Winged Aerostat Systems for Better Station Keeping for Aerial Surveillance Akshay A. Kanoria Aeronautical Engineering Department SardarVallabhbhai Institute of Technology, Vasad Anand, India E-mail: aksaerospace@gmail.com Rajkumar S. Pant Aerospace Engineering Department Indian Institute of Technology Bombay Mumbai, India E-mail: rkpant@aero.iitb.ac.in Abstract—An aerostat is a tethered balloon with an aerodynamically shaped envelope containing a lighter-than-air gas that generates bulk of the lifting force. Aerostats are used extensively as an aerial platform for many scientific and commercial applications. Conventional aerostats envelopes have an ellipsoidal shape, due to which they suffer from a large amount of horizontal displacement (called blowby) due to the ambient winds. If the drag force acting on aerostat is high, the resulting blowbyis higher and a longer tether is required to maintain the specified operating altitude; this results in lower payload capacity. Recent studies have shown that winged aerostats (which have an envelope with airfoil cross-section) can reduce blowbydue to a much higher lift/drag ratio. This paper presents a comparative analysis of the operational effectiveness of a winged and conventional aerostat for scientific data gathering in lower Himalayas at various ambient wind speeds. The winged aerostat is seen to be much smaller in size, and has a much lower reduction in operating altitude due to blowby. The paper also describes the design of a prototype winged aerostat currently under development. I. INTRODUCTION& BACKGROUND An aerostat is essentially an aerodynamically shapedballoon that is tethered to the ground. A gas having lowerdensity compared to ambient air (usually Hydrogen orHelium) is enclosed in the envelope and the difference intheir densities gives rise to buoyancy. In an aerostat,buoyancy is the major source of lift, whereas in Heavier-Than-Air systems (e.g., fixed-wing aircraft or rotorcraft),aerodynamic lift produced due to relative motion betweenthe ambient air and the vehicle is the major source of lift. Figure 1Components of RosAeroSystems Au-17 Aerostat[1] Fins are attached at the rear end of the aerostat envelopeto provide stability; they are usually in the form inflatedstructures, filled with lifting gas or air. The payload (usually a surveillance camera or Radar) is mounted on theenvelope. A series of ropes called confluence lines connectthe envelope to a single point called Confluence Point, towhich the main tether is attached, as shown in Fig. 1. Aerostats can remain stationary for long duration instable weather conditions, which makes them a very good choicefor surveillance, advertising, and raising antennae forwireless communication, to name a few. There are various types of Aerostats viz., Blimp shaped,Helikites, and Hybrid, as shown in Fig. 2. Figure 2 Balloon and Blimp type Aerostats [2] II. TETHER, MOORING & WINCHING SYSTEMS OF AN AEROSTAT For deployment in the field, an Aerostat also requires Tether, and a Mooring & Winching system. A brief description of thesecomponents is provided in the subsections that follow. A. Tether A single cable called the "tether" maintains the aerostatin its position above the launch point. The tether not onlyanchors the aerostat in fight, but also provides power for theelectronics payload and other airborne components, through the electricalconductors embedded in it. Thetether also incorporates a metallic braid within the outer jacket to safely conduct lightning currents to ground via themooring system. In addition, optical fibers can also be embeddedwithin the tether core to provide a secure andreliable communications and control link with the groundsupport system. A bidirectional serial data link connects thepayload with the ground control computer. Radar, TV andnarrow and wideband signals may be transmitted betweenthe ground station and the aerostat via secure, dedicatedoptical fibers. The fiber optic link provides 2011 International Conference on Mechanical and Aerospace Engineering (CMAE 2011) 273 978-1-4244-9506-1 C /11/$26.00 2011 IEEE