilot Derek Piggott, took place on 9 November 1961 with the SUMPA (Southampton University ́s Man Powered Aircraft). Perhaps the bestknown achievements of human-powered flights were crossing the English Channel (35.8 km) by Bryan Allen pedaling the Gossamer Albatross on June 12, 1979, and later on April 23, 1988 Kanellos Kanellopoulos established a distance record pedaling the Daedalus 88 from Crete to Santorini (119 km). Implementation of the herein suggested inflatable structure would reduce the weight of these competition aircrafts. The Gossamer Albatross weighed 32 kilograms and the Daedalus 88 weighed 31 kilograms. Currently the UK Royal Aeronautical Society organizes two human-powered flight competitions with prizes of £50,000 and £100,000, see reference [12]. The first prize requires competitors to fly approximately 26 miles (41.8 km) in one hour or less. An ultra-light aircraft with a glide ratio of 35:1, powered by an average cyclist-pilot could conquer this mark. The second prize, a sportoriented competition, requires flying at at least 10 [m/sec] speed for 7 minutes, demonstrating advanced maneuverability capability and disassembly/stowing of the vehicle in 20 minutes. An inexperienced cyclist can continuously deliver between 50 to 100 watts; an average cyclist can produce 200 watts of continuous power and up to 1,000 watts instantaneously. Some citations [14] indicate that Lance Armstrong, during the Tour de France, continuously produced 400 watts, up to 2,000 watts for a few seconds. Proposed Inflatable Structure The examples of inflatable wings cited in the previous section are characterized by being formed by a multitude of inflated (nearly cylindrical) cells of different width extending along the wing span adjacently joined to each other to approximately reproduce a selected airfoil shape, see Figure 1. The basic concept suggested by this paper is radically different. It consists of an inflatable spar attached to multiple inflatable ribs (similar to a conventional rigid structure configuration) covered by a flexible outer skin resulting into a smooth aerodynamic wing surface, see Figure 2.